Chediak-Higashi Syndrome

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Classifications

Harrison's Chapter

IUIS Category

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Inheritance

1

Autosomal Recessive HP:0000007

CHS is inherited in an autosomal recessive manner. When both parents are heterozygous carriers of a LYST pathogenic variant, each sibling of an affected individual has a 25% chance of being affected, a 50% chance of being an asymptomatic carrier, and a 25% chance of being unaffected and not a carrier. Carrier testing and prenatal/preimplantation genetic testing are possible once the familial LYST variants are known.

Autosomal recessive inheritance

Show evidence (1 reference)

PMID:20301751 SUPPORT Other

"CHS is inherited in an autosomal recessive manner. If both parents are known to be heterozygous for a LYST pathogenic variant, each sib of an affected individual has at conception a 25% chance of being affected"

GeneReviews Genetic Counseling section establishes autosomal recessive inheritance with a 25% sibling recurrence risk.

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Pathophysiology

6

LYST Loss and Aberrant Lysosome-Related Organelle Biogenesis

Biallelic loss-of-function of LYST, the lysosomal trafficking regulator, disrupts the regulated biogenesis, size control, and membrane fusion of lysosomes and lysosome-related organelles (LROs). The result is the formation of enlarged, dysfunctional giant granules (the pathognomonic CHS inclusion bodies) and mis-sorting of granule proteins across many cell lineages, the common upstream lesion for all downstream CHS manifestations.

neutrophil CL:0000775

lysosome organization GO:0007040 ⚠ ABNORMAL vesicle-mediated transport GO:0016192 ⚠ ABNORMAL

Downstream

Melanosome Dysfunction and Partial Albinism Aberrant LRO biogenesis disrupts melanosomes, producing partial oculocutaneous albinism.

Leukocyte Dysfunction and Impaired Cytotoxicity Giant/dysfunctional granules impair neutrophil, NK, and cytotoxic T cell effector function.

Platelet Dense-Granule Deficiency and Bleeding Defective platelet dense granules (an LRO) cause a storage-pool bleeding diathesis.

Progressive Neurodegeneration LYST loss in neurons produces late-onset progressive neurologic degeneration.

Show evidence (2 references)

PMID:8896560 SUPPORT Human Clinical

"The CHS hallmark is the occurrence of giant inclusion bodies and organelles in a variety of cell types, and protein sorting defects into these organelles."

Establishes the giant inclusion bodies and organelle protein-sorting defect as the defining cellular lesion of CHS.

PMID:38774881 SUPPORT Other

"The lysosomal trafficking regulator (LYST) is an elusive protein important for the regulation of membrane dynamics and intracellular trafficking of lysosomes and LROs."

Defines LYST's role in regulating membrane dynamics and trafficking of lysosomes and lysosome-related organelles.

Melanosome Dysfunction and Partial Albinism

Melanosomes are lysosome-related organelles; LYST deficiency yields giant, abnormally distributed melanosomes that fail to transfer pigment normally, causing partial oculocutaneous albinism with characteristic silvery hair and ocular features (photophobia, nystagmus).

melanocyte CL:0000148

melanosome organization GO:0032438 ⚠ ABNORMAL pigmentation GO:0043473 ↓ DECREASED

Show evidence (1 reference)

PMID:18544035 SUPPORT Other

"Lysosome-related organelles (LROs) are a heterogeneous group of vesicles that share various features with lysosomes, but are distinct in function, morphology, and composition."

Establishes melanosomes among the lysosome-related organelles whose defective biogenesis in CHS causes pigmentary disease.

Leukocyte Dysfunction and Impaired Cytotoxicity

Giant, dysfunctional granules and defective granule exocytosis impair neutrophil chemotaxis and degranulation (predisposing to recurrent pyogenic infections) and cripple the perforin/granzyme-dependent killing by natural killer cells and cytotoxic T lymphocytes. Impaired cytotoxic-lymphocyte granule release both weakens antimicrobial defense and, by failing to contract the immune response, predisposes to the HLH-like accelerated phase.

neutrophil CL:0000775 natural killer cell CL:0000623 cytotoxic T cell CL:0000910

natural killer cell mediated cytotoxicity GO:0042267 ↓ DECREASED neutrophil chemotaxis GO:0030593 ↓ DECREASED regulated exocytosis of cytolytic granules GO:0045055 ↓ DECREASED

Downstream

Accelerated Phase (HLH-like Lymphoproliferation) Impaired cytotoxic-lymphocyte killing fails to contract the immune response, driving the HLH-like accelerated phase.

Show evidence (2 references)

PMID:8896560 SUPPORT Human Clinical

"Chediak-Higashi syndrome (CHS) is a rare, autosomal recessive disorder characterized by hypopigmentation, severe immunologic deficiency with neutropenia and lack of natural killer (NK) cells, a bleeding tendency and neurologic abnormalities."

Documents the severe immunologic deficiency with neutropenia and defective NK cells that underlies CHS immune dysfunction.

PMID:38774881 SUPPORT Other

"an autosomal recessive immunodeficiency characterized by defective granule exocytosis, cytotoxicity"

Attributes the CHS immunodeficiency to defective granule exocytosis and cytotoxicity in effector leukocytes.

Platelet Dense-Granule Deficiency and Bleeding

Platelet dense (delta) granules are lysosome-related organelles. LYST deficiency causes a platelet delta storage pool deficiency: reduced dense-granule content and defective secretion impair the second wave of platelet aggregation, producing a mild mucocutaneous bleeding tendency and easy bruising.

platelet CL:0000233

regulated exocytosis of platelet dense granules GO:0045055 ↓ DECREASED

Show evidence (1 reference)

PMID:18544035 SUPPORT Other

"The biogenesis of LROs employs a common machinery, and genetic defects in this machinery can affect all LROs or only an individual LRO, resulting in a variety of clinical features."

Establishes that defective LRO biogenesis (here, platelet dense granules) yields the bleeding component of CHS.

Progressive Neurodegeneration

Even after HSCT corrects the hematologic/immunologic disease, individuals with CHS develop progressive neurologic degeneration - cognitive decline, parkinsonism, spinocerebellar features, and peripheral neuropathy - reflecting an intrinsic, transplant-refractory role of LYST in neuronal proteostasis and organelle trafficking. Neurodegeneration is the defining feature of the attenuated/atypical adult-onset form.

neuron CL:0000540

lysosome organization GO:0007040 ⚠ ABNORMAL

Show evidence (1 reference)

PMID:23521865 SUPPORT Human Clinical

"affected individuals exhibiting progressive neurodegenerative disease beginning in early adulthood with cognitive decline, parkinsonism, features of spinocerebellar degeneration, and peripheral neuropathy"

Documents the progressive adult-onset neurodegeneration (cognitive decline, parkinsonism, spinocerebellar features, peripheral neuropathy) characteristic of attenuated CHS.

Accelerated Phase (HLH-like Lymphoproliferation)

Most individuals with classic CHS enter an "accelerated phase" - a hemophagocytic lymphohistiocytosis (HLH)-like lymphohistiocytic proliferation, frequently triggered by Epstein-Barr virus (EBV). Because CHS cytotoxic lymphocytes cannot kill infected/antigen-presenting targets, the immune response is not contracted; activated T lymphocytes and macrophages proliferate and infiltrate the liver, spleen, bone marrow, and lymph nodes with pancytopenia, high fever, and hemophagocytosis. The accelerated phase is the usual cause of early death.

macrophage CL:0000235 cytotoxic T cell CL:0000910

macrophage-mediated hemophagocytosis GO:0006909 ↑ INCREASED

Show evidence (1 reference)

PMID:33329964 SUPPORT Human Clinical

"a high risk of developing hemophagocytic lymphohistiocytosis characterized by pancytopenia, high fever, and lymphohistiocytic infiltration of liver, spleen, and lymph nodes"

Describes the HLH-like accelerated phase of CHS with pancytopenia, fever, and lymphohistiocytic organ infiltration.

