CTLA4 Haploinsufficiency

Mendelian MONDO:0014493 Pathograph 47 Show in embeddings browser Primary Immunodeficiency Autoimmune Disorder Lymphoproliferative Disorder

CTLA4 haploinsufficiency, also called CHAI or CTLA4 insufficiency, is an autosomal dominant inborn error of immunity caused by heterozygous germline CTLA4 variants. Reduced CTLA4 abundance or defective protein function impairs regulatory T-cell control of CD80/CD86-dependent costimulation. Variable immune dysregulation includes hypogammaglobulinemia, lymphoproliferation, autoimmune cytopenias, enteropathy, lung disease and lymphocytic infiltration of other organs. Clinical penetrance is incomplete; functional defects can occur in apparently unaffected carriers. Missense alleles may impair dimerization, surface availability or ligand capture even when total protein staining is preserved.

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Classifications

IUIS Category

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Inheritance

Autosomal Dominant HP:0000006

CTLA4 haploinsufficiency is inherited as an autosomal dominant disorder with marked phenotypic variability and incomplete penetrance. Disease can arise through familial transmission or de novo heterozygous variants, and some mutation carriers remain clinically unaffected despite measurable CTLA-4 pathway dysfunction.

Autosomal dominant inheritance Penetrance: INCOMPLETE Expressivity: VARIABLE

Show evidence (4 references)

PMID:25329329 SUPPORT Human Clinical

"We studied a large family in which five individuals presented with a complex, autosomal dominant immune dysregulation syndrome characterized by hypogammaglobulinemia, recurrent infections and multiple autoimmune clinical features."

The discovery cohort establishes autosomal dominant inheritance for the syndrome caused by heterozygous CTLA4 mutations.

PMID:25213377 SUPPORT Human Clinical

"We identified germline heterozygous mutations in CTLA4 in subjects with severe immune dysregulation from four unrelated families."

Independent families with heterozygous germline CTLA4 variants confirm a dominant loss-of-function disease mechanism.

PMID:29729943 SUPPORT Human Clinical

"In total, ninety of the 133 CTLA4 mutation carriers (67.6%) were considered affected, as they had sought medical attention for disease-related symptoms."

The 2018 ascertained carrier cohort demonstrates incomplete clinical penetrance; the fraction is not a lifetime population estimate.

+ 1 more reference

Discussions and Knowledge Gaps

Which abnormalities require intrinsic CTLA4 function in conventional T cells or B cells, rather than loss of Treg-mediated restraint?

CONTROVERSY OPEN ctla4-cell-intrinsic-effects

Attached to

pathophysiology#Excess Effector T Cell Activation

The founding studies agree on deficient Treg suppression but differ in conventional T-cell hyperproliferation and detectable B-cell CTLA4. Mixed PBMC assays cannot isolate cell-intrinsic effects, and B-cell apoptosis and autoreactivity do not establish their initiating mechanism.

Show evidence (3 references)

PMID:25213377 SUPPORT In Vitro

"CTLA-4–deficient patient T cells were hyperproliferative, with an increased percentage expressing CD25 in response to T cell receptor stimulation"

Stimulated patient cultures show excess activation; this experiment alone does not establish a conventional T-cell-intrinsic defect.

PMID:25329329 SUPPORT In Vitro

"we did not observe any obvious alterations in conventional T cell proliferation (data not shown)."

The independent discovery study did not reproduce the proposed conventional T-cell phenotype under its assay conditions.

PMID:25329329 SUPPORT In Vitro

"we were unable to detect CTLA-4 expression on B cells in the conditions we tested"

B-cell CTLA4 detection differed between the founding studies.

Why does heterozygous CTLA4 deficiency produce human disease while heterozygous mice lack an obvious comparable phenotype?

HUMAN MODEL MISMATCH OPEN ctla4-murine-dose-response

Complete Ctla4 loss or lymphopenic adoptive-transfer models demonstrate checkpoint dependence but do not reproduce the dosage and incomplete penetrance of human heterozygosity.

Show evidence (1 reference)

PMID:25213377 SUPPORT Model Organism

"In contrast, heterozygous Ctla4 deficiency in mice shows no obvious phenotype"

The discovery study explicitly identifies the species and dosage mismatch.

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Pathophysiology

Reduced CTLA4 protein abundance

Many truncating or splice alleles reduce the abundance of membrane-associated CTLA4. Nonsense-mediated decay is demonstrated for p.Arg51Ter; splice defects can reduce full-length transcript while preserving soluble CTLA4. This quantitative mechanism does not describe every missense allele.

CTLA4 hgnc:2505

Downstream

Deficient CTLA4 ligand capture Reduced available receptor limits CTLA4-dependent ligand capture.

Show evidence (1 reference)

PMID:25213377 SUPPORT In Vitro

"Affected patients had reduced CTLA-4 protein and mRNA expression in sorted Treg cells relative to healthy donors; this reduction persisted after activation"

Patient Tregs demonstrate a quantitative CTLA4 defect that persists after activation.

Impaired CTLA4 dimerization

Mechanism confidence: Provisional

The p.Phe56Cys allele reduces disulfide-linked CTLA4 dimerization in transfected HEK293T cells. Total protein was preserved while surface abundance and ligand binding decreased. The relative contributions of dimerization, folding and trafficking remain unresolved; this is an allele-specific mechanism.

CTLA4 hgnc:2505

Experimental models

HEK293T Phe56Cys functional assays CELL LINE

Downstream

Deficient CTLA4 ligand capture Dimerization-defective p.Phe56Cys also reduces surface CTLA4 and CD80/CD86 binding; an isolated affinity change was not established.

Show evidence (1 reference)

PMID:42577265 SUPPORT In Vitro

"ectopic expression of the CTLA4 p.Phe56Cys variant rather than the wild-type CTLA4 in HEK293T cells resulted in reduced CTLA4 dimerization under non-reducing sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) conditions"

Non-reducing immunoblots support defective dimerization for this allele in an overexpression system.

Deficient CTLA4 ligand capture

CTLA4 variants reduce capture of CD80 and CD86. The defect can reflect reduced receptor availability or impaired function of expressed missense protein. Antibody staining alone can miss impaired ligand uptake.

CTLA4 hgnc:2505

CD80/CD86 binding GO:0005515 ↓ DECREASED

Experimental models

CHO cells expressing CTLA4 variants CELL LINE

HEK293T Phe56Cys functional assays CELL LINE

Downstream

Reduced CD80/CD86 transendocytosis Ligand capture is necessary for removal of costimulatory ligands from antigen-presenting cells.

Show evidence (2 references)

PMID:25329329 SUPPORT In Vitro

"Cells transfected with either T124P and R70W mutants were impaired in their ability to take up soluble CD80-Ig"

Expressed missense proteins have defective ligand uptake in transfected CHO cells.

PMID:28159733 SUPPORT In Vitro

"Thus, functionally significant mutations affecting the amount of CTLA-4, the quality of ligand binding, or its trafficking can be detected using this assay."

The functional assay integrates abundance, ligand binding and trafficking rather than isolating one property.

Reduced CD80/CD86 transendocytosis

CTLA4-insufficient Tregs remove costimulatory ligands from antigen-presenting cells inefficiently. Direct cell-to-cell CD80 uptake assays demonstrate this defect; soluble-ligand uptake is a useful but distinct surrogate.

regulatory T cell CL:0000815

CTLA4-mediated transendocytosis GO:0006898 ↓ DECREASED

Experimental models

Gene-edited patient T cells PRIMARY CELL CULTURE

Downstream

Impaired regulatory T-cell suppression Defective ligand removal compromises CTLA4-dependent suppression of responder T cells.

Show evidence (1 reference)

PMID:25329329 SUPPORT In Vitro

"Whereas Treg cells were generally present at elevated numbers in these individuals, their suppressive function, CTLA-4 ligand binding and transendocytosis of CD80 were impaired."

Carrier Tregs show impaired ligand removal as well as suppression.

Impaired regulatory T-cell suppression

Patient-derived regulatory T cells have impaired CTLA4-dependent suppressive function. Treg numbers can be normal or increased, although reduced frequencies occur in some families. Functional impairment and clinical disease do not correlate perfectly because apparently healthy carriers may also have abnormal assays.

regulatory T cell CL:0000815

negative regulation of T cell activation GO:0050868 ↓ DECREASED

Experimental models

Patient Treg suppression coculture CO CULTURE

Downstream

Excess Effector T Cell Activation Reduced Treg suppression permits excessive responder T-cell activation.

Autoreactive CD21-low B-cell expansion Altered peripheral tolerance may contribute to autoreactive B-cell accumulation; intrinsic and Treg-mediated mechanisms remain unresolved.

Show evidence (2 references)

PMID:25329329 SUPPORT In Vitro

"Treg cells from individuals with CTLA4 heterozygous mutations were unable to suppress CD4+ T cell proliferation as compared to healthy CTLA4+/+ controls"

Patient-derived Tregs fail a ligand-dependent suppression assay.

PMID:25329329 SUPPORT In Vitro

"Whereas Treg cells were generally present at elevated numbers in these individuals, their suppressive function, CTLA-4 ligand binding and transendocytosis of CD80 were impaired."

Carrier Tregs show impaired ligand removal as well as suppression.

Excess Effector T Cell Activation

Reduced checkpoint restraint permits excessive T-cell activation. Patient PBMC assays show hyperproliferation reversible by restoring CTLA4 function, but an intrinsic conventional T-cell defect has not been reproduced consistently and is distinct from established Treg dysfunction.

T cell CL:0000084

T cell activation GO:0042110 ↑ INCREASED

Experimental models

CTLA4 knockdown and rescue in human lymphocytes PRIMARY CELL CULTURE

Downstream

Lymphocytic Tissue Infiltration Dysregulated lymphocyte responses are associated with inflammatory organ infiltration.

Autoimmunity Loss of peripheral restraint contributes to tissue-directed autoimmune responses.

Non-malignant lymphoproliferation Loss of immune restraint accompanies persistent lymphoid expansion.

Show evidence (1 reference)

PMID:25213377 SUPPORT In Vitro

"CTLA-4–deficient patient T cells were hyperproliferative, with an increased percentage expressing CD25 in response to T cell receptor stimulation"

Stimulated patient cultures show excess activation; this experiment alone does not establish a conventional T-cell-intrinsic defect.

Lymphocytic Tissue Infiltration

Non-malignant lymphocytic infiltrates affect gut, lung, brain, marrow and other organs. Biopsies can contain CD4 or CD8 T cells, B cells and granulomas; infiltration is not exclusively a T-cell process.

lymphocyte CL:0000542

Animal models

Gene-corrected Ctla4-null T cells transferred into Rag2-null mice Mouse rescues

Downstream

Autoimmune enteropathy Gastrointestinal inflammatory infiltration accompanies enteropathy.

Pulmonary lymphocytic infiltration Lymphoid infiltration contributes to inflammatory lung disease.

Inflammatory central nervous system lesions Cerebral infiltration can cause neurologic dysfunction; other causes of neurologic symptoms must be distinguished.

Colitis Inflammatory tissue injury is associated with this gastrointestinal manifestation.

Intestinal villous atrophy Inflammatory tissue injury is associated with this gastrointestinal manifestation.

Show evidence (1 reference)

PMID:29729943 SUPPORT Human Clinical

"Forty-three affected mutation carriers (50%) had lymphocytic infiltrations into lung (n=27), gastrointestinal tract (n=17), brain (n=12), bone marrow (n=6, Figure 6 Panel E), kidney (n=6), or retroperitoneal tissue (n=4)."

Clinical biopsies and imaging identify a multiorgan infiltration phenotype; the cohort is ascertained rather than population based.

Autoreactive CD21-low B-cell expansion

The peripheral B-cell compartment is enriched for predominantly autoreactive CD21-low cells. These cells show poor receptor-driven proliferation and increased susceptibility to apoptosis; their origin from an intrinsic B-cell defect versus failed Treg control remains unresolved.

B cell CL:0000236

Downstream

Enhanced B-cell apoptosis The expanded CD21-low population exhibits increased cell death ex vivo.

Increased CD21-low B-cell proportion The expanded compartment is detectable by blood immunophenotyping.

Autoimmune thrombocytopenia Autoreactive humoral responses may contribute to platelet-directed autoimmunity; the intervening antigen-specific mechanism is not established.

Autoimmune hemolytic anemia Loss of B-cell tolerance may contribute to erythrocyte-directed autoimmunity.

Show evidence (2 references)

PMID:25213377 SUPPORT Human Clinical

"We found that the frequency of CD21lo B cells was greatly elevated in patients’ peripheral blood"

Patient immunophenotyping establishes expansion of the CD21-low compartment.

PMID:25213377 SUPPORT Human Clinical

"Patients also exhibited progressive loss of circulating B cells, associated with an increase of predominantly autoreactive CD21(lo) B cells and accumulation of B cells in nonlymphoid organs."

The discovery cohort demonstrates progressive B-cell depletion and altered B-cell subsets.

Enhanced B-cell apoptosis

Patient B cells, particularly the CD21-low compartment, show increased apoptosis ex vivo. This may contribute to peripheral B-cell depletion, but does not establish the only cause of low B-cell counts.

B cell CL:0000236

Downstream

Peripheral B-cell depletion Increased cell death is a proposed contributor to progressive B-cell loss.

Show evidence (1 reference)

PMID:25213377 SUPPORT In Vitro

"we observed heightened apoptosis in patient B cells"

Patient B cells exhibit increased cell death ex vivo.

Peripheral B-cell depletion

Circulating B-cell counts can progressively decline. Class-switched memory B-cell proportions are often reduced, but a global intrinsic class-switch failure is not established: stimulated naive patient B cells can switch and secrete immunoglobulin robustly.

B cell CL:0000236

Downstream

Hypogammaglobulinemia Loss and dysfunction of B-cell compartments may reduce humoral output; residual naive-cell switching can remain intact.

Reduced circulating B-cell count Peripheral B-cell depletion is measured on immunophenotyping.

Reduced class-switched memory B-cell proportion The disturbed B-cell compartment includes loss of the switched-memory subset; a selective differentiation block is not established.

Show evidence (1 reference)

PMID:25213377 SUPPORT Human Clinical

"Patients also exhibited progressive loss of circulating B cells, associated with an increase of predominantly autoreactive CD21(lo) B cells and accumulation of B cells in nonlymphoid organs."

The discovery cohort demonstrates progressive B-cell depletion and altered B-cell subsets.

Non-malignant lymphoproliferation

Dysregulated lymphocyte accumulation expands secondary lymphoid organs. This benign inflammatory phenotype is distinct from lymphoma, although both can occur in the same disorder.

Animal models

Gene-corrected Ctla4-null T cells transferred into Rag2-null mice Mouse rescues

Downstream

Lymphadenopathy Non-malignant lymphoid expansion produces organ enlargement.

Splenomegaly Non-malignant lymphoid expansion produces organ enlargement.

Hepatomegaly Non-malignant lymphoid expansion produces organ enlargement.

Show evidence (1 reference)

PMID:29729943 SUPPORT Human Clinical

"Sixty-two affected mutation carriers (73%) had non-malignant lymphoproliferation, including splenomegaly (n=51, Figure 3, Figure 5 Panel A), chronic lymphadenopathy (n=43), and hepatomegaly (n=17)."

The cohort identifies non-malignant lymphoid enlargement.

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Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.

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Phenotypes

Blood 9

Hypogammaglobulinemia VERY_FREQUENT Decreased circulating immunoglobulin concentration HP:0004313

Sequelae: Recurrent respiratory infections

Show evidence (1 reference)

PMID:29729943 SUPPORT Human Clinical

"Hypogammaglobulinemia was present in 84% (65/77), with low IgM in 30, low IgG in 42, and low IgA in 53 affected mutation carriers"

The measured subgroup supports the frequency; it is not the fraction of all variant carriers.

Autoimmune thrombocytopenia HP:0001973

Show evidence (1 reference)

PMID:29729943 SUPPORT Human Clinical

"Sixty-two percent of affected mutation carriers (55/89) had autoimmune cytopenia, including immune thrombocytopenia (n=41), autoimmune hemolytic anemia (n=37), pure red cell aplasia (PRCA) (n=2) or autoimmune neutropenia (n=16)."

The cohort reports specific autoimmune cytopenias within a clinically ascertained population.

Autoimmune hemolytic anemia HP:0001890

Show evidence (1 reference)

PMID:29729943 SUPPORT Human Clinical

The cohort reports specific autoimmune cytopenias within a clinically ascertained population.

Autoimmune neutropenia HP:0001904

Show evidence (1 reference)

PMID:29729943 SUPPORT Human Clinical

The cohort reports specific autoimmune cytopenias within a clinically ascertained population.

Lymphopenia Decreased total lymphocyte count HP:0001888

Show evidence (1 reference)

PMID:29729943 SUPPORT Human Clinical

"Thirty-nine percent (26/66) of affected mutation carriers with available immunological data had lymphopenia of which twenty-four were under immunosuppressive treatment at the time of data collection."

The source provides both the measured fraction and the major treatment confounder.

Reduced circulating B-cell count Decreased total B cell count HP:0010976

Show evidence (1 reference)

PMID:29729943 SUPPORT Human Clinical

"Absolute CD19+ B cell counts were reduced in 41% (26/58) of affected mutation carriers."

The reported count supports B-cell lymphopenia; no recalculated frequency band is asserted.

Reduced class-switched memory B-cell proportion Decreased class-switched memory B cell proportion HP:0030388

Show evidence (1 reference)

PMID:29729943 SUPPORT Human Clinical

"B cell subsets showed a decrease in switched memory B cells (23/30) and consecutively a relative increase in naïve B cells (14/29)."

Immunophenotyping documents the altered subset distribution.

Increased CD21-low B-cell proportion HP:0033207

Show evidence (1 reference)

PMID:25213377 SUPPORT Human Clinical

"Patients also exhibited progressive loss of circulating B cells, associated with an increase of predominantly autoreactive CD21(lo) B cells and accumulation of B cells in nonlymphoid organs."

The original cohort links CD21-low expansion with autoreactive B-cell phenotypes.

Lymphoma HP:0002665

Show evidence (1 reference)

PMID:30250467 SUPPORT Human Clinical

"There were ten lymphomas, five gastric cancers, one multiple myeloma, and one metastatic melanoma."

The malignancy cohort documents both tumor groups; it overlaps earlier carrier cohorts.

Cardiovascular 2

Lymphadenopathy HP:0002716

Show evidence (1 reference)

PMID:29729943 SUPPORT Human Clinical

"Sixty-two affected mutation carriers (73%) had non-malignant lymphoproliferation, including splenomegaly (n=51, Figure 3, Figure 5 Panel A), chronic lymphadenopathy (n=43), and hepatomegaly (n=17)."

The cohort documents these distinct lymphoproliferative manifestations.

Splenomegaly HP:0001744

Show evidence (1 reference)

PMID:29729943 SUPPORT Human Clinical

"Sixty-two affected mutation carriers (73%) had non-malignant lymphoproliferation, including splenomegaly (n=51, Figure 3, Figure 5 Panel A), chronic lymphadenopathy (n=43), and hepatomegaly (n=17)."

The cohort documents these distinct lymphoproliferative manifestations.

Digestive 9

Hepatomegaly HP:0002240

Show evidence (1 reference)

PMID:29729943 SUPPORT Human Clinical

"Sixty-two affected mutation carriers (73%) had non-malignant lymphoproliferation, including splenomegaly (n=51, Figure 3, Figure 5 Panel A), chronic lymphadenopathy (n=43), and hepatomegaly (n=17)."

The cohort documents these distinct lymphoproliferative manifestations.

Autoimmune enteropathy Abnormality of the gastrointestinal tract HP:0011024

Coarse binding: no hpo term

Ontology gap: HPO searches for autoimmune enteropathy and enteropathy found no specific autoimmune-enteropathy term. Protein-losing enteropathy, colitis and villous atrophy describe narrower manifestations and are not equivalent to the complete clinical syndrome.

Sequelae: Chronic diarrhea Failure to thrive

Show evidence (2 references)

PMID:35935971 SUPPORT Human Clinical

"Both patients underwent genetic testing given disease refractoriness and were ultimately diagnosed with cytotoxic T lymphocyte antigen 4 (CTLA4) haploinsufficiency."

Two refractory celiac-like cases demonstrate the enteropathy presentation.

url:https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf SUPPORT Human Clinical

"The underlying causes were autoimmune enteropathy (in 21 of 74 patients), inflammatory bowel disease (in 16 of 74), atrophic gastritis (in 14 of 74), and celiac disease (in 3 of 74)."

Full text of Egg et al., Therapeutic options for CTLA-4 insufficiency (PMID:34111452). The treatment cohort distinguishes different gastrointestinal diagnoses.

Chronic diarrhea HP:0002028

Show evidence (1 reference)

PMID:29729943 SUPPORT Human Clinical

"Diarrhea was frequent (n=51), ranging from mild to severe diarrhea with weight loss, wasting, and total parenteral nutrition-dependency."

The cohort documents a broad severity spectrum.

Intestinal villous atrophy HP:0011473

Show evidence (1 reference)

PMID:35935971 SUPPORT Human Clinical

"Duodenal mucosa with total villous atrophy, crypt hyperplasia, and patchy intraepithelial lymphocytosis, suggestive of celiac disease."

Biopsy documents villous injury in a genetically confirmed CTLA4 case.

Colitis HP:0002583

Show evidence (1 reference)

PMID:42577265 SUPPORT Human Clinical

"Re-review of intestinal pathology specimens revealed chronic active ileitis and colitis with intestinal villous atrophy, crypt shortening, loss of intestinal Paneth cells and goblet cells, lymphocytic infiltration, and prominent epithelial apoptotic bodies"

Histopathology in the Phe56Cys case documents colonic inflammation with epithelial injury.

Autoimmune hepatitis HP:5210421

Show evidence (1 reference)

PMID:31396201 SUPPORT Human Clinical

"She was initially diagnosed with autoimmune hepatitis at 20 months of age"

The case establishes autoimmune hepatitis as an early presentation.

Liver involvement OCCASIONAL Abnormality of the liver HP:0001392

Coarse binding: source unspecified

Show evidence (1 reference)

PMID:29729943 SUPPORT Human Clinical

"Arthritis (14%), growth retardation (14%), renal (12%) or liver (12%) involvement were less frequent"

The cohort reports these organ-level findings; the composite organ rates do not establish rates for specific diagnoses.

Gastric carcinoma Stomach cancer HP:0012126

Show evidence (3 references)

PMID:30250467 SUPPORT Human Clinical

"There were ten lymphomas, five gastric cancers, one multiple myeloma, and one metastatic melanoma."

The primary malignancy cohort documents gastric carcinoma.

PMID:30250467 SUPPORT Human Clinical

"The median age of onset was 32 years for lymphoma and 34 years for gastric cancer."

The source supplies a cohort-specific age of onset rather than an unspecified comparison with usual onset.

PMID:30250467 SUPPORT Human Clinical

"Seven lymphomas and three gastric cancers were EBV-associated."

Three of the five gastric cancers were EBV-associated. Association does not establish that EBV explains every cancer in CTLA4 insufficiency.

Atrophic gastritis HP:0002582

Show evidence (1 reference)

url:https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf SUPPORT Human Clinical

"atrophic gastritis (in 14 of 74)"

Full text of Egg et al., Therapeutic options for CTLA-4 insufficiency (PMID:34111452). The gastrointestinal subgroup included 14 patients with atrophic gastritis.

Endocrine 3

Hashimoto thyroiditis HP:0000872

Show evidence (1 reference)

PMID:35935971 SUPPORT Human Clinical

"including Hashimoto’s thyroiditis (diagnosed age 6), Addison’s disease (diagnosed age 8), cytopenias"

The enteropathy case documents autoimmune thyroid and adrenal disease.

Primary adrenal insufficiency HP:0008207

Show evidence (1 reference)

PMID:35935971 SUPPORT Human Clinical

"including Hashimoto’s thyroiditis (diagnosed age 6), Addison’s disease (diagnosed age 8), cytopenias"

The case establishes adrenal involvement without implying a cohort frequency.

Type I diabetes mellitus HP:0100651

Show evidence (1 reference)

PMID:29729943 SUPPORT Human Clinical

"First symptoms included autoimmune cytopenia (33%), respiratory manifestations (21%), enteropathy (17%), type 1 diabetes (8%)"

The source concerns first presentation, not overall lifetime diabetes frequency.

Genitourinary 1

Renal involvement OCCASIONAL Abnormality of the kidney HP:0000077

Coarse binding: source unspecified

Show evidence (1 reference)

PMID:29729943 SUPPORT Human Clinical

"Arthritis (14%), growth retardation (14%), renal (12%) or liver (12%) involvement were less frequent"

The cohort reports these organ-level findings; the composite organ rates do not establish rates for specific diagnoses.

Immune 5

Autoimmunity HP:0002960

Show evidence (1 reference)

PMID:25329329 SUPPORT Human Clinical

The discovery cohort explicitly establishes multi-organ autoimmunity as a core clinical feature of CTLA4 haploinsufficiency.

Recurrent respiratory infections HP:0002205

Show evidence (1 reference)

PMID:29729943 SUPPORT Human Clinical

"Respiratory tract involvement was common (68%; 61/90; Figure 5 Panels C, D, E; Figure 6 Panel A, B) including recurrent lower (n=48) and upper (n=41) respiratory tract infections, granulomatous-lymphocytic interstitial lung disease (GLILD) (n=32), and bronchiectasis (n=20)."

The source distinguishes infections, GLILD and bronchiectasis; their overlapping counts should not be added.

Inflammatory central nervous system lesions Autoimmune encephalitis HP:5210423

Show evidence (1 reference)

PMID:29729943 SUPPORT Human Clinical

"Three had autoimmune encephalitis or encephalomyelitis with cerebral perivascular lymphocytic infiltrations"

The cohort distinguishes directly inflammatory CNS disease from other neurologic complications.

Eczema Eczematoid dermatitis HP:0000964

Show evidence (1 reference)

url:https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf SUPPORT Human Clinical

"We observed 59 cases of recurrent eczema, with 25 of them diagnosed as atopic dermatitis by the treating dermatologist."

Full text of Egg et al., Therapeutic options for CTLA-4 insufficiency (PMID:34111452). The source distinguishes recurrent eczema from confirmed atopic dermatitis.

Psoriasiform dermatitis HP:0003765

Show evidence (1 reference)

url:https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf SUPPORT Human Clinical

"psoriatic skin irritation s in 15 patients"

Full text of Egg et al., Therapeutic options for CTLA-4 insufficiency (PMID:34111452). The cohort documents psoriatic skin disease.

Integument 2

Alopecia HP:0001596

Show evidence (1 reference)

url:https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf SUPPORT Human Clinical

"alopecia in 14, warts in 11, and vitiligo in 5."

Full text of Egg et al., Therapeutic options for CTLA-4 insufficiency (PMID:34111452). The 2022 treatment cohort lists alopecia among skin manifestations.

Vitiligo HP:0001045

Show evidence (1 reference)

url:https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf SUPPORT Human Clinical

"alopecia in 14, warts in 11, and vitiligo in 5."

Full text of Egg et al., Therapeutic options for CTLA-4 insufficiency (PMID:34111452). The cohort documents vitiligo in affected carriers.

Musculoskeletal 1

Arthritis OCCASIONAL HP:0001369

Show evidence (2 references)

PMID:29729943 SUPPORT Human Clinical

"Arthritis (14%), growth retardation (14%), renal (12%) or liver (12%) involvement were less frequent"

The cohort reports these organ-level findings; the composite organ rates do not establish rates for specific diagnoses.

PMID:31396201 SUPPORT Human Clinical

"she presented with polyarticular arthritis affecting large and small joints of the upper and lower limbs including the knees, ankles, elbows, and multiple small hand joints."

The Tyr139Cys case provides a specific polyarticular example.

Respiratory 2

Pulmonary lymphocytic infiltration Pulmonary interstitial lymphocyte infiltration HP:0033582

Show evidence (2 references)

PMID:29729943 SUPPORT Human Clinical

The source distinguishes infections, GLILD and bronchiectasis; their overlapping counts should not be added.

PMID:29729943 SUPPORT Human Clinical

Clinical biopsies and imaging identify a multiorgan infiltration phenotype; the cohort is ascertained rather than population based.

Bronchiectasis HP:0002110

Show evidence (1 reference)

PMID:29729943 SUPPORT Human Clinical

The source distinguishes infections, GLILD and bronchiectasis; their overlapping counts should not be added.

Growth 2

Failure to thrive HP:0001508

Show evidence (1 reference)

PMID:35935971 SUPPORT Human Clinical

"Patient 2 is a 14-year-old female who initially presented with diarrhea, vomiting, and failure to thrive before 1 year of age."

The second celiac-like case documents early growth failure.

Growth delay OCCASIONAL HP:0001510

Show evidence (1 reference)

PMID:29729943 SUPPORT Human Clinical

"Arthritis (14%), growth retardation (14%), renal (12%) or liver (12%) involvement were less frequent"

The cohort reports growth retardation without restricting it to one mechanism.

🧬

Genetic Associations

CTLA4 (CAUSATIVE)

Gene: CTLA4 hgnc:2505 gene page

Autosomal Dominant

Show evidence (5 references)

PMID:25329329 SUPPORT Human Clinical

"We identified a heterozygous nonsense mutation in exon 1 of CTLA4. Screening of 71 unrelated patients with comparable clinical phenotypes identified five additional families (nine individuals) with previously undescribed splice site and missense mutations in CTLA4."

This cohort study defines the mutational spectrum, showing that multiple heterozygous CTLA4 variant classes can cause the syndrome.

