Alopecia Areata

Autoimmune MONDO:0005340 Pathograph 16 Show in embeddings browser Autoimmune Disease Skin Disease

An autoimmune disease targeting hair follicles and causing non-scarring hair loss. Loss may remain patchy or progress to complete scalp involvement (alopecia totalis) or complete body-hair involvement (alopecia universalis). The follicular stem-cell compartment is spared, so regrowth remains possible.

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1
Inheritance
6
Pathophys.
1
Histopath.
5
Phenotypes
2
Gaps
16
Pathograph
4
Genes
7
Medical Actions
2
Datasets
4
Trials
1
Models
18
References
2
Deep Research
🏷

Classifications

Harrison's Part
DERMATOLOGY IMMUNE RHEUMATOLOGIC
👪

Inheritance

1
Polygenic Inheritance HP:0010982
Alopecia areata has a complex polygenic susceptibility architecture rather than a single-gene Mendelian inheritance pattern.
Polygenic Inheritance
Show evidence (1 reference)
PMID:20596022 SUPPORT Human Clinical
"We undertook a genome-wide association study (GWAS) in a sample of 1,054 cases and 3,278 controls and identified 139 single nucleotide polymorphisms that are significantly associated with AA (P <or= 5 x 10(-7))."
Multiple genome-wide significant susceptibility variants support a complex polygenic architecture.
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Discussions and Knowledge Gaps

2
Which elements of the CD8+NKG2D+/IFN-gamma/IL-15 circuit are necessary and sufficient in human alopecia areata?
HUMAN MODEL MISMATCH OPEN aa_mouse_human_causal_translation
Attached to
pathophysiology#CD8+ NKG2D+ T Cell Attack pathophysiology#IFN-gamma–IL-15 JAK-STAT Feedback animal_models#Mouse (Mus musculus)
Necessity, sufficiency, and cytokine-blockade results come from C3H/HeJ mice. Human lesions reproduce the infiltrate and transcriptional signatures, and human JAK-inhibitor trials support pathway relevance, but they do not establish every causal step in patients.
Show evidence (1 reference)
PMID:25129481 SUPPORT Model Organism
"Here, we show that cytotoxic CD8(+)NKG2D(+) T cells are both necessary and sufficient for the induction of AA in mouse models of disease."
The strongest causal claim is explicitly limited to mouse models.
How durable and safe are JAK-inhibitor responses during long-term treatment and after treatment cessation?
KNOWLEDGE GAP OPEN aa_jak_long_term_durability
Attached to
treatments#Baricitinib treatments#Ritlecitinib treatments#Deuruxolitinib
Randomized trials establish short-term hair regrowth, but comparative long-term safety, sustained response, and outcomes after withdrawal remain incompletely characterized.
Show evidence (1 reference)
PMID:39053611 SUPPORT Human Clinical
"Further studies are required to understand longer-term safety, efficacy, and impact of treatment cessation."
The phase-3 report explicitly identifies the long-term and cessation evidence gap.
⚙

Pathophysiology

6
Loss of Hair Follicle Immune Privilege
Collapse of the normally immunosuppressive anagen hair-follicle environment permits increased antigen presentation and immune surveillance around the lower follicle.
Hair Follicular Keratinocyte CL:2000092 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves Hair Follicular Keratinocyte (CL:2000092). CL:2000092 is a cell type from the Cell Ontology.
HLA-DRB1 hgnc:4948 HUGO Gene Nomenclature Committee (hgnc) Relation: this pathophysiological event involves this gene This pathophysiological event involves HLA-DRB1 (hgnc:4948). hgnc:4948 is a gene from the HUGO Gene Nomenclature Committee.
Immune Response GO:0006955 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves Immune Response (GO:0006955). GO:0006955 is a biological process from the Gene Ontology.
Downstream
Follicular Antigen and NKG2D-Ligand Display Loss of immune privilege enables increased follicular antigen-presentation and danger-ligand display.
Show evidence (2 references)
PMID:32682334 SUPPORT Other
"Anagen stage hair follicles (HFs) exhibit "immune privilege (IP)" from the level of the bulge downwards to the bulb."
This review establishes the normal immune-privileged state whose loss is modeled here.
PMID:38673994 SUPPORT Other
"Immune privilege collapse has been extensively investigated in AA pathogenesis, including the suppression of immunomodulatory factors (e.g., transforming growth factor-β (TGF-β), programmed death-ligand 1 (PDL1), interleukin-10 (IL-10), α-melanocyte-stimulating hormone (α-MSH), and macrophage..."
The review directly links immune-privilege collapse with reduced immunoregulation and increased follicular MHC expression.
Follicular Antigen and NKG2D-Ligand Display
Active lesions show increased antigen-presentation machinery and follicular ULBP3/MICA danger ligands that can engage NKG2D on cytotoxic lymphocytes.
Hair Follicular Keratinocyte CL:2000092 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves Hair Follicular Keratinocyte (CL:2000092). CL:2000092 is a cell type from the Cell Ontology.
HLA-DRB1 hgnc:4948 HUGO Gene Nomenclature Committee (hgnc) Relation: this pathophysiological event involves this gene This pathophysiological event involves HLA-DRB1 (hgnc:4948). hgnc:4948 is a gene from the HUGO Gene Nomenclature Committee. ULBP3 hgnc:14895 HUGO Gene Nomenclature Committee (hgnc) Relation: this pathophysiological event involves this gene This pathophysiological event involves ULBP3 (hgnc:14895). hgnc:14895 is a gene from the HUGO Gene Nomenclature Committee.
Antigen Processing and Presentation via MHC Class I GO:0002474 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves Antigen Processing and Presentation via MHC Class I, annotated with antigen processing and presentation of peptide antigen via MHC class I (GO:0002474). GO:0002474 is a biological process from the Gene Ontology.
Downstream
CD8+ NKG2D+ T Cell Attack Follicular NKG2D ligands engage and activate nearby CD8+NKG2D+ cytotoxic T cells.
Show evidence (2 references)
PMID:20596022 SUPPORT Human Clinical
"By probing the role of ULBP3 in disease pathogenesis, we also show that its expression in lesional scalp from patients with AA is markedly upregulated in the hair follicle dermal sheath during active disease."
Human lesional scalp directly shows upregulated follicular ULBP3.
PMID:25129481 SUPPORT Human Clinical
"a cytotoxic subset of CD8+NKG2D+ T cells within the infiltrate surrounding human AA hair follicles"
Human lesions contain the receptor-bearing infiltrate beside follicles expressing its danger ligands.
Impaired Regulatory T Cell Control
Susceptibility at CTLA4 and IL2RA implicates reduced regulatory T-cell control as an upstream modifier of follicular autoimmunity; direct functional impairment in patients remains incompletely established.
Regulatory T Cell CL:0000815 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves Regulatory T Cell (CL:0000815). CL:0000815 is a cell type from the Cell Ontology.
CTLA4 hgnc:2505 HUGO Gene Nomenclature Committee (hgnc) Relation: this pathophysiological event involves this gene This pathophysiological event involves CTLA4 (hgnc:2505). hgnc:2505 is a gene from the HUGO Gene Nomenclature Committee. IL2RA hgnc:6008 HUGO Gene Nomenclature Committee (hgnc) Relation: this pathophysiological event involves this gene This pathophysiological event involves IL2RA (hgnc:6008). hgnc:6008 is a gene from the HUGO Gene Nomenclature Committee.
Downstream
CD8+ NKG2D+ T Cell Attack Reduced regulatory control may permit expansion or persistence of pathogenic cytotoxic effectors.
Show evidence (1 reference)
PMID:20596022 SUPPORT Human Clinical
"Here we show an association with genomic regions containing several genes controlling the activation and proliferation of regulatory T cells (T(reg) cells), cytotoxic T lymphocyte-associated antigen 4 (CTLA4), interleukin (IL)-2/IL-21, IL-2 receptor A (IL-2RA; CD25) and Eos (also known as Ikaros..."
The GWAS implicates CTLA4 and IL2RA regulatory T-cell pathways but does not directly measure regulatory-cell function.
CD8+ NKG2D+ T Cell Attack
Peribulbar CD8+NKG2D+ cytotoxic T cells attack follicular targets. Transfer and depletion experiments establish this population as necessary and sufficient for disease transfer in the C3H/HeJ mouse model.
CD8-Positive Alpha-Beta T Cell CL:0000625 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves CD8-Positive Alpha-Beta T Cell, annotated with CD8-positive, alpha-beta T cell (CL:0000625). CL:0000625 is a cell type from the Cell Ontology.
KLRK1 hgnc:18788 HUGO Gene Nomenclature Committee (hgnc) Relation: this pathophysiological event involves this gene This pathophysiological event involves KLRK1 (hgnc:18788). hgnc:18788 is a gene from the HUGO Gene Nomenclature Committee.
T Cell-Mediated Cytotoxicity GO:0001913 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves T Cell-Mediated Cytotoxicity, annotated with T cell mediated cytotoxicity (GO:0001913). GO:0001913 is a biological process from the Gene Ontology.
Downstream
IFN-gamma–IL-15 JAK-STAT Feedback Effector-derived IFN-gamma induces follicular IL-15 and sustains a feed-forward cytotoxic program.
Patchy Hair Loss Cytotoxic autoimmune attack produces the defining non-scarring alopecia phenotype.
Alopecia Totalis Extensive follicular autoimmune attack may progress to complete scalp hair loss.
Alopecia Universalis Extensive follicular autoimmune attack may progress to complete body-hair loss.
Show evidence (2 references)
PMID:25129481 SUPPORT Model Organism
"Here, we show that cytotoxic CD8(+)NKG2D(+) T cells are both necessary and sufficient for the induction of AA in mouse models of disease."
Mouse transfer and depletion experiments establish a causal effector population.
PMID:37365384 SUPPORT Model Organism
"Pathogenic activity of CD44s-hiCD49dlo CD8+ T cells was mediated by NKG2D-dependent innate-like cytotoxicity, which was further augmented by IL-15 stimulation and triggered disease onset."
A second mouse study supports NKG2D-dependent cytotoxicity and IL-15 augmentation.
IFN-gamma–IL-15 JAK-STAT Feedback
IFN-gamma and common-gamma-chain cytokine signaling activates JAK-STAT in follicular and immune cells; follicular IL-15 supports the survival and cytotoxic function of IFN-gamma-producing CD8+NKG2D+ effectors.
CD8-Positive Alpha-Beta T Cell CL:0000625 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves CD8-Positive Alpha-Beta T Cell, annotated with CD8-positive, alpha-beta T cell (CL:0000625). CL:0000625 is a cell type from the Cell Ontology. Hair Follicular Keratinocyte CL:2000092 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves Hair Follicular Keratinocyte (CL:2000092). CL:2000092 is a cell type from the Cell Ontology.
IFNG hgnc:5438 HUGO Gene Nomenclature Committee (hgnc) Relation: this pathophysiological event involves this gene This pathophysiological event involves IFNG (hgnc:5438). hgnc:5438 is a gene from the HUGO Gene Nomenclature Committee. IL15 hgnc:5977 HUGO Gene Nomenclature Committee (hgnc) Relation: this pathophysiological event involves this gene This pathophysiological event involves IL15 (hgnc:5977). hgnc:5977 is a gene from the HUGO Gene Nomenclature Committee. IL2RA hgnc:6008 HUGO Gene Nomenclature Committee (hgnc) Relation: this pathophysiological event involves this gene This pathophysiological event involves IL2RA (hgnc:6008). hgnc:6008 is a gene from the HUGO Gene Nomenclature Committee.
JAK-STAT Signaling GO:0007259 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves JAK-STAT Signaling, annotated with cell surface receptor signaling pathway via JAK-STAT (GO:0007259). GO:0007259 is a biological process from the Gene Ontology. Response to Interferon-Gamma GO:0034341 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves Response to Interferon-Gamma, annotated with response to type II interferon (GO:0034341). GO:0034341 is a biological process from the Gene Ontology.
Downstream
Loss of Hair Follicle Immune Privilege Effector-derived IFN-gamma reinforces immune-privilege collapse and follicular IL-15 production.
Chemokine-Mediated Effector Recruitment The interferon response induces CXCL9, CXCL10, and CXCL11 expression in lesional skin.
Show evidence (2 references)
PMID:25129481 SUPPORT Human Clinical
"Global transcriptional profiling of mouse and human AA skin revealed gene expression signatures indicative of cytotoxic T cell infiltration, an interferon-γ (IFN-γ) response and upregulation of several γ-chain (γc) cytokines known to promote the activation and survival of IFN-γ-producing..."
Human and mouse lesional profiles jointly support the IFN/gamma-chain cytokine program.
PMID:25129481 SUPPORT Model Organism
"Systemically administered pharmacological inhibitors of Janus kinase (JAK) family protein tyrosine kinases, downstream effectors of the IFN-γ and γc cytokine receptors, eliminated the IFN signature and prevented the development of AA, while topical administration promoted hair regrowth and..."
JAK inhibition functionally perturbed the IFN/gamma-chain program in the mouse model.
Chemokine-Mediated Effector Recruitment
IFN-inducible chemokines and CXCL12 amplify inflammatory-cell accumulation around the follicle; CXCL12 blockade reduces cutaneous CD8+ cells and disease in mice.
Fibroblast of Dermis CL:0002551 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves Fibroblast of Dermis (CL:0002551). CL:0002551 is a cell type from the Cell Ontology.
CXCL12 hgnc:10672 HUGO Gene Nomenclature Committee (hgnc) Relation: this pathophysiological event involves this gene This pathophysiological event involves CXCL12 (hgnc:10672). hgnc:10672 is a gene from the HUGO Gene Nomenclature Committee.
Chemokine-Mediated Signaling Pathway GO:0070098 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves Chemokine-Mediated Signaling Pathway (GO:0070098). GO:0070098 is a biological process from the Gene Ontology.
Downstream
CD8+ NKG2D+ T Cell Attack Chemokine signaling supports accumulation of cytotoxic CD8+ effectors in skin.
Show evidence (2 references)
PMID:38338982 SUPPORT Model Organism
"CXCL12 expression is increased in AA mice, while s.c. injection of αCXCL12 significantly inhibited hair loss in AA mice and reduced the number of CD8+, MHC-I+, and MHC-II+ cells in the skin."
CXCL12 blockade reduces hair loss and cutaneous immune-cell accumulation in mice.
PMID:38338982 SUPPORT In Vitro
"Interferon-γ (IFNγ) treatment increased the secretion of CXCL12 from DFs through the signal transducer and activator of transcription 3 (STAT3) pathway, and αCXCL12 treatment protected the hair follicle from IFNγ in hair organ culture."
Dermal-fibroblast and hair-organ experiments link IFN signaling, CXCL12 secretion, and follicular injury.
✶