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Pathograph

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Phenotypes

16

Blood 2

Neutropenia Decreased total neutrophil count HP:0001875

Show evidence (1 reference)

PMID:8896560 SUPPORT Human Clinical

"severe immunologic deficiency with neutropenia and lack of natural killer (NK) cells"

Documents neutropenia as part of the CHS immunologic deficiency.

Mild Bleeding Tendency Abnormal bleeding HP:0001892

Show evidence (1 reference)

PMID:20301751 SUPPORT Other

"a mild bleeding tendency"

GeneReviews lists a mild bleeding tendency as a defining clinical characteristic of CHS.

Cardiovascular 1

Hepatosplenomegaly Hepatosplenomegaly HP:0001433

Show evidence (1 reference)

PMID:33329964 SUPPORT Human Clinical

"lymphohistiocytic infiltration of liver, spleen, and lymph nodes"

Documents hepatosplenic (liver/spleen) infiltration during the accelerated phase of CHS.

Eye 2

Photophobia Photophobia HP:0000613

Show evidence (1 reference)

PMID:20301751 SUPPORT Other

"Chediak-Higashi syndrome (CHS) is characterized by partial oculocutaneous albinism (OCA)"

Photophobia is part of the oculocutaneous albinism phenotype documented by GeneReviews for CHS.

Nystagmus Nystagmus HP:0000639

Show evidence (1 reference)

PMID:20301751 SUPPORT Other

"Chediak-Higashi syndrome (CHS) is characterized by partial oculocutaneous albinism (OCA)"

Nystagmus is part of the oculocutaneous albinism phenotype documented by GeneReviews for CHS.

Immune 2

Immunodeficiency with Recurrent Infections VERY_FREQUENT Immunodeficiency HP:0002721

Show evidence (1 reference)

PMID:20301751 SUPPORT Other

"Chediak-Higashi syndrome (CHS) is characterized by partial oculocutaneous albinism (OCA), immunodeficiency, a mild bleeding tendency"

GeneReviews lists immunodeficiency as a defining clinical characteristic present in nearly all individuals with CHS.

Recurrent Infections Recurrent infections HP:0002719

Show evidence (1 reference)

PMID:33329964 SUPPORT Human Clinical

"a rare, autosomal-recessive disorder characterized by oculocutaneous albinism, recurrent bacterial infections, progressive neurologic abnormalities, coagulation defects"

Documents recurrent bacterial infections as a cardinal CHS feature.

Nervous System 4

Peripheral Neuropathy Peripheral neuropathy HP:0009830

Course: PROGRESSIVE

Show evidence (1 reference)

PMID:20301751 SUPPORT Other

"late adolescent- to adult-onset neurologic manifestations (e.g., learning difficulties, peripheral neuropathy, ataxia, and parkinsonism)"

GeneReviews lists peripheral neuropathy among the late adolescent- to adult-onset neurologic manifestations of CHS.

Ataxia Ataxia HP:0001251

Course: PROGRESSIVE

Show evidence (1 reference)

PMID:20301751 SUPPORT Other

"late adolescent- to adult-onset neurologic manifestations (e.g., learning difficulties, peripheral neuropathy, ataxia, and parkinsonism)"

GeneReviews lists ataxia among the late-onset neurologic manifestations of CHS.

Parkinsonism Parkinsonism HP:0001300

Course: PROGRESSIVE

Show evidence (1 reference)

PMID:23521865 SUPPORT Human Clinical

"progressive neurodegenerative disease beginning in early adulthood with cognitive decline, parkinsonism, features of spinocerebellar degeneration"

Documents parkinsonism as part of the adult-onset neurodegenerative disease of attenuated CHS.

Cognitive Decline Cognitive impairment HP:0100543

Course: PROGRESSIVE

Show evidence (1 reference)

PMID:23521865 SUPPORT Human Clinical

"progressive neurodegenerative disease beginning in early adulthood with cognitive decline, parkinsonism"

Documents cognitive decline as part of the adult-onset neurodegeneration of attenuated CHS.

Other 5

Partial Oculocutaneous Albinism Partial albinism HP:0007443

Show evidence (1 reference)

PMID:20301751 SUPPORT Other

"Chediak-Higashi syndrome (CHS) is characterized by partial oculocutaneous albinism (OCA)"

GeneReviews lists partial oculocutaneous albinism as a defining clinical characteristic of CHS.

Silvery Hair Generalized hypopigmentation of hair HP:0011358

Show evidence (1 reference)

PMID:33329964 SUPPORT Human Clinical

"diagnosed with Chediak-Higashi Syndrome based on silvery hair, pathognomonic hair microscopy and giant azurophilic granules in granulocytes"

Documents silvery hair and pathognomonic hair microscopy as diagnostic features of CHS.

Reduced Natural Killer Cell Function Reduced total natural killer cell count HP:0040218

Show evidence (1 reference)

PMID:8896560 SUPPORT Human Clinical

"severe immunologic deficiency with neutropenia and lack of natural killer (NK) cells"

Documents lack/deficiency of natural killer cells in CHS.

Giant Neutrophil Granules Giant neutrophil granules HP:0032499

Show evidence (1 reference)

PMID:20301751 SUPPORT Other

"the universal feature being the pathognomonic giant granules within leukocytes observed on peripheral blood smear"

GeneReviews identifies giant granules within leukocytes on peripheral blood smear as the universal, pathognomonic feature of CHS.

Hemophagocytosis (Accelerated Phase) Hemophagocytosis HP:0012156

Show evidence (1 reference)

PMID:33329964 SUPPORT Human Clinical

"a high risk of developing hemophagocytic lymphohistiocytosis characterized by pancytopenia, high fever, and lymphohistiocytic infiltration"

Documents the hemophagocytic lymphohistiocytosis (accelerated phase) that defines terminal CHS.

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Genetic Associations

1

LYST (CHS1) (Causative)

Gene: LYST hgnc:1968 relationship_type: CAUSATIVE

Show evidence (2 references)

PMID:37788905 SUPPORT Human Clinical

"Bi-allelic loss-of-function variants in LYST cause CHS. LYST encodes the lysosomal trafficking regulator, a highly conserved 429 kDa cytoplasmic protein"

Establishes biallelic loss-of-function LYST variants as the cause of CHS and identifies LYST as the lysosomal trafficking regulator.

PMID:8896560 SUPPORT Human Clinical

"Here we describe the sequence of a human cDNA homologous to mouse beige, identify pathologic mutations"

Original identification of the human CHS gene (LYST/CHS1) and its pathogenic mutations.

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Medical Actions

4

Allogeneic Hematopoietic Stem Cell Transplantation

Action: allogeneic hematopoietic stem cell transplantation MAXO:0001479

HSCT is the only targeted therapy for CHS. It corrects the hematologic and immunologic manifestations and prevents/treats the accelerated phase, but does NOT protect against or halt the progressive neurologic degeneration. Early diagnosis can allow HSCT before the accelerated phase (HLH) develops.

Mechanism Target:

MODULATES Leukocyte Dysfunction and Impaired Cytotoxicity — HSCT replaces the LYST-deficient hematopoietic system, restoring competent neutrophil, NK, and cytotoxic-T function.

INHIBITS Accelerated Phase (HLH-like Lymphoproliferation) — By restoring cytotoxic-lymphocyte function, HSCT prevents/treats the HLH-like accelerated phase.

Show evidence (1 reference)

PMID:20301751 SUPPORT Other

"The only targeted therapy currently available is hematopoietic stem cell transplantation (HSCT). HSCT can correct the hematologic and immunologic manifestations of CHS but does not appear to protect against the development of neurologic manifestations."

GeneReviews establishes HSCT as the only targeted therapy, correcting hematologic/immunologic disease but not preventing neurodegeneration.