PMID:31396201 SUPPORT Human Clinical

"This variant lay within the highly conserved MYPPPY motif of CTLA-4: a critical structural determinant of ligand binding, which is also bound by the anti-CTLA-4 monoclonal antibody ipilimumab."

The case identifies a variant in the conserved ligand-binding motif; direct functional assays of this patient’s allele were not performed in this report.

PMID:25213377 SUPPORT Human Clinical

"We identified germline heterozygous mutations in CTLA4 in subjects with severe immune dysregulation from four unrelated families."

Confirms CTLA4 as the causal gene and anchors the disease as a heterozygous germline loss-of-function disorder.

+ 2 more references

Variants (10)

p.Arg51Ter

A nonsense allele associated with degradation of its transcript.

Show evidence (1 reference)

PMID:25213377 SUPPORT In Vitro

"cDNA analyses from A.I.1 T cells showed that the mutant allele mRNA was degraded >95%, consistent with nonsense-mediated decay"

Nonsense-mediated decay was measured in patient T cells.

p.Cys35Ter

An early truncating allele with no detectable protein in transfected CHO cells.

Show evidence (1 reference)

PMID:25329329 SUPPORT In Vitro

"we found no protein expression in cells transfected with the C35* (Family A) mutant"

Transfection excludes productive rescue by a nearby alternative start codon under these assay conditions.

p.Arg70Trp

An extracellular-domain missense allele with preserved expressed protein but reduced ligand uptake.

Show evidence (1 reference)

PMID:25329329 SUPPORT In Vitro

"Cells transfected with either T124P and R70W mutants were impaired in their ability to take up soluble CD80-Ig"

The CHO assay shows impaired uptake for this allele.

p.Thr124Pro

An extracellular-domain missense allele with impaired soluble CD80 uptake; protein notation is retained because nucleotide coordinates differ between cited reports.

Show evidence (1 reference)

PMID:25329329 SUPPORT In Vitro

"Cells transfected with either T124P and R70W mutants were impaired in their ability to take up soluble CD80-Ig"

The expressed mutant is functionally deficient in the ligand-uptake assay.

p.Pro137Arg

A ligand-binding-motif allele that can retain near-normal antibody staining despite defective ligand uptake.

Show evidence (1 reference)

PMID:28159733 SUPPORT In Vitro

"a much reduced slope was obtained with Tregs from a patient with a known ligand-binding defect (P137R)."

Ligand uptake relative to CTLA4 expression distinguishes this functional defect.

p.Tyr139Cys

A de novo MYPPPY-motif variant reported in a child with autoimmune hepatitis and polyarthritis.

Show evidence (2 references)

PMID:31396201 SUPPORT Human Clinical

"This variant lay within the highly conserved MYPPPY motif of CTLA-4: a critical structural determinant of ligand binding, which is also bound by the anti-CTLA-4 monoclonal antibody ipilimumab."

The clinical report locates the variant in a functional motif; it did not directly assay this patient’s mutant protein.

PMID:31396201 SUPPORT Human Clinical

"This variant was absent from both biological parents"

Parental sequencing established de novo occurrence.

NM_005214.5:c.167T>G (p.Phe56Cys)

An inherited allele with incomplete penetrance. HEK293T assays show reduced dimerization, surface expression and CD80/CD86 binding despite preserved total protein.

Show evidence (1 reference)

PMID:42577265 SUPPORT In Vitro

The 2026 functional study supports a dimerization defect for this allele.

c.457+2T>C

An inherited splice-site variant in a patient with refractory celiac-like enteropathy and reduced CTLA4 expression in memory Tregs.

Show evidence (2 references)

PMID:35935971 SUPPORT Human Clinical

"Research-based whole-exome sequencing was pursued at this time and confirmed previously unreported heterozygous CTLA4 mutation (c. 457 + 2T > C), suggestive of CTLA4 haploinsufficiency."

Sequencing identified the allele; associated reduced protein expression supports functional insufficiency without a demonstrated RNA-splicing assay.

PMID:35935971 SUPPORT Human Clinical

"it was confirmed that the disease-causing mutation was inherited from the patient’s father"

Family testing established paternal inheritance.

c.71_72del (p.Leu24ProfsTer35)

A de novo early frameshift in a second refractory celiac-like enteropathy case, with absent detectable CTLA4 in memory Tregs.

Show evidence (1 reference)

PMID:35935971 SUPPORT Human Clinical

"A previously unreported de novo heterozygous variant in CTLA4 in exon 1, c71_72del (p.Leu24Profs*35) was identified"

The case report documents de novo occurrence and subsequently confirms deficient CTLA4 staining.

p.Phe179CysfsTer29

A frameshift allele for which Treg CTLA4 expression was comparable to controls but CD80 uptake was impaired.

Show evidence (1 reference)

url:https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf SUPPORT In Vitro

"Although Treg cells with the variant p.F179Cfs*29 had normal CTLA-4 expression, the frequency of CD80 uptake in Treg cells was as reduced as in 3 additional deleterious variants"

Full text of Egg et al., Therapeutic options for CTLA-4 insufficiency (PMID:34111452). This allele illustrates functional insufficiency despite preserved staining.

💊

Medical Actions

Abatacept

Category: Therapeutic Action: Immunosuppressive Therapy NCIT:C15261

Agent: Abatacept NCIT:C28898

Platform: Protein replacement

CTLA4-Ig binds CD80/CD86 and limits CD28-dependent costimulation. Retrospective cohorts and small case series report benefit, especially for enteropathy and lymphoproliferation. The 2026 ABACHAI single-arm trial enrolled 18 adults with CTLA4 insufficiency and two with LRBA deficiency; pooled results showed improvement in lymphoproliferation and immune activation, but insufficient control of cytopenias and renal involvement. Responses are organ dependent and the trial did not provide a randomized comparator.

Mechanism Target:

INHIBITS Excess Effector T Cell Activation — Soluble CTLA4-Ig binds the shared CD80/CD86 ligands and limits costimulation.

Show evidence (1 reference)

PMID:36262801 SUPPORT Other

"Abatacept inhibits the CD80/86:CD28 co-stimulatory pathway by high affinity binding of the CTLA-4 domain to CD80 and CD86"

The protocol describes the pharmacologic rationale.

Show evidence (4 references)

PMID:42763023 SUPPORT Human Clinical

"Twenty patients were enrolled (18 with CTLA-4 insufficiency and 2 with LRBA deficiency)."

Trial outcomes pool two genetic disorders and should not be presented as a CTLA4-only effect estimate.

PMID:42763023 SUPPORT Human Clinical

"Abatacept reduced lymphoproliferation and immune activation and improved patient-reported quality of life and gastrointestinal symptom quality. Cytopenias and renal involvement were not sufficiently controlled."

The prospective study documents both benefit and important limits.

PMID:35935971 SUPPORT Human Clinical

"They are both now in complete clinical and endoscopic remission on abatacept."

Two pediatric-onset enteropathy cases achieved remission; this is uncontrolled case evidence.

+ 1 more reference

Belatacept

Category: Therapeutic Action: Immunosuppressive Therapy NCIT:C15261

Agent: Belatacept NCIT:C80255

Platform: Protein replacement

The higher-affinity CTLA4-Ig derivative has been used in a small number of affected carriers, sometimes with other immunosuppression. Historical reports combine abatacept and belatacept and do not establish separate efficacy rates.

Show evidence (1 reference)

PMID:29729943 SUPPORT Human Clinical

"In total, fourteen affected mutation carriers received the CTLA-4 fusion proteins abatacept or belatacept; eleven of whom responded with an improvement of their clinical symptoms."

The retrospective result combines both agents and overlapping manifestations.

Sirolimus

Category: Therapeutic Action: Immunosuppressive Therapy NCIT:C15261

Agent: Sirolimus NCIT:C1212

Platform: Small molecule

Sirolimus has been used for refractory cytopenias, lymphoproliferation and organ inflammation. Responses vary; infection and other adverse effects can limit treatment.

Show evidence (1 reference)

PMID:29729943 SUPPORT Human Clinical

"Thirteen affected mutation carriers were treated with the mTOR inhibitor sirolimus with a good response in eight"

The cohort reports benefit in some, but not all, treated carriers.

Rituximab

Category: Therapeutic Action: Immunosuppressive Therapy NCIT:C15261

Agent: Rituximab NCIT:C1702

Platform: Monoclonal antibody

B-cell depletion has been used for autoimmune cytopenias and lymphoproliferative or inflammatory organ disease. Responses vary by organ, and secondary antibody deficiency may require replacement immunoglobulin.

Show evidence (2 references)

url:https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf SUPPORT Human Clinical

"A total of 30 patients received rituximab (1-4 X 375 mg/ m 2), of whom 25 (83%) responded"

Full text of Egg et al., Therapeutic options for CTLA-4 insufficiency (PMID:34111452). The retrospective cohort reports responses in cytopenia patients, without a randomized comparison.

url:https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf SUPPORT Human Clinical

"8 patients in our cohort received IgRT because of secondary loss of antibodies after therapy with rituximab."

Full text of Egg et al., Therapeutic options for CTLA-4 insufficiency (PMID:34111452). The same cohort documents a clinically relevant consequence of B-cell depletion.

Systemic corticosteroids

Category: Therapeutic Action: Immunosuppressive Therapy NCIT:C15261

Agent: corticosteroid CHEBI:50858

Platform: Small molecule

Systemic corticosteroids are used for autoimmune cytopenias and inflammatory gastrointestinal, pulmonary, neurologic or skin disease. Responses can be temporary and relapse during tapering may prompt additional therapy.

Show evidence (1 reference)

url:https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf SUPPORT Human Clinical

"Systemic corticosteroids alleviated gastrointestinal symptoms in 19 cases temporarily (86%)."

Full text of Egg et al., Therapeutic options for CTLA-4 insufficiency (PMID:34111452). The GI result illustrates the limited durability of steroid response.

Oral budesonide

Category: Therapeutic Action: Immunosuppressive Therapy NCIT:C15261

Agent: Budesonide NCIT:C1027

Platform: Small molecule

Locally acting oral budesonide has been used for gastrointestinal inflammation, including as an adjunct while establishing abatacept treatment.

Show evidence (1 reference)

url:https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf SUPPORT Human Clinical

"Of the 11 patients who received oral budesonide (9 mg per day), 10 achieved a good clinical response."

Full text of Egg et al., Therapeutic options for CTLA-4 insufficiency (PMID:34111452). The cohort documents gastrointestinal responses under oral budesonide.

Azathioprine

Category: Therapeutic Action: Immunosuppressive Therapy NCIT:C15261

Agent: Azathioprine NCIT:C290

Platform: Small molecule

Azathioprine has been used for autoimmune hepatitis, enteropathy and inflammatory lung disease. Observed responses vary across manifestations.

Show evidence (2 references)

url:https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf SUPPORT Human Clinical

"Nine patients received azathioprine (50-150 mg per day), with 4 (44%) showing a positive response."

Full text of Egg et al., Therapeutic options for CTLA-4 insufficiency (PMID:34111452). The gastrointestinal subgroup provides direct treatment evidence.

PMID:31396201 SUPPORT Human Clinical

"due to steroid dependency azathioprine was introduced (20 mg per day). On this regime her liver enzymes normalized."

The Tyr139Cys case documents a hepatic response with combined treatment.

Mycophenolate

Category: Therapeutic Action: Immunosuppressive Therapy NCIT:C15261

Agent: Mycophenolate NCIT:C29272

Platform: Small molecule

Mycophenolate has been used for inflammatory lung disease and arthritis. The evidence consists of small retrospective subgroups and individual cases.

Show evidence (2 references)

url:https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf SUPPORT Human Clinical

"Mycophenolate (1000 mg per day) was given to 3 patients and 2 patients showed a reduction of the extent of GLILD"

Full text of Egg et al., Therapeutic options for CTLA-4 insufficiency (PMID:34111452). Two of three treated cases showed reduced lung involvement.

PMID:31396201 SUPPORT Human Clinical

"a switch from azathioprine to mycophenolate with a good response."

The reported child initially improved after the medication change.

Anti-TNF therapy

Category: Therapeutic Action: Immunosuppressive Therapy NCIT:C15261

Agent: Adalimumab NCIT:C65216 Infliximab NCIT:C1789

Platform: Monoclonal antibody

Adalimumab and infliximab have been tried for enteropathy or arthritis, with mixed responses. These are alternatives reported in cohorts rather than reliably effective substitutes for CTLA4-directed therapy.

Show evidence (2 references)

url:https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf SUPPORT Human Clinical

"Eight received anti-TNF-a biol ogics (eg, adalimumab, 20-80 mg per week, or infliximab, 5-10 mg/kg), with 4 positive responses (56%)."

Full text of Egg et al., Therapeutic options for CTLA-4 insufficiency (PMID:34111452). The source reports four responses among eight uses; its printed percentage is inconsistent, so no efficacy percentage is adopted.

PMID:35935971 SUPPORT Human Clinical

"She had a significant symptomatic response with adalimumab, but this was subsequently discontinued after the development of drug-induced lupus following the fifth dose."

The case documents both clinical response and treatment-limiting toxicity.

Vedolizumab

Category: Therapeutic Action: Immunosuppressive Therapy NCIT:C15261

Agent: Vedolizumab NCIT:C95798

Platform: Monoclonal antibody

Gut-directed integrin blockade has been reported as an option for refractory enteropathy, but responses are inconsistent across cases.

Show evidence (2 references)

url:https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf SUPPORT Other

"Alternative strategies should include consideration of sirolimus or the anti-a4β7 integrin mAb vedolizumab. 32 The latter was successful in treating the diarrhea in 2 patients."

Full text of Egg et al., Therapeutic options for CTLA-4 insufficiency (PMID:34111452). The 2022 management report cites two successful cases; this is limited clinical evidence.

PMID:42577265 SUPPORT Human Clinical

"Despite subsequent aggressive sequential therapy with conventional (mesalamine, azathioprine, thalidomide) and biological agents (infliximab, adalimumab, vedolizumab, and ustekinumab), his symptoms progressed over time"

The Phe56Cys case demonstrates failure of several empiric therapies, including vedolizumab.

Methotrexate

Category: Therapeutic Action: Immunosuppressive Therapy NCIT:C15261

Agent: Methotrexate NCIT:C642

Platform: Small molecule

Methotrexate has been used for psoriatic skin disease in a small treated subgroup. It is not uniformly suitable for patients with hepatic involvement.

Show evidence (2 references)

url:https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf SUPPORT Human Clinical

"3 received methotrexate (7.5-20 mg per week) with good effect"

Full text of Egg et al., Therapeutic options for CTLA-4 insufficiency (PMID:34111452). The skin subgroup reports improvement in three treated patients.

PMID:31396201 SUPPORT Human Clinical

"Methotrexate was not used due to her underlying liver disease."

The hepatic case illustrates why treatment choice depends on organ involvement.

Cyclosporine

Category: Therapeutic Action: Immunosuppressive Therapy NCIT:C15261

Agent: Cyclosporine NCIT:C406

Platform: Small molecule

Cyclosporine has been used for severe skin or lung infiltration and cytopenia; a skin response was reported in one of two treated cases.

Show evidence (1 reference)

url:https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf SUPPORT Human Clinical

"2 patients received cyclospori ne (2-5 mg/kg) for severe infiltration of skin and lung and for concomitant cytopenia. In 1 patient cyclosporine alleviated the skin lesions"

Full text of Egg et al., Therapeutic options for CTLA-4 insufficiency (PMID:34111452). The cohort provides only a small observational treatment experience.

Cyclophosphamide

Category: Therapeutic Action: Immunosuppressive Therapy NCIT:C15261

Agent: Cyclophosphamide NCIT:C405

Platform: Small molecule

Cyclophosphamide with corticosteroids has been used for inflammatory CNS lesions. Small retrospective experience does not establish comparative efficacy.

Show evidence (1 reference)

url:https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf SUPPORT Human Clinical

"Cyclophosphamide (2 X 200 mg/m 2) plus corticosteroids was tried in 3 cases (2 patients received 5 mg per day and 1 received 40 mg per day). Of these 3 patients, 2 showed a good clinical response"

Full text of Egg et al., Therapeutic options for CTLA-4 insufficiency (PMID:34111452). Two of three cases improved under a combination regimen.

Mercaptopurine

Category: Therapeutic Action: Immunosuppressive Therapy NCIT:C15261

Agent: Mercaptopurine NCIT:C195

Platform: Small molecule

A refractory celiac-like case had partial improvement with mercaptopurine, but cytopenias limited its use. This is case-level evidence rather than a general treatment recommendation.

Show evidence (1 reference)

PMID:35935971 SUPPORT Human Clinical

"She had partial symptomatic and endoscopic improvement with 6MP, but use was limited by cytopenias."

The case describes both benefit and toxicity.

Topical anti-inflammatory treatment

Category: Therapeutic Action: Immunosuppressive Therapy NCIT:C15261

Agent: Tacrolimus NCIT:C1311 Pimecrolimus NCIT:C47671

Platform: Small molecule

Topical corticosteroids and, when appropriate, topical tacrolimus or pimecrolimus are included in expert skin-management protocols. These recommendations do not establish CTLA4-specific comparative efficacy.

Show evidence (1 reference)

url:https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf SUPPORT Other

"As first-line therapy, we suggest topical treatment with corticosteroids and as second-line topical tac rolimus, respectively pimecrolimus for skin lesions in the face."

Full text of Egg et al., Therapeutic options for CTLA-4 insufficiency (PMID:34111452). The expert protocol describes local skin management.

Immunoglobulin replacement

Category: Therapeutic Action: Immunoglobulin Therapy NCIT:C62710

Platform: Protein replacement

Replacement immunoglobulin is used for clinically significant antibody deficiency and recurrent infections. It does not reliably prevent the autoimmune cytopenias of CTLA4 insufficiency.

Show evidence (2 references)

PMID:34111452 SUPPORT Human Clinical

"Immunoglobulin replacement was effective in prevention of infection."

The treatment cohort supports infection prevention.

url:https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf SUPPORT Human Clinical

"IgRT does not protect against this complication in CTLA-4 insufficiency"

Full text of Egg et al., Therapeutic options for CTLA-4 insufficiency (PMID:34111452). The cohort specifically discusses autoimmune cytopenia arising despite replacement therapy.

Immunomodulatory intravenous immunoglobulin

Category: Therapeutic Action: Immunoglobulin Therapy NCIT:C62710

Platform: Other

IVIG has also been used at immunomodulatory intensity for autoimmune cytopenia or inflammatory CNS disease, a distinct indication from antibody replacement.

Show evidence (1 reference)

url:https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf SUPPORT Human Clinical

"High-dose intravenous immunoglobulin (IVIG) (1 g/kg ) was added to steroids in 7 patients, with 6 (86%) showing beneficial effects."

Full text of Egg et al., Therapeutic options for CTLA-4 insufficiency (PMID:34111452). The CNS subgroup documents adjunctive IVIG with corticosteroids.

Thrombopoietin receptor agonists

Category: Therapeutic Action: Pharmacotherapy NCIT:C15986

TPO-receptor agonists have been tried for refractory immune thrombocytopenia, with limited response in the reported CTLA4 cohort.

Show evidence (1 reference)

url:https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf SUPPORT Human Clinical

"We documented 4 applications of TPO-RAs in our CTL A-4 cohort, but a satisfying stabilization of platelet count could be reached in only 1 case."

Full text of Egg et al., Therapeutic options for CTLA-4 insufficiency (PMID:34111452). Only one of four reported uses achieved satisfactory platelet stabilization.

Hematopoietic stem cell transplantation

Category: Therapeutic Action: Allogeneic Hematopoietic Stem Cell Transplantation NCIT:C46089

Platform: Cell therapy

Allogeneic HSCT can achieve durable disease remission in severe refractory immune dysregulation, but carries substantial transplant-related risk. The 2024 European cohort included both CTLA4 insufficiency and larger 2q33 deletions; its outcomes should not be treated as a pure CTLA4 estimate. Lower pretransplant disease activity was associated with better survival.

Show evidence (3 references)

PMID:39218359 SUPPORT Human Clinical

"At latest follow-up, disease of 28 of 30 surviving patients was in disease-free remission with median IDDA reduction of 16."

Surviving patients commonly achieved remission; this survivor fraction is not overall survival.

PMID:39218359 SUPPORT Human Clinical

"Cause of death was transplant related in 7 of 8 patients."

The cohort documents material transplant-related mortality.

PMID:39218359 SUPPORT Human Clinical

"Probability of OS and DFS was greater in patients with lower disease activity before HSCT (IDDA < 23, P = .002 and P = .006, respectively)."

The retrospective association supports attention to pretransplant disease burden.

Splenectomy considerations

Category: Therapeutic Action: Splenectomy NCIT:C15328

Platform: Surgery

Splenectomy has been used for severe cytopenia, but sustained responses were uncommon in the reported cohort. The 2022 expert protocol advises avoiding it when possible and considering medical therapy or HSCT according to disease severity.

Show evidence (1 reference)

url:https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf SUPPORT Human Clinical

"Of the cohort p atients, 16 had a splenectomy (median age 20 years), with only 4 (25%) showing a sustained response"

Full text of Egg et al., Therapeutic options for CTLA-4 insufficiency (PMID:34111452). The retrospective response rate argues against assuming durable control.

Antibiotic prophylaxis and infection treatment

Category: Therapeutic Action: Antibiotic Therapy NCIT:C15620

Antimicrobial prophylaxis and prompt treatment of infection are tailored to immune deficits, immunosuppression and structural lung disease. The cohort reported trimethoprim-sulfamethoxazole, azithromycin and postsplenectomy penicillin use.

Show evidence (1 reference)

url:https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf SUPPORT Human Clinical

"Antibiotic prophylaxis was given in 48 (39%) of the 123 cases. The most used antibiotic for prophylaxis was trimethoprim-sulfamethoxazole (in 2 4 patients) followed by azithromycin (in 6 patients). Penicillin was used prophylactically in 3 patients after splenectomy."

Full text of Egg et al., Therapeutic options for CTLA-4 insufficiency (PMID:34111452). The cohort documents actual prophylactic regimens; it does not establish comparative benefit.

Nutritional support

Category: Therapeutic Action: Nutritional Support NCIT:C15433

Severe enteropathy may require enteral feeding or parenteral nutrition. Gluten-free or lactose-restricted diets address demonstrated sensitivities; gluten avoidance alone may fail in CTLA4-associated celiac-like disease.

Show evidence (2 references)

PMID:42577265 SUPPORT Human Clinical

"requiring continuous nasogastric enteral nutrition and intermittent parenteral nutrition."

The severe enteropathy case required both routes of nutritional support.

PMID:35935971 SUPPORT Human Clinical

"We present two patients with celiac/celiac-like disease diagnosed in early childhood and refractory to the gluten-free diet."

The cases show that diet alone may not control genetically mediated enteropathy.

Endocrine replacement for associated autoimmunity

Category: Therapeutic

Treat documented autoimmune thyroid or adrenal insufficiency with appropriate endocrine replacement. A reported patient required levothyroxine, fludrocortisone and hydrocortisone in addition to immune-directed therapy.

Show evidence (1 reference)

PMID:35935971 SUPPORT Human Clinical

"Her co-morbid autoimmune diseases are well controlled with levothyroxine, fludrocortisone, hydrocortisone, and topical dermatologic therapies."

The case records replacement treatment for documented endocrine disease.

Longitudinal surveillance and family counseling

Category: Monitoring

Follow affected and apparently unaffected carriers for evolving immune dysregulation. Monitor lymphoproliferation and EBV/CMV complications, especially during immunosuppression, and investigate suspicious lesions. Counsel relatives about incomplete penetrance and possible late presentation.

Show evidence (2 references)

PMID:29729943 SUPPORT Human Clinical

"Family members should be counseled because disease manifestation can occur as late as 50 years of age. EBV- and cytomegalovirus-associated complications must be closely monitored."

The carrier cohort supports counseling and ongoing surveillance.

PMID:30250467 SUPPORT Human Clinical

"Hence, lymphoproliferation and EBV viral load in blood should be carefully monitored, especially when immunosuppressing affected CTLA4 mutation carriers."

The malignancy study emphasizes surveillance during immune-directed treatment.

Sulfasalazine

Category: Therapeutic Action: Pharmacotherapy NCIT:C15986

Agent: Sulfasalazine NCIT:C29469

Platform: Small molecule

Oral sulfasalazine is included as an initial enteropathy option in the 2022 expert management protocol. The recommendation is not a demonstrated CTLA4-specific response estimate or trial result.

Show evidence (1 reference)

url:https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf SUPPORT Other

"In cases of inflammation without known antigen, we recommend a stepwise protocol starting with (1) topical corticosteroids in the form of budesonide (a combination of standard budesonide for the small bowels and retard capsules for the large bowels) or use of oral sulfasalazine;"

Full text of Egg et al., Therapeutic options for CTLA-4 insufficiency (PMID:34111452). The authors propose this stepwise management option rather than report a sulfasalazine-treated cohort outcome.

🔬

Biochemical Markers

Soluble interleukin-2 receptor

Show evidence (1 reference)

PMID:35935971 SUPPORT Human Clinical

"Soluble IL-2 receptor (i.e., CD25) levels, which were characteristically high at the patient’s diagnosis of CTLA4 haploinsufficiency (9), were monitored on abatacept and trended downward to normal range."

A treated case provides longitudinal marker observations.

CTLA4 mRNA expression

Show evidence (2 references)

PMID:31156616 SUPPORT Human Clinical

"Patients in the NT and Aba groups represent different individuals in each group."

The study design precludes interpreting the group comparison as longitudinal treatment response.

PMID:31156616 SUPPORT Human Clinical

"Future studies evaluating larger patient cohorts are required to further expand this finding and potentially uncover a reliable biomarker for clinical management of these disorders."

The authors regard the proposed biomarker as unvalidated.

🔬

Diagnosis

Molecular diagnosis with variant interpretation

Sequence CTLA4 in patients with compatible immune dysregulation, including CVID-like disease or refractory enteropathy. Interpret novel variants with functional evidence and consider alternative checkpoint disorders such as LRBA and DEF6 deficiency.

Show evidence (1 reference)

PMID:35935971 SUPPORT Human Clinical

"Celiac disease cannot be distinguished from enteropathy secondary to CTLA4 deficiency solely by histopathology and, therefore, genetic testing is essential to identify this as an etiology of refractory celiac-like disease."

The case series supports molecular investigation when clinical and histologic findings overlap.

CTLA4 expression in memory regulatory T cells

Flow cytometry of CD45RA-negative Foxp3-positive memory Tregs provides a more informative comparison than total CD4 cells. Reduced staining supports a defect but normal staining does not exclude functional CTLA4 insufficiency.

Show evidence (2 references)

PMID:28159733 SUPPORT In Vitro

"Assessing total CTLA-4 expression levels was found to be optimal when restricting analysis to the CD45RA-Foxp3+ fraction."

The assay study identifies the most informative cell subset.

url:https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf SUPPORT In Vitro

"Although Treg cells with the variant p.F179Cfs*29 had normal CTLA-4 expression, the frequency of CD80 uptake in Treg cells was as reduced as in 3 additional deleterious variants"

Full text of Egg et al., Therapeutic options for CTLA-4 insufficiency (PMID:34111452). A patient-cell assay shows why expression alone can miss a functional defect.

Functional ligand uptake and transendocytosis

Measure uptake of CD80/CD86 ligands to evaluate functional impact, including variants with preserved antibody staining. Soluble ligand uptake integrates trafficking and binding; cell-to-cell assays directly assess transendocytosis. Neither assay alone predicts clinical penetrance.

Show evidence (1 reference)

PMID:28159733 SUPPORT In Vitro

"Finally, we developed a functionally orientated assay to measure ligand uptake by CTLA-4, which is sensitive to ligand-binding or -trafficking mutations, that would otherwise be difficult to detect and that is appropriate for testing novel mutations in CTLA-4 pathway genes."

The functional assay detects defects missed by abundance measurements.

Immunoglobulins and lymphocyte subsets

Assess serum immunoglobulins, antibody responses and lymphocyte subsets, including circulating B cells, switched memory cells and CD21-low cells. Interpret results in relation to immunosuppressive treatment and organ inflammation.

Show evidence (1 reference)

PMID:29729943 SUPPORT Human Clinical

"B cell subsets showed a decrease in switched memory B cells (23/30) and consecutively a relative increase in naïve B cells (14/29)."

The cohort identifies characteristic immunophenotypic abnormalities.

Organ evaluation and exclusion of competing causes

Investigate gastrointestinal, pulmonary or neurologic symptoms with appropriate imaging, functional assessment, endoscopy or biopsy. Distinguish immune infiltration from infection and malignancy before attributing lesions to CTLA4 insufficiency.

Show evidence (2 references)

PMID:35935971 SUPPORT Human Clinical

"exclusion of infectious etiologies of chronic diarrhea is a critical component of evaluation."

The GI report emphasizes excluding chronic infection.

url:https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf SUPPORT Other

"Hepatomegaly, splenomegaly, or regional lymphadeno pathy should be carefully monitored, and if malignancy is suspected, a biopsy should be performed."

Full text of Egg et al., Therapeutic options for CTLA-4 insufficiency (PMID:34111452). The expert protocol recommends evaluating suspicious lymphoproliferation rather than assuming it is benign.

📊

Prevalence

Published CTLA4 haploinsufficiency cases in 2021 systematic review

Cases In Literature Unknown

A 2021 systematic review assembled 222 published CTLA4-haploinsufficiency patients within 101 eligible studies covering both CTLA4 and LRBA disorders. This historical literature count does not estimate population prevalence. Later cohorts overlap earlier reports and should not be summed.

Show evidence (1 reference)

PMID:33788257 SUPPORT Human Clinical

"Overall, 434 (222 CHAI and 212 LATAIE) patients were found in 101 eligible studies."