Histopathology

1
Peribulbar T-Cell Infiltrate
T cells characteristically surround the hair-follicle bulb in lesional tissue.
Show evidence (1 reference)
PMID:25129481 SUPPORT Human Clinical
"Alopecia areata is a T cell–mediated autoimmune disease characterized phenotypically by hair loss and, histologically, by infiltrating T cells surrounding the hair follicle bulb"
The source explicitly states the characteristic peribulbar T-cell histology.
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Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.
Pathograph: causal mechanism network for Alopecia Areata Interactive directed graph showing how pathophysiology mechanisms, phenotypes, genetic factors and variants, experimental models, environmental triggers, and treatments relate through causal and linked edges.
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Phenotypes

5
Integument 1
Alopecia Universalis HP:0002289 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Alopecia Universalis (HP:0002289). HP:0002289 is a phenotype from the Human Phenotype Ontology.
Complete loss of scalp and body hair.
Show evidence (1 reference)
PMID:20596022 SUPPORT Human Clinical
"Autoimmunity develops against the hair follicle, resulting in non-scarring hair loss that may begin as patches that can coalesce and progress to cover the entire scalp (alopecia totalis) or eventually the entire body (alopecia universalis)"
The source explicitly defines progression to complete body-hair involvement.
Other 4
Patchy Hair Loss Patchy alopecia HP:0002232 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Patchy Alopecia (HP:0002232). HP:0002232 is a phenotype from the Human Phenotype Ontology.
Non-scarring patches may enlarge and coalesce; exclamation-mark hairs can be seen at active margins.
Show evidence (1 reference)
PMID:20596022 SUPPORT Human Clinical
"Autoimmunity develops against the hair follicle, resulting in non-scarring hair loss that may begin as patches that can coalesce and progress to cover the entire scalp (alopecia totalis) or eventually the entire body (alopecia universalis)"
The human disease description directly supports patchy, non-scarring hair loss.
Alopecia Totalis HP:0007418 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Alopecia Totalis (HP:0007418). HP:0007418 is a phenotype from the Human Phenotype Ontology.
Complete loss of scalp hair.
Show evidence (1 reference)
PMID:20596022 SUPPORT Human Clinical
"Autoimmunity develops against the hair follicle, resulting in non-scarring hair loss that may begin as patches that can coalesce and progress to cover the entire scalp (alopecia totalis) or eventually the entire body (alopecia universalis)"
The source explicitly defines progression to complete scalp involvement.
Nail Pitting Nail pits HP:0001803 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Nail Pits (HP:0001803). HP:0001803 is a phenotype from the Human Phenotype Ontology.
Frequency was not assigned because the reviewed source did not provide a cohort estimate.
Show evidence (1 reference)
PMID:38893003 SUPPORT Human Clinical
"Nail changes in AA include pitting, trachyonychia, leukonychia, red lunula, and miscellaneous alterations such as longitudinal ridging and brittle nails."
The review directly identifies nail pitting in alopecia areata.
Trachyonychia HP:0030804 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Trachyonychia (HP:0030804). HP:0030804 is a phenotype from the Human Phenotype Ontology.
Frequency was not assigned because the reviewed source did not provide a cohort estimate.
Show evidence (1 reference)
PMID:38893003 SUPPORT Human Clinical
"Nail changes in AA include pitting, trachyonychia, leukonychia, red lunula, and miscellaneous alterations such as longitudinal ridging and brittle nails."
The review directly identifies trachyonychia in alopecia areata.
🧬

Genetic Associations

4
HLA-DRB1 Susceptibility (Risk Factor)
Gene: HLA-DRB1 hgnc:4948 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is HLA-DRB1 (hgnc:4948). hgnc:4948 is a gene from the HUGO Gene Nomenclature Committee. relationship_type: SUSCEPTIBILITY variant_origin: GERMLINE
Show evidence (1 reference)
PMID:25608926 SUPPORT Human Clinical
"The strongest region of association is the major histocompatibility complex, where we fine-map four independent effects, all implicating human leukocyte antigen-DR as a key aetiologic driver."
Meta-analysis and fine-mapping make HLA-DR the strongest susceptibility region.
CTLA4 Susceptibility (Risk Factor)
Gene: CTLA4 hgnc:2505 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is CTLA4 (hgnc:2505). hgnc:2505 is a gene from the HUGO Gene Nomenclature Committee. relationship_type: SUSCEPTIBILITY variant_origin: GERMLINE
Show evidence (1 reference)
PMID:20596022 SUPPORT Human Clinical
"Here we show an association with genomic regions containing several genes controlling the activation and proliferation of regulatory T cells (T(reg) cells), cytotoxic T lymphocyte-associated antigen 4 (CTLA4), interleukin (IL)-2/IL-21, IL-2 receptor A (IL-2RA; CD25) and Eos (also known as Ikaros..."
The GWAS directly identifies the CTLA4-containing region as associated with alopecia areata.
IL2RA Susceptibility (Risk Factor)
Gene: IL2RA hgnc:6008 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is IL2RA (hgnc:6008). hgnc:6008 is a gene from the HUGO Gene Nomenclature Committee. relationship_type: SUSCEPTIBILITY variant_origin: GERMLINE
Show evidence (1 reference)
PMID:20596022 SUPPORT Human Clinical
"Here we show an association with genomic regions containing several genes controlling the activation and proliferation of regulatory T cells (T(reg) cells), cytotoxic T lymphocyte-associated antigen 4 (CTLA4), interleukin (IL)-2/IL-21, IL-2 receptor A (IL-2RA; CD25) and Eos (also known as Ikaros..."
The GWAS directly identifies the IL2RA-containing region as associated with alopecia areata.
ULBP3 Susceptibility (Risk Factor)
Gene: ULBP3 hgnc:14895 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is ULBP3 (hgnc:14895). hgnc:14895 is a gene from the HUGO Gene Nomenclature Committee. relationship_type: SUSCEPTIBILITY variant_origin: GERMLINE
Show evidence (1 reference)
PMID:20596022 SUPPORT Human Clinical
"A region of strong association resides within the ULBP (cytomegalovirus UL16-binding protein) gene cluster on chromosome 6q25.1, encoding activating ligands of the natural killer cell receptor NKG2D that have not previously been implicated in an autoimmune disease."
The GWAS directly identifies the ULBP gene cluster as a strong susceptibility region.
💊

Medical Actions

7
Topical Corticosteroids
Action: Topical Corticosteroid TherapyNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Topical Corticosteroid Therapy (NCIT:C122078). NCIT:C122078 is a clinical intervention from the NCI Thesaurus. NCIT:C122078
A consensus-supported option for children and for mild-to-moderate disease.
Show evidence (1 reference)
PMID:41699409 SUPPORT Other
"Regarding treatment, topical corticosteroids are recommended in children < 12 years. For patients aged ≥ 12 years, topical and intralesional corticosteroids could be used for mild-to-moderate AA, while Janus kinase inhibitors and systemic corticosteroids have a role in moderate-to-severe AA."
Current consensus states the age- and severity-specific role of topical corticosteroids.
Intralesional Corticosteroids
Action: Localized Corticosteroid TherapyNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Localized Corticosteroid Therapy (NCIT:C121367). NCIT:C121367 is a clinical intervention from the NCI Thesaurus. NCIT:C121367
A consensus first option for localized disease in adults.
Show evidence (1 reference)
PMID:33183894 SUPPORT Other
"Intralesional injectable corticotherapy was considered the first option for localized disease in adults."
Dermatology consensus directly supports intralesional corticosteroids for localized adult disease.
Systemic Corticosteroids
Action: Systemic Corticosteroid TherapyNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Systemic Corticosteroid Therapy (NCIT:C122080). NCIT:C122080 is a clinical intervention from the NCI Thesaurus. NCIT:C122080
A consensus-supported option for active, extensive or moderate-to-severe disease.
Show evidence (1 reference)
PMID:33183894 SUPPORT Other
"In extensive cases with signs of activity, systemic corticosteroid therapy should be considered and can be used together with immunosuppressants (corticosteroid-sparing agents)."
Dermatology consensus directly supports systemic corticosteroids in extensive active disease.
Diphencyprone Topical Immunotherapy
Action: PharmacotherapyNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Pharmacotherapy (NCIT:C15986). NCIT:C15986 is a clinical intervention from the NCI Thesaurus. NCIT:C15986
Agent: diphenylcyclopropenone CHEBI:53074 Chemical Entities of Biological Interest (CHEBI) Relation: this treatment uses this therapeutic agent This treatment uses diphenylcyclopropenone (CHEBI:53074). CHEBI:53074 is a therapeutic agent from Chemical Entities of Biological Interest.
Contact immunotherapy is a consensus option for stable, long-standing alopecia areata.
Show evidence (1 reference)
PMID:33183894 SUPPORT Other
"The use of an immunosensitizer (diphencyprone) is an option for stable long-term cases."
Dermatology consensus directly supports diphencyprone for stable long-term disease.
Baricitinib
Action: PharmacotherapyNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Pharmacotherapy (NCIT:C15986). NCIT:C15986 is a clinical intervention from the NCI Thesaurus. NCIT:C15986
Agent: baricitinib CHEBI:95341 Chemical Entities of Biological Interest (CHEBI) Relation: this treatment uses this therapeutic agent This treatment uses baricitinib (CHEBI:95341). CHEBI:95341 is a therapeutic agent from Chemical Entities of Biological Interest.
Oral JAK1/2 inhibitor with replicated randomized phase-3 efficacy in adults with severe alopecia areata.
Mechanism Target:
INHIBITS IFN-gamma–IL-15 JAK-STAT Feedback — Baricitinib inhibits JAK1/2 signaling downstream of inflammatory cytokine receptors.
Show evidence (1 reference)
PMID:35334197 SUPPORT Human Clinical
"Baricitinib, an oral, selective, reversible inhibitor of Janus kinases 1 and 2, may interrupt cytokine signaling implicated in the pathogenesis of alopecia areata."
The trial report identifies the drug's JAK1/2 mechanism and its relevance to pathogenic cytokine signaling.
Target Phenotypes: Patchy Hair Loss HP:0002232 Human Phenotype Ontology (HP) Relation: this treatment targets this phenotype This treatment targets Patchy Hair Loss, annotated with Patchy alopecia (HP:0002232). HP:0002232 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:35334197 SUPPORT Human Clinical
"In two phase 3 trials involving patients with severe alopecia areata, oral baricitinib was superior to placebo with respect to hair regrowth at 36 weeks."
Two randomized phase-3 trials directly demonstrate hair-regrowth efficacy.
Ritlecitinib
Action: PharmacotherapyNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Pharmacotherapy (NCIT:C15986). NCIT:C15986 is a clinical intervention from the NCI Thesaurus. NCIT:C15986
Agent: ritlecitinib CHEBI:229233 Chemical Entities of Biological Interest (CHEBI) Relation: this treatment uses this therapeutic agent This treatment uses ritlecitinib (CHEBI:229233). CHEBI:229233 is a therapeutic agent from Chemical Entities of Biological Interest.
Oral selective JAK3/TEC-family kinase inhibitor supported by a randomized phase-2b/3 trial in patients aged 12 years and older.
Mechanism Target:
INHIBITS IFN-gamma–IL-15 JAK-STAT Feedback — Ritlecitinib inhibits JAK3/TEC-family kinase signaling relevant to cytotoxic lymphocyte activation.
Show evidence (1 reference)
PMID:37062298 SUPPORT Human Clinical
"We investigated the efficacy and safety of ritlecitinib, an oral, selective dual JAK3/TEC family kinase inhibitor, in patients with alopecia areata."
The trial report directly identifies the drug's JAK3/TEC-family kinase mechanism.
Target Phenotypes: Patchy Hair Loss HP:0002232 Human Phenotype Ontology (HP) Relation: this treatment targets this phenotype This treatment targets Patchy Hair Loss, annotated with Patchy alopecia (HP:0002232). HP:0002232 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:37062298 SUPPORT Human Clinical
"Ritlecitinib was effective and well tolerated in patients aged 12 years and older with alopecia areata."
The randomized trial directly supports efficacy in adults and adolescents aged at least 12 years.
Deuruxolitinib
Action: PharmacotherapyNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Pharmacotherapy (NCIT:C15986). NCIT:C15986 is a clinical intervention from the NCI Thesaurus. NCIT:C15986
Agent: Deuruxolitinib NCIT:C175770 NCI Thesaurus (NCIT) Relation: this treatment uses this therapeutic agent This treatment uses Deuruxolitinib (NCIT:C175770). NCIT:C175770 is a therapeutic agent from the NCI Thesaurus.
Oral JAK1/2 inhibitor supported by a randomized phase-3 trial in adults with at least 50% scalp hair loss.
Mechanism Target:
INHIBITS IFN-gamma–IL-15 JAK-STAT Feedback — Deuruxolitinib inhibits JAK1/2 signaling downstream of inflammatory cytokine receptors.
Show evidence (1 reference)
PMID:39053611 SUPPORT Human Clinical
"The Phase 3 THRIVE-AA1 randomized, double-blinded, placebo-controlled trial (NCT04518995) evaluated the safety and efficacy of the oral JAK1/JAK2 inhibitor deuruxolitinib in adult patients with AA."
The trial report directly identifies deuruxolitinib as an oral JAK1/2 inhibitor.
Target Phenotypes: Patchy Hair Loss HP:0002232 Human Phenotype Ontology (HP) Relation: this treatment targets this phenotype This treatment targets Patchy Hair Loss, annotated with Patchy alopecia (HP:0002232). HP:0002232 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:39053611 SUPPORT Human Clinical
"Both doses of deuruxolitinib were effective for hair regrowth."
The randomized phase-3 trial directly supports hair-regrowth efficacy.
🔬

Diagnosis

2
Trichoscopy
Trichoscopy supports diagnosis and longitudinal monitoring of alopecia areata.
Trichoscopy NCIT:C116478 NCI Thesaurus (NCIT)
Show evidence (1 reference)
PMID:41699409 SUPPORT Other
"Trichoscopy is deemed essential for diagnosing and monitoring AA, while skin biopsy is reserved for when the cause of hair loss is unclear."
Current expert consensus supports trichoscopy for diagnosis and monitoring.
Skin Biopsy When the Cause Is Unclear
Histologic evaluation is reserved for diagnostically uncertain hair loss rather than routine use.
Skin Biopsy NCIT:C51692 NCI Thesaurus (NCIT)
Show evidence (1 reference)
PMID:41699409 SUPPORT Other
"Trichoscopy is deemed essential for diagnosing and monitoring AA, while skin biopsy is reserved for when the cause of hair loss is unclear."
Current expert consensus reserves biopsy for unclear causes of hair loss.
📊