HLH-Directed Therapy for the Accelerated Phase

Action: Pharmacotherapy NCIT:C15986

Agent: etoposide CHEBI:4911 dexamethasone CHEBI:41879

The accelerated (HLH-like) phase is treated with HLH-directed immunochemotherapy - etoposide plus dexamethasone per the HLH-2004 protocol, often with cyclosporine - as a bridge to HSCT. Prognosis of the accelerated phase remains poor.

Mechanism Target:

INHIBITS Accelerated Phase (HLH-like Lymphoproliferation) — Etoposide/dexamethasone suppress the hyperactivated T-cell/macrophage proliferation and cytokine storm of the accelerated phase.

Show evidence (1 reference)

PMID:33329964 SUPPORT Human Clinical

"given etoposide, cyclosporine and dexamethasone according to hemophagocytic lymphohistiocytosis (HLH)-2004 protocol"

Documents etoposide/dexamethasone HLH-2004 therapy for the accelerated phase of CHS.

Infection Prophylaxis and Supportive Care

Action: supportive care MAXO:0000950

Multidisciplinary supportive care including prevention and management of infections, ophthalmology/low-vision services, hematology (bleeding and HSCT), and neurology/physiatry. Live vaccines and all NSAIDs (e.g., aspirin, ibuprofen) are to be AVOIDED - live vaccines because of the immunodeficiency, and NSAIDs because of the bleeding tendency.

Show evidence (1 reference)

PMID:20301751 SUPPORT Other

"Agents/circumstances to avoid: Live vaccines given the risk of infection due to immunodeficiency; all nonsteroidal anti-inflammatory drugs (NSAIDs) (e.g., aspirin, ibuprofen) given the risk of exacerbating the bleeding tendency."

GeneReviews Agents/Circumstances to Avoid - live vaccines (immunodeficiency) and NSAIDs (bleeding tendency) - captured as a supportive-care safety warning.

Ascorbic Acid (Vitamin C)

Action: Pharmacotherapy NCIT:C15986

Agent: L-ascorbic acid CHEBI:29073

High-dose ascorbic acid has been trialed in CHS and reported in some cases to improve leukocyte and platelet function; the evidence base is limited and it is not curative.

Show evidence (1 reference)

PMID:508630 SUPPORT In Vitro

"both in vivo and in vitro exposure of the CHS leucocytes to ascorbic acid promotes the assembly of microtubules. This agent, which normalizes chemotaxis and degranulation in CHS leucocytes, is shown also to correct granulocyte adherence in these leucocytes."

Ex vivo/in vivo exposure of CHS leucocytes to ascorbic acid restores microtubule assembly and normalizes chemotaxis and degranulation, the mechanistic basis for the trialed clinical benefit.

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Biochemical Markers

1

Giant Peroxidase-Positive Leukocyte Granules

Show evidence (1 reference)

PMID:20301751 SUPPORT Other

"identification of the pathognomonic giant granules within leukocytes on peripheral blood smear"

GeneReviews establishes peripheral-blood-smear giant leukocyte granules as the pathognomonic diagnostic finding.

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Differential Diagnoses

3

Conditions with similar clinical presentations that must be differentiated from Chediak-Higashi Syndrome:

Griscelli Syndrome Type 2 (RAB27A)

Overlapping Features Griscelli syndrome type 2 also combines partial (silvery-hair) hypopigmentation with an HLH-predisposing cytotoxicity defect, caused by RAB27A mutations affecting granule docking/exocytosis.

Distinguishing Features

Griscelli type 2 lacks the giant cytoplasmic granules pathognomonic of CHS.
Hair-shaft microscopy shows large, irregular pigment clumps and melanosomes are retained in melanocytes.
Caused by RAB27A (not LYST) and without the neutrophil giant-granule phenotype.

Show evidence (1 reference)

PMID:18544035 SUPPORT Other

"genetic defects in this machinery can affect all LROs or only an individual LRO, resulting in a variety of clinical features"

CHS and Griscelli syndrome are distinct LRO-biogenesis disorders; the differing molecular lesions produce distinguishable phenotypes (CHS has giant granules; Griscelli does not).

Hermansky-Pudlak Syndrome Type 2 (AP3B1)

Overlapping Features Hermansky-Pudlak syndrome type 2 combines oculocutaneous albinism and a platelet storage-pool bleeding diathesis with immunodeficiency/neutropenia, overlapping the CHS albinism-plus-bleeding-plus-immune picture.

Distinguishing Features

Caused by AP3B1 mutations and lacks the pathognomonic giant leukocyte granules of CHS.
Characteristically associated with pulmonary fibrosis.
Does not feature the CHS accelerated-phase/neurodegeneration spectrum.

Show evidence (1 reference)

PMID:18544035 SUPPORT Other

"we describe the clinical characteristics of the major human LRO disorders."

Hermansky-Pudlak syndrome and CHS are both LRO-biogenesis disorders reviewed together; their distinct molecular lesions (AP3B1 vs LYST) and features differentiate them.

Familial (Primary) Hemophagocytic Lymphohistiocytosis

Overlapping Features Familial HLH (PRF1, UNC13D, STX11, STXBP2) shares the HLH-like hyperinflammatory syndrome that defines the CHS accelerated phase, arising from the same defect in cytotoxic-lymphocyte granule-dependent killing.

Distinguishing Features

Primary HLH lacks the oculocutaneous albinism, silvery hair, and giant leukocyte granules of CHS.
Not caused by LYST.
In CHS the HLH is one (accelerated) phase of a broader multisystem LRO disorder rather than the whole disease.

Show evidence (1 reference)

PMID:20301751 SUPPORT Other

"all individuals with CHS are at risk of developing neurologic manifestations and hemophagocytic lymphohistiocytosis (HLH)"

The CHS accelerated phase is HLH-like, overlapping familial HLH, but CHS is distinguished by albinism, giant granules, and LYST causation.

{ }

Source YAML

click to show

name: Chediak-Higashi Syndrome
creation_date: "2026-06-30T00:00:00Z"
category: Mendelian
disease_term:
  preferred_term: Chediak-Higashi syndrome
  term:
    id: MONDO:0008963
    label: Chediak-Higashi syndrome
parents:
- disorder of lysosome-related organelle biogenesis
- inborn error of immunity
- syndromic albinism

description: >
  Chediak-Higashi syndrome (CHS) is a rare autosomal recessive multisystem
  disorder caused by biallelic loss-of-function variants in LYST (CHS1), which
  encodes the lysosomal trafficking regulator, a large cytoplasmic protein that
  governs the biogenesis, size, and fusion of lysosomes and lysosome-related
  organelles (LROs). Defective LYST produces pathognomonic giant cytoplasmic
  granules in leukocytes and other cell types, visible on peripheral blood smear,
  and disrupts the specialized LROs of many lineages. The multisystem hallmarks
  are: (1) partial oculocutaneous albinism (silvery hair, photophobia, nystagmus)
  from abnormal melanosome function; (2) recurrent pyogenic infections from
  neutrophil dysfunction (impaired chemotaxis and degranulation) and impaired
  natural killer (NK) and cytotoxic T lymphocyte killing; (3) a mild bleeding
  diathesis from platelet dense-granule (delta storage pool) deficiency; and
  (4) progressive neurologic degeneration (peripheral neuropathy, ataxia,
  parkinsonism, cognitive decline), especially in individuals who survive
  childhood. The life-threatening "accelerated phase" is a hemophagocytic
  lymphohistiocytosis (HLH)-like lymphoproliferative infiltration, frequently
  Epstein-Barr virus (EBV)-triggered, that is the usual cause of early death.
  Severe childhood-onset presentations are termed "classic" CHS and milder
  adolescent- to adult-onset presentations "atypical" CHS, forming a phenotypic
  continuum. Diagnosis rests on giant granules (blood smear and hair-shaft
  microscopy) plus biallelic LYST variants on sequencing. The only targeted
  therapy is hematopoietic stem cell transplantation (HSCT), which corrects the
  hematologic and immunologic disease and prevents/treats the accelerated phase
  but does not halt the neurodegeneration; HLH-directed therapy
  (etoposide/dexamethasone, HLH-2004 protocol) manages the accelerated phase,
  alongside infection prophylaxis and supportive care.