The review gives a dated published-case count, not a population denominator or a current total.

📊

Related Datasets

CTLA4 haploinsufficiency and immune dysregulation dbgap:phs000797

We identified germline heterozygous mutations in CTLA4 in members of four families with severe immune dysregulation. Human CTLA4 haploinsufficiency caused dysregulation of FoxP3+ regulatory T (Treg) cells and lymphocytic infiltration of target organs, mimicking Ctla4 homozygous mice. Patients also exhibited a B cell phenotype, with progressive loss of B cells and accumulation of autoreactive CD21 lo B cells. This study demonstrates a critical quantitative role for CTLA-4 in human immune homeostasis.

Human family sequencing study underlying the discovery of germline CTLA4-associated immune dysregulation. Individual-level genomic data are subject to repository access controls.

🔬

Clinical Trials

DRKS00017736 PHASE_II COMPLETED

ABACHAI was an open-label, uncontrolled phase IIa study of weekly subcutaneous abatacept for 12 months in adults with CTLA4 insufficiency or LRBA deficiency. The 2026 publication reports 20 participants, including 18 with CTLA4 insufficiency. Infection control was the primary endpoint; organ response and quality of life were secondary endpoints.

Show evidence (3 references)

ICTRP:DRKS00017736 SUPPORT Other

"| Phase | 2 |"

The official registry specifies phase II.

ICTRP:DRKS00017736 SUPPORT Other

"| Date of completion | 28/06/2023 |"

The registry records study completion.

PMID:42763023 SUPPORT Human Clinical

"The primary endpoint was safety, defined as the number of episodes of failed infection control. Secondary endpoints included additional safety parameters, efficacy outcomes, and patient-reported quality of life."

The results paper specifies the endpoint hierarchy.

🧫

Experimental Models

CHO cells expressing CTLA4 variants CELL_LINE

CHO cells expressing individual CTLA4 alleles measure protein abundance and soluble CD80 uptake without co-expression of the human wild-type allele.

Publication

PMID:25329329

Pathograph links

Deficient CTLA4 ligand capture measures fidelity: moderate observes: molecular

Limitations: Variant overexpression without the wild-type allele does not reproduce human heterozygosity; uptake includes trafficking and binding.

Show evidence (1 reference)

PMID:25329329 SUPPORT In Vitro

"Full-length CTLA4 protein was detected in cells transfected with the CTLA4 mutants R70W (Family C) and T124P"

The transfected-cell system separates expressed protein from deficient uptake.

Patient Treg suppression coculture CO_CULTURE

Patient-derived Tregs are combined with healthy responder T cells and dendritic cells under ligand-dependent stimulation.

Publication

PMID:25329329

Pathograph links

Impaired regulatory T-cell suppression measures fidelity: moderate observes: cellular

Limitations: Assay conditions do not reproduce the full multicellular disease.

Show evidence (1 reference)

PMID:25329329 SUPPORT In Vitro

"Treg cells from individuals with CTLA4 heterozygous mutations were unable to suppress CD4+ T cell proliferation as compared to healthy CTLA4+/+ controls"

The coculture directly measures CTLA4-dependent regulatory suppression.

CTLA4 knockdown and rescue in human lymphocytes PRIMARY_CELL_CULTURE

CTLA4 knockdown in healthy PBMCs and wild-type expression or CTLA4-Ig treatment in patient cultures test the relationship between checkpoint abundance and proliferation.

Publication

PMID:25213377

Pathograph links

Excess Effector T Cell Activation rescues fidelity: moderate observes: cellular

Limitations: Mixed lymphocyte cultures do not isolate an intrinsic conventional T-cell defect; independent studies did not reproduce that interpretation.

Show evidence (1 reference)

PMID:25213377 SUPPORT In Vitro

"overexpression of wild-type CTLA-4 in patient T cells suppressed the hyperproliferation"

Restoration reverses the measured proliferation phenotype.

HEK293T Phe56Cys functional assays CELL_LINE

Transfected HEK293T cells compare disulfide-linked dimerization, total and surface CTLA4, and soluble CD80/CD86 binding.

Publication

PMID:42577265

Pathograph links

Impaired CTLA4 dimerization measures fidelity: moderate observes: molecular

Limitations: Ectopic expression in kidney-derived cells omits the heterozygous Treg context.

Deficient CTLA4 ligand capture measures fidelity: moderate observes: molecular

Limitations: Binding measurements are confounded by reduced surface expression and do not isolate affinity.

Show evidence (1 reference)

PMID:42577265 SUPPORT In Vitro

The assay demonstrates reduced dimerization in an ectopic expression system.

Gene-edited patient T cells PRIMARY_CELL_CULTURE

CRISPR-Cas9 and AAV6-directed homology repair at the first CTLA4 intron restore regulated CTLA4 expression and ligand transendocytosis in patient-derived T cells. This is preclinical rescue, not evidence of clinical benefit.

Publication

PMID:36288278

Pathograph links

Reduced CD80/CD86 transendocytosis rescues fidelity: moderate observes: cellular

Limitations: In-vitro correction does not establish the required corrected-cell fraction, durable clinical efficacy or long-term safety.

Show evidence (1 reference)

PMID:36288278 SUPPORT In Vitro

"Gene editing of T cells isolated from three patients with CTLA-4 insufficiency also restored CTLA-4 protein expression and rescued transendocytosis of CD80 and CD86 in vitro."

Three patient-derived cellular preparations showed restoration of function.

🐁

Animal Models

Gene-corrected Ctla4-null T cells transferred into Rag2-null mice

Edited donor T cells persist and prevent lymphoid enlargement and cardiac infiltration during a four-week adoptive-transfer experiment. This is correction of transferred cells, not germline correction of the recipient animal.

Species

Mouse

Genotype

Rag2-null recipients of edited or control Ctla4-null donor T cells

Publication

PMID:36288278

Pathograph links

Non-malignant lymphoproliferation rescues fidelity: moderate observes: organism

Limitations: Lymphopenic recipients of Ctla4-null cells differ from heterozygous human disease; follow-up lasted four weeks.

Lymphocytic Tissue Infiltration rescues fidelity: moderate observes: organism

Limitations: The measured tissue outcome was cardiac infiltration, not the complete human multiorgan spectrum.

Show evidence (2 references)

PMID:36288278 SUPPORT Model Organism

"Murine CTLA4-/- T cells were edited (gRNA 5, HDR donor 5) or mock edited and then adoptively transferred into adult Rag2-/- mice without conditioning."

The study defines the donor-cell and recipient genotypes.

PMID:36288278 SUPPORT Model Organism

"only mice from groups that had received mock-edited or GFP- T cells showed elevated cardiac tissue infiltration"

The edited-cell recipients were protected from the measured cardiac inflammatory phenotype.