Prevalence

1
Germany
Point Prevalence 210.0 per 100,000 >1 in 1,000
Population-based diagnosed prevalence for 2020; estimates vary substantially by region and study design.
Show evidence (1 reference)
PMID:41855094 SUPPORT Human Clinical
"Data from Germany show a population-based prevalence of AA of 0.22% (95% CI 0.21-0.22) for 2016 and 0.21% (95% CI 0.20-0.22) for 2020."
The guideline reports a 0.21% population-based prevalence in Germany in 2020.
📊

Related Datasets

2
Immunoregulatory Effects of Myeloid-Derived Suppressor Cell Exosomes in Mouse Model of Autoimmune Alopecia Areata massive:MSV000082825
We have demonstrated therapeutic efficacy of MDSC in mouse Alopecia Areata (AA). In the same AA model, we now asked whether MDSC exosomes (MDSC-Exo) can replace MDSC. MDSC-Exo from bone marrow cells (BMC) cultures of healthy donors could substantially facilitate treatment. With knowledge on MDSC-Exo being limited, their suitability needs to be verified in advance. Protein marker profiles suggest comparability of BMC- to ex vivo collected inflammatory MDSC/MDSC-Exo in mice with a chronic contact dermatitis, which is a therapeutic option in AA.
mouse PROTEOMICS
Located via OmicsDI, which aggregates across omics repositories; this record comes from massive. Only repositories with no other discovery route in this project and with a working accession resolver are curated from OmicsDI -- GEO, ArrayExpress, PRIDE, MetaboLights and EGA hits are excluded as duplicates of dedicated passes. Matched because the disease is named in the dataset's own title ("Alopecia Areata"). Retrieved 2026-08-02.
Genome Wide Association Studies in Alopecia Areata dbgap:phs000586
1054 unrelated alopecia areata patients were genotyped with the Illumina HumanHap550v3.0 genotyping chip. Allele frequencies were compared to publically available data from three population cohorts of controls.
Located via OmicsDI, which aggregates across omics repositories; this record comes from dbgap. Only repositories with no other discovery route in this project and with a working accession resolver are curated from OmicsDI -- GEO, ArrayExpress, PRIDE, MetaboLights and EGA hits are excluded as duplicates of dedicated passes. Matched because the disease is named in the dataset's own title ("Alopecia Areata"). Retrieved 2026-08-02.
🔬

Clinical Trials

4
NCT03570749 COMPLETED
Adaptive randomized placebo-controlled baricitinib study in adults with severe or very severe alopecia areata (BRAVE-AA1).
Show evidence (1 reference)
clinicaltrials:NCT03570749 SUPPORT Human Clinical
"This study is designed to select up to two doses of baricitinib (referred to as low dose and high dose) and assess their efficacy and safety for the treatment of severe or very severe alopecia areata."
The registry summary states the baricitinib dose-selection and efficacy/safety objectives.
NCT03899259 PHASE_III COMPLETED
Randomized placebo-controlled phase-3 baricitinib study in adults with severe or very severe alopecia areata (BRAVE-AA2).
Show evidence (1 reference)
clinicaltrials:NCT03899259 SUPPORT Human Clinical
"The reason for this study is to see if baricitinib is safe and effective in adults with severe or very severe alopecia areata (AA)."
The registry summary states the population and trial objective.
NCT03732807 COMPLETED
Global randomized placebo-controlled dose-ranging phase-2b/3 ritlecitinib study in adults and adolescents with at least 50% scalp hair loss (ALLEGRO).
Show evidence (1 reference)
clinicaltrials:NCT03732807 SUPPORT Human Clinical
"This is a global Phase 2b/3 study to evaluate the safety and effectiveness of an investigational study drug (called PF-06651600) in adults and adolescents (12 years and older) who have 50% or greater scalp hair loss."
The registry summary states the phase, age range, severity, and efficacy/safety objective.
NCT04518995 PHASE_III COMPLETED
Randomized placebo-controlled deuruxolitinib study in adults with at least 50% scalp hair loss (THRIVE-AA1).
Show evidence (1 reference)
clinicaltrials:NCT04518995 SUPPORT Human Clinical
"This study evaluates the safety and effectiveness of an investigational study drug (called CTP-543) in adults (18 years and older) who have 50% or greater scalp hair loss."
The registry summary states the intervention's former name, adult population, severity, and efficacy/safety objective.
🐁

Animal Models

1
C3H/HeJ recipients grafted with skin from spontaneously alopecic C3H/HeJ donors Mouse (Mus musculus)
A full-thickness skin graft from a spontaneously alopecic donor reliably transfers disease to normal-haired syngeneic recipients and supports causal lymphocyte-transfer, cytokine-blockade, and JAK-inhibition experiments.
Patchy Hair Loss
Species
Mouse (Mus musculus)
Genotype
C3H/HeJ recipients grafted with skin from spontaneously alopecic C3H/HeJ donors
Show evidence (2 references)
PMID:25129481 SUPPORT Model Organism
"Normal-haired C3H/HeJ mice were grafted at 8 weeks of age (during the second telogen) with skin from a C3H/HeJ mouse that developed AA spontaneously"
The methods define the syngeneic skin-graft model.
PMID:25129481 SUPPORT Model Organism
"Hair loss typically began at around 4–6 weeks after grafting. No sham grafted mouse developed hair loss."
Disease onset after affected grafts and absence after sham grafts establish the model phenotype.
{ }