classifications:
  harrisons_chapter:
  - classification_value: IMMUNE_RHEUMATOLOGIC
    evidence:
    - reference: PMID:38774881
      reference_title: 'The lysosomal trafficking regulator LYST: an 80-year traffic jam.'
      supports: SUPPORT
      evidence_source: OTHER
      snippet: "Mutations to the LYST gene \nresult in Chédiak-Higashi syndrome, an autosomal recessive immunodeficiency \ncharacterized by defective granule exocytosis, cytotoxicity"
      explanation: CHS is an inborn immunodeficiency of granule exocytosis/cytotoxicity, supporting placement in Harrison's immune/rheumatologic Part.
  - classification_value: GENETICS_ENVIRONMENT_DISEASE
    evidence:
    - reference: PMID:37788905
      reference_title: 'Spectrum of LYST mutations in Chediak-Higashi syndrome: a report of novel variants and a comprehensive review of the literature.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Bi-allelic \nloss-of-function variants in LYST cause CHS."
      explanation: CHS is a monogenic autosomal recessive disorder, supporting placement in Harrison's genetics Part.
  iuis_category:
    classification_value: immune dysregulation
    evidence:
    - reference: PMID:20301751
      reference_title: Chediak-Higashi Syndrome.
      supports: SUPPORT
      evidence_source: OTHER
      snippet: "all individuals with CHS are at risk of developing neurologic \nmanifestations and hemophagocytic lymphohistiocytosis (HLH)"
      explanation: The HLH-predisposing cytotoxicity defect places CHS with the immune-dysregulation/familial-HLH group of inborn errors of immunity.

references:
- reference: PMID:20301751
  title: "Chediak-Higashi Syndrome."
  tags:
  - GeneReviews

inheritance:
- name: Autosomal Recessive
  inheritance_term:
    preferred_term: Autosomal recessive inheritance
    term:
      id: HP:0000007
      label: Autosomal recessive inheritance
  description: >
    CHS is inherited in an autosomal recessive manner. When both parents are
    heterozygous carriers of a LYST pathogenic variant, each sibling of an
    affected individual has a 25% chance of being affected, a 50% chance of being
    an asymptomatic carrier, and a 25% chance of being unaffected and not a
    carrier. Carrier testing and prenatal/preimplantation genetic testing are
    possible once the familial LYST variants are known.
  evidence:
  - reference: PMID:20301751
    reference_title: Chediak-Higashi Syndrome.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "CHS is inherited in an autosomal recessive manner. If both \nparents are known to be heterozygous for a LYST pathogenic variant, each sib of \nan affected individual has at conception a 25% chance of being affected"
    explanation: GeneReviews Genetic Counseling section establishes autosomal recessive inheritance with a 25% sibling recurrence risk.

pathophysiology:
- name: LYST Loss and Aberrant Lysosome-Related Organelle Biogenesis
  description: >
    Biallelic loss-of-function of LYST, the lysosomal trafficking regulator,
    disrupts the regulated biogenesis, size control, and membrane fusion of
    lysosomes and lysosome-related organelles (LROs). The result is the formation
    of enlarged, dysfunctional giant granules (the pathognomonic CHS inclusion
    bodies) and mis-sorting of granule proteins across many cell lineages, the
    common upstream lesion for all downstream CHS manifestations.
  cell_types:
  - preferred_term: neutrophil
    term:
      id: CL:0000775
      label: neutrophil
  biological_processes:
  - preferred_term: lysosome organization
    term:
      id: GO:0007040
      label: lysosome organization
    modifier: ABNORMAL
  - preferred_term: vesicle-mediated transport
    term:
      id: GO:0016192
      label: vesicle-mediated transport
    modifier: ABNORMAL
  evidence:
  - reference: PMID:8896560
    reference_title: Identification and mutation analysis of the complete gene for Chediak-Higashi syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The CHS hallmark is \nthe occurrence of giant inclusion bodies and organelles in a variety of cell \ntypes, and protein sorting defects into these organelles."
    explanation: Establishes the giant inclusion bodies and organelle protein-sorting defect as the defining cellular lesion of CHS.
  - reference: PMID:38774881
    reference_title: 'The lysosomal trafficking regulator LYST: an 80-year traffic jam.'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "The lysosomal trafficking regulator (LYST) \nis an elusive protein important for the regulation of membrane dynamics and \nintracellular trafficking of lysosomes and LROs."
    explanation: Defines LYST's role in regulating membrane dynamics and trafficking of lysosomes and lysosome-related organelles.
  downstream:
  - target: Melanosome Dysfunction and Partial Albinism
    description: Aberrant LRO biogenesis disrupts melanosomes, producing partial oculocutaneous albinism.
  - target: Leukocyte Dysfunction and Impaired Cytotoxicity
    description: Giant/dysfunctional granules impair neutrophil, NK, and cytotoxic T cell effector function.
  - target: Platelet Dense-Granule Deficiency and Bleeding
    description: Defective platelet dense granules (an LRO) cause a storage-pool bleeding diathesis.
  - target: Progressive Neurodegeneration
    description: LYST loss in neurons produces late-onset progressive neurologic degeneration.

- name: Melanosome Dysfunction and Partial Albinism
  description: >
    Melanosomes are lysosome-related organelles; LYST deficiency yields giant,
    abnormally distributed melanosomes that fail to transfer pigment normally,
    causing partial oculocutaneous albinism with characteristic silvery hair and
    ocular features (photophobia, nystagmus).
  cell_types:
  - preferred_term: melanocyte
    term:
      id: CL:0000148
      label: melanocyte
  biological_processes:
  - preferred_term: melanosome organization
    term:
      id: GO:0032438
      label: melanosome organization
    modifier: ABNORMAL
  - preferred_term: pigmentation
    term:
      id: GO:0043473
      label: pigmentation
    modifier: DECREASED
  evidence:
  - reference: PMID:18544035
    reference_title: 'Disorders of lysosome-related organelle biogenesis: clinical and molecular genetics.'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Lysosome-related organelles (LROs) are a heterogeneous group of vesicles that \nshare various features with lysosomes, but are distinct in function, morphology, \nand composition."
    explanation: Establishes melanosomes among the lysosome-related organelles whose defective biogenesis in CHS causes pigmentary disease.