{ }

Source YAML

click to show

name: CTLA4 Haploinsufficiency
synonyms:
- CHAI
- CTLA-4 haploinsufficiency with autoimmune infiltration disease
- CTLA4 insufficiency
- ALPS type V
- Autoimmune lymphoproliferative syndrome type 5
- Immune dysregulation with autoimmunity, immunodeficiency, and lymphoproliferation
creation_date: '2026-04-12T17:04:40Z'
category: Mendelian
description: CTLA4 haploinsufficiency, also called CHAI or CTLA4 insufficiency, is an autosomal dominant inborn error of immunity caused by heterozygous germline CTLA4 variants. Reduced CTLA4 abundance or defective protein function impairs regulatory T-cell control of CD80/CD86-dependent costimulation. Variable immune dysregulation includes hypogammaglobulinemia, lymphoproliferation, autoimmune cytopenias, enteropathy, lung disease and lymphocytic infiltration of other organs. Clinical penetrance is incomplete; functional defects can occur in apparently unaffected carriers. Missense alleles may impair dimerization, surface availability or ligand capture even when total protein staining is preserved.
disease_term:
  preferred_term: CTLA4 haploinsufficiency
  term:
    id: MONDO:0014493
    label: autoimmune lymphoproliferative syndrome due to CTLA4 haploinsufficiency
parents:
- Primary Immunodeficiency
- Autoimmune Disorder
- Lymphoproliferative Disorder
classifications:
  iuis_category:
    classification_value: immune dysregulation
    notes: IUIS 2022 phenotypic classification Table 4 (diseases of immune dysregulation); CTLA4 haploinsufficiency (CHAI) is a checkpoint dysregulation IEI.
    evidence:
    - reference: PMID:35748970
      reference_title: 'Human Inborn Errors of Immunity: 2022 Update on the Classification from the International Union of Immunological Societies Expert Committee.'
      supports: SUPPORT
      evidence_source: OTHER
      snippet: CTLA4 haploinsufficiency (ALPS-V) CTLA4 AD 123890
      explanation: The CTLA4 row appears in Table 4, diseases of immune dysregulation, and specifies autosomal dominant inheritance.
inheritance:
- name: Autosomal Dominant
  inheritance_term:
    preferred_term: Autosomal dominant inheritance
    term:
      id: HP:0000006
      label: Autosomal dominant inheritance
  penetrance: INCOMPLETE
  expressivity: VARIABLE
  description: CTLA4 haploinsufficiency is inherited as an autosomal dominant disorder with marked phenotypic variability and incomplete penetrance. Disease can arise through familial transmission or de novo heterozygous variants, and some mutation carriers remain clinically unaffected despite measurable CTLA-4 pathway dysfunction.
  evidence:
  - reference: PMID:25329329
    reference_title: Autosomal dominant immune dysregulation syndrome in humans with CTLA4 mutations.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: We studied a large family in which five individuals presented with a complex, autosomal dominant immune dysregulation syndrome characterized by hypogammaglobulinemia, recurrent infections and multiple autoimmune clinical features.
    explanation: The discovery cohort establishes autosomal dominant inheritance for the syndrome caused by heterozygous CTLA4 mutations.
  - reference: PMID:25213377
    reference_title: Immune dysregulation in human subjects with heterozygous germline mutations in CTLA4.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: We identified germline heterozygous mutations in CTLA4 in subjects with severe immune dysregulation from four unrelated families.
    explanation: Independent families with heterozygous germline CTLA4 variants confirm a dominant loss-of-function disease mechanism.
  - reference: PMID:29729943
    reference_title: Phenotype, penetrance, and treatment of 133 cytotoxic T-lymphocyte antigen 4-insufficient subjects.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: In total, ninety of the 133 CTLA4 mutation carriers (67.6%) were considered affected, as they had sought medical attention for disease-related symptoms.
    explanation: The 2018 ascertained carrier cohort demonstrates incomplete clinical penetrance; the fraction is not a lifetime population estimate.
  - reference: PMID:29729943
    reference_title: Phenotype, penetrance, and treatment of 133 cytotoxic T-lymphocyte antigen 4-insufficient subjects.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Mutations in seven affected carriers had occurred de novo.
    explanation: Both inherited and de novo pathogenic variants occur.
prevalence:
- population: Published CTLA4 haploinsufficiency cases in 2021 systematic review
  prevalence_class: UNKNOWN
  notes: A 2021 systematic review assembled 222 published CTLA4-haploinsufficiency patients within 101 eligible studies covering both CTLA4 and LRBA disorders. This historical literature count does not estimate population prevalence. Later cohorts overlap earlier reports and should not be summed.
  evidence:
  - reference: PMID:33788257
    reference_title: 'Comprehensive comparison between 222 CTLA-4 haploinsufficiency and 212 LRBA deficiency patients: a systematic review.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Overall, 434 (222 CHAI and 212 LATAIE) patients were found in 101 eligible studies.
    explanation: The review gives a dated published-case count, not a population denominator or a current total.
  measure_type: CASES_IN_LITERATURE
genetic:
- name: CTLA4
  gene_term:
    preferred_term: CTLA4
    term:
      id: hgnc:2505
      label: CTLA4
  association: CAUSATIVE
  features: Heterozygous germline loss-of-function variants cause disease. Truncating and splice variants can reduce membrane CTLA4 abundance, whereas missense variants can impair dimerization or ligand capture. Variant location does not reliably predict clinical severity or penetrance. Large 2q33 deletions can include neighboring CD28 and ICOS and require separate interpretation.
  inheritance:
  - name: Autosomal Dominant
  evidence:
  - reference: PMID:25329329
    reference_title: Autosomal dominant immune dysregulation syndrome in humans with CTLA4 mutations.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: We identified a heterozygous nonsense mutation in exon 1 of CTLA4. Screening of 71 unrelated patients with comparable clinical phenotypes identified five additional families (nine individuals) with previously undescribed splice site and missense mutations in CTLA4.
    explanation: This cohort study defines the mutational spectrum, showing that multiple heterozygous CTLA4 variant classes can cause the syndrome.
  - reference: PMID:31396201
    reference_title: Preponderance of CTLA4 Variation Associated With Autosomal Dominant Immune Dysregulation in the MYPPPY Motif.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: 'This variant lay within the highly conserved MYPPPY motif of CTLA-4: a critical structural determinant of ligand binding, which is also bound by the anti-CTLA-4 monoclonal antibody ipilimumab.'
    explanation: The case identifies a variant in the conserved ligand-binding motif; direct functional assays of this patient’s allele were not performed in this report.
  - reference: PMID:25213377
    reference_title: Immune dysregulation in human subjects with heterozygous germline mutations in CTLA4.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: We identified germline heterozygous mutations in CTLA4 in subjects with severe immune dysregulation from four unrelated families.
    explanation: Confirms CTLA4 as the causal gene and anchors the disease as a heterozygous germline loss-of-function disorder.
  - reference: CGGV:assertion_e79675bd-3eef-4925-b4ef-3b7c48734f30-2020-12-15T050000.000Z
    reference_title: CTLA4 / autoimmune lymphoproliferative syndrome due to CTLA4 haploinsufficiency (Definitive)
    supports: SUPPORT
    evidence_source: OTHER
    snippet: CTLA4 | HGNC:2505 | autoimmune lymphoproliferative syndrome due to CTLA4 haploinsufficiency | MONDO:0014493 | AD | Definitive
    explanation: ClinGen classifies the CTLA4-autoimmune lymphoproliferative syndrome due to CTLA4 haploinsufficiency gene-disease relationship as definitive with autosomal dominant inheritance.
  - reference: PMID:29729943
    reference_title: Phenotype, penetrance, and treatment of 133 cytotoxic T-lymphocyte antigen 4-insufficient subjects.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: An association between genotype and onset, penetrance, or disease phenotype was not observed.
    explanation: The large carrier cohort did not establish a genotype-phenotype correlation.
  variants:
  - name: p.Arg51Ter
    description: A nonsense allele associated with degradation of its transcript.
    evidence:
    - reference: PMID:25213377
      reference_title: Immune dysregulation in human subjects with heterozygous germline mutations in CTLA4.
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: cDNA analyses from A.I.1 T cells showed that the mutant allele mRNA was degraded >95%, consistent with nonsense-mediated decay
      explanation: Nonsense-mediated decay was measured in patient T cells.
  - name: p.Cys35Ter
    description: An early truncating allele with no detectable protein in transfected CHO cells.
    evidence:
    - reference: PMID:25329329
      reference_title: Autosomal dominant immune dysregulation syndrome in humans with CTLA4 mutations.
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: we found no protein expression in cells transfected with the C35* (Family A) mutant
      explanation: Transfection excludes productive rescue by a nearby alternative start codon under these assay conditions.
  - name: p.Arg70Trp
    description: An extracellular-domain missense allele with preserved expressed protein but reduced ligand uptake.
    evidence:
    - reference: PMID:25329329
      reference_title: Autosomal dominant immune dysregulation syndrome in humans with CTLA4 mutations.
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: Cells transfected with either T124P and R70W mutants were impaired in their ability to take up soluble CD80-Ig
      explanation: The CHO assay shows impaired uptake for this allele.
  - name: p.Thr124Pro
    description: An extracellular-domain missense allele with impaired soluble CD80 uptake; protein notation is retained because nucleotide coordinates differ between cited reports.
    evidence:
    - reference: PMID:25329329
      reference_title: Autosomal dominant immune dysregulation syndrome in humans with CTLA4 mutations.
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: Cells transfected with either T124P and R70W mutants were impaired in their ability to take up soluble CD80-Ig
      explanation: The expressed mutant is functionally deficient in the ligand-uptake assay.
  - name: p.Pro137Arg
    description: A ligand-binding-motif allele that can retain near-normal antibody staining despite defective ligand uptake.
    evidence:
    - reference: PMID:28159733
      reference_title: Identifying functional defects in patients with immune dysregulation due to LRBA and CTLA-4 mutations.
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: a much reduced slope was obtained with Tregs from a patient with a known ligand-binding defect (P137R).
      explanation: Ligand uptake relative to CTLA4 expression distinguishes this functional defect.
  - name: p.Tyr139Cys
    description: A de novo MYPPPY-motif variant reported in a child with autoimmune hepatitis and polyarthritis.
    evidence:
    - reference: PMID:31396201
      reference_title: Preponderance of CTLA4 Variation Associated With Autosomal Dominant Immune Dysregulation in the MYPPPY Motif.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: 'This variant lay within the highly conserved MYPPPY motif of CTLA-4: a critical structural determinant of ligand binding, which is also bound by the anti-CTLA-4 monoclonal antibody ipilimumab.'
      explanation: The clinical report locates the variant in a functional motif; it did not directly assay this patient’s mutant protein.
    - reference: PMID:31396201
      reference_title: Preponderance of CTLA4 Variation Associated With Autosomal Dominant Immune Dysregulation in the MYPPPY Motif.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: This variant was absent from both biological parents
      explanation: Parental sequencing established de novo occurrence.
  - name: NM_005214.5:c.167T>G (p.Phe56Cys)
    description: An inherited allele with incomplete penetrance. HEK293T assays show reduced dimerization, surface expression and CD80/CD86 binding despite preserved total protein.
    evidence:
    - reference: PMID:42577265
      reference_title: Novel pathogenic CTLA4 missense variant associated with autoimmune enteropathy and systemic immune dysregulation.
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: ectopic expression of the CTLA4 p.Phe56Cys variant rather than the wild-type CTLA4 in HEK293T cells resulted in reduced CTLA4 dimerization under non-reducing sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) conditions
      explanation: The 2026 functional study supports a dimerization defect for this allele.
  - name: c.457+2T>C
    description: An inherited splice-site variant in a patient with refractory celiac-like enteropathy and reduced CTLA4 expression in memory Tregs.
    evidence:
    - reference: PMID:35935971
      reference_title: 'Cytotoxic T Lymphocyte Antigen 4 Haploinsufficiency Presenting As Refractory Celiac-Like Disease: Case Report.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Research-based whole-exome sequencing was pursued at this time and confirmed previously unreported heterozygous CTLA4 mutation (c. 457 + 2T > C), suggestive of CTLA4 haploinsufficiency.
      explanation: Sequencing identified the allele; associated reduced protein expression supports functional insufficiency without a demonstrated RNA-splicing assay.
    - reference: PMID:35935971
      reference_title: 'Cytotoxic T Lymphocyte Antigen 4 Haploinsufficiency Presenting As Refractory Celiac-Like Disease: Case Report.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: it was confirmed that the disease-causing mutation was inherited from the patient’s father
      explanation: Family testing established paternal inheritance.
  - name: c.71_72del (p.Leu24ProfsTer35)
    description: A de novo early frameshift in a second refractory celiac-like enteropathy case, with absent detectable CTLA4 in memory Tregs.
    evidence:
    - reference: PMID:35935971
      reference_title: 'Cytotoxic T Lymphocyte Antigen 4 Haploinsufficiency Presenting As Refractory Celiac-Like Disease: Case Report.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: A previously unreported de novo heterozygous variant in CTLA4 in exon 1, c71_72del (p.Leu24Profs*35) was identified
      explanation: The case report documents de novo occurrence and subsequently confirms deficient CTLA4 staining.
  - name: p.Phe179CysfsTer29
    description: A frameshift allele for which Treg CTLA4 expression was comparable to controls but CD80 uptake was impaired.
    evidence:
    - reference: url:https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf
      reference_title: https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: Although Treg cells with the variant p.F179Cfs*29 had normal CTLA-4 expression, the frequency of CD80 uptake in Treg cells was as reduced as in 3 additional deleterious variants
      explanation: Full text of Egg et al., Therapeutic options for CTLA-4 insufficiency (PMID:34111452). This allele illustrates functional insufficiency despite preserved staining.
pathophysiology:
- name: Reduced CTLA4 protein abundance
  biological_scale: MOLECULAR
  description: Many truncating or splice alleles reduce the abundance of membrane-associated CTLA4. Nonsense-mediated decay is demonstrated for p.Arg51Ter; splice defects can reduce full-length transcript while preserving soluble CTLA4. This quantitative mechanism does not describe every missense allele.
  gene:
    preferred_term: CTLA4
    term:
      id: hgnc:2505
      label: CTLA4
  evidence:
  - reference: PMID:25213377
    reference_title: Immune dysregulation in human subjects with heterozygous germline mutations in CTLA4.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: Affected patients had reduced CTLA-4 protein and mRNA expression in sorted Treg cells relative to healthy donors; this reduction persisted after activation
    explanation: Patient Tregs demonstrate a quantitative CTLA4 defect that persists after activation.
  downstream:
  - target: Deficient CTLA4 ligand capture
    description: Reduced available receptor limits CTLA4-dependent ligand capture.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:25329329
      reference_title: Autosomal dominant immune dysregulation syndrome in humans with CTLA4 mutations.
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: Whereas Treg cells were generally present at elevated numbers in these individuals, their suppressive function, CTLA-4 ligand binding and transendocytosis of CD80 were impaired.
      explanation: Carrier Tregs show impaired ligand removal as well as suppression.
- name: Impaired CTLA4 dimerization
  biological_scale: MOLECULAR
  mechanism_confidence: PROVISIONAL
  description: The p.Phe56Cys allele reduces disulfide-linked CTLA4 dimerization in transfected HEK293T cells. Total protein was preserved while surface abundance and ligand binding decreased. The relative contributions of dimerization, folding and trafficking remain unresolved; this is an allele-specific mechanism.
  gene:
    preferred_term: CTLA4
    term:
      id: hgnc:2505
      label: CTLA4
  evidence:
  - reference: PMID:42577265
    reference_title: Novel pathogenic CTLA4 missense variant associated with autoimmune enteropathy and systemic immune dysregulation.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: ectopic expression of the CTLA4 p.Phe56Cys variant rather than the wild-type CTLA4 in HEK293T cells resulted in reduced CTLA4 dimerization under non-reducing sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) conditions
    explanation: Non-reducing immunoblots support defective dimerization for this allele in an overexpression system.
  downstream:
  - target: Deficient CTLA4 ligand capture
    description: Dimerization-defective p.Phe56Cys also reduces surface CTLA4 and CD80/CD86 binding; an isolated affinity change was not established.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:42577265
      reference_title: Novel pathogenic CTLA4 missense variant associated with autoimmune enteropathy and systemic immune dysregulation.
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: ectopic expression of the CTLA4 p.Phe56Cys variant rather than the wild-type CTLA4 in HEK293T cells resulted in reduced CTLA4 dimerization under non-reducing sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) conditions
      explanation: Non-reducing immunoblots support defective dimerization for this allele in an overexpression system.
- name: Deficient CTLA4 ligand capture
  biological_scale: MOLECULAR
  description: CTLA4 variants reduce capture of CD80 and CD86. The defect can reflect reduced receptor availability or impaired function of expressed missense protein. Antibody staining alone can miss impaired ligand uptake.
  gene:
    preferred_term: CTLA4
    term:
      id: hgnc:2505
      label: CTLA4
  molecular_functions:
  - preferred_term: CD80/CD86 binding
    term:
      id: GO:0005515
      label: protein binding
    modifier: DECREASED
  evidence:
  - reference: PMID:25329329
    reference_title: Autosomal dominant immune dysregulation syndrome in humans with CTLA4 mutations.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: Cells transfected with either T124P and R70W mutants were impaired in their ability to take up soluble CD80-Ig
    explanation: Expressed missense proteins have defective ligand uptake in transfected CHO cells.
  - reference: PMID:28159733
    reference_title: Identifying functional defects in patients with immune dysregulation due to LRBA and CTLA-4 mutations.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: Thus, functionally significant mutations affecting the amount of CTLA-4, the quality of ligand binding, or its trafficking can be detected using this assay.
    explanation: The functional assay integrates abundance, ligand binding and trafficking rather than isolating one property.
  downstream:
  - target: Reduced CD80/CD86 transendocytosis
    description: Ligand capture is necessary for removal of costimulatory ligands from antigen-presenting cells.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:25329329
      reference_title: Autosomal dominant immune dysregulation syndrome in humans with CTLA4 mutations.
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: Whereas Treg cells were generally present at elevated numbers in these individuals, their suppressive function, CTLA-4 ligand binding and transendocytosis of CD80 were impaired.
      explanation: Carrier Tregs show impaired ligand removal as well as suppression.
  notes: The molecular-function binding uses the general GO protein-binding class, qualified as CD80/CD86 binding, because a ligand-specific GO molecular-function term was not resolved. Ligand capture assays also depend on surface abundance and trafficking.
- name: Reduced CD80/CD86 transendocytosis
  biological_scale: CELLULAR
  description: CTLA4-insufficient Tregs remove costimulatory ligands from antigen-presenting cells inefficiently. Direct cell-to-cell CD80 uptake assays demonstrate this defect; soluble-ligand uptake is a useful but distinct surrogate.
  cell_types:
  - preferred_term: regulatory T cell
    term:
      id: CL:0000815
      label: regulatory T cell
  biological_processes:
  - preferred_term: CTLA4-mediated transendocytosis
    term:
      id: GO:0006898
      label: receptor-mediated endocytosis
    modifier: DECREASED
  evidence:
  - reference: PMID:25329329
    reference_title: Autosomal dominant immune dysregulation syndrome in humans with CTLA4 mutations.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: Whereas Treg cells were generally present at elevated numbers in these individuals, their suppressive function, CTLA-4 ligand binding and transendocytosis of CD80 were impaired.
    explanation: Carrier Tregs show impaired ligand removal as well as suppression.
  downstream:
  - target: Impaired regulatory T-cell suppression
    description: Defective ligand removal compromises CTLA4-dependent suppression of responder T cells.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:25329329
      reference_title: Autosomal dominant immune dysregulation syndrome in humans with CTLA4 mutations.
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: Treg cells from individuals with CTLA4 heterozygous mutations were unable to suppress CD4+ T cell proliferation as compared to healthy CTLA4+/+ controls
      explanation: Patient-derived Tregs fail a ligand-dependent suppression assay.
- name: Impaired regulatory T-cell suppression
  biological_scale: CELLULAR
  description: Patient-derived regulatory T cells have impaired CTLA4-dependent suppressive function. Treg numbers can be normal or increased, although reduced frequencies occur in some families. Functional impairment and clinical disease do not correlate perfectly because apparently healthy carriers may also have abnormal assays.
  cell_types:
  - preferred_term: regulatory T cell
    term:
      id: CL:0000815
      label: regulatory T cell
  biological_processes:
  - preferred_term: negative regulation of T cell activation
    term:
      id: GO:0050868
      label: negative regulation of T cell activation
    modifier: DECREASED
  evidence:
  - reference: PMID:25329329
    reference_title: Autosomal dominant immune dysregulation syndrome in humans with CTLA4 mutations.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: Treg cells from individuals with CTLA4 heterozygous mutations were unable to suppress CD4+ T cell proliferation as compared to healthy CTLA4+/+ controls
    explanation: Patient-derived Tregs fail a ligand-dependent suppression assay.
  - reference: PMID:25329329
    reference_title: Autosomal dominant immune dysregulation syndrome in humans with CTLA4 mutations.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: Whereas Treg cells were generally present at elevated numbers in these individuals, their suppressive function, CTLA-4 ligand binding and transendocytosis of CD80 were impaired.
    explanation: Carrier Tregs show impaired ligand removal as well as suppression.
  downstream:
  - target: Excess Effector T Cell Activation
    description: Reduced Treg suppression permits excessive responder T-cell activation.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:25329329
      reference_title: Autosomal dominant immune dysregulation syndrome in humans with CTLA4 mutations.
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: Treg cells from individuals with CTLA4 heterozygous mutations were unable to suppress CD4+ T cell proliferation as compared to healthy CTLA4+/+ controls
      explanation: Patient-derived Tregs fail a ligand-dependent suppression assay.
  - target: Autoreactive CD21-low B-cell expansion
    description: Altered peripheral tolerance may contribute to autoreactive B-cell accumulation; intrinsic and Treg-mediated mechanisms remain unresolved.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:25213377
      reference_title: Immune dysregulation in human subjects with heterozygous germline mutations in CTLA4.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Patients also exhibited progressive loss of circulating B cells, associated with an increase of predominantly autoreactive CD21(lo) B cells and accumulation of B cells in nonlymphoid organs.
      explanation: The discovery cohort demonstrates progressive B-cell depletion and altered B-cell subsets.
- name: Excess Effector T Cell Activation
  biological_scale: CELLULAR
  description: Reduced checkpoint restraint permits excessive T-cell activation. Patient PBMC assays show hyperproliferation reversible by restoring CTLA4 function, but an intrinsic conventional T-cell defect has not been reproduced consistently and is distinct from established Treg dysfunction.
  cell_types:
  - preferred_term: T cell
    term:
      id: CL:0000084
      label: T cell
  biological_processes:
  - preferred_term: T cell activation
    term:
      id: GO:0042110
      label: T cell activation
    modifier: INCREASED
  evidence:
  - reference: PMID:25213377
    reference_title: Immune dysregulation in human subjects with heterozygous germline mutations in CTLA4.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: CTLA-4–deficient patient T cells were hyperproliferative, with an increased percentage expressing CD25 in response to T cell receptor stimulation
    explanation: Stimulated patient cultures show excess activation; this experiment alone does not establish a conventional T-cell-intrinsic defect.
  downstream:
  - target: Lymphocytic Tissue Infiltration
    description: Dysregulated lymphocyte responses are associated with inflammatory organ infiltration.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:29729943
      reference_title: Phenotype, penetrance, and treatment of 133 cytotoxic T-lymphocyte antigen 4-insufficient subjects.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Forty-three affected mutation carriers (50%) had lymphocytic infiltrations into lung (n=27), gastrointestinal tract (n=17), brain (n=12), bone marrow (n=6, Figure 6 Panel E), kidney (n=6), or retroperitoneal tissue (n=4).
      explanation: Clinical biopsies and imaging identify a multiorgan infiltration phenotype; the cohort is ascertained rather than population based.
  - target: Autoimmunity
    description: Loss of peripheral restraint contributes to tissue-directed autoimmune responses.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:25329329
      reference_title: Autosomal dominant immune dysregulation syndrome in humans with CTLA4 mutations.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: We studied a large family in which five individuals presented with a complex, autosomal dominant immune dysregulation syndrome characterized by hypogammaglobulinemia, recurrent infections and multiple autoimmune clinical features.
      explanation: The discovery cohort explicitly establishes multi-organ autoimmunity as a core clinical feature of CTLA4 haploinsufficiency.
  - target: Non-malignant lymphoproliferation
    description: Loss of immune restraint accompanies persistent lymphoid expansion.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:29729943
      reference_title: Phenotype, penetrance, and treatment of 133 cytotoxic T-lymphocyte antigen 4-insufficient subjects.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Sixty-two affected mutation carriers (73%) had non-malignant lymphoproliferation, including splenomegaly (n=51, Figure 3, Figure 5 Panel A), chronic lymphadenopathy (n=43), and hepatomegaly (n=17).
      explanation: The cohort identifies non-malignant lymphoid enlargement.
- name: Lymphocytic Tissue Infiltration
  biological_scale: TISSUE
  description: Non-malignant lymphocytic infiltrates affect gut, lung, brain, marrow and other organs. Biopsies can contain CD4 or CD8 T cells, B cells and granulomas; infiltration is not exclusively a T-cell process.
  cell_types:
  - preferred_term: lymphocyte
    term:
      id: CL:0000542
      label: lymphocyte
  evidence:
  - reference: PMID:29729943
    reference_title: Phenotype, penetrance, and treatment of 133 cytotoxic T-lymphocyte antigen 4-insufficient subjects.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Forty-three affected mutation carriers (50%) had lymphocytic infiltrations into lung (n=27), gastrointestinal tract (n=17), brain (n=12), bone marrow (n=6, Figure 6 Panel E), kidney (n=6), or retroperitoneal tissue (n=4).
    explanation: Clinical biopsies and imaging identify a multiorgan infiltration phenotype; the cohort is ascertained rather than population based.
  downstream:
  - target: Autoimmune enteropathy
    description: Gastrointestinal inflammatory infiltration accompanies enteropathy.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:29729943
      reference_title: Phenotype, penetrance, and treatment of 133 cytotoxic T-lymphocyte antigen 4-insufficient subjects.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Forty-three affected mutation carriers (50%) had lymphocytic infiltrations into lung (n=27), gastrointestinal tract (n=17), brain (n=12), bone marrow (n=6, Figure 6 Panel E), kidney (n=6), or retroperitoneal tissue (n=4).
      explanation: Clinical biopsies and imaging identify a multiorgan infiltration phenotype; the cohort is ascertained rather than population based.
  - target: Pulmonary lymphocytic infiltration
    description: Lymphoid infiltration contributes to inflammatory lung disease.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:29729943
      reference_title: Phenotype, penetrance, and treatment of 133 cytotoxic T-lymphocyte antigen 4-insufficient subjects.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Forty-three affected mutation carriers (50%) had lymphocytic infiltrations into lung (n=27), gastrointestinal tract (n=17), brain (n=12), bone marrow (n=6, Figure 6 Panel E), kidney (n=6), or retroperitoneal tissue (n=4).
      explanation: Clinical biopsies and imaging identify a multiorgan infiltration phenotype; the cohort is ascertained rather than population based.
  - target: Inflammatory central nervous system lesions
    description: Cerebral infiltration can cause neurologic dysfunction; other causes of neurologic symptoms must be distinguished.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:29729943
      reference_title: Phenotype, penetrance, and treatment of 133 cytotoxic T-lymphocyte antigen 4-insufficient subjects.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Forty-three affected mutation carriers (50%) had lymphocytic infiltrations into lung (n=27), gastrointestinal tract (n=17), brain (n=12), bone marrow (n=6, Figure 6 Panel E), kidney (n=6), or retroperitoneal tissue (n=4).
      explanation: Clinical biopsies and imaging identify a multiorgan infiltration phenotype; the cohort is ascertained rather than population based.
  - target: Colitis
    description: Inflammatory tissue injury is associated with this gastrointestinal manifestation.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:42577265
      reference_title: Novel pathogenic CTLA4 missense variant associated with autoimmune enteropathy and systemic immune dysregulation.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Re-review of intestinal pathology specimens revealed chronic active ileitis and colitis with intestinal villous atrophy, crypt shortening, loss of intestinal Paneth cells and goblet cells, lymphocytic infiltration, and prominent epithelial apoptotic bodies
      explanation: Histopathology in the Phe56Cys case documents colonic inflammation with epithelial injury.
  - target: Intestinal villous atrophy
    description: Inflammatory tissue injury is associated with this gastrointestinal manifestation.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:35935971
      reference_title: 'Cytotoxic T Lymphocyte Antigen 4 Haploinsufficiency Presenting As Refractory Celiac-Like Disease: Case Report.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Duodenal mucosa with total villous atrophy, crypt hyperplasia, and patchy intraepithelial lymphocytosis, suggestive of celiac disease.
      explanation: Biopsy documents villous injury in a genetically confirmed CTLA4 case.
- name: Autoreactive CD21-low B-cell expansion
  biological_scale: CELLULAR
  description: The peripheral B-cell compartment is enriched for predominantly autoreactive CD21-low cells. These cells show poor receptor-driven proliferation and increased susceptibility to apoptosis; their origin from an intrinsic B-cell defect versus failed Treg control remains unresolved.
  cell_types:
  - preferred_term: B cell
    term:
      id: CL:0000236
      label: B cell
  evidence:
  - reference: PMID:25213377
    reference_title: Immune dysregulation in human subjects with heterozygous germline mutations in CTLA4.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: We found that the frequency of CD21lo B cells was greatly elevated in patients’ peripheral blood
    explanation: Patient immunophenotyping establishes expansion of the CD21-low compartment.
  - reference: PMID:25213377
    reference_title: Immune dysregulation in human subjects with heterozygous germline mutations in CTLA4.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Patients also exhibited progressive loss of circulating B cells, associated with an increase of predominantly autoreactive CD21(lo) B cells and accumulation of B cells in nonlymphoid organs.
    explanation: The discovery cohort demonstrates progressive B-cell depletion and altered B-cell subsets.
  downstream:
  - target: Enhanced B-cell apoptosis
    description: The expanded CD21-low population exhibits increased cell death ex vivo.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:25213377
      reference_title: Immune dysregulation in human subjects with heterozygous germline mutations in CTLA4.
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: we observed heightened apoptosis in patient B cells
      explanation: Patient B cells exhibit increased cell death ex vivo.
  - target: Increased CD21-low B-cell proportion
    description: The expanded compartment is detectable by blood immunophenotyping.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:25213377
      reference_title: Immune dysregulation in human subjects with heterozygous germline mutations in CTLA4.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: We found that the frequency of CD21lo B cells was greatly elevated in patients’ peripheral blood
      explanation: Patient immunophenotyping establishes expansion of the CD21-low compartment.
  - target: Autoimmune thrombocytopenia
    description: Autoreactive humoral responses may contribute to platelet-directed autoimmunity; the intervening antigen-specific mechanism is not established.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:25213377
      reference_title: Immune dysregulation in human subjects with heterozygous germline mutations in CTLA4.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Our index patient—a 22-year-old female (A.II.1)—developed brain, gastrointestinal (GI), and lung lymphocytic infiltrates, autoimmune thrombocytopenia, and hypogammaglobulinemia in early childhood.
      explanation: The index family shows autoimmune thrombocytopenia as an early and severe hematologic manifestation.
  - target: Autoimmune hemolytic anemia
    description: Loss of B-cell tolerance may contribute to erythrocyte-directed autoimmunity.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:25213377
      reference_title: Immune dysregulation in human subjects with heterozygous germline mutations in CTLA4.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Patient B.I.1, previously diagnosed with common variable immunodeficiency (CVID), had hepatosplenomegaly, autoimmune hemolytic anemia (AIHA), autoimmune thrombocytopenia, pulmonary nodules, and cerebral infiltrative lesions.
      explanation: This affected patient demonstrates autoimmune hemolytic anemia within the broader CTLA4 haploinsufficiency phenotype.
- name: Enhanced B-cell apoptosis
  biological_scale: CELLULAR
  description: Patient B cells, particularly the CD21-low compartment, show increased apoptosis ex vivo. This may contribute to peripheral B-cell depletion, but does not establish the only cause of low B-cell counts.
  cell_types:
  - preferred_term: B cell
    term:
      id: CL:0000236
      label: B cell
  evidence:
  - reference: PMID:25213377
    reference_title: Immune dysregulation in human subjects with heterozygous germline mutations in CTLA4.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: we observed heightened apoptosis in patient B cells
    explanation: Patient B cells exhibit increased cell death ex vivo.
  downstream:
  - target: Peripheral B-cell depletion
    description: Increased cell death is a proposed contributor to progressive B-cell loss.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:25213377
      reference_title: Immune dysregulation in human subjects with heterozygous germline mutations in CTLA4.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Patients also exhibited progressive loss of circulating B cells, associated with an increase of predominantly autoreactive CD21(lo) B cells and accumulation of B cells in nonlymphoid organs.
      explanation: The discovery cohort demonstrates progressive B-cell depletion and altered B-cell subsets.
    - reference: PMID:25213377
      reference_title: Immune dysregulation in human subjects with heterozygous germline mutations in CTLA4.
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: we observed heightened apoptosis in patient B cells
      explanation: Patient B cells exhibit increased cell death ex vivo.
- name: Peripheral B-cell depletion
  biological_scale: CELLULAR
  description: 'Circulating B-cell counts can progressively decline. Class-switched memory B-cell proportions are often reduced, but a global intrinsic class-switch failure is not established: stimulated naive patient B cells can switch and secrete immunoglobulin robustly.'
  cell_types:
  - preferred_term: B cell
    term:
      id: CL:0000236
      label: B cell
  evidence:
  - reference: PMID:25213377
    reference_title: Immune dysregulation in human subjects with heterozygous germline mutations in CTLA4.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Patients also exhibited progressive loss of circulating B cells, associated with an increase of predominantly autoreactive CD21(lo) B cells and accumulation of B cells in nonlymphoid organs.
    explanation: The discovery cohort demonstrates progressive B-cell depletion and altered B-cell subsets.
  downstream:
  - target: Hypogammaglobulinemia
    description: Loss and dysfunction of B-cell compartments may reduce humoral output; residual naive-cell switching can remain intact.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:25213377
      reference_title: Immune dysregulation in human subjects with heterozygous germline mutations in CTLA4.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Patients also exhibited progressive loss of circulating B cells, associated with an increase of predominantly autoreactive CD21(lo) B cells and accumulation of B cells in nonlymphoid organs.
      explanation: The discovery cohort demonstrates progressive B-cell depletion and altered B-cell subsets.
  - target: Reduced circulating B-cell count
    description: Peripheral B-cell depletion is measured on immunophenotyping.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:25213377
      reference_title: Immune dysregulation in human subjects with heterozygous germline mutations in CTLA4.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Patients also exhibited progressive loss of circulating B cells, associated with an increase of predominantly autoreactive CD21(lo) B cells and accumulation of B cells in nonlymphoid organs.
      explanation: The discovery cohort demonstrates progressive B-cell depletion and altered B-cell subsets.
  - target: Reduced class-switched memory B-cell proportion
    description: The disturbed B-cell compartment includes loss of the switched-memory subset; a selective differentiation block is not established.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:29729943
      reference_title: Phenotype, penetrance, and treatment of 133 cytotoxic T-lymphocyte antigen 4-insufficient subjects.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: B cell subsets showed a decrease in switched memory B cells (23/30) and consecutively a relative increase in naïve B cells (14/29).
      explanation: Immunophenotyping documents the altered subset distribution.
- name: Non-malignant lymphoproliferation
  biological_scale: TISSUE
  description: Dysregulated lymphocyte accumulation expands secondary lymphoid organs. This benign inflammatory phenotype is distinct from lymphoma, although both can occur in the same disorder.
  evidence:
  - reference: PMID:29729943
    reference_title: Phenotype, penetrance, and treatment of 133 cytotoxic T-lymphocyte antigen 4-insufficient subjects.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Sixty-two affected mutation carriers (73%) had non-malignant lymphoproliferation, including splenomegaly (n=51, Figure 3, Figure 5 Panel A), chronic lymphadenopathy (n=43), and hepatomegaly (n=17).
    explanation: The cohort identifies non-malignant lymphoid enlargement.
  downstream:
  - target: Lymphadenopathy
    description: Non-malignant lymphoid expansion produces organ enlargement.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:29729943
      reference_title: Phenotype, penetrance, and treatment of 133 cytotoxic T-lymphocyte antigen 4-insufficient subjects.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Sixty-two affected mutation carriers (73%) had non-malignant lymphoproliferation, including splenomegaly (n=51, Figure 3, Figure 5 Panel A), chronic lymphadenopathy (n=43), and hepatomegaly (n=17).
      explanation: The cohort identifies non-malignant lymphoid enlargement.
  - target: Splenomegaly
    description: Non-malignant lymphoid expansion produces organ enlargement.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:29729943
      reference_title: Phenotype, penetrance, and treatment of 133 cytotoxic T-lymphocyte antigen 4-insufficient subjects.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Sixty-two affected mutation carriers (73%) had non-malignant lymphoproliferation, including splenomegaly (n=51, Figure 3, Figure 5 Panel A), chronic lymphadenopathy (n=43), and hepatomegaly (n=17).
      explanation: The cohort identifies non-malignant lymphoid enlargement.
  - target: Hepatomegaly
    description: Non-malignant lymphoid expansion produces organ enlargement.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:29729943