Source YAML

click to show 
name: Alopecia Areata
creation_date: '2025-12-19T01:12:52Z'
category: Autoimmune
parents:
- Autoimmune Disease
- Skin Disease
disease_term:
  preferred_term: Alopecia Areata
  term:
    id: MONDO:0005340
    label: alopecia areata
description: >-
  An autoimmune disease targeting hair follicles and causing non-scarring hair
  loss. Loss may remain patchy or progress to complete scalp involvement
  (alopecia totalis) or complete body-hair involvement (alopecia universalis).
  The follicular stem-cell compartment is spared, so regrowth remains possible.
inheritance:
- name: Polygenic Inheritance
  description: >-
    Alopecia areata has a complex polygenic susceptibility architecture rather
    than a single-gene Mendelian inheritance pattern.
  inheritance_term:
    preferred_term: Polygenic Inheritance
    term:
      id: HP:0010982
      label: Polygenic inheritance
  evidence:
  - reference: PMID:20596022
    reference_title: Genome-wide association study in alopecia areata implicates both innate and adaptive immunity.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      We undertook a genome-wide association study (GWAS) in a sample of 1,054 cases
      and 3,278 controls and identified 139 single nucleotide polymorphisms that are
      significantly associated with AA (P <or= 5 x 10(-7)).
    explanation: Multiple genome-wide significant susceptibility variants support a complex polygenic architecture.
prevalence:
- population: Germany
  measure_type: POINT_PREVALENCE
  prevalence_class: ABOVE_1_IN_1000
  rate_per_100000: 210.0
  notes: Population-based diagnosed prevalence for 2020; estimates vary substantially by region and study design.
  evidence:
  - reference: PMID:41855094
    reference_title: "S3 guideline diagnostics and therapy of alopecia areata - Part 1: Diagnostics and epidemiology."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Data from Germany show a population-based prevalence of AA of 0.22% (95% CI
      0.21-0.22) for 2016 and 0.21% (95% CI 0.20-0.22) for 2020.
    explanation: The guideline reports a 0.21% population-based prevalence in Germany in 2020.
pathophysiology:
- name: Loss of Hair Follicle Immune Privilege
  description: >-
    Collapse of the normally immunosuppressive anagen hair-follicle environment
    permits increased antigen presentation and immune surveillance around the
    lower follicle.
  biological_scale: TISSUE
  cell_types:
  - preferred_term: Hair Follicular Keratinocyte
    term:
      id: CL:2000092
      label: hair follicular keratinocyte
  biological_processes:
  - preferred_term: Immune Response
    term:
      id: GO:0006955
      label: immune response
  genes:
  - preferred_term: HLA-DRB1
    term:
      id: hgnc:4948
      label: HLA-DRB1
  evidence:
  - reference: PMID:32682334
    reference_title: Hair follicle immune privilege and its collapse in alopecia areata.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Anagen stage hair follicles (HFs) exhibit "immune privilege (IP)" from the
      level of the bulge downwards to the bulb.
    explanation: This review establishes the normal immune-privileged state whose loss is modeled here.
  - reference: PMID:38673994
    reference_title: "Pathogenesis of Alopecia Areata and Vitiligo: Commonalities and Differences."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Immune privilege collapse has been extensively investigated in AA
      pathogenesis, including the suppression of immunomodulatory factors (e.g.,
      transforming growth factor-β (TGF-β), programmed death-ligand 1 (PDL1),
      interleukin-10 (IL-10), α-melanocyte-stimulating hormone (α-MSH), and
      macrophage migration inhibitory factor (MIF)) and enhanced expression of the
      major histocompatibility complex (MHC) throughout hair follicles.
    explanation: The review directly links immune-privilege collapse with reduced immunoregulation and increased follicular MHC expression.
  downstream:
  - target: Follicular Antigen and NKG2D-Ligand Display
    description: Loss of immune privilege enables increased follicular antigen-presentation and danger-ligand display.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:38673994
      reference_title: "Pathogenesis of Alopecia Areata and Vitiligo: Commonalities and Differences."
      supports: SUPPORT
      evidence_source: OTHER
      snippet: >-
        Immune privilege collapse has been extensively investigated in AA
        pathogenesis, including the suppression of immunomodulatory factors (e.g.,
        transforming growth factor-β (TGF-β), programmed death-ligand 1 (PDL1),
        interleukin-10 (IL-10), α-melanocyte-stimulating hormone (α-MSH), and
        macrophage migration inhibitory factor (MIF)) and enhanced expression of the
        major histocompatibility complex (MHC) throughout hair follicles.
      explanation: The cited synthesis directly couples immune-privilege collapse to enhanced follicular MHC display.
- name: Follicular Antigen and NKG2D-Ligand Display
  description: >-
    Active lesions show increased antigen-presentation machinery and follicular
    ULBP3/MICA danger ligands that can engage NKG2D on cytotoxic lymphocytes.
  biological_scale: CELLULAR
  cell_types:
  - preferred_term: Hair Follicular Keratinocyte
    term:
      id: CL:2000092
      label: hair follicular keratinocyte
  biological_processes:
  - preferred_term: Antigen Processing and Presentation via MHC Class I
    term:
      id: GO:0002474
      label: antigen processing and presentation of peptide antigen via MHC class I
  genes:
  - preferred_term: HLA-DRB1
    term:
      id: hgnc:4948
      label: HLA-DRB1
  - preferred_term: ULBP3
    term:
      id: hgnc:14895
      label: ULBP3
  evidence:
  - reference: PMID:20596022
    reference_title: Genome-wide association study in alopecia areata implicates both innate and adaptive immunity.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      By probing the role of ULBP3 in disease pathogenesis, we also show that its
      expression in lesional scalp from patients with AA is markedly upregulated in
      the hair follicle dermal sheath during active disease.
    explanation: Human lesional scalp directly shows upregulated follicular ULBP3.
  - reference: PMID:25129481
    reference_title: Alopecia areata is driven by cytotoxic T lymphocytes and is reversed by JAK inhibition.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      a cytotoxic subset of CD8+NKG2D+ T cells within the infiltrate surrounding
      human AA hair follicles
    explanation: Human lesions contain the receptor-bearing infiltrate beside follicles expressing its danger ligands.
  downstream:
  - target: CD8+ NKG2D+ T Cell Attack
    description: Follicular NKG2D ligands engage and activate nearby CD8+NKG2D+ cytotoxic T cells.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:20596022
      reference_title: Genome-wide association study in alopecia areata implicates both innate and adaptive immunity.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        These results suggest that the autoimmune destruction in AA may be mediated
        in part by CD8+NKG2D+ cytotoxic T cells, whose activation may be induced by
        upregulation of ULBP3 in the dermal sheath of the hair follicle.
      explanation: The human tissue study proposes the ligand-to-effector link but does not experimentally prove it in patients.
- name: Impaired Regulatory T Cell Control
  description: >-
    Susceptibility at CTLA4 and IL2RA implicates reduced regulatory T-cell control
    as an upstream modifier of follicular autoimmunity; direct functional
    impairment in patients remains incompletely established.
  biological_scale: CELLULAR
  cell_types:
  - preferred_term: Regulatory T Cell
    term:
      id: CL:0000815
      label: regulatory T cell
  genes:
  - preferred_term: CTLA4
    term:
      id: hgnc:2505
      label: CTLA4
  - preferred_term: IL2RA
    term:
      id: hgnc:6008
      label: IL2RA
  evidence:
  - reference: PMID:20596022
    reference_title: Genome-wide association study in alopecia areata implicates both innate and adaptive immunity.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Here we show an association with genomic regions containing several genes
      controlling the activation and proliferation of regulatory T cells (T(reg)
      cells), cytotoxic T lymphocyte-associated antigen 4 (CTLA4), interleukin
      (IL)-2/IL-21, IL-2 receptor A (IL-2RA; CD25) and Eos (also known as Ikaros
      family zinc finger 4; IKZF4), as well as the human leukocyte antigen (HLA)
      region.
    explanation: The GWAS implicates CTLA4 and IL2RA regulatory T-cell pathways but does not directly measure regulatory-cell function.
  downstream:
  - target: CD8+ NKG2D+ T Cell Attack
    description: Reduced regulatory control may permit expansion or persistence of pathogenic cytotoxic effectors.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:20596022
      reference_title: Genome-wide association study in alopecia areata implicates both innate and adaptive immunity.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Here we show an association with genomic regions containing several genes
        controlling the activation and proliferation of regulatory T cells (T(reg)
        cells), cytotoxic T lymphocyte-associated antigen 4 (CTLA4), interleukin
        (IL)-2/IL-21, IL-2 receptor A (IL-2RA; CD25) and Eos (also known as Ikaros
        family zinc finger 4; IKZF4), as well as the human leukocyte antigen (HLA)
        region.
      explanation: Susceptibility implicates Treg-control pathways upstream of autoimmunity, while the precise link to CD8+NKG2D+ effectors is not directly tested.
- name: CD8+ NKG2D+ T Cell Attack
  description: >-
    Peribulbar CD8+NKG2D+ cytotoxic T cells attack follicular targets. Transfer
    and depletion experiments establish this population as necessary and
    sufficient for disease transfer in the C3H/HeJ mouse model.
  biological_scale: CELLULAR
  cell_types:
  - preferred_term: CD8-Positive Alpha-Beta T Cell
    term:
      id: CL:0000625
      label: CD8-positive, alpha-beta T cell
  biological_processes:
  - preferred_term: T Cell-Mediated Cytotoxicity
    term:
      id: GO:0001913
      label: T cell mediated cytotoxicity
  genes:
  - preferred_term: KLRK1
    term:
      id: hgnc:18788
      label: KLRK1
  evidence:
  - reference: PMID:25129481
    reference_title: Alopecia areata is driven by cytotoxic T lymphocytes and is reversed by JAK inhibition.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Here, we show that cytotoxic CD8(+)NKG2D(+) T cells are both necessary and
      sufficient for the induction of AA in mouse models of disease.
    explanation: Mouse transfer and depletion experiments establish a causal effector population.
  - reference: PMID:37365384
    reference_title: A virtual memory CD8(+) T cell-originated subset causes alopecia areata through innate-like cytotoxicity.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Pathogenic activity of CD44s-hiCD49dlo CD8+ T cells was mediated by
      NKG2D-dependent innate-like cytotoxicity, which was further augmented by IL-15
      stimulation and triggered disease onset.
    explanation: A second mouse study supports NKG2D-dependent cytotoxicity and IL-15 augmentation.
  downstream:
  - target: IFN-gamma–IL-15 JAK-STAT Feedback
    description: Effector-derived IFN-gamma induces follicular IL-15 and sustains a feed-forward cytotoxic program.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:25129481
      reference_title: Alopecia areata is driven by cytotoxic T lymphocytes and is reversed by JAK inhibition.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        We postulate that IFN-γ produced by CD8 T cells leads to the collapse of
        immune privilege in the hair follicle27, inducing further production of
        IL-15 (ref. 28) (Supplementary Figs. 5 and 6) and a feed-forward loop that
        promotes type I cellular autoimmunity.
      explanation: The authors postulate the effector-to-cytokine feed-forward link rather than directly testing it.
  - target: Patchy Hair Loss
    description: Cytotoxic autoimmune attack produces the defining non-scarring alopecia phenotype.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:25129481
      reference_title: Alopecia areata is driven by cytotoxic T lymphocytes and is reversed by JAK inhibition.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        Here, we show that cytotoxic CD8(+)NKG2D(+) T cells are both necessary and
        sufficient for the induction of AA in mouse models of disease.
      explanation: Experimental transfer and depletion link the effector population to alopecia areata induction in mice.
  - target: Alopecia Totalis
    description: Extensive follicular autoimmune attack may progress to complete scalp hair loss.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:20596022
      reference_title: Genome-wide association study in alopecia areata implicates both innate and adaptive immunity.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Autoimmunity develops against the hair follicle, resulting in non-scarring
        hair loss that may begin as patches that can coalesce and progress to cover
        the entire scalp (alopecia totalis) or eventually the entire body (alopecia
        universalis)
      explanation: Human disease progression links follicular autoimmunity to total scalp involvement, without isolating this effector subset.
  - target: Alopecia Universalis
    description: Extensive follicular autoimmune attack may progress to complete body-hair loss.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:20596022
      reference_title: Genome-wide association study in alopecia areata implicates both innate and adaptive immunity.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Autoimmunity develops against the hair follicle, resulting in non-scarring
        hair loss that may begin as patches that can coalesce and progress to cover
        the entire scalp (alopecia totalis) or eventually the entire body (alopecia
        universalis)
      explanation: Human disease progression links follicular autoimmunity to body-wide involvement, without isolating this effector subset.
- name: IFN-gamma–IL-15 JAK-STAT Feedback
  description: >-
    IFN-gamma and common-gamma-chain cytokine signaling activates JAK-STAT in
    follicular and immune cells; follicular IL-15 supports the survival and
    cytotoxic function of IFN-gamma-producing CD8+NKG2D+ effectors.
  biological_scale: MOLECULAR
  cell_types:
  - preferred_term: CD8-Positive Alpha-Beta T Cell
    term:
      id: CL:0000625
      label: CD8-positive, alpha-beta T cell
  - preferred_term: Hair Follicular Keratinocyte
    term:
      id: CL:2000092
      label: hair follicular keratinocyte
  biological_processes:
  - preferred_term: JAK-STAT Signaling
    term:
      id: GO:0007259
      label: cell surface receptor signaling pathway via JAK-STAT
  - preferred_term: Response to Interferon-Gamma
    term:
      id: GO:0034341
      label: response to type II interferon
  genes:
  - preferred_term: IFNG
    term:
      id: hgnc:5438
      label: IFNG
  - preferred_term: IL15
    term:
      id: hgnc:5977
      label: IL15
  - preferred_term: IL2RA
    term:
      id: hgnc:6008
      label: IL2RA
  evidence:
  - reference: PMID:25129481
    reference_title: Alopecia areata is driven by cytotoxic T lymphocytes and is reversed by JAK inhibition.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Global transcriptional profiling of mouse and human AA skin revealed gene
      expression signatures indicative of cytotoxic T cell infiltration, an
      interferon-γ (IFN-γ) response and upregulation of several γ-chain (γc)
      cytokines known to promote the activation and survival of IFN-γ-producing
      CD8(+)NKG2D(+) effector T cells.
    explanation: Human and mouse lesional profiles jointly support the IFN/gamma-chain cytokine program.
  - reference: PMID:25129481
    reference_title: Alopecia areata is driven by cytotoxic T lymphocytes and is reversed by JAK inhibition.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Systemically administered pharmacological inhibitors of Janus kinase (JAK)
      family protein tyrosine kinases, downstream effectors of the IFN-γ and γc
      cytokine receptors, eliminated the IFN signature and prevented the development
      of AA, while topical administration promoted hair regrowth and reversed
      established disease.
    explanation: JAK inhibition functionally perturbed the IFN/gamma-chain program in the mouse model.
  downstream:
  - target: Loss of Hair Follicle Immune Privilege
    description: Effector-derived IFN-gamma reinforces immune-privilege collapse and follicular IL-15 production.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:25129481
      reference_title: Alopecia areata is driven by cytotoxic T lymphocytes and is reversed by JAK inhibition.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        We postulate that IFN-γ produced by CD8 T cells leads to the collapse of
        immune privilege in the hair follicle27, inducing further production of
        IL-15 (ref. 28) (Supplementary Figs. 5 and 6) and a feed-forward loop that
        promotes type I cellular autoimmunity.
      explanation: The authors postulate this feedback-loop closure rather than directly testing it.
  - target: Chemokine-Mediated Effector Recruitment
    description: The interferon response induces CXCL9, CXCL10, and CXCL11 expression in lesional skin.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:25129481
      reference_title: Alopecia areata is driven by cytotoxic T lymphocytes and is reversed by JAK inhibition.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        IFN response genes, such as those encoding the IFN-inducible chemokines
        CXCL-9, CXCL-10 and CXCL-11
      explanation: Lesional human and mouse skin directly connect the IFN program with inducible chemokines.
- name: Chemokine-Mediated Effector Recruitment
  description: >-
    IFN-inducible chemokines and CXCL12 amplify inflammatory-cell accumulation
    around the follicle; CXCL12 blockade reduces cutaneous CD8+ cells and disease
    in mice.
  biological_scale: TISSUE
  cell_types:
  - preferred_term: Fibroblast of Dermis
    term:
      id: CL:0002551
      label: fibroblast of dermis
  biological_processes:
  - preferred_term: Chemokine-Mediated Signaling Pathway
    term:
      id: GO:0070098
      label: chemokine-mediated signaling pathway
  genes:
  - preferred_term: CXCL12
    term:
      id: hgnc:10672
      label: CXCL12
  evidence:
  - reference: PMID:38338982
    reference_title: CXCL12 Neutralizing Antibody Promotes Hair Growth in Androgenic Alopecia and Alopecia Areata.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      CXCL12 expression is increased in AA mice, while s.c. injection of αCXCL12
      significantly inhibited hair loss in AA mice and reduced the number of CD8+,
      MHC-I+, and MHC-II+ cells in the skin.
    explanation: CXCL12 blockade reduces hair loss and cutaneous immune-cell accumulation in mice.
  - reference: PMID:38338982
    reference_title: CXCL12 Neutralizing Antibody Promotes Hair Growth in Androgenic Alopecia and Alopecia Areata.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      Interferon-γ (IFNγ) treatment increased the secretion of CXCL12 from DFs
      through the signal transducer and activator of transcription 3 (STAT3)
      pathway, and αCXCL12 treatment protected the hair follicle from IFNγ in hair
      organ culture.
    explanation: Dermal-fibroblast and hair-organ experiments link IFN signaling, CXCL12 secretion, and follicular injury.
  downstream:
  - target: CD8+ NKG2D+ T Cell Attack
    description: Chemokine signaling supports accumulation of cytotoxic CD8+ effectors in skin.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:38338982
      reference_title: CXCL12 Neutralizing Antibody Promotes Hair Growth in Androgenic Alopecia and Alopecia Areata.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        CXCL12 expression is increased in AA mice, while s.c. injection of αCXCL12
        significantly inhibited hair loss in AA mice and reduced the number of CD8+,
        MHC-I+, and MHC-II+ cells in the skin.
      explanation: Blocking CXCL12 lowers total cutaneous CD8+ cells; the experiment does not isolate the NKG2D+ subset.
phenotypes:
- name: Patchy Hair Loss
  category: Dermatological
  phenotype_term:
    preferred_term: Patchy Alopecia
    term:
      id: HP:0002232
      label: Patchy alopecia
  notes: Non-scarring patches may enlarge and coalesce; exclamation-mark hairs can be seen at active margins.
  evidence:
  - reference: PMID:20596022
    reference_title: Genome-wide association study in alopecia areata implicates both innate and adaptive immunity.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Autoimmunity develops against the hair follicle, resulting in non-scarring
      hair loss that may begin as patches that can coalesce and progress to cover
      the entire scalp (alopecia totalis) or eventually the entire body (alopecia
      universalis)
    explanation: The human disease description directly supports patchy, non-scarring hair loss.
- name: Alopecia Totalis
  category: Dermatological
  phenotype_term:
    preferred_term: Alopecia Totalis
    term:
      id: HP:0007418
      label: Alopecia totalis
  notes: Complete loss of scalp hair.
  evidence:
  - reference: PMID:20596022
    reference_title: Genome-wide association study in alopecia areata implicates both innate and adaptive immunity.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Autoimmunity develops against the hair follicle, resulting in non-scarring
      hair loss that may begin as patches that can coalesce and progress to cover
      the entire scalp (alopecia totalis) or eventually the entire body (alopecia
      universalis)
    explanation: The source explicitly defines progression to complete scalp involvement.
- name: Alopecia Universalis
  category: Dermatological
  phenotype_term:
    preferred_term: Alopecia Universalis
    term:
      id: HP:0002289
      label: Alopecia universalis
  notes: Complete loss of scalp and body hair.
  evidence:
  - reference: PMID:20596022
    reference_title: Genome-wide association study in alopecia areata implicates both innate and adaptive immunity.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Autoimmunity develops against the hair follicle, resulting in non-scarring
      hair loss that may begin as patches that can coalesce and progress to cover
      the entire scalp (alopecia totalis) or eventually the entire body (alopecia
      universalis)
    explanation: The source explicitly defines progression to complete body-hair involvement.
- name: Nail Pitting
  category: Dermatological
  phenotype_term:
    preferred_term: Nail Pits
    term:
      id: HP:0001803
      label: Nail pits
  notes: Frequency was not assigned because the reviewed source did not provide a cohort estimate.
  evidence:
  - reference: PMID:38893003
    reference_title: "Alopecia Areata of the Nails: Diagnosis and Management."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Nail changes in AA include pitting, trachyonychia, leukonychia, red lunula,
      and miscellaneous alterations such as longitudinal ridging and brittle nails.
    explanation: The review directly identifies nail pitting in alopecia areata.
- name: Trachyonychia
  category: Dermatological
  phenotype_term:
    preferred_term: Trachyonychia
    term:
      id: HP:0030804
      label: Trachyonychia
  notes: Frequency was not assigned because the reviewed source did not provide a cohort estimate.
  evidence:
  - reference: PMID:38893003
    reference_title: "Alopecia Areata of the Nails: Diagnosis and Management."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Nail changes in AA include pitting, trachyonychia, leukonychia, red lunula,
      and miscellaneous alterations such as longitudinal ridging and brittle nails.
    explanation: The review directly identifies trachyonychia in alopecia areata.
histopathology:
- name: Peribulbar T-Cell Infiltrate
  description: T cells characteristically surround the hair-follicle bulb in lesional tissue.
  evidence:
  - reference: PMID:25129481
    reference_title: Alopecia areata is driven by cytotoxic T lymphocytes and is reversed by JAK inhibition.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Alopecia areata is a T cell–mediated autoimmune disease characterized
      phenotypically by hair loss and, histologically, by infiltrating T cells
      surrounding the hair follicle bulb
    explanation: The source explicitly states the characteristic peribulbar T-cell histology.
biochemical: []
genetic:
- name: HLA-DRB1 Susceptibility
  association: Risk Factor
  relationship_type: SUSCEPTIBILITY
  variant_origin: GERMLINE
  gene_term:
    preferred_term: HLA-DRB1
    term:
      id: hgnc:4948
      label: HLA-DRB1
  evidence:
  - reference: PMID:25608926
    reference_title: Genome-wide meta-analysis in alopecia areata resolves HLA associations and reveals two new susceptibility loci.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The strongest region of association is the major histocompatibility complex,
      where we fine-map four independent effects, all implicating human leukocyte
      antigen-DR as a key aetiologic driver.