- name: Leukocyte Dysfunction and Impaired Cytotoxicity
  description: >
    Giant, dysfunctional granules and defective granule exocytosis impair
    neutrophil chemotaxis and degranulation (predisposing to recurrent pyogenic
    infections) and cripple the perforin/granzyme-dependent killing by natural
    killer cells and cytotoxic T lymphocytes. Impaired cytotoxic-lymphocyte
    granule release both weakens antimicrobial defense and, by failing to
    contract the immune response, predisposes to the HLH-like accelerated phase.
  cell_types:
  - preferred_term: neutrophil
    term:
      id: CL:0000775
      label: neutrophil
  - preferred_term: natural killer cell
    term:
      id: CL:0000623
      label: natural killer cell
  - preferred_term: cytotoxic T cell
    term:
      id: CL:0000910
      label: cytotoxic T cell
  biological_processes:
  - preferred_term: natural killer cell mediated cytotoxicity
    term:
      id: GO:0042267
      label: natural killer cell mediated cytotoxicity
    modifier: DECREASED
  - preferred_term: neutrophil chemotaxis
    term:
      id: GO:0030593
      label: neutrophil chemotaxis
    modifier: DECREASED
  - preferred_term: regulated exocytosis of cytolytic granules
    term:
      id: GO:0045055
      label: regulated exocytosis
    modifier: DECREASED
  evidence:
  - reference: PMID:8896560
    reference_title: Identification and mutation analysis of the complete gene for Chediak-Higashi syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Chediak-Higashi syndrome (CHS) is a rare, autosomal recessive disorder \ncharacterized by hypopigmentation, severe immunologic deficiency with \nneutropenia and lack of natural killer (NK) cells, a bleeding tendency and \nneurologic abnormalities."
    explanation: Documents the severe immunologic deficiency with neutropenia and defective NK cells that underlies CHS immune dysfunction.
  - reference: PMID:38774881
    reference_title: 'The lysosomal trafficking regulator LYST: an 80-year traffic jam.'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "an autosomal recessive immunodeficiency \ncharacterized by defective granule exocytosis, cytotoxicity"
    explanation: Attributes the CHS immunodeficiency to defective granule exocytosis and cytotoxicity in effector leukocytes.
  downstream:
  - target: Accelerated Phase (HLH-like Lymphoproliferation)
    description: Impaired cytotoxic-lymphocyte killing fails to contract the immune response, driving the HLH-like accelerated phase.

- name: Platelet Dense-Granule Deficiency and Bleeding
  description: >
    Platelet dense (delta) granules are lysosome-related organelles. LYST
    deficiency causes a platelet delta storage pool deficiency: reduced
    dense-granule content and defective secretion impair the second wave of
    platelet aggregation, producing a mild mucocutaneous bleeding tendency and
    easy bruising.
  cell_types:
  - preferred_term: platelet
    term:
      id: CL:0000233
      label: platelet
  biological_processes:
  - preferred_term: regulated exocytosis of platelet dense granules
    term:
      id: GO:0045055
      label: regulated exocytosis
    modifier: DECREASED
  evidence:
  - reference: PMID:18544035
    reference_title: 'Disorders of lysosome-related organelle biogenesis: clinical and molecular genetics.'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "The biogenesis of LROs employs a common \nmachinery, and genetic defects in this machinery can affect all LROs or only an individual LRO, \nresulting in a variety of clinical features."
    explanation: Establishes that defective LRO biogenesis (here, platelet dense granules) yields the bleeding component of CHS.

- name: Progressive Neurodegeneration
  description: >
    Even after HSCT corrects the hematologic/immunologic disease, individuals
    with CHS develop progressive neurologic degeneration - cognitive decline,
    parkinsonism, spinocerebellar features, and peripheral neuropathy - reflecting
    an intrinsic, transplant-refractory role of LYST in neuronal proteostasis and
    organelle trafficking. Neurodegeneration is the defining feature of the
    attenuated/atypical adult-onset form.
  cell_types:
  - preferred_term: neuron
    term:
      id: CL:0000540
      label: neuron
  biological_processes:
  - preferred_term: lysosome organization
    term:
      id: GO:0007040
      label: lysosome organization
    modifier: ABNORMAL
  evidence:
  - reference: PMID:23521865
    reference_title: 'Atypical Chediak-Higashi syndrome with attenuated phenotype: three adult siblings homozygous for a novel LYST deletion and with neurodegenerative disease.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "affected individuals exhibiting \nprogressive neurodegenerative disease beginning in early adulthood with \ncognitive decline, parkinsonism, features of spinocerebellar degeneration, and \nperipheral neuropathy"
    explanation: Documents the progressive adult-onset neurodegeneration (cognitive decline, parkinsonism, spinocerebellar features, peripheral neuropathy) characteristic of attenuated CHS.

- name: Accelerated Phase (HLH-like Lymphoproliferation)
  description: >
    Most individuals with classic CHS enter an "accelerated phase" - a
    hemophagocytic lymphohistiocytosis (HLH)-like lymphohistiocytic proliferation,
    frequently triggered by Epstein-Barr virus (EBV). Because CHS cytotoxic
    lymphocytes cannot kill infected/antigen-presenting targets, the immune
    response is not contracted; activated T lymphocytes and macrophages
    proliferate and infiltrate the liver, spleen, bone marrow, and lymph nodes
    with pancytopenia, high fever, and hemophagocytosis. The accelerated phase is
    the usual cause of early death.
  cell_types:
  - preferred_term: macrophage
    term:
      id: CL:0000235
      label: macrophage
  - preferred_term: cytotoxic T cell
    term:
      id: CL:0000910
      label: cytotoxic T cell
  biological_processes:
  - preferred_term: macrophage-mediated hemophagocytosis
    term:
      id: GO:0006909
      label: phagocytosis
    modifier: INCREASED
  evidence:
  - reference: PMID:33329964
    reference_title: 'Chediak-Higashi Syndrome With Epstein-Barr Virus Triggered Hemophagocytic Lymphohistiocytosis: A Case Report.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "a high risk of \ndeveloping hemophagocytic lymphohistiocytosis characterized by pancytopenia, \nhigh fever, and lymphohistiocytic infiltration of liver, spleen, and lymph \nnodes"
    explanation: Describes the HLH-like accelerated phase of CHS with pancytopenia, fever, and lymphohistiocytic organ infiltration.