      reference_title: Phenotype, penetrance, and treatment of 133 cytotoxic T-lymphocyte antigen 4-insufficient subjects.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Sixty-two affected mutation carriers (73%) had non-malignant lymphoproliferation, including splenomegaly (n=51, Figure 3, Figure 5 Panel A), chronic lymphadenopathy (n=43), and hepatomegaly (n=17).
      explanation: The cohort identifies non-malignant lymphoid enlargement.
phenotypes:
- name: Hypogammaglobulinemia
  category: Immunologic
  description: Low immunoglobulin concentrations occurred in 65 of 77 evaluated affected carriers in the 2018 cohort. Antibody deficiency may coexist with autoimmunity and lymphoproliferation.
  phenotype_term:
    preferred_term: Hypogammaglobulinemia
    term:
      id: HP:0004313
      label: Decreased circulating immunoglobulin concentration
  evidence:
  - reference: PMID:29729943
    reference_title: Phenotype, penetrance, and treatment of 133 cytotoxic T-lymphocyte antigen 4-insufficient subjects.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Hypogammaglobulinemia was present in 84% (65/77), with low IgM in 30, low IgG in 42, and low IgA in 53 affected mutation carriers
    explanation: The measured subgroup supports the frequency; it is not the fraction of all variant carriers.
  frequency: VERY_FREQUENT
  sequelae:
  - target: Recurrent respiratory infections
    description: Antibody deficiency contributes to infection susceptibility; cellular immune defects and immunosuppression are additional contributors.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:34111452
      reference_title: Therapeutic options for CTLA-4 insufficiency.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Immunoglobulin replacement was effective in prevention of infection.
      explanation: The cohort response to antibody replacement supports a contribution from antibody deficiency, without attributing all infections to that mechanism.
- category: Immunologic
  name: Autoimmunity
  description: Autoimmune disease is central to the syndrome and may affect the hematologic, gastrointestinal, dermatologic, endocrine, hepatic, or neurologic systems.
  phenotype_term:
    preferred_term: Autoimmunity
    term:
      id: HP:0002960
      label: Autoimmunity
  evidence:
  - reference: PMID:25329329
    reference_title: Autosomal dominant immune dysregulation syndrome in humans with CTLA4 mutations.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: We studied a large family in which five individuals presented with a complex, autosomal dominant immune dysregulation syndrome characterized by hypogammaglobulinemia, recurrent infections and multiple autoimmune clinical features.
    explanation: The discovery cohort explicitly establishes multi-organ autoimmunity as a core clinical feature of CTLA4 haploinsufficiency.
- name: Lymphadenopathy
  category: Lymphatic
  description: Chronic lymphadenopathy affected 43 carriers in the 2018 cohort; benign enlargement requires distinction from lymphoma.
  phenotype_term:
    preferred_term: Lymphadenopathy
    term:
      id: HP:0002716
      label: Lymphadenopathy
  evidence:
  - reference: PMID:29729943
    reference_title: Phenotype, penetrance, and treatment of 133 cytotoxic T-lymphocyte antigen 4-insufficient subjects.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Sixty-two affected mutation carriers (73%) had non-malignant lymphoproliferation, including splenomegaly (n=51, Figure 3, Figure 5 Panel A), chronic lymphadenopathy (n=43), and hepatomegaly (n=17).
    explanation: The cohort documents these distinct lymphoproliferative manifestations.
- name: Splenomegaly
  category: Lymphatic
  description: Splenic enlargement is a common component of non-malignant lymphoproliferation; 51 affected carriers were reported in the 2018 cohort.
  phenotype_term:
    preferred_term: Splenomegaly
    term:
      id: HP:0001744
      label: Splenomegaly
  evidence:
  - reference: PMID:29729943
    reference_title: Phenotype, penetrance, and treatment of 133 cytotoxic T-lymphocyte antigen 4-insufficient subjects.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Sixty-two affected mutation carriers (73%) had non-malignant lymphoproliferation, including splenomegaly (n=51, Figure 3, Figure 5 Panel A), chronic lymphadenopathy (n=43), and hepatomegaly (n=17).
    explanation: The cohort documents these distinct lymphoproliferative manifestations.
- name: Hepatomegaly
  category: Hepatic
  description: Hepatomegaly accompanied lymphoproliferative disease in 17 affected carriers in the 2018 cohort.
  phenotype_term:
    preferred_term: Hepatomegaly
    term:
      id: HP:0002240
      label: Hepatomegaly
  evidence:
  - reference: PMID:29729943
    reference_title: Phenotype, penetrance, and treatment of 133 cytotoxic T-lymphocyte antigen 4-insufficient subjects.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Sixty-two affected mutation carriers (73%) had non-malignant lymphoproliferation, including splenomegaly (n=51, Figure 3, Figure 5 Panel A), chronic lymphadenopathy (n=43), and hepatomegaly (n=17).
    explanation: The cohort documents these distinct lymphoproliferative manifestations.
- name: Autoimmune thrombocytopenia
  category: Hematologic
  description: Immune thrombocytopenia may be severe, relapsing or part of multilineage autoimmune cytopenia.
  phenotype_term:
    preferred_term: Autoimmune thrombocytopenia
    term:
      id: HP:0001973
      label: Autoimmune thrombocytopenia
  evidence:
  - reference: PMID:29729943
    reference_title: Phenotype, penetrance, and treatment of 133 cytotoxic T-lymphocyte antigen 4-insufficient subjects.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Sixty-two percent of affected mutation carriers (55/89) had autoimmune cytopenia, including immune thrombocytopenia (n=41), autoimmune hemolytic anemia (n=37), pure red cell aplasia (PRCA) (n=2) or autoimmune neutropenia (n=16).
    explanation: The cohort reports specific autoimmune cytopenias within a clinically ascertained population.
- name: Autoimmune hemolytic anemia
  category: Hematologic
  description: Autoimmune hemolysis may occur alone or with thrombocytopenia as Evans syndrome.
  phenotype_term:
    preferred_term: Autoimmune hemolytic anemia
    term:
      id: HP:0001890
      label: Autoimmune hemolytic anemia
  evidence:
  - reference: PMID:29729943
    reference_title: Phenotype, penetrance, and treatment of 133 cytotoxic T-lymphocyte antigen 4-insufficient subjects.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Sixty-two percent of affected mutation carriers (55/89) had autoimmune cytopenia, including immune thrombocytopenia (n=41), autoimmune hemolytic anemia (n=37), pure red cell aplasia (PRCA) (n=2) or autoimmune neutropenia (n=16).
    explanation: The cohort reports specific autoimmune cytopenias within a clinically ascertained population.
- name: Autoimmune neutropenia
  category: Hematologic
  description: Neutrophil-directed autoimmune cytopenia was reported in 16 affected carriers in the 2018 cohort.
  phenotype_term:
    preferred_term: Autoimmune neutropenia
    term:
      id: HP:0001904
      label: Autoimmune neutropenia
  evidence:
  - reference: PMID:29729943
    reference_title: Phenotype, penetrance, and treatment of 133 cytotoxic T-lymphocyte antigen 4-insufficient subjects.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Sixty-two percent of affected mutation carriers (55/89) had autoimmune cytopenia, including immune thrombocytopenia (n=41), autoimmune hemolytic anemia (n=37), pure red cell aplasia (PRCA) (n=2) or autoimmune neutropenia (n=16).
    explanation: The cohort reports specific autoimmune cytopenias within a clinically ascertained population.
- name: Lymphopenia
  category: Immunologic
  description: Reduced total lymphocyte counts occurred in 26 of 66 assessed affected carriers; most were receiving immunosuppression, which complicates attribution.
  phenotype_term:
    preferred_term: Lymphopenia
    term:
      id: HP:0001888
      label: Decreased total lymphocyte count
  evidence:
  - reference: PMID:29729943
    reference_title: Phenotype, penetrance, and treatment of 133 cytotoxic T-lymphocyte antigen 4-insufficient subjects.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Thirty-nine percent (26/66) of affected mutation carriers with available immunological data had lymphopenia of which twenty-four were under immunosuppressive treatment at the time of data collection.
    explanation: The source provides both the measured fraction and the major treatment confounder.
- name: Reduced circulating B-cell count
  category: Immunologic
  description: Circulating B-cell numbers may progressively decline. In the 2018 cohort, 26 of 58 assessed carriers had reduced counts; the printed percentage in the source is inconsistent with that fraction.
  phenotype_term:
    preferred_term: Reduced circulating B-cell count
    term:
      id: HP:0010976
      label: Decreased total B cell count
  evidence:
  - reference: PMID:29729943
    reference_title: Phenotype, penetrance, and treatment of 133 cytotoxic T-lymphocyte antigen 4-insufficient subjects.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Absolute CD19+ B cell counts were reduced in 41% (26/58) of affected mutation carriers.
    explanation: The reported count supports B-cell lymphopenia; no recalculated frequency band is asserted.
- name: Reduced class-switched memory B-cell proportion
  category: Immunologic
  description: Class-switched memory B-cell proportions are often reduced despite retained class-switch capacity in stimulated naive cells.
  phenotype_term:
    preferred_term: Reduced class-switched memory B-cell proportion
    term:
      id: HP:0030388
      label: Decreased class-switched memory B cell proportion
  evidence:
  - reference: PMID:29729943
    reference_title: Phenotype, penetrance, and treatment of 133 cytotoxic T-lymphocyte antigen 4-insufficient subjects.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: B cell subsets showed a decrease in switched memory B cells (23/30) and consecutively a relative increase in naïve B cells (14/29).
    explanation: Immunophenotyping documents the altered subset distribution.
- name: Increased CD21-low B-cell proportion
  category: Immunologic
  description: The expanded CD21-low compartment is enriched for autoreactivity and accompanies immune dysregulation.
  phenotype_term:
    preferred_term: Increased CD21-low B-cell proportion
    term:
      id: HP:0033207
      label: Increased CD21low B cell proportion
  evidence:
  - reference: PMID:25213377
    reference_title: Immune dysregulation in human subjects with heterozygous germline mutations in CTLA4.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Patients also exhibited progressive loss of circulating B cells, associated with an increase of predominantly autoreactive CD21(lo) B cells and accumulation of B cells in nonlymphoid organs.
    explanation: The original cohort links CD21-low expansion with autoreactive B-cell phenotypes.
- name: Recurrent respiratory infections
  category: Respiratory
  description: Recurrent upper and lower respiratory infections accompany antibody and cellular immune abnormalities; immunosuppression can add infection risk.
  phenotype_term:
    preferred_term: Recurrent respiratory infections
    term:
      id: HP:0002205
      label: Recurrent respiratory infections
  evidence:
  - reference: PMID:29729943
    reference_title: Phenotype, penetrance, and treatment of 133 cytotoxic T-lymphocyte antigen 4-insufficient subjects.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Respiratory tract involvement was common (68%; 61/90; Figure 5 Panels C, D, E; Figure 6 Panel A, B) including recurrent lower (n=48) and upper (n=41) respiratory tract infections, granulomatous-lymphocytic interstitial lung disease (GLILD) (n=32), and bronchiectasis (n=20).
    explanation: The source distinguishes infections, GLILD and bronchiectasis; their overlapping counts should not be added.
- name: Pulmonary lymphocytic infiltration
  category: Respiratory
  description: Inflammatory lung disease includes GLILD, with lymphoid infiltrates and sometimes granulomas. GLILD was reported in 32 of 90 affected carriers in the 2018 cohort.
  phenotype_term:
    preferred_term: Pulmonary lymphocytic infiltration
    term:
      id: HP:0033582
      label: Pulmonary interstitial lymphocyte infiltration
  evidence:
  - reference: PMID:29729943
    reference_title: Phenotype, penetrance, and treatment of 133 cytotoxic T-lymphocyte antigen 4-insufficient subjects.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Respiratory tract involvement was common (68%; 61/90; Figure 5 Panels C, D, E; Figure 6 Panel A, B) including recurrent lower (n=48) and upper (n=41) respiratory tract infections, granulomatous-lymphocytic interstitial lung disease (GLILD) (n=32), and bronchiectasis (n=20).
    explanation: The source distinguishes infections, GLILD and bronchiectasis; their overlapping counts should not be added.
  - reference: PMID:29729943
    reference_title: Phenotype, penetrance, and treatment of 133 cytotoxic T-lymphocyte antigen 4-insufficient subjects.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Forty-three affected mutation carriers (50%) had lymphocytic infiltrations into lung (n=27), gastrointestinal tract (n=17), brain (n=12), bone marrow (n=6, Figure 6 Panel E), kidney (n=6), or retroperitoneal tissue (n=4).
    explanation: Clinical biopsies and imaging identify a multiorgan infiltration phenotype; the cohort is ascertained rather than population based.
- name: Bronchiectasis
  category: Respiratory
  description: Bronchiectasis was reported in 20 affected carriers in the 2018 cohort, often in the setting of recurrent infection or chronic inflammatory lung disease.
  phenotype_term:
    preferred_term: Bronchiectasis
    term:
      id: HP:0002110
      label: Bronchiectasis
  evidence:
  - reference: PMID:29729943
    reference_title: Phenotype, penetrance, and treatment of 133 cytotoxic T-lymphocyte antigen 4-insufficient subjects.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Respiratory tract involvement was common (68%; 61/90; Figure 5 Panels C, D, E; Figure 6 Panel A, B) including recurrent lower (n=48) and upper (n=41) respiratory tract infections, granulomatous-lymphocytic interstitial lung disease (GLILD) (n=32), and bronchiectasis (n=20).
    explanation: The source distinguishes infections, GLILD and bronchiectasis; their overlapping counts should not be added.
- name: Autoimmune enteropathy
  category: Gastrointestinal
  description: Immune-mediated enteropathy may resemble inflammatory bowel disease or refractory celiac disease. It is distinct from infectious diarrhea and can be severe despite limited disease elsewhere.
  phenotype_term:
    preferred_term: Autoimmune enteropathy
    term:
      id: HP:0011024
      label: Abnormality of the gastrointestinal tract
    coarse_binding_basis: NO_HPO_TERM
    term_gap: HPO searches for autoimmune enteropathy and enteropathy found no specific autoimmune-enteropathy term. Protein-losing enteropathy, colitis and villous atrophy describe narrower manifestations and are not equivalent to the complete clinical syndrome.
  evidence:
  - reference: PMID:35935971
    reference_title: 'Cytotoxic T Lymphocyte Antigen 4 Haploinsufficiency Presenting As Refractory Celiac-Like Disease: Case Report.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Both patients underwent genetic testing given disease refractoriness and were ultimately diagnosed with cytotoxic T lymphocyte antigen 4 (CTLA4) haploinsufficiency.
    explanation: Two refractory celiac-like cases demonstrate the enteropathy presentation.
  - reference: url:https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf
    reference_title: https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The underlying causes were autoimmune enteropathy (in 21 of 74 patients), inflammatory bowel disease (in 16 of 74), atrophic gastritis (in 14 of 74), and celiac disease (in 3 of 74).
    explanation: Full text of Egg et al., Therapeutic options for CTLA-4 insufficiency (PMID:34111452). The treatment cohort distinguishes different gastrointestinal diagnoses.
  sequelae:
  - target: Chronic diarrhea
    description: Immune-mediated intestinal disease can produce persistent diarrhea; infectious diarrhea remains a separate differential.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:35935971
      reference_title: 'Cytotoxic T Lymphocyte Antigen 4 Haploinsufficiency Presenting As Refractory Celiac-Like Disease: Case Report.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: She was referred to gastroenterology at age 6 for persistent non-bloody diarrhea with all growth parameters <5th percentile for age and had laboratory and endoscopic evaluation consistent with celiac disease
      explanation: The refractory celiac-like CTLA4 case links enteropathy with persistent diarrhea and impaired growth.
  - target: Failure to thrive
    description: Severe intestinal disease and ongoing fluid and nutrient loss can impair childhood growth.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:35935971
      reference_title: 'Cytotoxic T Lymphocyte Antigen 4 Haploinsufficiency Presenting As Refractory Celiac-Like Disease: Case Report.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: she continued to have diarrhea and secondary hypokalemia, iron deficiency anemia, and poor growth
      explanation: Persistent enteropathy accompanied electrolyte and nutritional consequences and impaired growth in the reported child.
- name: Chronic diarrhea
  category: Gastrointestinal
  description: Persistent diarrhea ranges from mild symptoms to severe fluid and nutrient loss requiring nutritional support.
  phenotype_term:
    preferred_term: Chronic diarrhea
    term:
      id: HP:0002028
      label: Chronic diarrhea
  evidence:
  - reference: PMID:29729943
    reference_title: Phenotype, penetrance, and treatment of 133 cytotoxic T-lymphocyte antigen 4-insufficient subjects.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Diarrhea was frequent (n=51), ranging from mild to severe diarrhea with weight loss, wasting, and total parenteral nutrition-dependency.
    explanation: The cohort documents a broad severity spectrum.
- name: Intestinal villous atrophy
  category: Gastrointestinal
  description: Celiac-like enteropathy can show villous atrophy and intraepithelial lymphocytosis; histology alone does not establish ordinary celiac disease.
  phenotype_term:
    preferred_term: Intestinal villous atrophy
    term:
      id: HP:0011473
      label: Villous atrophy
  evidence:
  - reference: PMID:35935971
    reference_title: 'Cytotoxic T Lymphocyte Antigen 4 Haploinsufficiency Presenting As Refractory Celiac-Like Disease: Case Report.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Duodenal mucosa with total villous atrophy, crypt hyperplasia, and patchy intraepithelial lymphocytosis, suggestive of celiac disease.
    explanation: Biopsy documents villous injury in a genetically confirmed CTLA4 case.
- name: Colitis
  category: Gastrointestinal
  description: Colonic inflammation may accompany autoimmune enteropathy and mimic idiopathic inflammatory bowel disease.
  phenotype_term:
    preferred_term: Colitis
    term:
      id: HP:0002583
      label: Colitis
  evidence:
  - reference: PMID:42577265
    reference_title: Novel pathogenic CTLA4 missense variant associated with autoimmune enteropathy and systemic immune dysregulation.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Re-review of intestinal pathology specimens revealed chronic active ileitis and colitis with intestinal villous atrophy, crypt shortening, loss of intestinal Paneth cells and goblet cells, lymphocytic infiltration, and prominent epithelial apoptotic bodies
    explanation: Histopathology in the Phe56Cys case documents colonic inflammation with epithelial injury.
- name: Inflammatory central nervous system lesions
  category: Neurologic
  description: Autoimmune encephalitis or encephalomyelitis with cerebral perivascular lymphocytic infiltration is documented. Other neurologic symptoms can arise from hemorrhage, thrombosis, infection or unrelated diagnoses and should not all be attributed to direct immune inflammation.
  phenotype_term:
    preferred_term: Autoimmune encephalitis or encephalomyelitis
    term:
      id: HP:5210423
      label: Autoimmune encephalitis
  evidence:
  - reference: PMID:29729943
    reference_title: Phenotype, penetrance, and treatment of 133 cytotoxic T-lymphocyte antigen 4-insufficient subjects.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Three had autoimmune encephalitis or encephalomyelitis with cerebral perivascular lymphocytic infiltrations
    explanation: The cohort distinguishes directly inflammatory CNS disease from other neurologic complications.
- name: Eczema
  category: Dermatologic
  description: Recurrent eczema was reported in 59 patients in the 123-affected-patient treatment cohort; only a subset had a dermatologist-confirmed atopic dermatitis diagnosis.
  phenotype_term:
    preferred_term: Eczema
    term:
      id: HP:0000964
      label: Eczematoid dermatitis
  evidence:
  - reference: url:https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf
    reference_title: https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: We observed 59 cases of recurrent eczema, with 25 of them diagnosed as atopic dermatitis by the treating dermatologist.
    explanation: Full text of Egg et al., Therapeutic options for CTLA-4 insufficiency (PMID:34111452). The source distinguishes recurrent eczema from confirmed atopic dermatitis.
- name: Alopecia
  category: Dermatologic
  description: Hair loss occurs within the variable autoimmune skin spectrum.
  phenotype_term:
    preferred_term: Alopecia
    term:
      id: HP:0001596
      label: Alopecia
  evidence:
  - reference: url:https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf
    reference_title: https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: alopecia in 14, warts in 11, and vitiligo in 5.
    explanation: Full text of Egg et al., Therapeutic options for CTLA-4 insufficiency (PMID:34111452). The 2022 treatment cohort lists alopecia among skin manifestations.
- name: Vitiligo
  category: Dermatologic
  description: Vitiligo is a reported autoimmune skin manifestation.
  phenotype_term:
    preferred_term: Vitiligo
    term:
      id: HP:0001045
      label: Vitiligo
  evidence:
  - reference: url:https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf
    reference_title: https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: alopecia in 14, warts in 11, and vitiligo in 5.
    explanation: Full text of Egg et al., Therapeutic options for CTLA-4 insufficiency (PMID:34111452). The cohort documents vitiligo in affected carriers.
- name: Arthritis
  category: Musculoskeletal
  description: Inflammatory arthritis affected 14% of the 2018 affected-carrier cohort and can be polyarticular.
  phenotype_term:
    preferred_term: Arthritis
    term:
      id: HP:0001369
      label: Arthritis
  evidence:
  - reference: PMID:29729943
    reference_title: Phenotype, penetrance, and treatment of 133 cytotoxic T-lymphocyte antigen 4-insufficient subjects.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Arthritis (14%), growth retardation (14%), renal (12%) or liver (12%) involvement were less frequent
    explanation: The cohort reports these organ-level findings; the composite organ rates do not establish rates for specific diagnoses.
  - reference: PMID:31396201
    reference_title: Preponderance of CTLA4 Variation Associated With Autosomal Dominant Immune Dysregulation in the MYPPPY Motif.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: she presented with polyarticular arthritis affecting large and small joints of the upper and lower limbs including the knees, ankles, elbows, and multiple small hand joints.
    explanation: The Tyr139Cys case provides a specific polyarticular example.
  frequency: OCCASIONAL
- name: Hashimoto thyroiditis
  category: Endocrine
  description: Autoimmune thyroid disease can accompany enteropathy and other organ autoimmunity.
  phenotype_term:
    preferred_term: Hashimoto thyroiditis
    term:
      id: HP:0000872
      label: Hashimoto thyroiditis
  evidence:
  - reference: PMID:35935971
    reference_title: 'Cytotoxic T Lymphocyte Antigen 4 Haploinsufficiency Presenting As Refractory Celiac-Like Disease: Case Report.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: including Hashimoto’s thyroiditis (diagnosed age 6), Addison’s disease (diagnosed age 8), cytopenias
    explanation: The enteropathy case documents autoimmune thyroid and adrenal disease.
- name: Primary adrenal insufficiency
  category: Endocrine
  description: Addison disease is a reported endocrine autoimmune manifestation.
  phenotype_term:
    preferred_term: Primary adrenal insufficiency
    term:
      id: HP:0008207
      label: Primary adrenal insufficiency
  evidence:
  - reference: PMID:35935971
    reference_title: 'Cytotoxic T Lymphocyte Antigen 4 Haploinsufficiency Presenting As Refractory Celiac-Like Disease: Case Report.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: including Hashimoto’s thyroiditis (diagnosed age 6), Addison’s disease (diagnosed age 8), cytopenias
    explanation: The case establishes adrenal involvement without implying a cohort frequency.
- name: Type I diabetes mellitus
  category: Endocrine
  description: Insulin-dependent autoimmune diabetes can be an early manifestation of immune dysregulation.
  phenotype_term:
    preferred_term: Type I diabetes mellitus
    term:
      id: HP:0100651
      label: Type I diabetes mellitus
  evidence:
  - reference: PMID:29729943
    reference_title: Phenotype, penetrance, and treatment of 133 cytotoxic T-lymphocyte antigen 4-insufficient subjects.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: First symptoms included autoimmune cytopenia (33%), respiratory manifestations (21%), enteropathy (17%), type 1 diabetes (8%)
    explanation: The source concerns first presentation, not overall lifetime diabetes frequency.
- name: Autoimmune hepatitis
  category: Hepatic
  description: Autoimmune hepatitis may precede other manifestations; the Tyr139Cys child presented in infancy with hepatic autoimmunity and later polyarthritis.
  phenotype_term:
    preferred_term: Autoimmune hepatitis
    term:
      id: HP:5210421
      label: Autoimmune hepatitis
  evidence:
  - reference: PMID:31396201
    reference_title: Preponderance of CTLA4 Variation Associated With Autosomal Dominant Immune Dysregulation in the MYPPPY Motif.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: She was initially diagnosed with autoimmune hepatitis at 20 months of age
    explanation: The case establishes autoimmune hepatitis as an early presentation.
- name: Failure to thrive
  category: Growth
  description: Severe enteropathy can impair nutrition and growth.
  phenotype_term:
    preferred_term: Failure to thrive
    term:
      id: HP:0001508
      label: Failure to thrive
  evidence:
  - reference: PMID:35935971
    reference_title: 'Cytotoxic T Lymphocyte Antigen 4 Haploinsufficiency Presenting As Refractory Celiac-Like Disease: Case Report.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Patient 2 is a 14-year-old female who initially presented with diarrhea, vomiting, and failure to thrive before 1 year of age.
    explanation: The second celiac-like case documents early growth failure.
- name: Renal involvement
  category: Renal
  description: Renal involvement was reported in 12% of the 2018 affected-carrier cohort; this composite includes heterogeneous renal disease and does not establish a specific lesion frequency.
  phenotype_term:
    preferred_term: Renal involvement
    term:
      id: HP:0000077
      label: Abnormality of the kidney
    coarse_binding_basis: SOURCE_UNSPECIFIED
  evidence:
  - reference: PMID:29729943
    reference_title: Phenotype, penetrance, and treatment of 133 cytotoxic T-lymphocyte antigen 4-insufficient subjects.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Arthritis (14%), growth retardation (14%), renal (12%) or liver (12%) involvement were less frequent
    explanation: The cohort reports these organ-level findings; the composite organ rates do not establish rates for specific diagnoses.
  frequency: OCCASIONAL
- name: Liver involvement
  category: Hepatic
  description: The 2018 cohort reported liver involvement in 12%; hepatomegaly and autoimmune hepatitis are separately represented clinical findings.
  phenotype_term:
    preferred_term: Liver involvement
    term:
      id: HP:0001392
      label: Abnormality of the liver
    coarse_binding_basis: SOURCE_UNSPECIFIED
  evidence:
  - reference: PMID:29729943
    reference_title: Phenotype, penetrance, and treatment of 133 cytotoxic T-lymphocyte antigen 4-insufficient subjects.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Arthritis (14%), growth retardation (14%), renal (12%) or liver (12%) involvement were less frequent
    explanation: The cohort reports these organ-level findings; the composite organ rates do not establish rates for specific diagnoses.
  frequency: OCCASIONAL
- name: Lymphoma
  category: Neoplastic
  description: Hodgkin and non-Hodgkin lymphomas occur, often with EBV association. Immunodeficiency, inflammation and treatment exposures complicate causal attribution.
  phenotype_term:
    preferred_term: Lymphoma
    term:
      id: HP:0002665
      label: Lymphoma
  evidence:
  - reference: PMID:30250467
    reference_title: Increased Risk for Malignancies in 131 Affected CTLA4 Mutation Carriers.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: There were ten lymphomas, five gastric cancers, one multiple myeloma, and one metastatic melanoma.
    explanation: The malignancy cohort documents both tumor groups; it overlaps earlier carrier cohorts.
- name: Gastric carcinoma
  category: Neoplastic
  description: Gastric carcinoma occurs in affected carriers, often after chronic enteropathy or atrophic gastritis. The malignancy cohort reported a median gastric-cancer onset age of 34 years and EBV association in three of five gastric cancers.
  phenotype_term:
    preferred_term: Gastric carcinoma
    term:
      id: HP:0012126
      label: Stomach cancer
  evidence:
  - reference: PMID:30250467
    reference_title: Increased Risk for Malignancies in 131 Affected CTLA4 Mutation Carriers.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: There were ten lymphomas, five gastric cancers, one multiple myeloma, and one metastatic melanoma.
    explanation: The primary malignancy cohort documents gastric carcinoma.
  - reference: PMID:30250467
    reference_title: Increased Risk for Malignancies in 131 Affected CTLA4 Mutation Carriers.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The median age of onset was 32 years for lymphoma and 34 years for gastric cancer.
    explanation: The source supplies a cohort-specific age of onset rather than an unspecified comparison with usual onset.
  - reference: PMID:30250467
    reference_title: Increased Risk for Malignancies in 131 Affected CTLA4 Mutation Carriers.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Seven lymphomas and three gastric cancers were EBV-associated.
    explanation: Three of the five gastric cancers were EBV-associated. Association does not establish that EBV explains every cancer in CTLA4 insufficiency.
- name: Growth delay
  category: Growth
  description: Growth retardation occurred in 14% of the 2018 affected-carrier cohort; nutritional and endocrine contributors can differ between patients.
  phenotype_term:
    preferred_term: Growth delay
    term:
      id: HP:0001510
      label: Growth delay
  evidence:
  - reference: PMID:29729943
    reference_title: Phenotype, penetrance, and treatment of 133 cytotoxic T-lymphocyte antigen 4-insufficient subjects.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Arthritis (14%), growth retardation (14%), renal (12%) or liver (12%) involvement were less frequent
    explanation: The cohort reports growth retardation without restricting it to one mechanism.
  frequency: OCCASIONAL
- name: Atrophic gastritis
  category: Gastrointestinal
  description: Atrophic gastritis is part of the gastrointestinal autoimmune spectrum and warrants distinction from enteropathy and malignancy.
  phenotype_term:
    preferred_term: Atrophic gastritis
    term:
      id: HP:0002582
      label: Atrophic gastritis
  evidence:
  - reference: url:https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf
    reference_title: https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: atrophic gastritis (in 14 of 74)
    explanation: Full text of Egg et al., Therapeutic options for CTLA-4 insufficiency (PMID:34111452). The gastrointestinal subgroup included 14 patients with atrophic gastritis.
- name: Psoriasiform dermatitis
  category: Dermatologic
  description: Psoriasiform skin disease occurs alongside other autoimmune skin findings; cohort counts differ slightly between passages, so no precise rate is assigned.
  phenotype_term:
    preferred_term: Psoriasiform dermatitis
    term:
      id: HP:0003765
      label: Psoriasiform dermatitis
  evidence:
  - reference: url:https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf
    reference_title: https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: psoriatic skin irritation s in 15 patients
    explanation: Full text of Egg et al., Therapeutic options for CTLA-4 insufficiency (PMID:34111452). The cohort documents psoriatic skin disease.
treatments:
- name: Abatacept
  description: CTLA4-Ig binds CD80/CD86 and limits CD28-dependent costimulation. Retrospective cohorts and small case series report benefit, especially for enteropathy and lymphoproliferation. The 2026 ABACHAI single-arm trial enrolled 18 adults with CTLA4 insufficiency and two with LRBA deficiency; pooled results showed improvement in lymphoproliferation and immune activation, but insufficient control of cytopenias and renal involvement. Responses are organ dependent and the trial did not provide a randomized comparator.
  action_category: THERAPEUTIC
  treatment_term:
    preferred_term: Immunosuppressive Therapy
    term:
      id: NCIT:C15261
      label: Immunosuppressive Therapy
    therapeutic_agent:
    - preferred_term: Abatacept
      term:
        id: NCIT:C28898
        label: Abatacept
  evidence:
  - reference: PMID:42763023
    reference_title: ABACHAI - Safety and efficacy of abatacept (s.c.) in patients with CTLA4 insufficiency or LRBA deficiency, a phase II clinical trial.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Twenty patients were enrolled (18 with CTLA-4 insufficiency and 2 with LRBA deficiency).
    explanation: Trial outcomes pool two genetic disorders and should not be presented as a CTLA4-only effect estimate.
  - reference: PMID:42763023
    reference_title: ABACHAI - Safety and efficacy of abatacept (s.c.) in patients with CTLA4 insufficiency or LRBA deficiency, a phase II clinical trial.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Abatacept reduced lymphoproliferation and immune activation and improved patient-reported quality of life and gastrointestinal symptom quality. Cytopenias and renal involvement were not sufficiently controlled.
    explanation: The prospective study documents both benefit and important limits.
  - reference: PMID:35935971
    reference_title: 'Cytotoxic T Lymphocyte Antigen 4 Haploinsufficiency Presenting As Refractory Celiac-Like Disease: Case Report.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: They are both now in complete clinical and endoscopic remission on abatacept.
    explanation: Two pediatric-onset enteropathy cases achieved remission; this is uncontrolled case evidence.
  - reference: PMID:42763023
    reference_title: ABACHAI - Safety and efficacy of abatacept (s.c.) in patients with CTLA4 insufficiency or LRBA deficiency, a phase II clinical trial.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Three patients had five severe infections during treatment (incidence rate 0.27 per patient-year), comparable to the year preceding enrolment. No EBV or CMV reactivations occurred.
    explanation: The safety finding is limited to the trial population and observation period.
  therapeutic_modality: PROTEIN_REPLACEMENT
  target_mechanisms:
  - target: Excess Effector T Cell Activation
    treatment_effect: INHIBITS
    description: Soluble CTLA4-Ig binds the shared CD80/CD86 ligands and limits costimulation.
    evidence:
    - reference: PMID:36262801
      reference_title: 'The ABACHAI clinical trial protocol: Safety and efficacy of abatacept (s.c.) in patients with CTLA-4 insufficiency or LRBA deficiency: A non controlled phase 2 clinical trial.'
      supports: SUPPORT
      evidence_source: OTHER
      snippet: Abatacept inhibits the CD80/86:CD28 co-stimulatory pathway by high affinity binding of the CTLA-4 domain to CD80 and CD86
      explanation: The protocol describes the pharmacologic rationale.
  notes: The trial reported five severe infections in three participants, with no EBV or CMV reactivation during the study. This does not eliminate infection risk or negate reactivation reported in earlier immunosuppressed cohorts.
- name: Belatacept
  description: The higher-affinity CTLA4-Ig derivative has been used in a small number of affected carriers, sometimes with other immunosuppression. Historical reports combine abatacept and belatacept and do not establish separate efficacy rates.
  action_category: THERAPEUTIC
  treatment_term:
    preferred_term: Immunosuppressive Therapy
    term:
      id: NCIT:C15261
      label: Immunosuppressive Therapy
    therapeutic_agent:
    - preferred_term: Belatacept
      term:
        id: NCIT:C80255
        label: Belatacept
  evidence:
  - reference: PMID:29729943
    reference_title: Phenotype, penetrance, and treatment of 133 cytotoxic T-lymphocyte antigen 4-insufficient subjects.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: In total, fourteen affected mutation carriers received the CTLA-4 fusion proteins abatacept or belatacept; eleven of whom responded with an improvement of their clinical symptoms.
    explanation: The retrospective result combines both agents and overlapping manifestations.
  therapeutic_modality: PROTEIN_REPLACEMENT
- name: Sirolimus
  description: Sirolimus has been used for refractory cytopenias, lymphoproliferation and organ inflammation. Responses vary; infection and other adverse effects can limit treatment.
  action_category: THERAPEUTIC
  treatment_term:
    preferred_term: Immunosuppressive Therapy
    term:
      id: NCIT:C15261
      label: Immunosuppressive Therapy
    therapeutic_agent:
    - preferred_term: Sirolimus
      term:
        id: NCIT:C1212
        label: Sirolimus
  evidence:
  - reference: PMID:29729943
    reference_title: Phenotype, penetrance, and treatment of 133 cytotoxic T-lymphocyte antigen 4-insufficient subjects.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Thirteen affected mutation carriers were treated with the mTOR inhibitor sirolimus with a good response in eight
    explanation: The cohort reports benefit in some, but not all, treated carriers.
  therapeutic_modality: SMALL_MOLECULE
- name: Rituximab
  description: B-cell depletion has been used for autoimmune cytopenias and lymphoproliferative or inflammatory organ disease. Responses vary by organ, and secondary antibody deficiency may require replacement immunoglobulin.
  action_category: THERAPEUTIC
  treatment_term:
    preferred_term: Immunosuppressive Therapy
    term:
      id: NCIT:C15261
      label: Immunosuppressive Therapy
    therapeutic_agent:
    - preferred_term: Rituximab
      term:
        id: NCIT:C1702
        label: Rituximab
  evidence:
  - reference: url:https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf
    reference_title: https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: A total of 30 patients received rituximab (1-4 X 375 mg/ m 2), of whom 25 (83%) responded
    explanation: Full text of Egg et al., Therapeutic options for CTLA-4 insufficiency (PMID:34111452). The retrospective cohort reports responses in cytopenia patients, without a randomized comparison.
  - reference: url:https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf
    reference_title: https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: 8 patients in our cohort received IgRT because of secondary loss of antibodies after therapy with rituximab.
    explanation: Full text of Egg et al., Therapeutic options for CTLA-4 insufficiency (PMID:34111452). The same cohort documents a clinically relevant consequence of B-cell depletion.
  therapeutic_modality: MONOCLONAL_ANTIBODY
- name: Systemic corticosteroids
  description: Systemic corticosteroids are used for autoimmune cytopenias and inflammatory gastrointestinal, pulmonary, neurologic or skin disease. Responses can be temporary and relapse during tapering may prompt additional therapy.
  action_category: THERAPEUTIC
  treatment_term:
    preferred_term: Immunosuppressive Therapy
    term:
      id: NCIT:C15261
      label: Immunosuppressive Therapy
    therapeutic_agent:
    - preferred_term: corticosteroid
      term:
        id: CHEBI:50858
        label: corticosteroid
  evidence:
  - reference: url:https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf
    reference_title: https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Systemic corticosteroids alleviated gastrointestinal symptoms in 19 cases temporarily (86%).
    explanation: Full text of Egg et al., Therapeutic options for CTLA-4 insufficiency (PMID:34111452). The GI result illustrates the limited durability of steroid response.
  therapeutic_modality: SMALL_MOLECULE
- name: Oral budesonide
  description: Locally acting oral budesonide has been used for gastrointestinal inflammation, including as an adjunct while establishing abatacept treatment.
  action_category: THERAPEUTIC
  treatment_term:
    preferred_term: Immunosuppressive Therapy
    term:
      id: NCIT:C15261
      label: Immunosuppressive Therapy
    therapeutic_agent:
    - preferred_term: Budesonide
      term:
        id: NCIT:C1027
        label: Budesonide
  evidence:
  - reference: url:https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf
    reference_title: https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Of the 11 patients who received oral budesonide (9 mg per day), 10 achieved a good clinical response.
    explanation: Full text of Egg et al., Therapeutic options for CTLA-4 insufficiency (PMID:34111452). The cohort documents gastrointestinal responses under oral budesonide.
  therapeutic_modality: SMALL_MOLECULE
- name: Azathioprine
  description: Azathioprine has been used for autoimmune hepatitis, enteropathy and inflammatory lung disease. Observed responses vary across manifestations.
  action_category: THERAPEUTIC
  treatment_term:
    preferred_term: Immunosuppressive Therapy
    term:
      id: NCIT:C15261
      label: Immunosuppressive Therapy
    therapeutic_agent:
    - preferred_term: Azathioprine
      term:
        id: NCIT:C290
        label: Azathioprine
  evidence:
  - reference: url:https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf
    reference_title: https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Nine patients received azathioprine (50-150 mg per day), with 4 (44%) showing a positive response.
    explanation: Full text of Egg et al., Therapeutic options for CTLA-4 insufficiency (PMID:34111452). The gastrointestinal subgroup provides direct treatment evidence.
  - reference: PMID:31396201
    reference_title: Preponderance of CTLA4 Variation Associated With Autosomal Dominant Immune Dysregulation in the MYPPPY Motif.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: due to steroid dependency azathioprine was introduced (20 mg per day). On this regime her liver enzymes normalized.
    explanation: The Tyr139Cys case documents a hepatic response with combined treatment.
  therapeutic_modality: SMALL_MOLECULE
- name: Mycophenolate
  description: Mycophenolate has been used for inflammatory lung disease and arthritis. The evidence consists of small retrospective subgroups and individual cases.