    explanation: Meta-analysis and fine-mapping make HLA-DR the strongest susceptibility region.
- name: CTLA4 Susceptibility
  association: Risk Factor
  relationship_type: SUSCEPTIBILITY
  variant_origin: GERMLINE
  gene_term:
    preferred_term: CTLA4
    term:
      id: hgnc:2505
      label: CTLA4
  evidence:
  - reference: PMID:20596022
    reference_title: Genome-wide association study in alopecia areata implicates both innate and adaptive immunity.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Here we show an association with genomic regions containing several genes
      controlling the activation and proliferation of regulatory T cells (T(reg)
      cells), cytotoxic T lymphocyte-associated antigen 4 (CTLA4), interleukin
      (IL)-2/IL-21, IL-2 receptor A (IL-2RA; CD25) and Eos (also known as Ikaros
      family zinc finger 4; IKZF4), as well as the human leukocyte antigen (HLA)
      region.
    explanation: The GWAS directly identifies the CTLA4-containing region as associated with alopecia areata.
- name: IL2RA Susceptibility
  association: Risk Factor
  relationship_type: SUSCEPTIBILITY
  variant_origin: GERMLINE
  gene_term:
    preferred_term: IL2RA
    term:
      id: hgnc:6008
      label: IL2RA
  evidence:
  - reference: PMID:20596022
    reference_title: Genome-wide association study in alopecia areata implicates both innate and adaptive immunity.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Here we show an association with genomic regions containing several genes
      controlling the activation and proliferation of regulatory T cells (T(reg)
      cells), cytotoxic T lymphocyte-associated antigen 4 (CTLA4), interleukin
      (IL)-2/IL-21, IL-2 receptor A (IL-2RA; CD25) and Eos (also known as Ikaros
      family zinc finger 4; IKZF4), as well as the human leukocyte antigen (HLA)
      region.
    explanation: The GWAS directly identifies the IL2RA-containing region as associated with alopecia areata.
- name: ULBP3 Susceptibility
  association: Risk Factor
  relationship_type: SUSCEPTIBILITY
  variant_origin: GERMLINE
  gene_term:
    preferred_term: ULBP3
    term:
      id: hgnc:14895
      label: ULBP3
  evidence:
  - reference: PMID:20596022
    reference_title: Genome-wide association study in alopecia areata implicates both innate and adaptive immunity.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      A region of strong association resides within the ULBP (cytomegalovirus
      UL16-binding protein) gene cluster on chromosome 6q25.1, encoding activating
      ligands of the natural killer cell receptor NKG2D that have not previously been
      implicated in an autoimmune disease.
    explanation: The GWAS directly identifies the ULBP gene cluster as a strong susceptibility region.
environmental: []
diagnosis:
- name: Trichoscopy
  description: Trichoscopy supports diagnosis and longitudinal monitoring of alopecia areata.
  diagnosis_term:
    preferred_term: Trichoscopy
    term:
      id: NCIT:C116478
      label: Dermoscopy
  evidence:
  - reference: PMID:41699409
    reference_title: "Epidemiology, Diagnosis and Management of Alopecia Areata: An Asia-Pacific Modified Delphi Expert Panel Recommendations."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Trichoscopy is deemed essential for diagnosing and monitoring AA, while skin
      biopsy is reserved for when the cause of hair loss is unclear.
    explanation: Current expert consensus supports trichoscopy for diagnosis and monitoring.
- name: Skin Biopsy When the Cause Is Unclear
  description: Histologic evaluation is reserved for diagnostically uncertain hair loss rather than routine use.
  diagnosis_term:
    preferred_term: Skin Biopsy
    term:
      id: NCIT:C51692
      label: Skin Biopsy
  evidence:
  - reference: PMID:41699409
    reference_title: "Epidemiology, Diagnosis and Management of Alopecia Areata: An Asia-Pacific Modified Delphi Expert Panel Recommendations."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Trichoscopy is deemed essential for diagnosing and monitoring AA, while skin
      biopsy is reserved for when the cause of hair loss is unclear.
    explanation: Current expert consensus reserves biopsy for unclear causes of hair loss.
treatments:
- name: Topical Corticosteroids
  description: A consensus-supported option for children and for mild-to-moderate disease.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Topical Corticosteroid Therapy
    term:
      id: NCIT:C122078
      label: Topical Corticosteroid Therapy
  evidence:
  - reference: PMID:41699409
    reference_title: "Epidemiology, Diagnosis and Management of Alopecia Areata: An Asia-Pacific Modified Delphi Expert Panel Recommendations."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Regarding treatment, topical corticosteroids are recommended in children < 12
      years. For patients aged ≥ 12 years, topical and intralesional corticosteroids
      could be used for mild-to-moderate AA, while Janus kinase inhibitors and
      systemic corticosteroids have a role in moderate-to-severe AA.
    explanation: Current consensus states the age- and severity-specific role of topical corticosteroids.
- name: Intralesional Corticosteroids
  description: A consensus first option for localized disease in adults.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Localized Corticosteroid Therapy
    term:
      id: NCIT:C121367
      label: Localized Corticosteroid Therapy
  evidence:
  - reference: PMID:33183894
    reference_title: Consensus on the treatment of alopecia areata - Brazilian Society of Dermatology.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Intralesional injectable corticotherapy was considered the first option for
      localized disease in adults.
    explanation: Dermatology consensus directly supports intralesional corticosteroids for localized adult disease.
- name: Systemic Corticosteroids
  description: A consensus-supported option for active, extensive or moderate-to-severe disease.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Systemic Corticosteroid Therapy
    term:
      id: NCIT:C122080
      label: Systemic Corticosteroid Therapy
  evidence:
  - reference: PMID:33183894
    reference_title: Consensus on the treatment of alopecia areata - Brazilian Society of Dermatology.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      In extensive cases with signs of activity, systemic corticosteroid therapy
      should be considered and can be used together with immunosuppressants
      (corticosteroid-sparing agents).
    explanation: Dermatology consensus directly supports systemic corticosteroids in extensive active disease.
- name: Diphencyprone Topical Immunotherapy
  description: Contact immunotherapy is a consensus option for stable, long-standing alopecia areata.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: diphenylcyclopropenone
      term:
        id: CHEBI:53074
        label: diphenylcyclopropenone
  evidence:
  - reference: PMID:33183894
    reference_title: Consensus on the treatment of alopecia areata - Brazilian Society of Dermatology.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: The use of an immunosensitizer (diphencyprone) is an option for stable long-term cases.
    explanation: Dermatology consensus directly supports diphencyprone for stable long-term disease.
- name: Baricitinib
  description: Oral JAK1/2 inhibitor with replicated randomized phase-3 efficacy in adults with severe alopecia areata.
  therapeutic_modality: SMALL_MOLECULE
  target_mechanisms:
  - target: IFN-gamma–IL-15 JAK-STAT Feedback
    treatment_effect: INHIBITS
    description: Baricitinib inhibits JAK1/2 signaling downstream of inflammatory cytokine receptors.
    evidence:
    - reference: PMID:35334197
      reference_title: Two Phase 3 Trials of Baricitinib for Alopecia Areata.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Baricitinib, an oral, selective, reversible inhibitor of Janus kinases 1
        and 2, may interrupt cytokine signaling implicated in the pathogenesis of
        alopecia areata.
      explanation: The trial report identifies the drug's JAK1/2 mechanism and its relevance to pathogenic cytokine signaling.
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: baricitinib
      term:
        id: CHEBI:95341
        label: baricitinib
  target_phenotypes:
  - preferred_term: Patchy Hair Loss
    term:
      id: HP:0002232
      label: Patchy alopecia
  evidence:
  - reference: PMID:35334197
    reference_title: Two Phase 3 Trials of Baricitinib for Alopecia Areata.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      In two phase 3 trials involving patients with severe alopecia areata, oral
      baricitinib was superior to placebo with respect to hair regrowth at 36 weeks.
    explanation: Two randomized phase-3 trials directly demonstrate hair-regrowth efficacy.
- name: Ritlecitinib
  description: Oral selective JAK3/TEC-family kinase inhibitor supported by a randomized phase-2b/3 trial in patients aged 12 years and older.
  therapeutic_modality: SMALL_MOLECULE
  target_mechanisms:
  - target: IFN-gamma–IL-15 JAK-STAT Feedback
    treatment_effect: INHIBITS
    description: Ritlecitinib inhibits JAK3/TEC-family kinase signaling relevant to cytotoxic lymphocyte activation.
    evidence:
    - reference: PMID:37062298
      reference_title: "Efficacy and safety of ritlecitinib in adults and adolescents with alopecia areata: a randomised, double-blind, multicentre, phase 2b-3 trial."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        We investigated the efficacy and safety of ritlecitinib, an oral,
        selective dual JAK3/TEC family kinase inhibitor, in patients with alopecia
        areata.
      explanation: The trial report directly identifies the drug's JAK3/TEC-family kinase mechanism.
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: ritlecitinib
      term:
        id: CHEBI:229233
        label: ritlecitinib
  target_phenotypes:
  - preferred_term: Patchy Hair Loss
    term:
      id: HP:0002232
      label: Patchy alopecia
  evidence:
  - reference: PMID:37062298
    reference_title: "Efficacy and safety of ritlecitinib in adults and adolescents with alopecia areata: a randomised, double-blind, multicentre, phase 2b-3 trial."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Ritlecitinib was effective and well tolerated in patients aged 12 years and
      older with alopecia areata.
    explanation: The randomized trial directly supports efficacy in adults and adolescents aged at least 12 years.
- name: Deuruxolitinib
  description: Oral JAK1/2 inhibitor supported by a randomized phase-3 trial in adults with at least 50% scalp hair loss.
  therapeutic_modality: SMALL_MOLECULE
  target_mechanisms:
  - target: IFN-gamma–IL-15 JAK-STAT Feedback
    treatment_effect: INHIBITS
    description: Deuruxolitinib inhibits JAK1/2 signaling downstream of inflammatory cytokine receptors.
    evidence:
    - reference: PMID:39053611
      reference_title: "Efficacy and safety of deuruxolitinib, an oral selective Janus kinase inhibitor, in adults with alopecia areata: Results from the Phase 3 randomized, controlled trial (THRIVE-AA1)."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        The Phase 3 THRIVE-AA1 randomized, double-blinded, placebo-controlled trial
        (NCT04518995) evaluated the safety and efficacy of the oral JAK1/JAK2
        inhibitor deuruxolitinib in adult patients with AA.
      explanation: The trial report directly identifies deuruxolitinib as an oral JAK1/2 inhibitor.
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: Deuruxolitinib
      term:
        id: NCIT:C175770
        label: Deuruxolitinib
  target_phenotypes:
  - preferred_term: Patchy Hair Loss
    term:
      id: HP:0002232
      label: Patchy alopecia
  evidence:
  - reference: PMID:39053611
    reference_title: "Efficacy and safety of deuruxolitinib, an oral selective Janus kinase inhibitor, in adults with alopecia areata: Results from the Phase 3 randomized, controlled trial (THRIVE-AA1)."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Both doses of deuruxolitinib were effective for hair regrowth.
    explanation: The randomized phase-3 trial directly supports hair-regrowth efficacy.
animal_models:
- species: Mouse (Mus musculus)
  genotype: C3H/HeJ recipients grafted with skin from spontaneously alopecic C3H/HeJ donors
  description: >-
    A full-thickness skin graft from a spontaneously alopecic donor reliably
    transfers disease to normal-haired syngeneic recipients and supports causal
    lymphocyte-transfer, cytokine-blockade, and JAK-inhibition experiments.
  associated_phenotypes:
  - Patchy Hair Loss
  evidence:
  - reference: PMID:25129481
    reference_title: Alopecia areata is driven by cytotoxic T lymphocytes and is reversed by JAK inhibition.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Normal-haired C3H/HeJ mice were grafted at 8 weeks of age (during the second
      telogen) with skin from a C3H/HeJ mouse that developed AA spontaneously
    explanation: The methods define the syngeneic skin-graft model.
  - reference: PMID:25129481
    reference_title: Alopecia areata is driven by cytotoxic T lymphocytes and is reversed by JAK inhibition.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: Hair loss typically began at around 4–6 weeks after grafting. No sham grafted mouse developed hair loss.
    explanation: Disease onset after affected grafts and absence after sham grafts establish the model phenotype.
datasets:
- accession: massive:MSV000082825
  title: Immunoregulatory Effects of Myeloid-Derived Suppressor Cell Exosomes in Mouse Model of Autoimmune Alopecia Areata
  organism:
    preferred_term: mouse
    term:
      id: NCBITaxon:10090
      label: Mus musculus
  data_type: PROTEOMICS
  description: We have demonstrated therapeutic efficacy of MDSC in mouse Alopecia Areata (AA). In the same AA model, we now asked whether MDSC exosomes (MDSC-Exo) can replace MDSC. MDSC-Exo from bone marrow cells (BMC) cultures of healthy donors could substantially facilitate treatment. With knowledge on MDSC-Exo being limited, their suitability needs to be verified in advance. Protein marker profiles suggest comparability of BMC- to ex vivo collected inflammatory MDSC/MDSC-Exo in mice with a chronic contact dermatitis, which is a therapeutic option in AA.
  notes: Located via OmicsDI, which aggregates across omics repositories; this record comes from massive. Only repositories with no other discovery route in this project and with a working accession resolver are curated from OmicsDI -- GEO, ArrayExpress, PRIDE, MetaboLights and EGA hits are excluded as duplicates of dedicated passes. Matched because the disease is named in the dataset's own title ("Alopecia Areata"). Retrieved 2026-08-02.
- accession: dbgap:phs000586
  title: Genome Wide Association Studies in Alopecia Areata
  description: 1054 unrelated alopecia areata patients were genotyped with the Illumina HumanHap550v3.0 genotyping chip. Allele frequencies were compared to publically available data from three population cohorts of controls.
  notes: Located via OmicsDI, which aggregates across omics repositories; this record comes from dbgap. Only repositories with no other discovery route in this project and with a working accession resolver are curated from OmicsDI -- GEO, ArrayExpress, PRIDE, MetaboLights and EGA hits are excluded as duplicates of dedicated passes. Matched because the disease is named in the dataset's own title ("Alopecia Areata"). Retrieved 2026-08-02.
clinical_trials:
- name: NCT03570749
  description: Adaptive randomized placebo-controlled baricitinib study in adults with severe or very severe alopecia areata (BRAVE-AA1).
  status: COMPLETED
  evidence:
  - reference: clinicaltrials:NCT03570749
    reference_title: A Multicenter, Randomized, Double-Blind, Placebo-Controlled, Operationally Seamless, Adaptive Phase 2/3 Study to Evaluate the Efficacy and Safety of Baricitinib in Adult Patients With Severe or Very Severe Alopecia Areata
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      This study is designed to select up to two doses of baricitinib (referred to
      as low dose and high dose) and assess their efficacy and safety for the
      treatment of severe or very severe alopecia areata.
    explanation: The registry summary states the baricitinib dose-selection and efficacy/safety objectives.
- name: NCT03899259
  phase: PHASE_III
  status: COMPLETED
  description: Randomized placebo-controlled phase-3 baricitinib study in adults with severe or very severe alopecia areata (BRAVE-AA2).
  evidence:
  - reference: clinicaltrials:NCT03899259
    reference_title: A Multicenter, Randomized, Double-Blind, Placebo- Controlled, Phase 3 Study to Evaluate the Efficacy and Safety of Baricitinib in Adult Patients With Severe or Very Severe Alopecia Areata
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The reason for this study is to see if baricitinib is safe and effective in
      adults with severe or very severe alopecia areata (AA).
    explanation: The registry summary states the population and trial objective.
- name: NCT03732807
  status: COMPLETED
  description: Global randomized placebo-controlled dose-ranging phase-2b/3 ritlecitinib study in adults and adolescents with at least 50% scalp hair loss (ALLEGRO).
  evidence:
  - reference: clinicaltrials:NCT03732807
    reference_title: A PHASE 2B/3 RANDOMIZED, DOUBLE-BLIND, PLACEBO-CONTROLLED, DOSE-RANGING STUDY TO INVESTIGATE THE EFFICACY AND SAFETY OF PF-06651600 IN ADULT AND ADOLESCENT ALOPECIA AREATA (AA) SUBJECTS WITH 50% OR GREATER SCALP HAIR LOSS
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      This is a global Phase 2b/3 study to evaluate the safety and effectiveness of
      an investigational study drug (called PF-06651600) in adults and adolescents
      (12 years and older) who have 50% or greater scalp hair loss.
    explanation: The registry summary states the phase, age range, severity, and efficacy/safety objective.
- name: NCT04518995
  phase: PHASE_III
  status: COMPLETED
  description: Randomized placebo-controlled deuruxolitinib study in adults with at least 50% scalp hair loss (THRIVE-AA1).
  evidence:
  - reference: clinicaltrials:NCT04518995
    reference_title: A Double-Blind, Randomized, Placebo-Controlled Study to Evaluate the Efficacy and Safety of CTP-543 in Adult Patients With Moderate to Severe Alopecia Areata (THRIVE-AA1)
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      This study evaluates the safety and effectiveness of an investigational study
      drug (called CTP-543) in adults (18 years and older) who have 50% or greater
      scalp hair loss.
    explanation: The registry summary states the intervention's former name, adult population, severity, and efficacy/safety objective.
discussions:
- discussion_id: aa_mouse_human_causal_translation
  prompt: Which elements of the CD8+NKG2D+/IFN-gamma/IL-15 circuit are necessary and sufficient in human alopecia areata?
  kind: HUMAN_MODEL_MISMATCH
  status: OPEN
  attaches_to:
  - pathophysiology#CD8+ NKG2D+ T Cell Attack
  - pathophysiology#IFN-gamma–IL-15 JAK-STAT Feedback
  - animal_models#Mouse (Mus musculus)
  rationale: >-
    Necessity, sufficiency, and cytokine-blockade results come from C3H/HeJ mice.
    Human lesions reproduce the infiltrate and transcriptional signatures, and
    human JAK-inhibitor trials support pathway relevance, but they do not establish
    every causal step in patients.
  evidence:
  - reference: PMID:25129481
    reference_title: Alopecia areata is driven by cytotoxic T lymphocytes and is reversed by JAK inhibition.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Here, we show that cytotoxic CD8(+)NKG2D(+) T cells are both necessary and
      sufficient for the induction of AA in mouse models of disease.
    explanation: The strongest causal claim is explicitly limited to mouse models.
- discussion_id: aa_jak_long_term_durability
  prompt: How durable and safe are JAK-inhibitor responses during long-term treatment and after treatment cessation?
  kind: KNOWLEDGE_GAP
  status: OPEN
  attaches_to:
  - treatments#Baricitinib
  - treatments#Ritlecitinib
  - treatments#Deuruxolitinib
  rationale: >-
    Randomized trials establish short-term hair regrowth, but comparative long-term
    safety, sustained response, and outcomes after withdrawal remain incompletely
    characterized.
  evidence:
  - reference: PMID:39053611
    reference_title: "Efficacy and safety of deuruxolitinib, an oral selective Janus kinase inhibitor, in adults with alopecia areata: Results from the Phase 3 randomized, controlled trial (THRIVE-AA1)."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Further studies are required to understand longer-term safety, efficacy, and impact of treatment cessation.
    explanation: The phase-3 report explicitly identifies the long-term and cessation evidence gap.
classifications:
  harrisons_chapter:
  - classification_value: DERMATOLOGY
  - classification_value: IMMUNE_RHEUMATOLOGIC
review_notes: >-
  Publication-readiness review completed 2026-08-04. The Falcon research artifact
  was used only as a lead because it contained an incorrect MONDO identifier and
  mismatched HPO labels. Reviewed but not promoted: PTPN22 susceptibility (not
  supported by the landmark GWAS used here); psychological stress and viral
  infection as triggers (insufficient claim-level evidence); circulating
  anti-hair-follicle antibodies as a biochemical finding (not established as a
  routine diagnostic marker); phenotype frequency bands (no cited cohort
  estimates); Autoimmunity (HP:0002960) as a separate phenotype because it is the
  disease class and mechanism here rather than an additional clinical finding;
  CXCL12-neutralizing antibody as a treatment (mouse and organ-culture
  evidence only); and adjunctive minoxidil (consensus mention without efficacy data
  in the reviewed record). Nail pits and trachyonychia were retained as phenotypes
  but not linked into the follicular causal graph because the reviewed evidence does
  not establish that mechanism. A premature anagen-to-catagen hair-cycle
  intermediate was reviewed but not modeled because no exact supporting snippet
  was available in the audited caches. Autoimmune thyroid disease, vitiligo,
  atopic dermatitis, and Down syndrome comorbidity assertions were not promoted
  because they were not supported by the reviewed research artifacts or fetched
  claim-level sources. Regulatory status was checked during review; structured treatment
  efficacy is anchored to primary randomized trials rather than approval language.
references:
- reference: PMID:20596022
  title: Genome-wide association study in alopecia areata implicates both innate and adaptive immunity.
- reference: PMID:25129481
  title: Alopecia areata is driven by cytotoxic T lymphocytes and is reversed by JAK inhibition.
- reference: PMID:25608926
  title: Genome-wide meta-analysis in alopecia areata resolves HLA associations and reveals two new susceptibility loci.
- reference: PMID:32682334
  title: Hair follicle immune privilege and its collapse in alopecia areata.
- reference: PMID:33183894
  title: Consensus on the treatment of alopecia areata - Brazilian Society of Dermatology.
- reference: PMID:35334197
  title: Two Phase 3 Trials of Baricitinib for Alopecia Areata.
- reference: PMID:37062298
  title: "Efficacy and safety of ritlecitinib in adults and adolescents with alopecia areata: a randomised, double-blind, multicentre, phase 2b-3 trial."
- reference: PMID:37365384
  title: A virtual memory CD8(+) T cell-originated subset causes alopecia areata through innate-like cytotoxicity.
- reference: PMID:38338982
  title: CXCL12 Neutralizing Antibody Promotes Hair Growth in Androgenic Alopecia and Alopecia Areata.
- reference: PMID:38673994
  title: "Pathogenesis of Alopecia Areata and Vitiligo: Commonalities and Differences."
- reference: PMID:38893003
  title: "Alopecia Areata of the Nails: Diagnosis and Management."
- reference: PMID:39053611
  title: "Efficacy and safety of deuruxolitinib, an oral selective Janus kinase inhibitor, in adults with alopecia areata: Results from the Phase 3 randomized, controlled trial (THRIVE-AA1)."
- reference: PMID:41699409
  title: "Epidemiology, Diagnosis and Management of Alopecia Areata: An Asia-Pacific Modified Delphi Expert Panel Recommendations."
- reference: PMID:41855094
  title: "S3 guideline diagnostics and therapy of alopecia areata - Part 1: Diagnostics and epidemiology."
- reference: clinicaltrials:NCT03570749
  title: A Multicenter, Randomized, Double-Blind, Placebo-Controlled, Operationally Seamless, Adaptive Phase 2/3 Study to Evaluate the Efficacy and Safety of Baricitinib in Adult Patients With Severe or Very Severe Alopecia Areata
- reference: clinicaltrials:NCT03732807
  title: A PHASE 2B/3 RANDOMIZED, DOUBLE-BLIND, PLACEBO-CONTROLLED, DOSE-RANGING STUDY TO INVESTIGATE THE EFFICACY AND SAFETY OF PF-06651600 IN ADULT AND ADOLESCENT ALOPECIA AREATA (AA) SUBJECTS WITH 50% OR GREATER SCALP HAIR LOSS
- reference: clinicaltrials:NCT03899259
  title: A Multicenter, Randomized, Double-Blind, Placebo- Controlled, Phase 3 Study to Evaluate the Efficacy and Safety of Baricitinib in Adult Patients With Severe or Very Severe Alopecia Areata
- reference: clinicaltrials:NCT04518995
  title: A Double-Blind, Randomized, Placebo-Controlled Study to Evaluate the Efficacy and Safety of CTP-543 in Adult Patients With Moderate to Severe Alopecia Areata (THRIVE-AA1)
📚