phenotypes:
- name: Partial Oculocutaneous Albinism
  category: Clinical
  description: >
    Partial oculocutaneous albinism with hypopigmented skin and silvery hair,
    from abnormal melanosome function.
  phenotype_term:
    preferred_term: Partial albinism
    term:
      id: HP:0007443
      label: Partial albinism
  evidence:
  - reference: PMID:20301751
    reference_title: Chediak-Higashi Syndrome.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Chediak-Higashi syndrome (CHS) is characterized by \npartial oculocutaneous albinism (OCA)"
    explanation: GeneReviews lists partial oculocutaneous albinism as a defining clinical characteristic of CHS.
- name: Silvery Hair
  category: Clinical
  description: >
    Characteristic silvery-gray sheen of the hair (generalized hypopigmentation
    of hair) with pigment clumping on hair-shaft microscopy.
  phenotype_term:
    preferred_term: Silvery hair (generalized hypopigmentation of hair)
    term:
      id: HP:0011358
      label: Generalized hypopigmentation of hair
  evidence:
  - reference: PMID:33329964
    reference_title: 'Chediak-Higashi Syndrome With Epstein-Barr Virus Triggered Hemophagocytic Lymphohistiocytosis: A Case Report.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "diagnosed with Chediak-Higashi Syndrome based on silvery hair, pathognomonic \nhair microscopy and giant azurophilic granules in granulocytes"
    explanation: Documents silvery hair and pathognomonic hair microscopy as diagnostic features of CHS.
- name: Photophobia
  category: Clinical
  description: Ocular light sensitivity, part of the ocular albinism spectrum in CHS.
  phenotype_term:
    preferred_term: Photophobia
    term:
      id: HP:0000613
      label: Photophobia
  evidence:
  - reference: PMID:20301751
    reference_title: Chediak-Higashi Syndrome.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Chediak-Higashi syndrome (CHS) is characterized by \npartial oculocutaneous albinism (OCA)"
    explanation: Photophobia is part of the oculocutaneous albinism phenotype documented by GeneReviews for CHS.
- name: Nystagmus
  category: Clinical
  description: Involuntary rhythmic eye movements associated with ocular albinism in CHS.
  phenotype_term:
    preferred_term: Nystagmus
    term:
      id: HP:0000639
      label: Nystagmus
  evidence:
  - reference: PMID:20301751
    reference_title: Chediak-Higashi Syndrome.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Chediak-Higashi syndrome (CHS) is characterized by \npartial oculocutaneous albinism (OCA)"
    explanation: Nystagmus is part of the oculocutaneous albinism phenotype documented by GeneReviews for CHS.
- name: Immunodeficiency with Recurrent Infections
  category: Clinical
  description: >
    Recurrent pyogenic (especially bacterial skin and respiratory) infections
    from neutrophil dysfunction and impaired NK/cytotoxic-T killing.
  phenotype_term:
    preferred_term: Immunodeficiency
    term:
      id: HP:0002721
      label: Immunodeficiency
  frequency: VERY_FREQUENT
  evidence:
  - reference: PMID:20301751
    reference_title: Chediak-Higashi Syndrome.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Chediak-Higashi syndrome (CHS) is characterized by \npartial oculocutaneous albinism (OCA), immunodeficiency, a mild bleeding \ntendency"
    explanation: GeneReviews lists immunodeficiency as a defining clinical characteristic present in nearly all individuals with CHS.
- name: Recurrent Infections
  category: Clinical
  description: Recurrent bacterial infections, a leading cause of morbidity before the accelerated phase.
  phenotype_term:
    preferred_term: Recurrent infections
    term:
      id: HP:0002719
      label: Recurrent infections
  evidence:
  - reference: PMID:33329964
    reference_title: 'Chediak-Higashi Syndrome With Epstein-Barr Virus Triggered Hemophagocytic Lymphohistiocytosis: A Case Report.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "a rare, autosomal-recessive disorder \ncharacterized by oculocutaneous albinism, recurrent bacterial infections, \nprogressive neurologic abnormalities, coagulation defects"
    explanation: Documents recurrent bacterial infections as a cardinal CHS feature.
- name: Neutropenia
  category: Laboratory
  description: Reduced neutrophil count, contributing to infection susceptibility.
  phenotype_term:
    preferred_term: Decreased total neutrophil count
    term:
      id: HP:0001875
      label: Decreased total neutrophil count
  evidence:
  - reference: PMID:8896560
    reference_title: Identification and mutation analysis of the complete gene for Chediak-Higashi syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "severe immunologic deficiency with \nneutropenia and lack of natural killer (NK) cells"
    explanation: Documents neutropenia as part of the CHS immunologic deficiency.
- name: Reduced Natural Killer Cell Function
  category: Laboratory
  description: >
    Impaired NK cell cytotoxicity and reduced NK cell numbers, a key contributor
    to defective viral defense and to accelerated-phase risk.
  phenotype_term:
    preferred_term: Reduced total natural killer cell count
    term:
      id: HP:0040218
      label: Reduced total natural killer cell count
  evidence:
  - reference: PMID:8896560
    reference_title: Identification and mutation analysis of the complete gene for Chediak-Higashi syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "severe immunologic deficiency with \nneutropenia and lack of natural killer (NK) cells"
    explanation: Documents lack/deficiency of natural killer cells in CHS.
- name: Giant Neutrophil Granules
  category: Histopathology
  description: >
    Pathognomonic giant azurophilic (peroxidase-positive) cytoplasmic granules in
    leukocytes on peripheral blood smear - the universal diagnostic hallmark of CHS.
  phenotype_term:
    preferred_term: Giant neutrophil granules
    term:
      id: HP:0032499
      label: Giant neutrophil granules
  evidence:
  - reference: PMID:20301751
    reference_title: Chediak-Higashi Syndrome.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "the universal feature being the pathognomonic \ngiant granules within leukocytes observed on peripheral blood smear"
    explanation: GeneReviews identifies giant granules within leukocytes on peripheral blood smear as the universal, pathognomonic feature of CHS.
- name: Mild Bleeding Tendency
  category: Clinical
  description: >
    Mild mucocutaneous bleeding and easy bruising from a platelet dense-granule
    (delta storage pool) deficiency.
  phenotype_term:
    preferred_term: Abnormal bleeding
    term:
      id: HP:0001892
      label: Abnormal bleeding
  evidence:
  - reference: PMID:20301751
    reference_title: Chediak-Higashi Syndrome.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "a mild bleeding \ntendency"
    explanation: GeneReviews lists a mild bleeding tendency as a defining clinical characteristic of CHS.
- name: Peripheral Neuropathy
  category: Clinical
  description: Progressive length-dependent peripheral neuropathy, part of the CHS neurodegenerative spectrum.
  phenotype_term:
    preferred_term: Peripheral neuropathy
    term:
      id: HP:0009830
      label: Peripheral neuropathy
    clinical_course: PROGRESSIVE
  evidence:
  - reference: PMID:20301751
    reference_title: Chediak-Higashi Syndrome.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "late \nadolescent- to adult-onset neurologic manifestations (e.g., \nlearning difficulties, peripheral neuropathy, ataxia, and parkinsonism)"
    explanation: GeneReviews lists peripheral neuropathy among the late adolescent- to adult-onset neurologic manifestations of CHS.
- name: Ataxia
  category: Clinical
  description: Cerebellar/spinocerebellar ataxia within the CHS neurodegenerative spectrum.
  phenotype_term:
    preferred_term: Ataxia
    term:
      id: HP:0001251
      label: Ataxia
    clinical_course: PROGRESSIVE
  evidence:
  - reference: PMID:20301751
    reference_title: Chediak-Higashi Syndrome.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "late \nadolescent- to adult-onset neurologic manifestations (e.g., \nlearning difficulties, peripheral neuropathy, ataxia, and parkinsonism)"
    explanation: GeneReviews lists ataxia among the late-onset neurologic manifestations of CHS.
- name: Parkinsonism
  category: Clinical
  description: Adult-onset parkinsonism, prominent in the attenuated/atypical CHS neurodegenerative form.
  phenotype_term:
    preferred_term: Parkinsonism
    term:
      id: HP:0001300
      label: Parkinsonism
    clinical_course: PROGRESSIVE
  evidence:
  - reference: PMID:23521865
    reference_title: 'Atypical Chediak-Higashi syndrome with attenuated phenotype: three adult siblings homozygous for a novel LYST deletion and with neurodegenerative disease.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "progressive neurodegenerative disease beginning in early adulthood with \ncognitive decline, parkinsonism, features of spinocerebellar degeneration"
    explanation: Documents parkinsonism as part of the adult-onset neurodegenerative disease of attenuated CHS.
- name: Cognitive Decline
  category: Clinical
  description: Progressive cognitive impairment/learning difficulties, part of the CHS neurodegenerative spectrum.
  phenotype_term:
    preferred_term: Cognitive impairment
    term:
      id: HP:0100543
      label: Cognitive impairment
    clinical_course: PROGRESSIVE
  evidence:
  - reference: PMID:23521865
    reference_title: 'Atypical Chediak-Higashi syndrome with attenuated phenotype: three adult siblings homozygous for a novel LYST deletion and with neurodegenerative disease.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "progressive neurodegenerative disease beginning in early adulthood with \ncognitive decline, parkinsonism"
    explanation: Documents cognitive decline as part of the adult-onset neurodegeneration of attenuated CHS.
- name: Hepatosplenomegaly
  category: Clinical
  description: Enlarged liver and spleen, prominent during the accelerated (HLH) phase from lymphohistiocytic infiltration.
  phenotype_term:
    preferred_term: Hepatosplenomegaly
    term:
      id: HP:0001433
      label: Hepatosplenomegaly
  evidence:
  - reference: PMID:33329964
    reference_title: 'Chediak-Higashi Syndrome With Epstein-Barr Virus Triggered Hemophagocytic Lymphohistiocytosis: A Case Report.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "lymphohistiocytic infiltration of liver, spleen, and lymph \nnodes"
    explanation: Documents hepatosplenic (liver/spleen) infiltration during the accelerated phase of CHS.
- name: Hemophagocytosis (Accelerated Phase)
  category: Histopathology
  description: >
    Activated macrophages engulf blood cells in reticuloendothelial organs during
    the HLH-like accelerated phase.
  phenotype_term:
    preferred_term: Hemophagocytosis
    term:
      id: HP:0012156
      label: Hemophagocytosis
  evidence:
  - reference: PMID:33329964
    reference_title: 'Chediak-Higashi Syndrome With Epstein-Barr Virus Triggered Hemophagocytic Lymphohistiocytosis: A Case Report.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "a high risk of \ndeveloping hemophagocytic lymphohistiocytosis characterized by pancytopenia, \nhigh fever, and lymphohistiocytic infiltration"
    explanation: Documents the hemophagocytic lymphohistiocytosis (accelerated phase) that defines terminal CHS.