  action_category: THERAPEUTIC
  treatment_term:
    preferred_term: Immunosuppressive Therapy
    term:
      id: NCIT:C15261
      label: Immunosuppressive Therapy
    therapeutic_agent:
    - preferred_term: Mycophenolate
      term:
        id: NCIT:C29272
        label: Mycophenolate
  evidence:
  - reference: url:https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf
    reference_title: https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Mycophenolate (1000 mg per day) was given to 3 patients and 2 patients showed a reduction of the extent of GLILD
    explanation: Full text of Egg et al., Therapeutic options for CTLA-4 insufficiency (PMID:34111452). Two of three treated cases showed reduced lung involvement.
  - reference: PMID:31396201
    reference_title: Preponderance of CTLA4 Variation Associated With Autosomal Dominant Immune Dysregulation in the MYPPPY Motif.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: a switch from azathioprine to mycophenolate with a good response.
    explanation: The reported child initially improved after the medication change.
  therapeutic_modality: SMALL_MOLECULE
- name: Anti-TNF therapy
  description: Adalimumab and infliximab have been tried for enteropathy or arthritis, with mixed responses. These are alternatives reported in cohorts rather than reliably effective substitutes for CTLA4-directed therapy.
  action_category: THERAPEUTIC
  treatment_term:
    preferred_term: Immunosuppressive Therapy
    term:
      id: NCIT:C15261
      label: Immunosuppressive Therapy
    therapeutic_agent:
    - preferred_term: Adalimumab
      term:
        id: NCIT:C65216
        label: Adalimumab
    - preferred_term: Infliximab
      term:
        id: NCIT:C1789
        label: Infliximab
  evidence:
  - reference: url:https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf
    reference_title: https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Eight received anti-TNF-a biol ogics (eg, adalimumab, 20-80 mg per week, or infliximab, 5-10 mg/kg), with 4 positive responses (56%).
    explanation: Full text of Egg et al., Therapeutic options for CTLA-4 insufficiency (PMID:34111452). The source reports four responses among eight uses; its printed percentage is inconsistent, so no efficacy percentage is adopted.
  - reference: PMID:35935971
    reference_title: 'Cytotoxic T Lymphocyte Antigen 4 Haploinsufficiency Presenting As Refractory Celiac-Like Disease: Case Report.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: She had a significant symptomatic response with adalimumab, but this was subsequently discontinued after the development of drug-induced lupus following the fifth dose.
    explanation: The case documents both clinical response and treatment-limiting toxicity.
  therapeutic_modality: MONOCLONAL_ANTIBODY
- name: Vedolizumab
  description: Gut-directed integrin blockade has been reported as an option for refractory enteropathy, but responses are inconsistent across cases.
  action_category: THERAPEUTIC
  treatment_term:
    preferred_term: Immunosuppressive Therapy
    term:
      id: NCIT:C15261
      label: Immunosuppressive Therapy
    therapeutic_agent:
    - preferred_term: Vedolizumab
      term:
        id: NCIT:C95798
        label: Vedolizumab
  evidence:
  - reference: url:https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf
    reference_title: https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf
    supports: SUPPORT
    evidence_source: OTHER
    snippet: Alternative strategies should include consideration of sirolimus or the anti-a4β7 integrin mAb vedolizumab. 32 The latter was successful in treating the diarrhea in 2 patients.
    explanation: Full text of Egg et al., Therapeutic options for CTLA-4 insufficiency (PMID:34111452). The 2022 management report cites two successful cases; this is limited clinical evidence.
  - reference: PMID:42577265
    reference_title: Novel pathogenic CTLA4 missense variant associated with autoimmune enteropathy and systemic immune dysregulation.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Despite subsequent aggressive sequential therapy with conventional (mesalamine, azathioprine, thalidomide) and biological agents (infliximab, adalimumab, vedolizumab, and ustekinumab), his symptoms progressed over time
    explanation: The Phe56Cys case demonstrates failure of several empiric therapies, including vedolizumab.
  therapeutic_modality: MONOCLONAL_ANTIBODY
  notes: In the p.Phe56Cys case, mesalamine, azathioprine, thalidomide, infliximab, adalimumab, vedolizumab and ustekinumab were unsuccessful sequential treatments before the molecular diagnosis. This negative experience does not establish these drugs as effective CTLA4-directed treatment options.
- name: Methotrexate
  description: Methotrexate has been used for psoriatic skin disease in a small treated subgroup. It is not uniformly suitable for patients with hepatic involvement.
  action_category: THERAPEUTIC
  treatment_term:
    preferred_term: Immunosuppressive Therapy
    term:
      id: NCIT:C15261
      label: Immunosuppressive Therapy
    therapeutic_agent:
    - preferred_term: Methotrexate
      term:
        id: NCIT:C642
        label: Methotrexate
  evidence:
  - reference: url:https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf
    reference_title: https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: 3 received methotrexate (7.5-20 mg per week) with good effect
    explanation: Full text of Egg et al., Therapeutic options for CTLA-4 insufficiency (PMID:34111452). The skin subgroup reports improvement in three treated patients.
  - reference: PMID:31396201
    reference_title: Preponderance of CTLA4 Variation Associated With Autosomal Dominant Immune Dysregulation in the MYPPPY Motif.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Methotrexate was not used due to her underlying liver disease.
    explanation: The hepatic case illustrates why treatment choice depends on organ involvement.
  therapeutic_modality: SMALL_MOLECULE
- name: Cyclosporine
  description: Cyclosporine has been used for severe skin or lung infiltration and cytopenia; a skin response was reported in one of two treated cases.
  action_category: THERAPEUTIC
  treatment_term:
    preferred_term: Immunosuppressive Therapy
    term:
      id: NCIT:C15261
      label: Immunosuppressive Therapy
    therapeutic_agent:
    - preferred_term: Cyclosporine
      term:
        id: NCIT:C406
        label: Cyclosporine
  evidence:
  - reference: url:https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf
    reference_title: https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: 2 patients received cyclospori ne (2-5 mg/kg) for severe infiltration of skin and lung and for concomitant cytopenia. In 1 patient cyclosporine alleviated the skin lesions
    explanation: Full text of Egg et al., Therapeutic options for CTLA-4 insufficiency (PMID:34111452). The cohort provides only a small observational treatment experience.
  therapeutic_modality: SMALL_MOLECULE
- name: Cyclophosphamide
  description: Cyclophosphamide with corticosteroids has been used for inflammatory CNS lesions. Small retrospective experience does not establish comparative efficacy.
  action_category: THERAPEUTIC
  treatment_term:
    preferred_term: Immunosuppressive Therapy
    term:
      id: NCIT:C15261
      label: Immunosuppressive Therapy
    therapeutic_agent:
    - preferred_term: Cyclophosphamide
      term:
        id: NCIT:C405
        label: Cyclophosphamide
  evidence:
  - reference: url:https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf
    reference_title: https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Cyclophosphamide (2 X 200 mg/m 2) plus corticosteroids was tried in 3 cases (2 patients received 5 mg per day and 1 received 40 mg per day). Of these 3 patients, 2 showed a good clinical response
    explanation: Full text of Egg et al., Therapeutic options for CTLA-4 insufficiency (PMID:34111452). Two of three cases improved under a combination regimen.
  therapeutic_modality: SMALL_MOLECULE
- name: Mercaptopurine
  description: A refractory celiac-like case had partial improvement with mercaptopurine, but cytopenias limited its use. This is case-level evidence rather than a general treatment recommendation.
  action_category: THERAPEUTIC
  treatment_term:
    preferred_term: Immunosuppressive Therapy
    term:
      id: NCIT:C15261
      label: Immunosuppressive Therapy
    therapeutic_agent:
    - preferred_term: Mercaptopurine
      term:
        id: NCIT:C195
        label: Mercaptopurine
  evidence:
  - reference: PMID:35935971
    reference_title: 'Cytotoxic T Lymphocyte Antigen 4 Haploinsufficiency Presenting As Refractory Celiac-Like Disease: Case Report.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: She had partial symptomatic and endoscopic improvement with 6MP, but use was limited by cytopenias.
    explanation: The case describes both benefit and toxicity.
  therapeutic_modality: SMALL_MOLECULE
- name: Topical anti-inflammatory treatment
  description: Topical corticosteroids and, when appropriate, topical tacrolimus or pimecrolimus are included in expert skin-management protocols. These recommendations do not establish CTLA4-specific comparative efficacy.
  action_category: THERAPEUTIC
  treatment_term:
    preferred_term: Immunosuppressive Therapy
    term:
      id: NCIT:C15261
      label: Immunosuppressive Therapy
    therapeutic_agent:
    - preferred_term: Tacrolimus
      term:
        id: NCIT:C1311
        label: Tacrolimus
    - preferred_term: Pimecrolimus
      term:
        id: NCIT:C47671
        label: Pimecrolimus
  evidence:
  - reference: url:https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf
    reference_title: https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf
    supports: SUPPORT
    evidence_source: OTHER
    snippet: As first-line therapy, we suggest topical treatment with corticosteroids and as second-line topical tac rolimus, respectively pimecrolimus for skin lesions in the face.
    explanation: Full text of Egg et al., Therapeutic options for CTLA-4 insufficiency (PMID:34111452). The expert protocol describes local skin management.
  therapeutic_modality: SMALL_MOLECULE
- name: Immunoglobulin replacement
  description: Replacement immunoglobulin is used for clinically significant antibody deficiency and recurrent infections. It does not reliably prevent the autoimmune cytopenias of CTLA4 insufficiency.
  action_category: THERAPEUTIC
  treatment_term:
    preferred_term: Immunoglobulin Therapy
    term:
      id: NCIT:C62710
      label: Immunoglobulin Therapy
  evidence:
  - reference: PMID:34111452
    reference_title: Therapeutic options for CTLA-4 insufficiency.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Immunoglobulin replacement was effective in prevention of infection.
    explanation: The treatment cohort supports infection prevention.
  - reference: url:https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf
    reference_title: https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: IgRT does not protect against this complication in CTLA-4 insufficiency
    explanation: Full text of Egg et al., Therapeutic options for CTLA-4 insufficiency (PMID:34111452). The cohort specifically discusses autoimmune cytopenia arising despite replacement therapy.
  therapeutic_modality: PROTEIN_REPLACEMENT
- name: Immunomodulatory intravenous immunoglobulin
  description: IVIG has also been used at immunomodulatory intensity for autoimmune cytopenia or inflammatory CNS disease, a distinct indication from antibody replacement.
  action_category: THERAPEUTIC
  treatment_term:
    preferred_term: Immunoglobulin Therapy
    term:
      id: NCIT:C62710
      label: Immunoglobulin Therapy
  evidence:
  - reference: url:https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf
    reference_title: https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: High-dose intravenous immunoglobulin (IVIG) (1 g/kg ) was added to steroids in 7 patients, with 6 (86%) showing beneficial effects.
    explanation: Full text of Egg et al., Therapeutic options for CTLA-4 insufficiency (PMID:34111452). The CNS subgroup documents adjunctive IVIG with corticosteroids.
  therapeutic_modality: OTHER
- name: Thrombopoietin receptor agonists
  description: TPO-receptor agonists have been tried for refractory immune thrombocytopenia, with limited response in the reported CTLA4 cohort.
  action_category: THERAPEUTIC
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
  evidence:
  - reference: url:https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf
    reference_title: https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: We documented 4 applications of TPO-RAs in our CTL A-4 cohort, but a satisfying stabilization of platelet count could be reached in only 1 case.
    explanation: Full text of Egg et al., Therapeutic options for CTLA-4 insufficiency (PMID:34111452). Only one of four reported uses achieved satisfactory platelet stabilization.
- name: Hematopoietic stem cell transplantation
  action_category: THERAPEUTIC
  therapeutic_modality: CELL_THERAPY
  description: Allogeneic HSCT can achieve durable disease remission in severe refractory immune dysregulation, but carries substantial transplant-related risk. The 2024 European cohort included both CTLA4 insufficiency and larger 2q33 deletions; its outcomes should not be treated as a pure CTLA4 estimate. Lower pretransplant disease activity was associated with better survival.
  evidence:
  - reference: PMID:39218359
    reference_title: 'Hematopoietic stem cell transplantation for CTLA-4 insufficiency across Europe: A European Society for Blood and Marrow Transplantation Inborn Errors Working Party study.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: At latest follow-up, disease of 28 of 30 surviving patients was in disease-free remission with median IDDA reduction of 16.
    explanation: Surviving patients commonly achieved remission; this survivor fraction is not overall survival.
  - reference: PMID:39218359
    reference_title: 'Hematopoietic stem cell transplantation for CTLA-4 insufficiency across Europe: A European Society for Blood and Marrow Transplantation Inborn Errors Working Party study.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Cause of death was transplant related in 7 of 8 patients.
    explanation: The cohort documents material transplant-related mortality.
  - reference: PMID:39218359
    reference_title: 'Hematopoietic stem cell transplantation for CTLA-4 insufficiency across Europe: A European Society for Blood and Marrow Transplantation Inborn Errors Working Party study.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Probability of OS and DFS was greater in patients with lower disease activity before HSCT (IDDA < 23, P = .002 and P = .006, respectively).
    explanation: The retrospective association supports attention to pretransplant disease burden.
  treatment_term:
    preferred_term: Allogeneic Hematopoietic Stem Cell Transplantation
    term:
      id: NCIT:C46089
      label: Allogeneic Hematopoietic Stem Cell Transplantation
- name: Splenectomy considerations
  action_category: THERAPEUTIC
  therapeutic_modality: SURGERY
  description: Splenectomy has been used for severe cytopenia, but sustained responses were uncommon in the reported cohort. The 2022 expert protocol advises avoiding it when possible and considering medical therapy or HSCT according to disease severity.
  evidence:
  - reference: url:https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf
    reference_title: https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Of the cohort p atients, 16 had a splenectomy (median age 20 years), with only 4 (25%) showing a sustained response
    explanation: Full text of Egg et al., Therapeutic options for CTLA-4 insufficiency (PMID:34111452). The retrospective response rate argues against assuming durable control.
  treatment_term:
    preferred_term: Splenectomy
    term:
      id: NCIT:C15328
      label: Splenectomy
- name: Antibiotic prophylaxis and infection treatment
  action_category: THERAPEUTIC
  description: Antimicrobial prophylaxis and prompt treatment of infection are tailored to immune deficits, immunosuppression and structural lung disease. The cohort reported trimethoprim-sulfamethoxazole, azithromycin and postsplenectomy penicillin use.
  evidence:
  - reference: url:https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf
    reference_title: https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Antibiotic prophylaxis was given in 48 (39%) of the 123 cases. The most used antibiotic for prophylaxis was trimethoprim-sulfamethoxazole (in 2 4 patients) followed by azithromycin (in 6 patients). Penicillin was used prophylactically in 3 patients after splenectomy.
    explanation: Full text of Egg et al., Therapeutic options for CTLA-4 insufficiency (PMID:34111452). The cohort documents actual prophylactic regimens; it does not establish comparative benefit.
  treatment_term:
    preferred_term: Antibiotic Therapy
    term:
      id: NCIT:C15620
      label: Antibiotic Therapy
- name: Nutritional support
  action_category: THERAPEUTIC
  description: Severe enteropathy may require enteral feeding or parenteral nutrition. Gluten-free or lactose-restricted diets address demonstrated sensitivities; gluten avoidance alone may fail in CTLA4-associated celiac-like disease.
  evidence:
  - reference: PMID:42577265
    reference_title: Novel pathogenic CTLA4 missense variant associated with autoimmune enteropathy and systemic immune dysregulation.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: requiring continuous nasogastric enteral nutrition and intermittent parenteral nutrition.
    explanation: The severe enteropathy case required both routes of nutritional support.
  - reference: PMID:35935971
    reference_title: 'Cytotoxic T Lymphocyte Antigen 4 Haploinsufficiency Presenting As Refractory Celiac-Like Disease: Case Report.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: We present two patients with celiac/celiac-like disease diagnosed in early childhood and refractory to the gluten-free diet.
    explanation: The cases show that diet alone may not control genetically mediated enteropathy.
  treatment_term:
    preferred_term: Nutritional Support
    term:
      id: NCIT:C15433
      label: Nutritional Support
- name: Endocrine replacement for associated autoimmunity
  action_category: THERAPEUTIC
  description: Treat documented autoimmune thyroid or adrenal insufficiency with appropriate endocrine replacement. A reported patient required levothyroxine, fludrocortisone and hydrocortisone in addition to immune-directed therapy.
  evidence:
  - reference: PMID:35935971
    reference_title: 'Cytotoxic T Lymphocyte Antigen 4 Haploinsufficiency Presenting As Refractory Celiac-Like Disease: Case Report.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Her co-morbid autoimmune diseases are well controlled with levothyroxine, fludrocortisone, hydrocortisone, and topical dermatologic therapies.
    explanation: The case records replacement treatment for documented endocrine disease.
- name: Longitudinal surveillance and family counseling
  action_category: MONITORING
  description: Follow affected and apparently unaffected carriers for evolving immune dysregulation. Monitor lymphoproliferation and EBV/CMV complications, especially during immunosuppression, and investigate suspicious lesions. Counsel relatives about incomplete penetrance and possible late presentation.
  evidence:
  - reference: PMID:29729943
    reference_title: Phenotype, penetrance, and treatment of 133 cytotoxic T-lymphocyte antigen 4-insufficient subjects.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Family members should be counseled because disease manifestation can occur as late as 50 years of age. EBV- and cytomegalovirus-associated complications must be closely monitored.
    explanation: The carrier cohort supports counseling and ongoing surveillance.
  - reference: PMID:30250467
    reference_title: Increased Risk for Malignancies in 131 Affected CTLA4 Mutation Carriers.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Hence, lymphoproliferation and EBV viral load in blood should be carefully monitored, especially when immunosuppressing affected CTLA4 mutation carriers.
    explanation: The malignancy study emphasizes surveillance during immune-directed treatment.
  notes: Needs an allowed action term for combined surveillance and counseling. NCIT Surveillance and Patient Monitoring fall outside the TreatmentActionTerm closure.
- name: Sulfasalazine
  action_category: THERAPEUTIC
  therapeutic_modality: SMALL_MOLECULE
  description: Oral sulfasalazine is included as an initial enteropathy option in the 2022 expert management protocol. The recommendation is not a demonstrated CTLA4-specific response estimate or trial result.
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: Sulfasalazine
      term:
        id: NCIT:C29469
        label: Sulfasalazine
  evidence:
  - reference: url:https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf
    reference_title: https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf
    supports: SUPPORT
    evidence_source: OTHER
    snippet: In cases of inflammation without known antigen, we recommend a stepwise protocol starting with (1) topical corticosteroids in the form of budesonide (a combination of standard budesonide for the small bowels and retard capsules for the large bowels) or use of oral sulfasalazine;
    explanation: Full text of Egg et al., Therapeutic options for CTLA-4 insufficiency (PMID:34111452). The authors propose this stepwise management option rather than report a sulfasalazine-treated cohort outcome.
datasets:
- accession: dbgap:phs000797
  title: CTLA4 haploinsufficiency and immune dysregulation
  description: We identified germline heterozygous mutations in  CTLA4  in members of four families with severe immune dysregulation. Human  CTLA4  haploinsufficiency caused dysregulation of FoxP3+ regulatory T (Treg) cells and lymphocytic infiltration of target organs, mimicking  Ctla4  homozygous mice. Patients also exhibited a B cell phenotype, with progressive loss of B cells and accumulation of autoreactive CD21 lo  B cells. This study demonstrates a critical quantitative role for CTLA-4 in human immune homeostasis.
  notes: Human family sequencing study underlying the discovery of germline CTLA4-associated immune dysregulation. Individual-level genomic data are subject to repository access controls.
notes: CTLA4 insufficiency encompasses both quantitative haploinsufficiency and defective function of expressed protein. Clinical cohorts are overlapping and variably ascertained; their case counts and treatment responses should not be pooled as independent observations. Current functional assays can detect pathway defects in asymptomatic carriers and do not by themselves establish future clinical penetrance. The ORBi PDF is the author postprint of Egg et al., Therapeutic options for CTLA-4 insufficiency (PMID:34111452; DOI:10.1016/j.jaci.2021.04.039). It provides the full-text treatment and functional-assay evidence for that publication, not an independent study.
discussions:
- discussion_id: ctla4-cell-intrinsic-effects
  kind: CONTROVERSY
  status: OPEN
  prompt: Which abnormalities require intrinsic CTLA4 function in conventional T cells or B cells, rather than loss of Treg-mediated restraint?
  attaches_to:
  - pathophysiology#Excess Effector T Cell Activation
  rationale: The founding studies agree on deficient Treg suppression but differ in conventional T-cell hyperproliferation and detectable B-cell CTLA4. Mixed PBMC assays cannot isolate cell-intrinsic effects, and B-cell apoptosis and autoreactivity do not establish their initiating mechanism.
  evidence:
  - reference: PMID:25213377
    reference_title: Immune dysregulation in human subjects with heterozygous germline mutations in CTLA4.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: CTLA-4–deficient patient T cells were hyperproliferative, with an increased percentage expressing CD25 in response to T cell receptor stimulation
    explanation: Stimulated patient cultures show excess activation; this experiment alone does not establish a conventional T-cell-intrinsic defect.
  - reference: PMID:25329329
    reference_title: Autosomal dominant immune dysregulation syndrome in humans with CTLA4 mutations.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: we did not observe any obvious alterations in conventional T cell proliferation (data not shown).
    explanation: The independent discovery study did not reproduce the proposed conventional T-cell phenotype under its assay conditions.
  - reference: PMID:25329329
    reference_title: Autosomal dominant immune dysregulation syndrome in humans with CTLA4 mutations.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: we were unable to detect CTLA-4 expression on B cells in the conditions we tested
    explanation: B-cell CTLA4 detection differed between the founding studies.
- discussion_id: ctla4-murine-dose-response
  kind: HUMAN_MODEL_MISMATCH
  status: OPEN
  prompt: Why does heterozygous CTLA4 deficiency produce human disease while heterozygous mice lack an obvious comparable phenotype?
  rationale: Complete Ctla4 loss or lymphopenic adoptive-transfer models demonstrate checkpoint dependence but do not reproduce the dosage and incomplete penetrance of human heterozygosity.
  evidence:
  - reference: PMID:25213377
    reference_title: Immune dysregulation in human subjects with heterozygous germline mutations in CTLA4.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: In contrast, heterozygous Ctla4 deficiency in mice shows no obvious phenotype
    explanation: The discovery study explicitly identifies the species and dosage mismatch.
diagnosis:
- name: Molecular diagnosis with variant interpretation
  description: Sequence CTLA4 in patients with compatible immune dysregulation, including CVID-like disease or refractory enteropathy. Interpret novel variants with functional evidence and consider alternative checkpoint disorders such as LRBA and DEF6 deficiency.
  evidence:
  - reference: PMID:35935971
    reference_title: 'Cytotoxic T Lymphocyte Antigen 4 Haploinsufficiency Presenting As Refractory Celiac-Like Disease: Case Report.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Celiac disease cannot be distinguished from enteropathy secondary to CTLA4 deficiency solely by histopathology and, therefore, genetic testing is essential to identify this as an etiology of refractory celiac-like disease.
    explanation: The case series supports molecular investigation when clinical and histologic findings overlap.
- name: CTLA4 expression in memory regulatory T cells
  description: Flow cytometry of CD45RA-negative Foxp3-positive memory Tregs provides a more informative comparison than total CD4 cells. Reduced staining supports a defect but normal staining does not exclude functional CTLA4 insufficiency.
  evidence:
  - reference: PMID:28159733
    reference_title: Identifying functional defects in patients with immune dysregulation due to LRBA and CTLA-4 mutations.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: Assessing total CTLA-4 expression levels was found to be optimal when restricting analysis to the CD45RA-Foxp3+ fraction.
    explanation: The assay study identifies the most informative cell subset.
  - reference: url:https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf
    reference_title: https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: Although Treg cells with the variant p.F179Cfs*29 had normal CTLA-4 expression, the frequency of CD80 uptake in Treg cells was as reduced as in 3 additional deleterious variants
    explanation: Full text of Egg et al., Therapeutic options for CTLA-4 insufficiency (PMID:34111452). A patient-cell assay shows why expression alone can miss a functional defect.
- name: Functional ligand uptake and transendocytosis
  description: Measure uptake of CD80/CD86 ligands to evaluate functional impact, including variants with preserved antibody staining. Soluble ligand uptake integrates trafficking and binding; cell-to-cell assays directly assess transendocytosis. Neither assay alone predicts clinical penetrance.
  evidence:
  - reference: PMID:28159733
    reference_title: Identifying functional defects in patients with immune dysregulation due to LRBA and CTLA-4 mutations.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: Finally, we developed a functionally orientated assay to measure ligand uptake by CTLA-4, which is sensitive to ligand-binding or -trafficking mutations, that would otherwise be difficult to detect and that is appropriate for testing novel mutations in CTLA-4 pathway genes.
    explanation: The functional assay detects defects missed by abundance measurements.
- name: Immunoglobulins and lymphocyte subsets
  description: Assess serum immunoglobulins, antibody responses and lymphocyte subsets, including circulating B cells, switched memory cells and CD21-low cells. Interpret results in relation to immunosuppressive treatment and organ inflammation.
  evidence:
  - reference: PMID:29729943
    reference_title: Phenotype, penetrance, and treatment of 133 cytotoxic T-lymphocyte antigen 4-insufficient subjects.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: B cell subsets showed a decrease in switched memory B cells (23/30) and consecutively a relative increase in naïve B cells (14/29).
    explanation: The cohort identifies characteristic immunophenotypic abnormalities.
- name: Organ evaluation and exclusion of competing causes
  description: Investigate gastrointestinal, pulmonary or neurologic symptoms with appropriate imaging, functional assessment, endoscopy or biopsy. Distinguish immune infiltration from infection and malignancy before attributing lesions to CTLA4 insufficiency.
  evidence:
  - reference: PMID:35935971
    reference_title: 'Cytotoxic T Lymphocyte Antigen 4 Haploinsufficiency Presenting As Refractory Celiac-Like Disease: Case Report.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: exclusion of infectious etiologies of chronic diarrhea is a critical component of evaluation.
    explanation: The GI report emphasizes excluding chronic infection.
  - reference: url:https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf
    reference_title: https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf
    supports: SUPPORT
    evidence_source: OTHER
    snippet: Hepatomegaly, splenomegaly, or regional lymphadeno pathy should be carefully monitored, and if malignancy is suspected, a biopsy should be performed.
    explanation: Full text of Egg et al., Therapeutic options for CTLA-4 insufficiency (PMID:34111452). The expert protocol recommends evaluating suspicious lymphoproliferation rather than assuming it is benign.
clinical_trials:
- name: DRKS00017736
  phase: PHASE_II
  status: COMPLETED
  description: ABACHAI was an open-label, uncontrolled phase IIa study of weekly subcutaneous abatacept for 12 months in adults with CTLA4 insufficiency or LRBA deficiency. The 2026 publication reports 20 participants, including 18 with CTLA4 insufficiency. Infection control was the primary endpoint; organ response and quality of life were secondary endpoints.
  evidence:
  - reference: ICTRP:DRKS00017736
    reference_title: Safety and Efficacy of abatacept (s.c.) in patients with CTLA4 insufficiency or LRBA deficiency
    supports: SUPPORT
    evidence_source: OTHER
    snippet: '| Phase | 2 |'
    explanation: The official registry specifies phase II.
  - reference: ICTRP:DRKS00017736
    reference_title: Safety and Efficacy of abatacept (s.c.) in patients with CTLA4 insufficiency or LRBA deficiency
    supports: SUPPORT
    evidence_source: OTHER
    snippet: '| Date of completion | 28/06/2023 |'
    explanation: The registry records study completion.
  - reference: PMID:42763023
    reference_title: ABACHAI - Safety and efficacy of abatacept (s.c.) in patients with CTLA4 insufficiency or LRBA deficiency, a phase II clinical trial.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The primary endpoint was safety, defined as the number of episodes of failed infection control. Secondary endpoints included additional safety parameters, efficacy outcomes, and patient-reported quality of life.
    explanation: The results paper specifies the endpoint hierarchy.
experimental_models:
- name: CHO cells expressing CTLA4 variants
  experimental_model_type: CELL_LINE
  description: CHO cells expressing individual CTLA4 alleles measure protein abundance and soluble CD80 uptake without co-expression of the human wild-type allele.
  publication: PMID:25329329
  modeled_mechanisms:
  - target: Deficient CTLA4 ligand capture
    relationship: MEASURES
    fidelity: MODERATE
    model_scale: MOLECULAR
    limitations: Variant overexpression without the wild-type allele does not reproduce human heterozygosity; uptake includes trafficking and binding.
  evidence:
  - reference: PMID:25329329
    reference_title: Autosomal dominant immune dysregulation syndrome in humans with CTLA4 mutations.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: Full-length CTLA4 protein was detected in cells transfected with the CTLA4 mutants R70W (Family C) and T124P
    explanation: The transfected-cell system separates expressed protein from deficient uptake.
- name: Patient Treg suppression coculture
  experimental_model_type: CO_CULTURE
  description: Patient-derived Tregs are combined with healthy responder T cells and dendritic cells under ligand-dependent stimulation.
  publication: PMID:25329329
  modeled_mechanisms:
  - target: Impaired regulatory T-cell suppression
    relationship: MEASURES
    fidelity: MODERATE
    model_scale: CELLULAR
    limitations: Assay conditions do not reproduce the full multicellular disease.
  evidence:
  - reference: PMID:25329329
    reference_title: Autosomal dominant immune dysregulation syndrome in humans with CTLA4 mutations.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: Treg cells from individuals with CTLA4 heterozygous mutations were unable to suppress CD4+ T cell proliferation as compared to healthy CTLA4+/+ controls
    explanation: The coculture directly measures CTLA4-dependent regulatory suppression.
- name: CTLA4 knockdown and rescue in human lymphocytes
  experimental_model_type: PRIMARY_CELL_CULTURE
  description: CTLA4 knockdown in healthy PBMCs and wild-type expression or CTLA4-Ig treatment in patient cultures test the relationship between checkpoint abundance and proliferation.
  publication: PMID:25213377
  modeled_mechanisms:
  - target: Excess Effector T Cell Activation
    relationship: RESCUES
    fidelity: MODERATE
    model_scale: CELLULAR
    limitations: Mixed lymphocyte cultures do not isolate an intrinsic conventional T-cell defect; independent studies did not reproduce that interpretation.
  evidence:
  - reference: PMID:25213377
    reference_title: Immune dysregulation in human subjects with heterozygous germline mutations in CTLA4.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: overexpression of wild-type CTLA-4 in patient T cells suppressed the hyperproliferation
    explanation: Restoration reverses the measured proliferation phenotype.
- name: HEK293T Phe56Cys functional assays
  experimental_model_type: CELL_LINE
  description: Transfected HEK293T cells compare disulfide-linked dimerization, total and surface CTLA4, and soluble CD80/CD86 binding.
  publication: PMID:42577265
  modeled_mechanisms:
  - target: Impaired CTLA4 dimerization
    relationship: MEASURES
    fidelity: MODERATE
    model_scale: MOLECULAR
    limitations: Ectopic expression in kidney-derived cells omits the heterozygous Treg context.
  - target: Deficient CTLA4 ligand capture
    relationship: MEASURES
    fidelity: MODERATE
    model_scale: MOLECULAR
    limitations: Binding measurements are confounded by reduced surface expression and do not isolate affinity.
  evidence:
  - reference: PMID:42577265
    reference_title: Novel pathogenic CTLA4 missense variant associated with autoimmune enteropathy and systemic immune dysregulation.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: ectopic expression of the CTLA4 p.Phe56Cys variant rather than the wild-type CTLA4 in HEK293T cells resulted in reduced CTLA4 dimerization under non-reducing sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) conditions (which allows visualization of disulfide bond-dependent dimers, see Methods)
    explanation: The assay demonstrates reduced dimerization in an ectopic expression system.
- name: Gene-edited patient T cells
  experimental_model_type: PRIMARY_CELL_CULTURE
  description: CRISPR-Cas9 and AAV6-directed homology repair at the first CTLA4 intron restore regulated CTLA4 expression and ligand transendocytosis in patient-derived T cells. This is preclinical rescue, not evidence of clinical benefit.
  publication: PMID:36288278
  modeled_mechanisms:
  - target: Reduced CD80/CD86 transendocytosis
    relationship: RESCUES
    fidelity: MODERATE
    model_scale: CELLULAR
    limitations: In-vitro correction does not establish the required corrected-cell fraction, durable clinical efficacy or long-term safety.
  evidence:
  - reference: PMID:36288278
    reference_title: Therapeutic gene editing of T cells to correct CTLA-4 insufficiency.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: Gene editing of T cells isolated from three patients with CTLA-4 insufficiency also restored CTLA-4 protein expression and rescued transendocytosis of CD80 and CD86 in vitro.
    explanation: Three patient-derived cellular preparations showed restoration of function.
animal_models:
- name: Gene-corrected Ctla4-null T cells transferred into Rag2-null mice
  species: Mouse
  genotype: Rag2-null recipients of edited or control Ctla4-null donor T cells
  description: Edited donor T cells persist and prevent lymphoid enlargement and cardiac infiltration during a four-week adoptive-transfer experiment. This is correction of transferred cells, not germline correction of the recipient animal.
  publication: PMID:36288278
  modeled_mechanisms:
  - target: Non-malignant lymphoproliferation
    relationship: RESCUES
    fidelity: MODERATE
    model_scale: ORGANISM
    limitations: Lymphopenic recipients of Ctla4-null cells differ from heterozygous human disease; follow-up lasted four weeks.
  - target: Lymphocytic Tissue Infiltration
    relationship: RESCUES
    fidelity: MODERATE
    model_scale: ORGANISM
    limitations: The measured tissue outcome was cardiac infiltration, not the complete human multiorgan spectrum.
  evidence:
  - reference: PMID:36288278
    reference_title: Therapeutic gene editing of T cells to correct CTLA-4 insufficiency.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: Murine CTLA4-/- T cells were edited (gRNA 5, HDR donor 5) or mock edited and then adoptively transferred into adult Rag2-/- mice without conditioning.
    explanation: The study defines the donor-cell and recipient genotypes.
  - reference: PMID:36288278
    reference_title: Therapeutic gene editing of T cells to correct CTLA-4 insufficiency.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: only mice from groups that had received mock-edited or GFP- T cells showed elevated cardiac tissue infiltration
    explanation: The edited-cell recipients were protected from the measured cardiac inflammatory phenotype.
biochemical:
- name: Soluble interleukin-2 receptor
  notes: A nonspecific marker of immune activation, used longitudinally in some CTLA4 cases. Improvement under treatment is not a validated diagnostic threshold or a substitute for clinical assessment.
  evidence:
  - reference: PMID:35935971
    reference_title: 'Cytotoxic T Lymphocyte Antigen 4 Haploinsufficiency Presenting As Refractory Celiac-Like Disease: Case Report.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Soluble IL-2 receptor (i.e., CD25) levels, which were characteristically high at the patient’s diagnosis of CTLA4 haploinsufficiency (9), were monitored on abatacept and trended downward to normal range.
    explanation: A treated case provides longitudinal marker observations.
- name: CTLA4 mRNA expression
  notes: Investigational marker studied in small mixed CTLA4/LRBA and melanoma groups. Treated and untreated groups comprised different individuals, and healthy comparator analyses included asymptomatic carriers. The data do not demonstrate within-patient normalization or a validated severity predictor.
  evidence:
  - reference: PMID:31156616
    reference_title: CTLA4 Message Reflects Pathway Disruption in Monogenic Disorders and Under Therapeutic Blockade.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Patients in the NT and Aba groups represent different individuals in each group.
    explanation: The study design precludes interpreting the group comparison as longitudinal treatment response.
  - reference: PMID:31156616
    reference_title: CTLA4 Message Reflects Pathway Disruption in Monogenic Disorders and Under Therapeutic Blockade.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Future studies evaluating larger patient cohorts are required to further expand this finding and potentially uncover a reliable biomarker for clinical management of these disorders.
    explanation: The authors regard the proposed biomarker as unvalidated.
references:
- reference: CGGV:assertion_e79675bd-3eef-4925-b4ef-3b7c48734f30-2020-12-15T050000.000Z
  title: CTLA4 / autoimmune lymphoproliferative syndrome due to CTLA4 haploinsufficiency (Definitive)
- reference: ICTRP:DRKS00017736
  title: Safety and Efficacy of abatacept (s.c.) in patients with CTLA4 insufficiency or LRBA deficiency
- reference: PMID:25213377
  title: Immune dysregulation in human subjects with heterozygous germline mutations in CTLA4.
- reference: PMID:25329329
  title: Autosomal dominant immune dysregulation syndrome in humans with CTLA4 mutations.
- reference: PMID:28159733
  title: Identifying functional defects in patients with immune dysregulation due to LRBA and CTLA-4 mutations.
- reference: PMID:29729943
  title: Phenotype, penetrance, and treatment of 133 cytotoxic T-lymphocyte antigen 4-insufficient subjects.
- reference: PMID:30250467
  title: Increased Risk for Malignancies in 131 Affected CTLA4 Mutation Carriers.
- reference: PMID:31156616
  title: CTLA4 Message Reflects Pathway Disruption in Monogenic Disorders and Under Therapeutic Blockade.
- reference: PMID:31396201
  title: Preponderance of CTLA4 Variation Associated With Autosomal Dominant Immune Dysregulation in the MYPPPY Motif.
- reference: PMID:33788257
  title: 'Comprehensive comparison between 222 CTLA-4 haploinsufficiency and 212 LRBA deficiency patients: a systematic review.'
- reference: PMID:34111452
  title: Therapeutic options for CTLA-4 insufficiency.
- reference: PMID:35748970
  title: 'Human Inborn Errors of Immunity: 2022 Update on the Classification from the International Union of Immunological Societies Expert Committee.'
- reference: PMID:35935971
  title: 'Cytotoxic T Lymphocyte Antigen 4 Haploinsufficiency Presenting As Refractory Celiac-Like Disease: Case Report.'
- reference: PMID:36262801
  title: 'The ABACHAI clinical trial protocol: Safety and efficacy of abatacept (s.c.) in patients with CTLA-4 insufficiency or LRBA deficiency: A non controlled phase 2 clinical trial.'
- reference: PMID:36288278
  title: Therapeutic gene editing of T cells to correct CTLA-4 insufficiency.
- reference: PMID:39218359
  title: 'Hematopoietic stem cell transplantation for CTLA-4 insufficiency across Europe: A European Society for Blood and Marrow Transplantation Inborn Errors Working Party study.'
- reference: PMID:42577265
  title: Novel pathogenic CTLA4 missense variant associated with autoimmune enteropathy and systemic immune dysregulation.
- reference: PMID:42763023
  title: ABACHAI - Safety and efficacy of abatacept (s.c.) in patients with CTLA4 insufficiency or LRBA deficiency, a phase II clinical trial.
- reference: url:https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf
  title: https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf

📚

References & Deep Research

References

CGGV:assertion_e79675bd-3eef-4925-b4ef-3b7c48734f30-2020-12-15T050000.000Z

CTLA4 / autoimmune lymphoproliferative syndrome due to CTLA4 haploinsufficiency (Definitive)

No top-level findings curated for this source.

ICTRP:DRKS00017736

Safety and Efficacy of abatacept (s.c.) in patients with CTLA4 insufficiency or LRBA deficiency

No top-level findings curated for this source.

PMID:25213377

Immune dysregulation in human subjects with heterozygous germline mutations in CTLA4.

No top-level findings curated for this source.

PMID:25329329

Autosomal dominant immune dysregulation syndrome in humans with CTLA4 mutations.

No top-level findings curated for this source.

PMID:28159733

Identifying functional defects in patients with immune dysregulation due to LRBA and CTLA-4 mutations.

No top-level findings curated for this source.

PMID:29729943

Phenotype, penetrance, and treatment of 133 cytotoxic T-lymphocyte antigen 4-insufficient subjects.

No top-level findings curated for this source.

PMID:30250467

Increased Risk for Malignancies in 131 Affected CTLA4 Mutation Carriers.

No top-level findings curated for this source.

PMID:31156616

CTLA4 Message Reflects Pathway Disruption in Monogenic Disorders and Under Therapeutic Blockade.

No top-level findings curated for this source.

PMID:31396201

Preponderance of CTLA4 Variation Associated With Autosomal Dominant Immune Dysregulation in the MYPPPY Motif.

No top-level findings curated for this source.

PMID:33788257

Comprehensive comparison between 222 CTLA-4 haploinsufficiency and 212 LRBA deficiency patients: a systematic review.

No top-level findings curated for this source.

PMID:34111452

Therapeutic options for CTLA-4 insufficiency.

No top-level findings curated for this source.

PMID:35748970

Human Inborn Errors of Immunity: 2022 Update on the Classification from the International Union of Immunological Societies Expert Committee.

No top-level findings curated for this source.

PMID:35935971

Cytotoxic T Lymphocyte Antigen 4 Haploinsufficiency Presenting As Refractory Celiac-Like Disease: Case Report.

No top-level findings curated for this source.

PMID:36262801

The ABACHAI clinical trial protocol: Safety and efficacy of abatacept (s.c.) in patients with CTLA-4 insufficiency or LRBA deficiency: A non controlled phase 2 clinical trial.

No top-level findings curated for this source.

PMID:36288278

Therapeutic gene editing of T cells to correct CTLA-4 insufficiency.

No top-level findings curated for this source.

PMID:39218359

Hematopoietic stem cell transplantation for CTLA-4 insufficiency across Europe: A European Society for Blood and Marrow Transplantation Inborn Errors Working Party study.

No top-level findings curated for this source.

PMID:42577265

Novel pathogenic CTLA4 missense variant associated with autoimmune enteropathy and systemic immune dysregulation.

No top-level findings curated for this source.

PMID:42763023

ABACHAI - Safety and efficacy of abatacept (s.c.) in patients with CTLA4 insufficiency or LRBA deficiency, a phase II clinical trial.

No top-level findings curated for this source.

url:https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf

https://orbi.uliege.be/bitstream/2268/308264/1/PIIS0091674921008915.pdf

No top-level findings curated for this source.

Deep Research

Deep research results are used as seeds for research; they do not undergo the same validation as the main records and may contain errors. How we use deep research.

Asta ▸

Asta Literature Retrieval: Pathophysiology and clinical mechanisms of CTLA4 Haploinsufficiency. Core disease mechanisms, molecular and cellular...

Asta Scientific Corpus Retrieval 20 citations 2026-04-12T10:11:01.163696

Asta Literature Retrieval: Pathophysiology and clinical mechanisms of CTLA4 Haploinsufficiency. Core disease mechanisms, molecular and cellular...

This report is retrieval-only and is generated directly from Asta results.

Papers retrieved: 20
Snippets retrieved: 20

Relevant Papers

[1] CTLA4 Message Reflects Pathway Disruption in Monogenic Disorders and Under Therapeutic Blockade

Authors: Josselyn E Garcia-Perez, Ryan M. Baxter, D. Kong, R. Tobin, M. McCarter et al.
Year: 2019
Venue: Frontiers in Immunology
URL: https://www.semanticscholar.org/paper/b4e3547d18e57d28d09ecb5698e011ff3fae6f59
DOI: 10.3389/fimmu.2019.00998
PMID: 31156616
PMCID: 6532297
Citations: 16
Summary: Assessment of CTLA4 mRNA expression in CTLA-4-haploinsufficiency, LRBA-deficiency, and ipilimumab-treated melanoma patients demonstrated an inverse correlation between theCTLA4 message and degree of CTla-4 pathway disruption, suggesting that CTLA2 mRNA levels may be a quantifiable surrogate for altered CTLA3 expression.
Evidence snippets:
Snippet 1 (score: 0.464) > CTLA-4 is an important immune checkpoint that modulates tolerance, in which CTLA-4 pathway engagement promotes Treg suppressive function, while its blockade enhances T cell activation. In the absence of a competently functioning CTLA-4 pathway, autoimmunity ensues. Despite differing in genetic origins, the irrevocably linked biology of CTLA-4 and LRBA leads CTLA-4 haploinsufficiency and LRBA deficiency patients to similar clinical ends. Although there have been many attempts to understand underlying disease mechanisms in CTLA-4 haploinsufficiency and LRBA deficiency and correlate genotype with phenotype, none have been successful thus far (13,29). Similarly, investigations into predictive parameters or disease biomarkers that might identify those patients at risk of developing autoimmune complications after CTLA-4 blockade have been unrevealing. In this perspective, we observe an apparent correlation between CTLA4 mRNA levels and the degree of CTLA-4 pathway disruption. In CTLA-4 haploinsufficient and LRBA deficient patients, those that are abatacept non-treated show higher levels of CTLA4 mRNA expression than abatacept-treated patients, who show CTLA4 mRNA expression levels similar to healthy controls. Consistent with this correlation of CTLA-4 pathway disruption, ipilimumab-treated patients demonstrate the highest CTLA4 mRNA expression levels compared to the monogenic patients or healthy controls; particularly, the ipilimumab-treated patients who developed autoimmunity were those who had the highest CTLA4 mRNA expression (most CTLA-4 pathway disruption). These findings represent the first study comparing genetic vs. therapeutic disruptions to the CTLA-4 pathway and suggest the evaluation of CTLA4 mRNA expression as a proxy for severity of CTLA-4 pathway disruption in patients receiving anti-CTLA-4 immunotherapy. Future studies evaluating larger patient cohorts are required to further expand this finding and potentially uncover a reliable biomarker for clinical management of these disorders.

[2] Non-infectious Complications of Common Variable Immunodeficiency: Updated Clinical Spectrum, Sequelae, and Insights to Pathogenesis

Authors: Hsi-en Ho, C. Cunningham-Rundles
Year: 2020
Venue: Frontiers in Immunology
URL: https://www.semanticscholar.org/paper/002847d6f73acda4dbf3e61275000d7b56b68496
DOI: 10.3389/fimmu.2020.00149
PMID: 32117289
PMCID: 7025475
Citations: 175
Influential citations: 15
Summary: Detailed clinical spectrum, organ-specific pathologies and associated sequelae from 623 CVID patients followed in New York since 1974 were analyzed, and recent insights to pathogenesis were reviewed.
Evidence snippets:
Snippet 1 (score: 0.461) > osis, resulting in reduced APC-mediated T cell activation. CTLA4 is essential for the function of Treg cells, which are responsible for maintaining self-tolerance and immune homeostasis. Homozygous recessive LRBA mutations have mostly been identified in childhood onset disease, but compound heterozygous mutations have been identified in adult CVID cohorts (40)(41)(42). In LRBA deficient patients, there are concurrent B cell defects (disturbed development, defective activation, poor plasmablast formation) manifesting as hypogammaglobulinemia, and T cell dysregulation (decreased Treg cell markers, expansion of T follicular helper cells, contraction of T follicular regulatory cells) that may contribute to inflammatory complications (38,42). Clinically, these patients are affected by recurrent infections, autoimmunity, lymphoid hyperplasia, as well as severe inflammatory bowel disease in some (40)(41)(42). Heterozygous CTLA4 mutations, on the other hand, can lead to haploinsufficiency, impaired protein dimerization, or impaired ligand binding, causing an autosomal dominant syndrome with variable penetrance (43)(44)(45)(46). Clinically, this highly variable syndrome is marked by antibody deficiency (84%), lymphoproliferation (73%), autoimmune cytopenia (62%), as well as lung (68%) and gastrointestinal (59%) diseases, amongst additional non-infectious complications, in a large cohort study (n = 133) (46). The elucidation of this molecular pathway and the availability of CTLA4 fusion proteins (abatacept, belatacept) have allowed for the potential for targeted treatment approach. In select cases, the loss of CTLA4 in LRBA deficiency has been successfully treated with abatacept (38). Similarly, some subjects with CTLA4 haploinsufficiency have had positive clinical response to abatacept or belatacept (11/14 subjects in one series) (46). Phosphoinositide 3-kinase (PI3

[3] Non-Celiac Villous Atrophy—A Problem Still Underestimated

Authors: K. Napiórkowska-Baran, Paweł Treichel, Adam Wawrzeńczyk, Ewa Alska, Robert Zacniewski et al.
Year: 2025
Venue: Life
URL: https://www.semanticscholar.org/paper/426f4a37580e1c18878b8d584ac0df940b949cb2
DOI: 10.3390/life15071098
PMID: 40724600
PMCID: 12301050
Citations: 2
Summary: An in-depth understanding of the heterogeneous etiology of NCVA is critical to improving diagnostic accuracy and optimizing therapeutic strategies, and future research should prioritize the identification of specific biomarkers and the development of targeted interventions to address the unique mechanisms underlying NCVA, thereby improving patient management and outcomes.
Evidence snippets:
Snippet 1 (score: 0.453) > Genetic and environmental factors contribute significantly to the pathogenesis of NCVA. These factors act independently and synergistically to affect immune regulation, inflammatory responses, and intestinal health. Genetic predispositions, such as those in monogenic immune disorders, are fundamental to understanding NCVA. Conditions like CTLA4 haploinsufficiency and IL10RA mutations exemplify how specific genetic aberrations lead to immune dysregulation. CTLA4 haploinsufficiency is implicated in autoimmune enteropathy, primarily through dysregulated T-cell activity, culminating in sustained inflammation and tissue destruction in the small intestine. Similarly, mutations in the IL10RA gene, particularly prominent in early-onset inflammatory bowel disease (IBD), disrupt critical anti-inflammatory pathways, allowing unrestrained inflammatory responses that damage the intestinal villi. These findings underscore the importance of genetic analyses in identifying hereditary causes of NCVA, which not only aid in diagnosis but also highlight potential therapeutic targets, such as cytokine modulation or T-cell suppression, tailored to the specific genetic mechanism involved [5,27]. > Regional trends in genetic mutations, such as the prevalence of IL10RA mutations in Southeast Asia, point to the need for geographically specific screening programs. In endemic regions, the burden of NCVA resulting from these mutations underscores how local epidemiological factors must guide diagnostic strategies and public health interventions. For example, infections endemic to these areas may exacerbate genetically predisposed inflammation, illustrating a gene-environment interaction that warrants proactive regional genetic and clinical monitoring. Targeted genetic testing, combined with an understanding of local environmental influences, facilitates early identification and prevention of complications in high-risk populations [27]. > Genetic testing is crucial in identifying CTLA4 haploinsufficiency, which often underlies autoimmune enteropathies. Identifying inherited mutations allows early intervention through therapies such as immunomodulation, targeting specific genetic mechanisms re-sponsible for disease progression. Moreover, the findings argue for family screening, since relatives of affected individuals may share genetic susceptibilities.

[4] Chronically Activated T-cells Retain Their Inflammatory Properties in Common Variable Immunodeficiency

Authors: Roos-Marijn Berbers, M. van der Wal, J. V. van Montfrans, P. Ellerbroek, Virgil A. S. H. Dalm et al.
Year: 2021
Venue: Journal of Clinical Immunology
URL: https://www.semanticscholar.org/paper/1dc4de90022a3d4abaabc387e7674af8d7181a2d
DOI: 10.1007/s10875-021-01084-6
PMID: 34247288
PMCID: 8452589
Citations: 24
Influential citations: 1
Summary: CVIDid was characterized by chronic activation of peripheral T-cells with preserved inflammatory potential rather than functional exhaustion, and increased tissue migratory capacity, and combined studies of T-cell dysfunction and circulating inflammatory proteins may direct future treatment strategies.
Evidence snippets:
Snippet 1 (score: 0.442) > In addition to this chronically activated T-cell state, we observed a decreased ability of Tregs to upregulate CTLA4, while CTLA4 expression was increased in the whole CD4 + population. Expression of CTLA4 by Tregs is an important mechanism by which Tregs mediate their suppressive function [33]. Clinical CTLA4 haploinsufficiency often results in a CVIDid phenotype with hypogammaglobulinemia and autoimmune disease, and functional Treg dysfunction has been described [19]. In this study, the T-cell profile of the patient with CTLA4 haploinsufficiency was often not very different from the other non-genetic CVIDid patients. Therefore, the expression of CTLA4 in Tregs of non-genetic CVIDid patients may be relevant to the overall underlying pathophysiology of CVIDid and warrants further research. A recent study shows that abatacept, a CTLA4 fusion protein, was safe and effective in the treatment of CVIDid with interstitial lung disease [34]. As the population of CVIDid patients with low CTLA4 + CD27 + Tregs represented a mix of patients with pulmonary inflammation but also other organ-specific autoimmunity (data not shown), abatacept may be efficacious in other CVIDid patients as well. In addition, longitudinal monitoring of CTLA4 Treg expression in CVIDid may indicate whether it can be used as a biomarker for disease exacerbation and/or therapeutic response. > Despite these overall differences between CVIDid and CVIDio, the heterogeneity within the CVIDid group was substantial. Subgroup analyses of patients with organspecific autoimmunity did not yield insightful patterns, except that GLILD patients were often more extreme in all observed differences (data not shown). In addition, disease severity did not always reflect immune activation.

[5] Anti-CTLA-4 Induced Inflammatory Bowel Disease: Is There A More Etiological Treatment? Lessons From CTLA-4 Haploinsufficiency

Authors: Athina Theocharidou, Georgios Germanidis
Year: 2018
Venue: Gastroenterology: Medicine & Research
URL: https://www.semanticscholar.org/paper/d5d6f885c8265794ece2edfa012aec3a0fa4fce7
DOI: 10.31031/GMR.2018.01.000525
Summary: The immunological characteristics of anti-CTLA-4 and anti-PD-1-related colitis have been up to now poorly described and may need to be better described.
Evidence snippets:
Snippet 1 (score: 0.433) > Although the frequency of FoxP3+ Treg cells within the CD4+ T cell compartment was increased in individuals with a heterozygous CTLA4 mutation compared to healthy CTLA4+/+ controls, affected patients had reduced CTLA-4 protein (similarly as to use a neutralizing CTLA-4 antibody) and mRNA expression in sorted Treg cells relative to healthy donors; this reduction persisted, and deficit was even more pronounced after T cell activation [3]. These results demonstrate the complex spectrum of clinical complications that can be anticipated from CTLA-4-blocking drugs. Consistent with these findings, treatment with the CTLA-4 mimetic, CTLA-4-Ig (abatacept), suppressed patients T cell hyperproliferation in vitro and could be a potential therapeutic intervention for CTLA-4deficient patients [3]. Therefore, human CTLA-4 haploinsufficiency demonstrates a critical quantitative role for CTLA-4 in governing T and B lymphocyte homeostasis [3]. CTLA-4 can function by removal of its ligands (CD80 and CD86) from antigen presenting cells via transendocytosis. > These CTLA-4 ligands are shared with the stimulatory receptor CD28, whose engagement drives T cell activation, cytokine production and memory T cell differentiation. Depletion of the costimulatory ligands CD80 and CD86 by CTLA-4 reduces antigen presenting cell-mediated activation of conventional T cells via CD28, resulting in dominant suppression of T cell activation [4]. Treg cells from individuals with CTLA4 heterozygous mutations were unable to suppress CD4+ T cell proliferation as compared to healthy CTLA4+/+ controls. > Taken together, these data indicate that two functional CTLA4 alleles appear necessary to drive the high levels of protein required in activated Treg cells, and in this condition their overall suppressive activity is impaired by CTLA-4 mutations. The relative role of CTLA-4 in Treg cells versus conventional T cells remains unexplained and additional work is needed to interprete the T cell-intrinsic hyperproliferation in these patients bearing CTLA4 mutations.

[6] Cytotoxic T Lymphocyte Antigen 4 Haploinsufficiency Presenting As Refractory Celiac-Like Disease: Case Report

Authors: Lauren V Collen, C. Salgado, B. Bao, E. Janssen, D. Weir et al.
Year: 2022
Venue: Frontiers in Immunology
URL: https://www.semanticscholar.org/paper/6069ef76f4203c38aa8a45e4d9e13bd2918981b6
DOI: 10.3389/fimmu.2022.894648
PMID: 35935971
PMCID: 9352891
Citations: 6
Summary: Two patients with celiac/celiac-like disease diagnosed in early childhood and refractory to the gluten-free diet are presented and diagnosed with cytotoxic T lymphocyte antigen 4 (CTLA4) haploinsufficiency, which has incomplete penetrance and significant phenotypic heterogeneity.
Evidence snippets:
Snippet 1 (score: 0.420) > To our knowledge, this is the first detailed report of CTLA4 haploinsufficiency presenting with refractory celiac-like disease as the primary manifestation. These cases highlight the value of keeping a high index of suspicion for CTLA4 haploinsufficiency in patients with refractory celiac disease, especially when multiple autoimmune diseases or a suggestive family history are present. Importantly, case 2 highlights that CTLA4 haploinsufficiency can mimic refractory celiac disease, even in the absence of other features suggestive of immunodeficiency or autoimmunity. > Identification of CTLA4 haploinsufficiency has important implications for therapeutics and cancer risk. From a therapeutic standpoint, both cases are examples of lifechanging responses to abatacept, a fusion protein that binds to CD80 and CD86 receptors on antigen-presenting cells (APCs), blocking interactions with CD28 and thereby inhibiting T cell activation. This precision medicine approach directly addresses the mechanism by which CTLA4 haploinsufficiency results in immune dysregulation. Abatacept is currently approved only for use in rheumatoid arthritis (RA) and, notably, both patients 1 and 2 required higher dosing than is typically used in RA to achieve a complete response. The largest report on therapeutic approaches to CTLA4 haploinsufficiency, which includes 123 patients, comments on responses to systemic and topical corticosteroids, abatacept, azathioprine, sirolimus, and tumor necrosis factor-a inhibitors in the subset of 74 patients (60%) with gastrointestinal involvement. Of these patients, nine of 74 used abatacept, and all nine had an initial clinical response, although two ultimately discontinued abatacept after diarrhea recurred. These nine patients notably used different dosing than reported in our patients (subcutaneous weekly dosing versus higher, less frequent intravenous dosing), and none of the nine patients who used abatacept were reported to have presented with celiac-like disease (11).

[7] Primary immune regulatory disorders: Undiagnosed needles in the haystack?

Authors: A. Flinn, A. Gennery
Year: 2022
Venue: Orphanet Journal of Rare Diseases
URL: https://www.semanticscholar.org/paper/14a105e193d6ba770039349397c083d49b466f0f
DOI: 10.1186/s13023-022-02249-1
PMID: 35241125
PMCID: 8895571
Citations: 20
Influential citations: 2
Summary: Due to the rarity of these conditions, worldwide collaboration and data-sharing is essential to improve knowledge of the clinical spectrum and disease course in PIRD, and to optimize therapeutic strategies including identification of which patients can benefit from hematopoietic stem cell transplant.
Evidence snippets:
Snippet 1 (score: 0.412) > LRBA deficiency is caused by biallelic mutations in LRBA gene, resulting in loss of or reduced expression of LRBA protein. LRBA deficiency and CTLA haploinsufficiency share a similar underlying pathophysiology; LRBA plays an essential role in recycling CTLA4 from intracellular vesicles to the cell surface and therefore impairs the availability of CTLA4 in Treg-mediated immune regulation [30]. Like other PIRDs, there is significant variability in the clinical phenotype and a lack of genotype-phenotype correlation [30][31][32][33][34]. Patients with residual protein expression exhibit a less severe clinical course compared to those with absent LRBA protein [34]. LRBA deficiency typically presents in the first two decades of life, although the timing of onset varies widely during this period [32]. Autoimmunity is the most common clinical manifestation, with splenomegaly, pneumonia, lymphoproliferation and enteropathy being other common clinical features [31][32][33]35]. Autoimmune cytopenias are a prominent feature, but a wide spectrum of autoimmune diseases including type 1 diabetes mellitus, hepatitis, thyroid disease, and arthritis are reported and patients often exhibit polyautoimmunity [32,33,36]. Reduced class-switched memory B-lymphocytes, Tregs and immunoglobulin levels are the most common abnormalities in immune parameters [35]. As expected, due to the shared pathogenetic mechanisms, the phenotype of LRBA deficiency overlaps significantly with that of CTLA haploinsufficiency, although severe infections appear to be a more prominent feature in LRBA deficiency [34,37]. A recent analysis of long-term outcomes in a large cohort of patients with LRBA deficiency demonstrated the superior effect of targeted therapy with abatacept or sirolimus with decreased disease activity scores compared to conventional immune suppression [34]. Treatment with allogeneic HSCT can result in complete disease remission, but higher disease burden pre HSCT is associated with a worse outcome [34].

[8] New therapeutic targets in rare genetic skeletal diseases

Authors: M. Briggs, Peter A. Bell, M. Wright, K. A. Pirog
Year: 2015
Venue: Expert Opinion on Orphan Drugs
URL: https://www.semanticscholar.org/paper/1363107f71ae6d2d60abca471cddf3da5d13644b
DOI: 10.1517/21678707.2015.1083853
PMID: 26635999
PMCID: 4643203
Citations: 37
Influential citations: 1
Summary: An overview of disease mechanisms that are shared amongst groups of different GSDs and potential therapeutic approaches that are under investigation are described to generate critical mass for the identification and validation of novel therapeutic targets and biomarkers.
Evidence snippets:
Snippet 1 (score: 0.404) > proteins of the cartilage ECM such as type II collagen [50]. However, emerging knowledge suggests that the primary genetic defect may be less important than the cells' response to the expression of the mutant gene product [107]. Moreover, the largely overlooked response of a cell (i.e. chondrocyte) to the abnormal extracellular environment is also important for disease progression as illustrated by several GSDs discussed in this review. > It is important that 'omics'-based approaches and technologies are systematically applied to the study of rare GSDs so that definitive reference profiles and disease signatures are generated for each phenotype. These can then be used in a Systems Biology approach to identify both common and dissimilar pathological signatures and disease mechanisms. This approach is entirely dependent upon relevant in vitro and in vivo models (and also novel 'disease-mechanism phenocopies' [107]) for testing new diagnostic and prognostic tools and for determining the molecular mechanisms that underpin the pathophysiology so that effective therapeutic treatments can be developed and validated. This approach will eventually lead to personalized treatments and care strategies centred on shared disease mechanisms with the use of relevant biomarkers to monitor the efficacy of treatment and disease progression. > It is vital that all relevant stakeholders are involved from the outset in defining the appropriate outcomes of any potential therapeutic regime. The perceptions of a successful therapy can differ widely between the clinical academic community and the relevant patient-support groups and it is vital that there is engagement on all these issues. > In summary, the identification of causative genes and mutations for GSDs over the last 20 years, coupled with the generation and in-depth analysis of a plethora of relevant cell and mouse models, has derived new knowledge on disease mechanisms and suggested potential therapeutic targets. The fast-evolving hypothesis that clinically disparate diseases can share common disease mechanisms is a powerful concept that will generate critical mass for the identification and validation of novel therapeutic targets and biomarkers.