References & Deep Research

References

18
PMID:20596022
Genome-wide association study in alopecia areata implicates both innate and adaptive immunity.
No top-level findings curated for this source.
PMID:25129481
Alopecia areata is driven by cytotoxic T lymphocytes and is reversed by JAK inhibition.
No top-level findings curated for this source.
PMID:25608926
Genome-wide meta-analysis in alopecia areata resolves HLA associations and reveals two new susceptibility loci.
No top-level findings curated for this source.
PMID:32682334
Hair follicle immune privilege and its collapse in alopecia areata.
No top-level findings curated for this source.
PMID:33183894
Consensus on the treatment of alopecia areata - Brazilian Society of Dermatology.
No top-level findings curated for this source.
PMID:35334197
Two Phase 3 Trials of Baricitinib for Alopecia Areata.
No top-level findings curated for this source.
PMID:37062298
Efficacy and safety of ritlecitinib in adults and adolescents with alopecia areata: a randomised, double-blind, multicentre, phase 2b-3 trial.
No top-level findings curated for this source.
PMID:37365384
A virtual memory CD8(+) T cell-originated subset causes alopecia areata through innate-like cytotoxicity.
No top-level findings curated for this source.
PMID:38338982
CXCL12 Neutralizing Antibody Promotes Hair Growth in Androgenic Alopecia and Alopecia Areata.
No top-level findings curated for this source.
PMID:38673994
Pathogenesis of Alopecia Areata and Vitiligo: Commonalities and Differences.
No top-level findings curated for this source.
PMID:38893003
Alopecia Areata of the Nails: Diagnosis and Management.
No top-level findings curated for this source.
PMID:39053611
Efficacy and safety of deuruxolitinib, an oral selective Janus kinase inhibitor, in adults with alopecia areata: Results from the Phase 3 randomized, controlled trial (THRIVE-AA1).
No top-level findings curated for this source.
PMID:41699409
Epidemiology, Diagnosis and Management of Alopecia Areata: An Asia-Pacific Modified Delphi Expert Panel Recommendations.
No top-level findings curated for this source.
PMID:41855094
S3 guideline diagnostics and therapy of alopecia areata - Part 1: Diagnostics and epidemiology.
No top-level findings curated for this source.
clinicaltrials:NCT03570749
A Multicenter, Randomized, Double-Blind, Placebo-Controlled, Operationally Seamless, Adaptive Phase 2/3 Study to Evaluate the Efficacy and Safety of Baricitinib in Adult Patients With Severe or Very Severe Alopecia Areata
No top-level findings curated for this source.
clinicaltrials:NCT03732807
A PHASE 2B/3 RANDOMIZED, DOUBLE-BLIND, PLACEBO-CONTROLLED, DOSE-RANGING STUDY TO INVESTIGATE THE EFFICACY AND SAFETY OF PF-06651600 IN ADULT AND ADOLESCENT ALOPECIA AREATA (AA) SUBJECTS WITH 50% OR GREATER SCALP HAIR LOSS
No top-level findings curated for this source.
clinicaltrials:NCT03899259
A Multicenter, Randomized, Double-Blind, Placebo- Controlled, Phase 3 Study to Evaluate the Efficacy and Safety of Baricitinib in Adult Patients With Severe or Very Severe Alopecia Areata
No top-level findings curated for this source.
clinicaltrials:NCT04518995
A Double-Blind, Randomized, Placebo-Controlled Study to Evaluate the Efficacy and Safety of CTP-543 in Adult Patients With Moderate to Severe Alopecia Areata (THRIVE-AA1)
No top-level findings curated for this source.