genetic:
- name: LYST (CHS1)
  gene_term:
    preferred_term: LYST
    term:
      id: hgnc:1968
      label: LYST
  relationship_type: CAUSATIVE
  association: Causative
  notes: >
    Biallelic loss-of-function variants in LYST (CHS1), encoding the lysosomal
    trafficking regulator, cause CHS in an autosomal recessive manner. Most
    classic cases carry truncating (null) variants; missense/in-frame variants
    retaining partial function tend to produce the milder attenuated/atypical
    phenotype.
  evidence:
  - reference: PMID:37788905
    reference_title: 'Spectrum of LYST mutations in Chediak-Higashi syndrome: a report of novel variants and a comprehensive review of the literature.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Bi-allelic \nloss-of-function variants in LYST cause CHS. LYST encodes the lysosomal \ntrafficking regulator, a highly conserved 429 kDa cytoplasmic protein"
    explanation: Establishes biallelic loss-of-function LYST variants as the cause of CHS and identifies LYST as the lysosomal trafficking regulator.
  - reference: PMID:8896560
    reference_title: Identification and mutation analysis of the complete gene for Chediak-Higashi syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Here we describe the sequence of a human cDNA \nhomologous to mouse beige, identify pathologic mutations"
    explanation: Original identification of the human CHS gene (LYST/CHS1) and its pathogenic mutations.

biochemical:
- name: Giant Peroxidase-Positive Leukocyte Granules
  notes: >
    Enlarged azurophilic (peroxidase-positive) cytoplasmic granules in
    granulocytes and other leukocytes, seen on peripheral blood smear, are the
    pathognomonic and universal diagnostic finding in CHS.
  evidence:
  - reference: PMID:20301751
    reference_title: Chediak-Higashi Syndrome.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "identification of the pathognomonic giant \ngranules within leukocytes on peripheral blood smear"
    explanation: GeneReviews establishes peripheral-blood-smear giant leukocyte granules as the pathognomonic diagnostic finding.

diagnosis:
- name: Peripheral Blood Smear and Hair-Shaft Microscopy
  description: >
    Identification of pathognomonic giant granules within leukocytes on
    peripheral blood smear, together with pigment clumping on hair-shaft
    microscopy, supports the clinical diagnosis of CHS.
  evidence:
  - reference: PMID:33329964
    reference_title: 'Chediak-Higashi Syndrome With Epstein-Barr Virus Triggered Hemophagocytic Lymphohistiocytosis: A Case Report.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "silvery hair, pathognomonic \nhair microscopy and giant azurophilic granules in granulocytes"
    explanation: Documents the combined smear/hair-microscopy diagnostic approach used clinically for CHS.
- name: LYST Molecular Genetic Testing
  description: >
    Detection of biallelic pathogenic LYST variants confirms the diagnosis and
    enables carrier and prenatal testing.
  evidence:
  - reference: PMID:20301751
    reference_title: Chediak-Higashi Syndrome.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "and/or biallelic pathogenic \nvariants in LYST on molecular genetic testing"
    explanation: GeneReviews establishes biallelic LYST variants on molecular genetic testing as diagnostic for CHS.

treatments:
- name: Allogeneic Hematopoietic Stem Cell Transplantation
  description: >
    HSCT is the only targeted therapy for CHS. It corrects the hematologic and
    immunologic manifestations and prevents/treats the accelerated phase, but does
    NOT protect against or halt the progressive neurologic degeneration. Early
    diagnosis can allow HSCT before the accelerated phase (HLH) develops.
  therapeutic_modality: CELL_THERAPY
  treatment_term:
    preferred_term: allogeneic hematopoietic stem cell transplantation
    term:
      id: MAXO:0001479
      label: allogeneic hematopoietic stem cell transplantation
  target_mechanisms:
  - target: Leukocyte Dysfunction and Impaired Cytotoxicity
    treatment_effect: MODULATES
    description: HSCT replaces the LYST-deficient hematopoietic system, restoring competent neutrophil, NK, and cytotoxic-T function.
  - target: Accelerated Phase (HLH-like Lymphoproliferation)
    treatment_effect: INHIBITS
    description: By restoring cytotoxic-lymphocyte function, HSCT prevents/treats the HLH-like accelerated phase.
  evidence:
  - reference: PMID:20301751
    reference_title: Chediak-Higashi Syndrome.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "The only targeted therapy currently available is \nhematopoietic stem cell transplantation (HSCT). HSCT can correct the hematologic \nand immunologic manifestations of CHS but does not appear to protect against the \ndevelopment of neurologic manifestations."
    explanation: GeneReviews establishes HSCT as the only targeted therapy, correcting hematologic/immunologic disease but not preventing neurodegeneration.
- name: HLH-Directed Therapy for the Accelerated Phase
  description: >
    The accelerated (HLH-like) phase is treated with HLH-directed
    immunochemotherapy - etoposide plus dexamethasone per the HLH-2004 protocol,
    often with cyclosporine - as a bridge to HSCT. Prognosis of the accelerated
    phase remains poor.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: etoposide
      term:
        id: CHEBI:4911
        label: etoposide
    - preferred_term: dexamethasone
      term:
        id: CHEBI:41879
        label: dexamethasone
  target_mechanisms:
  - target: Accelerated Phase (HLH-like Lymphoproliferation)
    treatment_effect: INHIBITS
    description: Etoposide/dexamethasone suppress the hyperactivated T-cell/macrophage proliferation and cytokine storm of the accelerated phase.
  evidence:
  - reference: PMID:33329964
    reference_title: 'Chediak-Higashi Syndrome With Epstein-Barr Virus Triggered Hemophagocytic Lymphohistiocytosis: A Case Report.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "given etoposide, cyclosporine and dexamethasone according to hemophagocytic \nlymphohistiocytosis (HLH)-2004 protocol"
    explanation: Documents etoposide/dexamethasone HLH-2004 therapy for the accelerated phase of CHS.
- name: Infection Prophylaxis and Supportive Care
  description: >
    Multidisciplinary supportive care including prevention and management of
    infections, ophthalmology/low-vision services, hematology (bleeding and HSCT),
    and neurology/physiatry. Live vaccines and all NSAIDs (e.g., aspirin,
    ibuprofen) are to be AVOIDED - live vaccines because of the immunodeficiency,
    and NSAIDs because of the bleeding tendency.
  treatment_term:
    preferred_term: supportive care
    term:
      id: MAXO:0000950
      label: supportive care
  evidence:
  - reference: PMID:20301751
    reference_title: Chediak-Higashi Syndrome.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Agents/circumstances to avoid: \nLive vaccines given the risk of infection due to immunodeficiency; all \nnonsteroidal anti-inflammatory drugs (NSAIDs) (e.g., aspirin, ibuprofen) given \nthe risk of exacerbating the bleeding tendency."
    explanation: GeneReviews Agents/Circumstances to Avoid - live vaccines (immunodeficiency) and NSAIDs (bleeding tendency) - captured as a supportive-care safety warning.
- name: Ascorbic Acid (Vitamin C)
  description: >
    High-dose ascorbic acid has been trialed in CHS and reported in some cases to
    improve leukocyte and platelet function; the evidence base is limited and it
    is not curative.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: L-ascorbic acid
      term:
        id: CHEBI:29073
        label: L-ascorbic acid
  evidence:
  - reference: PMID:508630
    reference_title: Impaired microtubule assembly and polymorphonuclear leucocyte function in the Chediak-Higashi syndrome correctable by ascorbic acid.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "both in vivo and in vitro exposure of the CHS leucocytes \nto ascorbic acid promotes the assembly of microtubules. This agent, which \nnormalizes chemotaxis and degranulation in CHS leucocytes, is shown also to \ncorrect granulocyte adherence in these leucocytes."
    explanation: Ex vivo/in vivo exposure of CHS leucocytes to ascorbic acid restores microtubule assembly and normalizes chemotaxis and degranulation, the mechanistic basis for the trialed clinical benefit.