[9] Studying human immunodeficiencies in humans: advances in fundamental concepts and therapeutic interventions

Authors: H. Su
Year: 2017
Venue: F1000Research
URL: https://www.semanticscholar.org/paper/a0f21f92e996a7ed4bc95bf85a5648a07127fc33
DOI: 10.12688/f1000research.10594.1
PMID: 28408979
PMCID: 5373415
Citations: 1
Summary: Immunodeficiencies reveal the crucial role of the immune system in defending the body against microbial pathogens and have provided insights into how gene products normally function in the natural environment.
Evidence snippets:
Snippet 1 (score: 0.402) > B cell memory generation, concurrent lymphoproliferation and hypogammaglobulinemia, and increased infections including poor control of EBV and cytomegalovirus infections. With the knowledge of the signaling pathway affected, the mTOR inhibitor sirolimus has been used in these patients and clinical improvement observed. Fortuitously, targeted therapy using small molecular inhibitors of PI3Kδ are being developed for the treatment of cancers, in which somatic gain-of-function mutations of PIK3CD are sometimes found. Thus, PASLI as an orphan disease provides the perfect opportunity to demonstrate precision medicine in action by using the same drugs designed for another purpose. Clinical trials are ongoing to test their efficacy in this disease. > A second example comes from recent work elucidating the molecular mechanism by which LATAIE disease (for "LRBA deficiency with autoantibodies, regulatory T [Treg] cell defects, autoimmune infiltration, and enteropathy"), due to genetic deficiency of the LRBA adaptor protein, causes a mixed picture of autoimmunity and humoral immunodeficiency and responds to CTLA4-Ig (abatacept) treatment 45 . This therapeutic intervention helped to establish the mechanism by which LRBA deficiency phenocopies CHAI disease (for "CTLA4 haploinsufficiency with autoimmune infiltration") 23,24 . Both molecules are interconnected in the same pathway whereby LRBA normally regulates the intracellular vesicle trafficking of, and is required for, cell surface expression of CTLA4. CTLA4 expression, especially on Treg cells, in turn restrains lymphocyte responses and indirectly regulates B cell responses. Furthermore, by defining that LRBA normally helps prevent CTLA4 deposition and degradation in lysosomes, treatment with hydroxychloroquine, a lysosome blocker that is already clinically used for the treatment of lupus, could also be helpful in the treatment of LRBA deficiency. > Together, these two examples illustrate that the unbiased identification of causative gene mutations in human patients leads to knowledge of potential mechanistic targets with immediate clinical implications. Translation of this knowledge has sped up because of the increased development of new biological immun

[10] Targeting Hepatic Stellate Cells for the Prevention and Treatment of Liver Cirrhosis and Hepatocellular Carcinoma: Strategies and Clinical Translation

Authors: Hao Xiong, Jinsheng Guo
Year: 2025
Venue: Pharmaceuticals
URL: https://www.semanticscholar.org/paper/76e92127053136900f7e3f10e2c9278251ced5d2
DOI: 10.3390/ph18040507
PMID: 40283943
PMCID: 12030350
Citations: 8
Summary: HSC-targeted approaches using specific surface markers and receptors may enable the selective delivery of drugs, oligonucleotides, and therapeutic peptides that exert optimized anti-fibrotic and anti-HCC effects.
Evidence snippets:
Snippet 1 (score: 0.396) > Significant progress has been made in elucidating the cellular and molecular mechanisms of liver fibrosis; however, only a few findings have been successfully translated into clinical applications. Firstly, the high cost of drug development and target validation necessitates prolonged timelines and substantial financial investment. Secondly, as regulatory requirements become more stringent, there is an increasing demand for drugs with well-defined clinical efficacy and safety profiles. Moreover, the efficacy observed in animal models often fails to fully translate to clinical settings due to differences in pharmacokinetics, extracellular matrix (ECM) cross-linking, and disease pathophysiology. Despite advancements in anti-fibrotic drug development, accurately identifying ideal noninvasive biomarkers for fibrotic activity and establishing consensus on optimal clinical endpoints remain significant challenges [113,114]. > Currently, addressing the underlying cause remains the only proven strategy to halt or reverse liver fibrosis progression, while the development of effective anti-fibrotic therapies continues to pose a major challenge in liver disease management. Over the past few decades, substantial progress has been made in elucidating the cellular and molecular mechanisms underlying liver fibrosis. Liver fibrosis is a complex pathological change involving multiple cells, factors, and pathways, and the study of the cellular and molecular mechanisms of its occurrence and development provides an important theoretical basis and therapeutic target for clinical drug development. It is anticipated that improved animal models and well-designed clinical trials will facilitate the successful translation of anti-fibrotic research into effective clinical treatments in the near future.

[11] Chemotherapy and Mechanisms of Resistance in Breast Cancer

Authors: A. Oliveira, R. E. Santos, F. F. O. Rodrigues
Year: 2012
Venue: Unknown venue
URL: https://www.semanticscholar.org/paper/502a86d8bcd7208be6f539fcceba631f82f25a7d
DOI: 10.5772/24629
Summary: The addition of adjuvant polychemotherapy in advanced breast cancer showed gain by controlling survival of micrometastases in patients with lymph nodes affected by cancer or not.
Evidence snippets:
Snippet 1 (score: 0.385) > The main reasons responsible for treatment failure in cancer patients are the mechanisms of drug resistance and emergence of disseminated disease (Terek et al, 2003). We identified two types of resistance most relevant to BC: primary resistance, which corresponds to the clinical situation where the patient showed no response to therapy, and secondary or acquired resistance in which, initially, there is an observed response and a subsequent failure of the treatment regimen (Kroger et al, 1999). Several mechanisms may cause the phenotype of multidrug resistance to chemotherapy drugs and are well characterized in in vitro experiments, including alterations in systemic pharmacology (pharmacokinetics and metabolism), extracellular mechanisms (tumor environment, multicellular drug resistance), and cellular mechanisms (cellular pharmacology, activation and inactivation of drugs, modification of specific targets and regulatory pathways of apoptosis) (Leonessa et al, 2003, Riddick et al, 2005. Identification of factors that affect cell metabolism, which are related to drug resistance, will enable the identification of which patients are at particular risk of treatment failure. Among the biochemical and molecular mechanisms of drug resistance, we stress: changes in the activity of topoisomerase II, alterations in the DNA repair mechanism, overexpression of P-glycoprotein; high intracellular concentrations of enzymes purification of cellular metabolism -among them enzymes the family of glutathione S-transferases (GSTs) and changes in the mechanisms of signaling via c-Jun N-terminal kinase 1 (JNK1) -and "apoptosis signal-regulating kinase (ASK1) required for activation of the" mitogenactivated protein (MAP kinases) in apoptosis and cellular restoration. These pathways are also mediated by proteins encoded by genes of GSTs (O'Brien, Tew, 1996;Burg, Mulder, 2002, L'Ecuyer et al, 2004). Different response rates to particular chemotherapy regimens, as observed in patient groups with the same biological characteristics and stage, suggest the existence of different mechanisms of drug resistance, probably induced by genetic alterations (Hayes, Pulford, 1995;O'Brien , Tew, 1996;Pakunlu et al, 2003). Among the mechanisms of purification of cellular metabolism involved in the

[12] Molecular and Cellular Heterogeneity in Rheumatoid Arthritis: Mechanisms and Clinical Implications

Authors: Jianan Zhao, Shicheng Guo, Steven J. Schrodi, D. He
Year: 2021
Venue: Frontiers in Immunology
URL: https://www.semanticscholar.org/paper/c94ff7b93e79668e765719486b267d8485231fe6
DOI: 10.3389/fimmu.2021.790122
PMID: 34899757
PMCID: 8660630
Citations: 123
Influential citations: 3
Summary: This review discusses the source of pathophysiological heterogeneity derived from genetic, molecular, and cellular heterogeneity and their possible impact on precision medicine and personalized treatment of rheumatoid arthritis and provides a suggestive framework for implementing preclinical and clinical experimental results into clinical practice.
Evidence snippets:
Snippet 1 (score: 0.384) > RA is a heritable autoimmnune disease mediated by genetic (15), epigenetic (11,16), genetic-epigenetic (17) and genetic-environment (18) interactions while treatment usually take epigenetics and immnue factors as therapeutic targets (19). These inherited factors influence the heterogeneity of disease progression and determine the underlying set of cellular and molecular mechanisms. The role of heritability has been dissected in linkage and association studies, revealing the molecular variation underlying RA risk variability. The most evident aspects include (i) class II HLA genes, primarily HLA-DRB1, segregate variants that elevate RA risk 2-3-fold through aberrant antigen presentation (20)(21)(22); (ii) the 620W allele of the protein tyrosine phosphatase nonreceptor 22 (PTPN22) gene, which generates various effects across numerous immune cell types and confers elevated risk of autoimmunity (15,23); (iii) chemokine receptor genes, including C-C chemokine receptor 6 (CCR6) (15,24,25); (iv) peptidyl arginine deiminase type IV (PADI4), which encodes peptidylarginine deiminase type 4 (involved in protein citrullination) (26,27); (v) the transcription factor-encoding gene signal transducer and activator of transcription 4 protein (STAT4) (15,25), (vi) cytotoxic T-lymphocyte antigen 4 (CTLA4), encoding for the cytotoxic T-cell associated protein (25,28), and (vii) the B-cell cell surface receptor gene, CD40 (29,30). Although these genetic factors predispose individuals to RA, patients exhibit a wide variety of combinations of these variants. This genetic variation across patients is considered to partially drive the heterogeneity in RA pathophysiology, clinical presentation, and response to therapies (31) (See Table 1).

[13] Future research trends in understanding the mechanisms underlying allergic diseases for improved patient care

Authors: H. Breiteneder, Z. Diamant, T. Eiwegger, W. Fokkens, C. Traidl‐Hoffmann et al.
Year: 2019
Venue: Allergy
URL: https://www.semanticscholar.org/paper/e19b0755c4f4903f68377333676edebf9bd73c89
DOI: 10.1111/all.13851
PMID: 31056763
PMCID: 6973012
Citations: 90
Influential citations: 3
Summary: Recent developments in research and patient care and future trends in the discipline are reviewed and topics on food allergy, biologics, small molecules, and novel therapeutic concepts in allergen‐specific immunotherapy for airway disease are highlighted.
Evidence snippets:
Snippet 1 (score: 0.383) > The past decades have witnessed extensive progress in unraveling cellular and molecular mechanisms of immune regulation in asthma, allergic diseases, organ transplantation, autoimmune diseases, tumor biology, and chronic infections. 1,2 Consequently, a better understanding of the functions, the reciprocal regulation, and the counterbalance of subsets of immune and inflammatory cells but also structural cells-for example, epithelial and vascular cells, airway smooth muscle cells, neuroendocrine system-that interact via various intercellular messengers will indicate avenues for immune interventions and novel treatment modalities of allergic diseases and immunological disorders. It is generally expected that drug development in the next decades will show a significant shift from chemicals to biologicals. > After more than 20 years without any breakthrough drug becoming available for patients, several disciplines including allergology are now experiencing extraordinary times with the recent licensing of several major biological drugs and novel allergen-specific immunotherapy (AIT) vaccines. Several biological modifiers of the immune response targeting intracellular messengers or their receptors have been developed to date. [3][4][5][6][7][8] In addition, a number of promising small molecule drugs and vaccines are in the development pipeline. [9][10][11] This new era is now calling for the development of biomarkers and phenoand endotyping of diseases for customized patient care, which is termed stratified medicine, precision medicine, or personalized medicine. 4 Distinguishing phenotypes of a complex disease covers the observable clinically relevant properties of the disease but does not show a direct relationship to disease etiology and pathophysiology. In a complex condition, such as asthma, different pathogenetic mechanisms can induce similar clinical manifestations; however, they may require different treatment approaches. 12,13 These pathophysiological mechanisms underlying disease subgroups are addressed by the term "endotype." [12][13][14] Classification of complex diseases based on the concept of endotypes provides advantages for epidemiological, genetic, and drug-related studies. Accurate endotyping by using reliable biomarkers reflects the natural history of the disease and aims to predict the response to (targeted) treatments. 15 Recent studies have focused on better understanding

[14] Molecular insights into the premature aging disease progeria

Authors: Sandra Vidak, R. Foisner
Year: 2016
Venue: Histochemistry and Cell Biology
URL: https://www.semanticscholar.org/paper/60fb3b46bb7e42d5d08cc3b7cbc783b118300c31
DOI: 10.1007/s00418-016-1411-1
PMID: 26847180
PMCID: 4796323
Citations: 105
Influential citations: 3
Summary: Changes in mechanosignaling, altered chromatin organization and impaired genome stability, and changes in signaling pathways, leading to impaired regulation of adult stem cells, defective extracellular matrix production and premature cell senescence are discussed.
Evidence snippets:
Snippet 1 (score: 0.382) > The number of molecular biological studies aiming at the identification of lamin-mediated molecular disease mechanisms involved in HGPS increased tremendously following the surprising discovery that LMNA is causally linked to the premature aging disease HGPS in 2003. Despite numerous cellular pathways that were identified to be affected by the expression of the mutant lamin A protein (Fig. 2), the mechanistic details behind these effects are still unclear in most cases. Knowledge based on what was already known on lamin biology before the protein was linked to HGPS and findings on novel roles of lamins in diverse pathways in recent years allowed the launch of translational studies and the efficient search for drug targets and therapeutic approaches within a short time period. The results of the first clinical trials taught us that some improvements of the disease phenotypes can be achieved by FTI treatment, but they also made clear that we need a much better understanding of the underlying disease mechanisms to be able to tackle specific aspects of the disease in a more focused approach. It will also be important to elucidate which of the numerous pathways found to be impaired in HGPS are most relevant for and causally involved in the pathologies, and which ones are just bystanders.

[15] LifeTime and improving European healthcare through cell-based interceptive medicine

Authors: N. Rajewsky, G. Almouzni, S. Gorski, S. Aerts, I. Amit et al.
Year: 2020
Venue: Nature
URL: https://www.semanticscholar.org/paper/d626a4acb560c1ef16ea394cb4dccf277882d119
DOI: 10.1038/s41586-020-2715-9
PMID: 32894860
PMCID: 7656507
Citations: 138
Influential citations: 2
Summary: The LifeTime initiative is an ambitious, multidisciplinary programme that aims to improve healthcare by tracking individual human cells during disease processes and responses to treatment in order to develop and implement cell-based interceptive medicine in Europe over the next decade.
Evidence snippets:
Snippet 1 (score: 0.380) > , a major challenge is a lack of understanding of the early events in disease onset to enable the development of disease-modifying therapies. The lack of access to longitudinal samples from patients necessitates the establishment of cohorts of patient-derived disease models to understand the cellular heterogeneity associated with disease. The discovery of pathways and biomarkers that will allow the stratification of patients on the basis of the cellular mechanisms that drive a disease will make it possible to design new clinical trials to reevaluate drugs that were previously tested without such stratification, and to broaden the drug target portfolio. > As seen during the coronavirus disease 2019 (COVID-19) pandemic, it is important to be able to understand infection mechanisms and the host response in order to rapidly identify the most likely effective treatment for an infection. At the same time, the continuous rise of antimicrobial resistance requires the discovery of new therapeutic strategies. A key medical challenge for infectious diseases is to understand the cellular response to infections and to develop precision, immune-based therapeutic strategies to combat infections. > Chronic inflammatory diseases impose a high burden owing to their long-term debilitating consequences, which result from the structural destruction of affected organs or tissues. Current therapies treat the symptoms but do not cure or fully control the chronic inflammatory pathophysiology. While different targeted therapies exist, they are expensive and their success is limited by high rates of non-response to treatment. Consequently, there is an urgent need to explore and understand how cellular heterogeneity contributes to the pathology of inflammatory diseases 61 and how this relates to the predicted course of disease and the response of a patient to one of the numerous available therapies. > Many cardiovascular and metabolic diseases lack effective therapies owing to a lack of knowledge of their underlying causes and the link between abnormal cardiac cell structure or function and pathophysiology. The identified medical priority is to understand the cellular and molecular mechanisms involved, in order to enable early diagnosis and the design of new mechanism-based therapies for precise clinical treatment. > The LifeTime disease roadmaps can be divided broadly into three phases 7 : first, immediate research into the identified medical challenges using established, scaled single-cell technologies, computational tools and disease models; second, the development of new technologies that are required

[16] Pharmacogenomic characterization of gemcitabine response – a framework for data integration to enable personalized medicine

Authors: Michael Harris, K. Bhuvaneshwar, Thanemozhi Natarajan, L. Sheahan, Difei Wang et al.
Year: 2013
Venue: Pharmacogenetics and Genomics
URL: https://www.semanticscholar.org/paper/1382ddf84b87736a73c2f2f81164ca876c29f4c4
DOI: 10.1097/FPC.0000000000000015
PMID: 24401833
PMCID: 3888473
Citations: 16
Summary: This in-silico study identified gene variants significantly associated with gemcitabine response that may help to personalize treatment in the clinic and gain insights into drug response mechanisms and to facilitate clinical trial design and regulatory reviews.
Evidence snippets:
Snippet 1 (score: 0.380) > Understanding the genetic and molecular mechanisms underlying complex diseases such as cancer is extremely challenging. Genome-wide association studies (GWAS) have been extensively used in the past decade to discover important genetic variants. However, the identified SNPs explain only a small proportion of the phenotypic variation, and the predictive power of these SNPs remains low for many complex diseases [10]. To fully elucidate genetic underpinnings of disease a systems biology approach is necessary to characterize variants, mRNA, copy number, proteins, and metabolites, as well as their cellular interactions [11]. Gene set and pathway association analyses are playing an increasingly important role in explaining disease mechanisms through the identification of functional genetic interactions [12]. Many gene-disease association analyses are based on SNP genotype profiling or gene expression studies. However, SNPs can influence many downstream processes including the expression levels of multiple genes and/or protein levels, and variations in expression levels can directly or indirectly impact disease progression and even drug response [13]. An integrative approach combining multiple data types can more accurately capture pathway associations [12] for discovery of clinically actionable variants. > Statistical approaches commonly used to associate variants with disease and/or drug response Fisher's exact test (FET) is commonly used in the association of germline polymorphisms with drug response [14]. The use of probabilistic networks in conjunction with traditional statistical models for mining relationships and associations from genotype-phenotype data is well established [15]. Probabilistic network methods for pharmacogenomics and newer methods such as the Markov Blanket concept may be helpful to better analyze these complex genotype-phenotype associations [16]. Considering the complexity of both cancer prognosis and individual drug response to chemotherapeutics, application of these association methods in conjunction with novel informatics and data integration approaches is necessary to identify clinically relevant variants for validation studies and ultimately testing in the clinic for pharmacogenomics applications.

[17] Mitochondrial Dysfunction in Diabetes: Shedding Light on a Widespread Oversight

Authors: F. Iheagwam, A. J. Joseph, E. D. Adedoyin, Olawumi Toyin Iheagwam, Samuel Akpoyowvare Ejoh
Year: 2025
Venue: Pathophysiology
URL: https://www.semanticscholar.org/paper/dbf8042761c1a5fc50f8cd894cc498505abac7cb
DOI: 10.3390/pathophysiology32010009
PMID: 39982365
PMCID: 12077258
Citations: 24
Summary: This review aims to elucidate the complex link between mitochondrial dysfunction and diabetes, covering the spectrum of diabetes types, the role of mitochondria in insulin resistance, highlighting pathophysiological mechanisms, mitochondrial DNA damage, and altered mitochondrial biogenesis and dynamics.
Evidence snippets:
Snippet 1 (score: 0.379) > The landscape of DM research is continuously evolving, with emerging technologies and approaches offering new insights into the pathophysiology of the disease and potential therapeutic targets. Advancements in omics technologies, encompassing genomes, transcriptomics, proteomics, and metabolomics, have transformed the molecular mechanisms underlying DM [134]. High-throughput sequencing techniques enable comprehensive analysis of genetic variants, gene expression profiles, protein abundance, and metabolite levels associated with DM and its complications [135]. Single-cell omics approaches provide unprecedented resolution and granularity, allowing researchers to dissect cellular heterogeneity and identify novel cell types, subpopulations, and signalling pathways involved in DM pathogenesis. Integrating multi-omics data sets offers a systems-level perspective of DM, unravelling complex networks of molecular interactions and regulatory circuits underlying disease progression [136]. > In addition to omics technologies, advances in imaging modalities, such as MRI, PET, and optical imaging, enable non-invasive visualisation and quantification of metabolic, functional, and structural changes. Molecular imaging probes targeting specific biomarkers and metabolic pathways provide valuable insights into disease mechanisms and treatment responses in preclinical and clinical settings [85]. Despite significant progress in DM research, numerous unanswered questions and knowledge gaps persist, hindering the ability to develop effective prevention and treatment strategies. Key areas requiring further investigation include the role of epigenetics, environmental factors, and the microbiome in DM susceptibility and progression. Moreover, the interaction between environmental cues and genetic predisposition remains incompletely understood, highlighting the need for comprehensive multi-omics studies and large-scale epidemiological analyses to identify gene-environment interactions and modifiable risk factors for DM [137]. Furthermore, the heterogeneity of DM phenotypes and clinical outcomes poses a challenge for personalised medicine approaches, necessitating robust biomarkers and predictive models to stratify patients based on disease subtypes, prognosis, and treatment response [138].

[18] From molecular signatures to predictive biomarkers: modeling disease pathophysiology and drug mechanism of action

Authors: A. Heinzel, P. Perco, G. Mayer, R. Oberbauer, A. Lukas et al.
Year: 2014
Venue: Frontiers in Cell and Developmental Biology
URL: https://www.semanticscholar.org/paper/36d6c03a528c1358c0ae5b667cca5ce73b2fbee5
DOI: 10.3389/fcell.2014.00037
PMID: 25364744
PMCID: 4207010
Citations: 23
Summary: This work exemplifies a computational workflow for expanding from statistics-based association analysis toward deriving molecular pathway and process models for characterizing phenotypes and drug mechanism of action, in turn providing precision medicine hypotheses utilizing predictive biomarkers.
Evidence snippets:
Snippet 1 (score: 0.376) > In such scenario a biomarker needs to serve as proxy of key mechanistic factors characterizing and driving a disease on a patient-specific level, combined with educating on the specific interference of disease mechanism with drug mechanism of action. For capturing these constraints a detailed molecular map of a clinical phenotype and its interference with a drug mechanism of action is needed, and here integration of Omics profiling adds to identifying such mechanisms (Fechete et al., 2011;Mühlberger et al., 2012). > An a priori stratification of patients based on an appropriately chosen biomarker panel reflecting the pathophysiology of a given patient (group) allowing to determine a match with a specific drug's mechanism of action appears as promising approach. As recently discussed by Himmelfarb et al. fresh approaches are critical in finding therapies to kidney disease benefiting patients, outlining the importance of improving the translational aspect in clinical research (Himmelfarb and Tuttle, 2013). Here, omics technologies have added significantly to the data landscape characterizing chronic kidney disease, however, in a first instance mainly expanding the candidate set of apparently relevant processes and pathways, going in hand with a large number of biomarker candidates, which individually hamper clinically relevant assessment on disease progression (Fechete et al., 2011;Hellemons et al., 2012). > Integrative approaches in the realm of Systems Biology have been proposed for reaching a consensus description of chronic kidney disease pathophysiology, including molecular models of DN as well as of the reno-cardial axis (He et al., 2012;Komorowsky et al., 2012;Mayer et al., 2012;Heinzel et al., 2013). Still, a translation process needs to be followed, joining disease pathophysiology, stratification markers allowing enrichment strategies, combined with on a molecular mechanistic level matching drugs for allowing precision medicine (Mirnezami et al., 2012). In this work we exemplify such procedure on DN being the major clinical presentation leading to end stage renal disease.

[19] Human Inborn Errors of Immunity: 2022 Update on the Classification from the International Union of Immunological Societies Expert Committee

Authors: S. Tangye, W. Al-Herz, A. Bousfiha, C. Cunningham-Rundles, J. Franco et al.
Year: 2022
Venue: Journal of Clinical Immunology
URL: https://www.semanticscholar.org/paper/ac4b6624d4dce3dfcad27f1114ce4a63eda1b45d
DOI: 10.1007/s10875-022-01289-3
PMID: 35748970
PMCID: 9244088
Citations: 855
Influential citations: 56
Summary: This report documents the key clinical and laboratory features of 55 novel monogenic gene defects, and 1 phenocopy due to autoantibodies, that have either been discovered since the previous update or were characterized earlier but have since been confirmed or expanded in subsequent studies.
Evidence snippets:
Snippet 1 (score: 0.376) > Inborn errors of immunity (IEI) are caused by damaging germline variants in single genes. IEI present clinically as increased susceptibility to infections, autoimmunity, autoinflammatory diseases, allergy, bone marrow failure, and/or malignancy. While individually rare, the aggregated number of individuals with an IEI represents a significant health burden [1]. Genetic variants cause disease by altering the encoded gene product, such as by abolishing or reducing protein expression and function (null/hypomorphic) or modifying the protein to acquire gain-of-function (GOF) [2][3][4][5]. Mechanisms of disease in IEI depend on the nature of the variant as well as the mode of inheritance. Thus, monoallelic variants can cause disease by haploinsufficiency, negative dominance, or GOF. In contrast, biallelic genetic lesions (homozygous, compound heterozygous) cause autosomal recessive (AR) traits by loss of expression, loss of function (LOF), GOF, or even neomorphic function of the encoded protein, while X-linked recessive traits arise from LOF or GOF variants on the X chromosome, either in hemizygosity in males, or homozygous state in females. > The fact that some monogenic variants are pathogenic clearly highlights the non-redundant and fundamental roles of individual genes and proteins, and associated pathways and cell types, in the development and function of leukocytes and non-hematopoietic cells that contribute to immune homeostasis and host defense [6,7]. Thus, IEI represent an elegant model linking defined monogenic defects with clinical phenotypes of immune dysregulation. IEI have also revealed mechanisms of disease pathogenesis in, and enabled the implementation of gene-or pathway-specific therapies for the treatment of, rare and common conditions and established fundamental aspects of human immunology [8][9][10]. Thus, the study of IEI has enabled profound advances in molecular medicine and human biology. > Since 1970, an international expert committee comprising pediatric and adult clinical immunologists, clinician/scientists and researchers in basic immunology -initially

[20] 18O-assisted dynamic metabolomics for individualized diagnostics and treatment of human diseases

Authors: E. Nemutlu, Song Zhang, N. Juranic, A. Terzic, S. Macura et al.
Year: 2012
Venue: Croatian Medical Journal
URL: https://www.semanticscholar.org/paper/880f053c7f060db4b990e447d0a22c4b69372ddb
DOI: 10.3325/cmj.2012.53.529
PMID: 23275318
PMCID: 3541579
Citations: 28
Summary: The potential use of dynamic phosphometabolomic platform for disease diagnostics currently under development at Mayo Clinic is described and discussed briefly.
Evidence snippets:
Snippet 1 (score: 0.375) > Living cells represent an integrated and interacting network of genes, transcripts, proteins, small signaling molecules, and metabolites that define cellular phenotype and function. Traditionally the focus of biomedical research was on individual genes, single protein targets, single metabolites, and metabolic or signaling pathways. This "molecular reductionist" paradigm was based on the assumption that identifying genetic variations and molecular components would lead to discovery of cures for human diseases. However, most of diseases are complex and multi-factorial and the disease phenotype is determined by the alterations of multiple genes, pathways, proteins and metabolites (at cellular, tissue, and organismal levels). Therefore, an integrated "omics" approach is more viable direction for uncovering alterations in metabolic networks, disease mechanisms, and mechanisms of drug effects. > Recent advent of large-scale metabolomics and fluxomic (metabolite dynamics and metabolic flux analysis) completed the "omics revolution" (Figure 1), where genomics, transcriptomics, proteomics, metabolomics, and fluxomics all together complement phenotype determination of living organism. Such integrated "omics" cascades provide a framework for advances in system and network biology, integrative physiology, and system medicine as well as system pharmacology and regenerative medicine. Noteworthy is the "reverse omic" approach or "metabolomicsinformed pharmacogenomics, " where discovery of specific metabolite changes have led to discovery of genetic alterations (2). Therefore, bringing new "omics" technologies to clinical practice will improve disease diagnostics and treatment by targeting drugs and procedures for each unique transcriptomic and metabolomic profiles.

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References

Deep Research

Asta Literature Retrieval: Pathophysiology and clinical mechanisms of CTLA4 Haploinsufficiency. Core disease mechanisms, molecular and cellular...

Relevant Papers

[1] CTLA4 Message Reflects Pathway Disruption in Monogenic Disorders and Under Therapeutic Blockade

[2] Non-infectious Complications of Common Variable Immunodeficiency: Updated Clinical Spectrum, Sequelae, and Insights to Pathogenesis

[3] Non-Celiac Villous Atrophy—A Problem Still Underestimated

[4] Chronically Activated T-cells Retain Their Inflammatory Properties in Common Variable Immunodeficiency

[5] Anti-CTLA-4 Induced Inflammatory Bowel Disease: Is There A More Etiological Treatment? Lessons From CTLA-4 Haploinsufficiency

[6] Cytotoxic T Lymphocyte Antigen 4 Haploinsufficiency Presenting As Refractory Celiac-Like Disease: Case Report

[7] Primary immune regulatory disorders: Undiagnosed needles in the haystack?

[8] New therapeutic targets in rare genetic skeletal diseases

[9] Studying human immunodeficiencies in humans: advances in fundamental concepts and therapeutic interventions

[10] Targeting Hepatic Stellate Cells for the Prevention and Treatment of Liver Cirrhosis and Hepatocellular Carcinoma: Strategies and Clinical Translation

[11] Chemotherapy and Mechanisms of Resistance in Breast Cancer

[12] Molecular and Cellular Heterogeneity in Rheumatoid Arthritis: Mechanisms and Clinical Implications

[13] Future research trends in understanding the mechanisms underlying allergic diseases for improved patient care

[14] Molecular insights into the premature aging disease progeria

[15] LifeTime and improving European healthcare through cell-based interceptive medicine

[16] Pharmacogenomic characterization of gemcitabine response – a framework for data integration to enable personalized medicine

[17] Mitochondrial Dysfunction in Diabetes: Shedding Light on a Widespread Oversight

[18] From molecular signatures to predictive biomarkers: modeling disease pathophysiology and drug mechanism of action

[19] Human Inborn Errors of Immunity: 2022 Update on the Classification from the International Union of Immunological Societies Expert Committee

[20] 18O-assisted dynamic metabolomics for individualized diagnostics and treatment of human diseases

Notes