Deep Research

2
Disorder ▸

Disorder

  • Name: Alopecia Areata
  • Category: Autoimmune
  • Existing deep-research providers: falcon
  • Existing evidence reference count in YAML: 17

Key Pathophysiology Nodes

  • Loss of Hair Follicle Immune Privilege
  • CD8+ T Cell-Mediated Attack
  • JAK-STAT Signaling Activation
  • Chemokine-Mediated Immune Cell Recruitment
  • Deep research literature mapping

Citation Inventory (for evidence mapping)

  • DOI:10.1073/pnas.2305764120
  • DOI:10.3389/fimmu.2024.1444777
  • DOI:10.3389/fimmu.2025.1621492
  • DOI:10.3389/fimmu.2025.1681163
  • DOI:10.3390/ijms25084409
  • DOI:10.3390/ijms25115652
  • DOI:10.53582/amj255170s
Falcon ▸
Disease Pathophysiology Research Report
Edison Scientific Literature 20 citations 2025-12-18T09:55:17.181477

Disease Pathophysiology Research Report

Target Disease - Disease Name: Alopecia Areata (AA) - MONDO ID: MONDO:0005392 - Category: Autoimmune

Pathophysiology description Alopecia areata is a T cell–mediated, non-scarring autoimmune disease of the anagen hair follicle driven by collapse of hair-follicle immune privilege (IP) and a self-amplifying IFN-γ–IL-15–JAK/STAT axis. Under homeostasis, anagen follicles suppress antigen presentation and maintain local immunosuppression (e.g., TGF-β, PD‑L1, IL‑10, α‑MSH, MIF) with low MHC I/II expression. In AA, IP collapses with upregulation of MHC I and II on follicular keratinocytes and antigen-presenting cells, increased expression of stress ligands (MICA, ULBP3/6), and recruitment/activation of cytotoxic CD8+ NKG2D+ T cells that recognize these ligands and deliver cytotoxic mediators (granzyme, perforin). This response is orchestrated by interferons and γ-chain cytokines: IFN‑γ induces IL‑15 production in follicular epithelium; IL‑15 sustains and amplifies CD8+ and NK cell effector programs through JAK1/JAK3 signaling, forming a local positive feedback loop that perpetuates disease. Lesional skin shows prominent IFN-response chemokines (CXCL9/CXCL10/CXCL11), and multi-omic and single-cell data support a central role for clonally expanded, tissue-resident CD8+ effectors, with contributions from Th1/Th17 CD4+ cells, NK cells, dendritic cells (including plasmacytoid DCs), and mast cells. Oxidative and other cellular stressors are implicated in NKG2D-ligand induction and IP failure. Spatially, the bulb (growth compartment) and, in some reports, the bulge (stem cell niche) exhibit IP alterations and pathologic infiltration, which correlate with premature anagen→catagen transitions and clinical hair loss. Therapeutically, targeting the JAK–STAT node reverses the pathogenic transcriptional program and supports regrowth, and emerging approaches modulate upstream chemokine axes such as CXCL12/CXCR4 in preclinical models (URLs and dates below). (yamaguchi2024pathogenesisofalopecia pages 2-4, lee2023functionalinterrogationof pages 6-7, simeonovski2025disruptionofhair pages 5-7, kim2025alopeciaareatafrom pages 2-4, zhao2025frommechanismsto pages 1-2, an2024humanizedcxcl12antibody pages 1-2)

Core Pathophysiology - Primary mechanisms - Hair follicle immune privilege collapse: loss of local immunosuppressive milieu and increased antigen presentation (MHC I/II) in anagen follicles permit autoreactive T cell recognition. (yamaguchi2024pathogenesisofalopecia pages 2-4, zhao2025frommechanismsto pages 1-2) - IFN‑γ–IL‑15–JAK/STAT amplification: IFN‑γ induces IL‑15 in follicular keratinocytes; IL‑15 activates CD8+ and NK cells via JAK1/3; multiple cytokines converge on JAK–STAT to drive cytotoxic and chemokine programs. (yamaguchi2024pathogenesisofalopecia pages 2-4, simeonovski2025disruptionofhair pages 5-7, kim2025alopeciaareatafrom pages 2-4) - CD8+ NKG2D+ T cell cytotoxicity: recognition of stress ligands (MICA, ULBP3/6) triggers effector functions and hair cycle disruption. (lee2023functionalinterrogationof pages 6-7, yamaguchi2024pathogenesisofalopecia pages 2-4) - Chemokine recruitment: CXCL9/10/11 (IFN-inducible) recruit CXCR3+ Th1 and CD8+ T cells; CXCL12/CXCR4 supports effector accumulation in preclinical AA. (yamaguchi2024pathogenesisofalopecia pages 2-4, an2024humanizedcxcl12antibody pages 1-2) - Oxidative and cellular stress: promotes NKG2D ligand expression (e.g., MICA, ULBP3/6) and contributes to IP collapse. (yamaguchi2024pathogenesisofalopecia pages 2-4) - Dysregulated molecular pathways - JAK–STAT cascade downstream of IFNs and γ-chain cytokines (IL‑2, IL‑7, IL‑15). (simeonovski2025disruptionofhair pages 5-7, lee2023functionalinterrogationof pages 6-7) - Antigen processing and presentation via MHC I and II. (yamaguchi2024pathogenesisofalopecia pages 2-4, simeonovski2025disruptionofhair pages 5-7) - Chemokine-mediated signaling (CXCL9/10/11–CXCR3; CXCL12–CXCR4). (yamaguchi2024pathogenesisofalopecia pages 2-4, an2024humanizedcxcl12antibody pages 1-2) - Affected cellular processes - Cytotoxic T cell activation, tissue residency, clonal expansion; impaired local regulation (Tregs). (lee2023functionalinterrogationof pages 6-7, kim2025alopeciaareatafrom pages 2-4) - Premature anagen→catagen transition and follicular miniaturization without scarring. (kim2025alopeciaareatafrom pages 2-4)

Key Molecular Players - Genes/Proteins (HGNC) - IFNG (IFN‑γ), IL15, JAK1, JAK2, JAK3: core of the amplification loop and its signaling node. (yamaguchi2024pathogenesisofalopecia pages 2-4, simeonovski2025disruptionofhair pages 5-7) - KLRK1 (NKG2D) on CD8+ T cells/NK cells; ligands MICA, ULBP3/6 on stressed follicular cells. (lee2023functionalinterrogationof pages 6-7, yamaguchi2024pathogenesisofalopecia pages 2-4) - CXCL9/CXCL10 (IFN-response chemokines); CXCL12 and its receptor CXCR4. (yamaguchi2024pathogenesisofalopecia pages 2-4, an2024humanizedcxcl12antibody pages 1-2) - Chemical entities - JAK inhibitors (e.g., baricitinib, ritlecitinib): block pathogenic cytokine signaling; effective but relapse after cessation is common per reviews and trials. (simeonovski2025disruptionofhair pages 5-7, kim2025alopeciaareatafrom pages 2-4) - CXCL12-neutralizing antibody: delayed AA onset and reduced CD8+ activation in a mouse model. (an2024humanizedcxcl12antibody pages 1-2) - Cell types (CL) - CD8+ cytotoxic T lymphocyte (CTL): primary disease driver; depletion prevents and reverses AA in mouse models. (lee2023functionalinterrogationof pages 6-7) - NK cells: contribute to innate cytotoxicity via NKG2D. (udovic2024decipheringthecomplex pages 5-7) - Dendritic cells (including plasmacytoid DCs): IFN‑α production and antigen presentation that promote chemokine cascades and T-cell recruitment. (yamaguchi2024pathogenesisofalopecia pages 2-4) - Mast cells: augment local inflammation and tissue damage. (simeonovski2025disruptionofhair pages 5-7) - Regulatory T cells (Tregs): dysfunction or insufficiency correlates with loss of suppression; expanded Tregs are protective in models. (lee2023functionalinterrogationof pages 6-7) - Anatomical locations (UBERON) - Hair follicle (scalp) with emphasis on bulb and bulge compartments showing IP alterations and immune infiltration. (yamaguchi2024pathogenesisofalopecia pages 2-4, kim2025alopeciaareatafrom pages 2-4)

Biological Processes (GO annotations) - Antigen presentation via MHC class I and II: increased on follicular epithelium/APCs in AA (GO:0002474; GO:0002504). (yamaguchi2024pathogenesisofalopecia pages 2-4, simeonovski2025disruptionofhair pages 5-7) - JAK–STAT signaling cascade (GO:0007259): integrates IFN and γ-chain cytokines; therapeutically targeted. (simeonovski2025disruptionofhair pages 5-7) - Response to interferon-gamma (GO:0034341): upregulated in lesional skin. (yamaguchi2024pathogenesisofalopecia pages 2-4) - Chemokine-mediated signaling pathway (GO:0070098): CXCL9/10/11–CXCR3; CXCL12–CXCR4 trafficking. (yamaguchi2024pathogenesisofalopecia pages 2-4, an2024humanizedcxcl12antibody pages 1-2) - Positive regulation of T cell–mediated cytotoxicity (GO:0001916): NKG2D ligand induction on follicular cells. (yamaguchi2024pathogenesisofalopecia pages 2-4) - Cellular response to oxidative stress (GO:0006979): contributes to NKG2D-ligand induction and IP collapse. (yamaguchi2024pathogenesisofalopecia pages 2-4)

Cellular Components - Follicular keratinocyte membranes and immune synapses: sites of MHC I/II upregulation and NKG2D ligand display enabling CD8+ cytotoxic engagement. (yamaguchi2024pathogenesisofalopecia pages 2-4) - Peribulbar and intrafollicular niches: chemokine-rich microenvironments recruiting CXCR3+/CXCR4+ effector T cells and innate lymphocytes. (yamaguchi2024pathogenesisofalopecia pages 2-4, an2024humanizedcxcl12antibody pages 1-2)

Disease Progression - Sequence of events 1) Triggering stressors (e.g., oxidative stress, infections, drugs) perturb follicular IP; pDC-derived IFN‑α and local IFN‑γ signatures rise with chemokines CXCL9/10/11. (yamaguchi2024pathogenesisofalopecia pages 2-4) 2) Follicular keratinocytes upregulate MHC I/II and NKG2D ligands (MICA, ULBP3/6). (yamaguchi2024pathogenesisofalopecia pages 2-4) 3) Recruitment/activation of CD8+ NKG2D+ T cells and NK cells; IFN‑γ production induces IL‑15 in follicular epithelium; IL‑15 via JAK1/3 sustains cytotoxic effectors (positive feedback). (yamaguchi2024pathogenesisofalopecia pages 2-4, lee2023functionalinterrogationof pages 6-7) 4) Effector cytotoxicity and cytokines precipitate premature anagen exit and hair shedding; TRM-like CD8+ clones persist, predisposing to relapse. (lee2023functionalinterrogationof pages 6-7, kim2025alopeciaareatafrom pages 2-4) - Quantitative data (recent) - Human single-cell profiling: T cells 23.74% vs 11.49% and CD8+ 9.85% vs 4.11% in AA vs control skin. (lee2023functionalinterrogationof pages 6-7) - Preclinical CXCL12 blockade: CD8+ T cells rose from 8.1% (control) to 68.9% (AA), reduced to 37% with anti‑CXCL12; AA onset was delayed and JAK/STAT activation in CD8+ T cells was attenuated. (an2024humanizedcxcl12antibody pages 6-9)

Phenotypic Manifestations (HP terms and links to mechanisms) - Patchy non-scarring alopecia, ophiasis, alopecia totalis/universalis; exclamation point hairs; nail pitting. These phenotypes reflect episodic, perifollicular cytotoxic inflammation and premature anagen termination without fibrosis. (kim2025alopeciaareatafrom pages 2-4)

Evidence highlights and expert analyses (2023–2024 priority) - CD8+ T cells as disease drivers and depletion effects: Single-cell and in vivo depletion in graft-induced C3H/HeJ model demonstrate CD8+ T cell depletion uniquely prevents and reverses AA, whereas depleting CD4+, NK, B, or γδ T cells does not. Human skin shows convergent CD8+ effector trajectories and enrichment. (lee2023functionalinterrogationof pages 6-7) - CXCL12/CXCR4 axis modulation: A humanized anti‑CXCL12 antibody delayed onset, reduced CD8+ infiltration and activation, and reversed type II IFN/chemotaxis gene signatures in AA mice, indicating a tractable upstream chemokine axis. (an2024humanizedcxcl12antibody pages 1-2, an2024humanizedcxcl12antibody pages 6-9) - Oxidative stress and NKG2D ligands: Reviews summarizing human and experimental data support oxidative stress as a contributor to HF-IP collapse and upregulation of MICA/ULBP3/6, thereby licensing NKG2D+ cytotoxic responses. (yamaguchi2024pathogenesisofalopecia pages 2-4) - Drug-induced HF-IP collapse (clinical translational insight): EGFR/MAPK inhibitor–associated folliculitis in patients shows bulge CD8+ infiltration, upregulation of MHC I/II and β2‑microglobulin, and reduced TGF‑β1, indicating that perturbations in growth factor signaling can collapse HF IP in humans; this supports MHC-driven mechanisms seen in AA. (yamaguchi2024pathogenesisofalopecia pages 2-4)

Current applications and real-world implementations - JAK inhibitors in clinical practice: JAK inhibition (e.g., baricitinib, ritlecitinib) effectively suppresses the IFN‑γ/IL‑15–JAK/STAT axis and induces regrowth in moderate–severe AA, with relapse often upon withdrawal, underscoring disease memory at the TRM/TCR-clone level. (simeonovski2025disruptionofhair pages 5-7, kim2025alopeciaareatafrom pages 2-4) - Emerging targets: Chemokine pathway interventions (e.g., anti‑CXCL12) demonstrate efficacy in mouse AA by reducing CD8+ activation and IFN-linked signatures, supporting trials that explore upstream trafficking control. (an2024humanizedcxcl12antibody pages 1-2)

Statistics and data from recent studies - Human lesional skin single-cell profiling shows significant enrichment of T cells and especially CD8+ cytotoxic states in AA compared to control (23.74% vs 11.49% T cells; 9.85% vs 4.11% CD8+), supporting a CD8-centered pathophysiology. (lee2023functionalinterrogationof pages 6-7) - In AA mice, anti‑CXCL12 reduced the pathogenic CD8+ T cell fraction from 68.9% (AA) to 37%, with concomitant reversal of chemotaxis/type II IFN gene programs, and delayed clinical onset. (an2024humanizedcxcl12antibody pages 6-9) - Epidemiology context: Global AA prevalence increased from 20.43M (1990) to 30.89M (2021), highlighting public health impact and the need for durable therapies targeting central immunopathology. (zhao2025frommechanismsto pages 1-2)

Gene/protein annotations with ontology terms - HGNC: IFNG (IFN‑γ); IL15; JAK1; JAK2; JAK3; KLRK1 (NKG2D); MICA; ULBP3; ULBP6; CXCL9; CXCL10; CXCL12; CXCR4. Roles detailed above. (yamaguchi2024pathogenesisofalopecia pages 2-4, lee2023functionalinterrogationof pages 6-7, an2024humanizedcxcl12antibody pages 1-2)

Phenotype associations (HPO) - HP:0002299 (Alopecia areata); HP:0001596 (Nail pitting); HP:0001595 (Alopecia totalis); HP:0002293 (Alopecia universalis). Mechanistically linked to intermittent CD8+ cytotoxic infiltration and IFN‑γ–IL‑15–JAK/STAT activity without scarring. (kim2025alopeciaareatafrom pages 2-4)

Cell type involvement (CL terms) - CL:0000625 (CD8+ T cell): disease driver; CL:0000623 (NK cell): innate effector; CL:0000451 (dendritic cell): antigen presentation, IFN‑α (pDC) signaling; CL:0000097 (mast cell): inflammatory amplification; CL:0000815 (regulatory T cell): impaired regulation. (lee2023functionalinterrogationof pages 6-7, yamaguchi2024pathogenesisofalopecia pages 2-4, simeonovski2025disruptionofhair pages 5-7)

Anatomical locations (UBERON terms) - UBERON:0002062 (Hair follicle). Pathology centered at the hair bulb; bulge niche implicated in persistence/relapse; perifollicular dermis is an inflammatory niche. (yamaguchi2024pathogenesisofalopecia pages 2-4, kim2025alopeciaareatafrom pages 2-4)

Chemical entities (selected; mechanisms) - JAK inhibitors (e.g., baricitinib, ritlecitinib): suppress IFN‑γ/IL‑15–JAK/STAT signaling; effective for regrowth; relapse common after cessation. (simeonovski2025disruptionofhair pages 5-7, kim2025alopeciaareatafrom pages 2-4) - Anti‑CXCL12 antibody (preclinical): reduces CD8+ activation, reverses chemotaxis/type II IFN signatures, delays AA onset. (an2024humanizedcxcl12antibody pages 1-2)

Embedded artifact summarizing key entities and evidence | Category | Entity (standard term) | Ontology/ID (where applicable) | Role in AA Pathophysiology | Key Evidence (citation, year) | |---|---|---|---|---| | Immune effector cell | CD8+ NKG2D+ T cell | HGNC:KLRK1 | Principal cytotoxic effectors attacking anagen HF after IP collapse; produce IFN-γ, granzyme/perforin; depletion prevents/reverses AA in mouse models | (lee2023functionalinterrogationof pages 6-7), (yamaguchi2024pathogenesisofalopecia pages 2-4) | | Cytokine | IFNG (Interferon-gamma) | HGNC:IFNG | Upstream driver that increases MHC I on follicular keratinocytes and induces IL-15, amplifying cytotoxic loop | (yamaguchi2024pathogenesisofalopecia pages 2-4), (kim2025alopeciaareatafrom pages 2-4) | | Cytokine | IL15 (Interleukin-15) | HGNC:IL15 | Supports survival/activation of CD8+ and NK cells in follicle; key mediator of local feed-forward JAK/STAT activation | (yamaguchi2024pathogenesisofalopecia pages 2-4), (simeonovski2025disruptionofhair pages 5-7) | | Signaling kinases | JAK1 / JAK2 / JAK3 | HGNC:JAK1; JAK2; JAK3 | Signal transducers for IFN/IL-15 family cytokines; central therapeutic target (JAK inhibitors) | (simeonovski2025disruptionofhair pages 5-7), (lee2023functionalinterrogationof pages 6-7) | | Chemokines | CXCL9 / CXCL10 | HGNC:CXCL9; CXCL10 | IFN-response chemokines that recruit CXCR3+ Th1/CD8 cells to peribulbar region | (yamaguchi2024pathogenesisofalopecia pages 2-4), (udovic2024decipheringthecomplex pages 5-7) | | Stress ligands | MICA | HGNC:MICA | NKG2D ligand upregulated on stressed follicular cells, engages CD8+/NK NKG2D to trigger cytotoxicity | (yamaguchi2024pathogenesisofalopecia pages 2-4), (udovic2024decipheringthecomplex pages 5-7) | | Stress ligands | ULBP3 / ULBP6 | HGNC:ULBP3; ULBP6 | NKG2D ligands implicated in AA-specific stress signaling and immune recognition | (yamaguchi2024pathogenesisofalopecia pages 2-4), (udovic2024decipheringthecomplex pages 5-7) | | Anatomy (HF compartment) | Hair follicle bulb | UBERON:hair_follicle_bulb | Site of anagen cycling and primary target of CD8+ peribulbar infiltrates in AA | (yamaguchi2024pathogenesisofalopecia pages 2-4), (lee2023functionalinterrogationof pages 6-7) | | Anatomy (HF compartment) | Hair follicle bulge | UBERON:hair_follicle_bulge | Stem cell niche affected by immune-privilege collapse; related to relapse and regenerative failure | (kim2025alopeciaareatafrom pages 2-4), (yamaguchi2024pathogenesisofalopecia pages 2-4) | | Cell type | Keratinocyte (follicular) | CL:Keratinocyte | Source of IL-15 and MHC upregulation; presents antigens and expresses stress ligands | (yamaguchi2024pathogenesisofalopecia pages 2-4), (an2024humanizedcxcl12antibody pages 1-2) | | Cell type | Dendritic cell (incl. pDC) | CL:Dendritic_cell | pDCs produce IFN-α to initiate IFN-driven chemokine cascades (CXCL10) and augment T-cell recruitment | (yamaguchi2024pathogenesisofalopecia pages 2-4), (kim2025alopeciaareatafrom pages 4-5) | | Cell type | Natural killer (NK) cell | CL:NK_cell | Contribute innate cytotoxicity via NKG2D recognition of stressed follicular ligands | (udovic2024decipheringthecomplex pages 5-7), (yamaguchi2024pathogenesisofalopecia pages 2-4) | | Cell type | Mast cell | CL:Mast_cell | Participate in local inflammation, release mediators that may disrupt HF immune privilege | (simeonovski2025disruptionofhair pages 5-7), (udovic2024decipheringthecomplex pages 5-7) | | Cell type (regulatory) | Regulatory T cell (Treg) | CL:Regulatory_T_cell | Defective/local dysfunction contributes to loss of suppression and permits autoreactive CD8+ activity | (lee2023functionalinterrogationof pages 6-7), (kim2025alopeciaareatafrom pages 2-4) | | Biological process (GO) | Antigen presentation (MHC I / II) | GO: antigen presentation (MHC I/II) | Upregulated in HF after IP collapse enabling autoreactive T-cell recognition of follicular antigens | (simeonovski2025disruptionofhair pages 5-7), (yamaguchi2024pathogenesisofalopecia pages 2-4) | | Biological process (GO) | JAK–STAT signaling cascade | GO: JAK-STAT pathway | Integrates IFN/IL-15 signals to drive effector gene programs; target of JAK inhibitors that restore hair growth | (simeonovski2025disruptionofhair pages 5-7), (lee2023functionalinterrogationof pages 6-7) | | Biological process (GO) | Chemokine-mediated signaling | GO: chemokine signaling | Directs recruitment/positioning of CXCR3+ and CXCR4+ lymphocytes to follicular niches | (yamaguchi2024pathogenesisofalopecia pages 2-4), (an2024humanizedcxcl12antibody pages 1-2) | | Biological process (GO) | Oxidative stress response | GO: oxidative stress response | Cellular stress/ROS can induce NKG2D ligands and promote HF-IP collapse, potentiating immune recognition | (yamaguchi2024pathogenesisofalopecia pages 2-4), (udovic2024decipheringthecomplex pages 5-7) | | Chemokine axis | CXCL12 / CXCR4 axis | HGNC:CXCL12 / CXCR4 (chemokine axis) | Fibroblast/ORS-derived CXCL12 promotes T-cell recruitment and activation; CXCL12 neutralization reduced CD8+ activation and delayed AA onset in mice | (an2024humanizedcxcl12antibody pages 1-2), (an2024humanizedcxcl12antibody pages 6-9) | | Therapeutic class | Baricitinib / Ritlecitinib (JAK inhibitors) | Drug: JAK inhibitor | Clinical JAK inhibitors block IFN/IL-15 signaling, induce regrowth but relapse is common after cessation; approvals and Phase-3 data support efficacy | (simeonovski2025disruptionofhair pages 5-7), (, 2025) |

Table: Compact reference table listing major cells, molecules, pathways, anatomical sites, and therapeutics implicated in alopecia areata pathophysiology with concise roles and primary evidence citations from the collected context (pqac IDs). This supports rapid integration into a disease knowledge base.

Evidence items (recent, with URLs and publication dates) - Lee EY et al. Functional interrogation of lymphocyte subsets in alopecia areata using single-cell RNA sequencing. PNAS. Jul 2023. https://doi.org/10.1073/pnas.2305764120. Key findings: CD8+ T cell enrichment (9.85% vs 4.11%); in vivo, anti‑CD8 uniquely prevented and reversed AA; NK/B/γδ depletion ineffective. (lee2023functionalinterrogationof pages 6-7) - Yamaguchi HL et al. Pathogenesis of Alopecia Areata and Vitiligo: Commonalities and Differences. IJMS. Apr 2024. https://doi.org/10.3390/ijms25084409. Key findings: HF-IP collapse; MHC upregulation; NKG2D-ligand (MICA, ULBP3/6) relevance; IFN‑γ and IL‑15 axis; elevated CXCL9/10. (yamaguchi2024pathogenesisofalopecia pages 2-4) - An S et al. Humanized CXCL12 antibody delays onset and modulates immune response in AA mice. Frontiers Immunol. Oct 2024. https://doi.org/10.3389/fimmu.2024.1444777. Key findings: CD8+ rose to 68.9% in AA; reduced to 37% with anti‑CXCL12; JAK/STAT activation attenuated; onset delayed. (an2024humanizedcxcl12antibody pages 1-2, an2024humanizedcxcl12antibody pages 6-9) - Udović IŠ et al. Deciphering the Complex Immunopathogenesis of Alopecia Areata. IJMS. May 2024. https://doi.org/10.3390/ijms25115652. Key findings: CD8+NKG2D+ as key drivers; IFN‑γ/IL‑15 feedback; JAK-STAT implication; NKG2D ligands MICA/ULBP3/6. (udovic2024decipheringthecomplex pages 5-7) - Kim S‑Y et al. Alopecia areata: from immunopathogenesis to emerging therapeutic approaches. Frontiers Immunol. Nov 2025. https://doi.org/10.3389/fimmu.2025.1681163. Key findings: CD8+NKG2D+ central; TRM/clonal persistence; relapse after JAKi cessation; bulge IP involvement. (kim2025alopeciaareatafrom pages 2-4) - Zhao H‑B et al. From mechanisms to therapies: current advances in AA immunopathology. Frontiers Immunol. Sep 2025. https://doi.org/10.3389/fimmu.2025.1621492. Key findings: global burden; multi-cellular immune imbalance; centrality of JAK–STAT. (zhao2025frommechanismsto pages 1-2)

Notes and limitations - Where possible, 2023–2024 sources were prioritized for mechanism and quantitative data (notably Lee 2023 PNAS and An 2024 Frontiers Immunology). Some contextual reviews from 2025 are included to synthesize emerging consensus on TRM/clonal persistence and therapeutic directions. (lee2023functionalinterrogationof pages 6-7, an2024humanizedcxcl12antibody pages 1-2, kim2025alopeciaareatafrom pages 2-4)

References

  1. (yamaguchi2024pathogenesisofalopecia pages 2-4): Hiroki L. Yamaguchi, Yuji Yamaguchi, and Elena Peeva. Pathogenesis of alopecia areata and vitiligo: commonalities and differences. International Journal of Molecular Sciences, 25:4409, Apr 2024. URL: https://doi.org/10.3390/ijms25084409, doi:10.3390/ijms25084409. This article has 31 citations and is from a poor quality or predatory journal.

  2. (lee2023functionalinterrogationof pages 6-7): Eunice Y. Lee, Zhenpeng Dai, Abhinav Jaiswal, Eddy Hsi Chun Wang, Niroshana Anandasabapathy, and Angela M. Christiano. Functional interrogation of lymphocyte subsets in alopecia areata using single-cell rna sequencing. Proceedings of the National Academy of Sciences of the United States of America, 120 29:e2305764120, Jul 2023. URL: https://doi.org/10.1073/pnas.2305764120, doi:10.1073/pnas.2305764120. This article has 25 citations and is from a highest quality peer-reviewed journal.

  3. (simeonovski2025disruptionofhair pages 5-7): Viktor Simeonovski, Maja Dimova, Marko Kostovski, Julija Mitrova Telenta, Elena Mircheska Arsovska, and Liljana Labachevska Gjatovska. Disruption of hair follicle immune privilege in alopecia areata: enigmatic mechanisms and emerging concepts. Academic Medical Journal, 5:70-80, Jun 2025. URL: https://doi.org/10.53582/amj255170s, doi:10.53582/amj255170s. This article has 0 citations.

  4. (kim2025alopeciaareatafrom pages 2-4): Su-Young Kim, Hyun Joo Lee, Jihye Heo, Beom Joon Kim, and Joon Seok. Alopecia areata: from immunopathogenesis to emerging therapeutic approaches. Frontiers in Immunology, Nov 2025. URL: https://doi.org/10.3389/fimmu.2025.1681163, doi:10.3389/fimmu.2025.1681163. This article has 0 citations and is from a peer-reviewed journal.

  5. (zhao2025frommechanismsto pages 1-2): Huai-Bo Zhao, Ya-Nan Zhang, Yan Qiang, Guo-Mi Wang, Li-Wei Wang, Wen-cheng Jiang, and Xi Chen. From mechanisms to therapies: current advances breakthroughs in alopecia areata immunopathology. Frontiers in Immunology, Sep 2025. URL: https://doi.org/10.3389/fimmu.2025.1621492, doi:10.3389/fimmu.2025.1621492. This article has 4 citations and is from a peer-reviewed journal.

  6. (an2024humanizedcxcl12antibody pages 1-2): Seungchan An, Mei Zheng, In Guk Park, Sang Gyu Park, Minsoo Noh, and Jong-Hyuk Sung. Humanized cxcl12 antibody delays onset and modulates immune response in alopecia areata mice: insights from single-cell rna sequencing. Frontiers in Immunology, Oct 2024. URL: https://doi.org/10.3389/fimmu.2024.1444777, doi:10.3389/fimmu.2024.1444777. This article has 7 citations and is from a peer-reviewed journal.

  7. (udovic2024decipheringthecomplex pages 5-7): Ingrid Šutić Udović, Nika Hlača, Larisa Prpić Massari, Ines Brajac, Marija Kaštelan, and Marijana Vičić. Deciphering the complex immunopathogenesis of alopecia areata. International Journal of Molecular Sciences, 25:5652, May 2024. URL: https://doi.org/10.3390/ijms25115652, doi:10.3390/ijms25115652. This article has 44 citations and is from a poor quality or predatory journal.

  8. (an2024humanizedcxcl12antibody pages 6-9): Seungchan An, Mei Zheng, In Guk Park, Sang Gyu Park, Minsoo Noh, and Jong-Hyuk Sung. Humanized cxcl12 antibody delays onset and modulates immune response in alopecia areata mice: insights from single-cell rna sequencing. Frontiers in Immunology, Oct 2024. URL: https://doi.org/10.3389/fimmu.2024.1444777, doi:10.3389/fimmu.2024.1444777. This article has 7 citations and is from a peer-reviewed journal.

  9. (kim2025alopeciaareatafrom pages 4-5): Su-Young Kim, Hyun Joo Lee, Jihye Heo, Beom Joon Kim, and Joon Seok. Alopecia areata: from immunopathogenesis to emerging therapeutic approaches. Frontiers in Immunology, Nov 2025. URL: https://doi.org/10.3389/fimmu.2025.1681163, doi:10.3389/fimmu.2025.1681163. This article has 0 citations and is from a peer-reviewed journal.