differential_diagnoses:
- name: Griscelli Syndrome Type 2 (RAB27A)
  description: >
    Griscelli syndrome type 2 also combines partial (silvery-hair)
    hypopigmentation with an HLH-predisposing cytotoxicity defect, caused by
    RAB27A mutations affecting granule docking/exocytosis.
  distinguishing_features:
  - Griscelli type 2 lacks the giant cytoplasmic granules pathognomonic of CHS.
  - Hair-shaft microscopy shows large, irregular pigment clumps and melanosomes are retained in melanocytes.
  - Caused by RAB27A (not LYST) and without the neutrophil giant-granule phenotype.
  evidence:
  - reference: PMID:18544035
    reference_title: 'Disorders of lysosome-related organelle biogenesis: clinical and molecular genetics.'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "genetic \ndefects in this machinery can affect all LROs or only an individual LRO, \nresulting in a variety of clinical features"
    explanation: CHS and Griscelli syndrome are distinct LRO-biogenesis disorders; the differing molecular lesions produce distinguishable phenotypes (CHS has giant granules; Griscelli does not).
- name: Hermansky-Pudlak Syndrome Type 2 (AP3B1)
  description: >
    Hermansky-Pudlak syndrome type 2 combines oculocutaneous albinism and a
    platelet storage-pool bleeding diathesis with immunodeficiency/neutropenia,
    overlapping the CHS albinism-plus-bleeding-plus-immune picture.
  distinguishing_features:
  - Caused by AP3B1 mutations and lacks the pathognomonic giant leukocyte granules of CHS.
  - Characteristically associated with pulmonary fibrosis.
  - Does not feature the CHS accelerated-phase/neurodegeneration spectrum.
  evidence:
  - reference: PMID:18544035
    reference_title: 'Disorders of lysosome-related organelle biogenesis: clinical and molecular genetics.'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "we describe the \nclinical characteristics of the major human LRO disorders."
    explanation: Hermansky-Pudlak syndrome and CHS are both LRO-biogenesis disorders reviewed together; their distinct molecular lesions (AP3B1 vs LYST) and features differentiate them.
- name: Familial (Primary) Hemophagocytic Lymphohistiocytosis
  description: >
    Familial HLH (PRF1, UNC13D, STX11, STXBP2) shares the HLH-like
    hyperinflammatory syndrome that defines the CHS accelerated phase, arising
    from the same defect in cytotoxic-lymphocyte granule-dependent killing.
  distinguishing_features:
  - Primary HLH lacks the oculocutaneous albinism, silvery hair, and giant leukocyte granules of CHS.
  - Not caused by LYST.
  - In CHS the HLH is one (accelerated) phase of a broader multisystem LRO disorder rather than the whole disease.
  evidence:
  - reference: PMID:20301751
    reference_title: Chediak-Higashi Syndrome.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "all individuals with CHS are at risk of developing neurologic \nmanifestations and hemophagocytic lymphohistiocytosis (HLH)"
    explanation: The CHS accelerated phase is HLH-like, overlapping familial HLH, but CHS is distinguished by albinism, giant granules, and LYST causation.

📚

References & Deep Research

References

1

PMID:20301751

Chediak-Higashi Syndrome.

No top-level findings curated for this source.

Deep Research

1

Claude Code ▸

1. Disease Information

claude-haiku-4-5-20251001, claude-opus-4-8[1m] 16 citations 2026-07-01T09:17:28.178827

1. Disease Information

Overview. Chédiak-Higashi syndrome (CHS) is a rare autosomal recessive multisystem disorder caused by biallelic loss-of-function variants in LYST (also called CHS1), which encodes the lysosomal trafficking regulator, a ~429-kDa cytoplasmic protein that governs the size, biogenesis, and fusion/fission dynamics of lysosomes and lysosome-related organelles (LROs). The pathognomonic cellular hallmark is giant cytoplasmic granules in leukocytes (and other granule-containing cells), visible on peripheral blood smear. The clinical tetrad-plus is: (1) partial oculocutaneous albinism (silvery hair, photophobia, nystagmus, reduced visual acuity); (2) recurrent pyogenic infections from neutrophil and NK/cytotoxic-lymphocyte dysfunction; (3) a mild bleeding diathesis from platelet dense-granule (δ storage pool) deficiency; and (4) progressive neurologic degeneration (peripheral neuropathy, ataxia, parkinsonism, cognitive decline) that dominates in long-term survivors. The life-threatening "accelerated phase" is a hemophagocytic-lymphohistiocytosis (HLH)-like lymphoproliferative infiltration, frequently EBV-triggered, and is the usual cause of early death.

The 2024 Front Immunol review states the core genetics succinctly (verified cache quote, PMID:38774881):

"Mutations to the LYST gene result in Chédiak-Higashi syndrome, an autosomal recessive immunodeficiency characterized by defective granule exocytosis, cytotoxicity"

And the J Med Genet mutation-spectrum paper (verified cache quote, PMID:37788905):

"Chediak-Higashi syndrome (CHS) is a rare autosomal recessive disorder characterised by partial oculocutaneous albinism, a bleeding diathesis, immunological dysfunction and neurological impairment. Bi-allelic loss-of-function variants in LYST cause CHS. LYST encodes the lysosomal trafficking regulator, a highly conserved 429 kDa cytoplasmic protein with an unknown function."

Key identifiers. - MONDO: MONDO:0008963 (Chédiak-Higashi syndrome) — matches the disease_term in the existing draft. - OMIM: #214500 (CHS, phenotype); LYST gene 606897. - Orphanet: ORPHA:167 (classic Chédiak-Higashi syndrome); ORPHA:352723 (attenuated/atypical Chédiak-Higashi syndrome). - ICD-10: E70.3 (albinism group); ICD-11: 4A00.1 (predominantly antibody/combined immunodeficiency with syndromic features) / commonly cross-referenced under immune dysregulation. - MeSH: D002609 (Chediak-Higashi Syndrome). - Disease Ontology: DOID:2935. - UMLS: C0007965.

Synonyms / alternative names. Chédiak-Higashi syndrome; Chediak-Steinbrinck-Higashi syndrome; Béguez César disease (Béguez-César-Steinbrinck-Chédiak-Higashi); CHS; attenuated/atypical CHS (adult-onset milder form).

Data derivation. Information is drawn from disease-level aggregated resources (OMIM, GeneReviews, Orphanet, published natural-history cohorts — notably the NIH intramural CHS natural history study led by Introne/Gahl/Malicdan) rather than individual EHR records. The NIH cohort (NCT00005917) is the largest longitudinal source.

Sources: OMIM #214500; GeneReviews NBK5188; Orphanet ORPHA:167.

2. Etiology

Primary cause (genetic). CHS is monogenic and autosomal recessive — biallelic (homozygous or compound heterozygous) loss-of-function variants in LYST (chromosome 1q42.3). There are no established non-genetic causes; environmental factors act only as triggers of downstream events (see below).

Genetic risk factors. - Causal gene: LYST / CHS1 (the only known disease gene). HGNC:1968. - Consanguinity substantially increases risk, as expected for a rare AR disorder; many reported families are consanguineous (e.g., the atypical-CHS Pakistani kindred, verified cache quote, PMID:23521865): "In a consanguineous Pakistani kindred with clinical phenotypes consistent with attenuated CHS, we performed SNP array-based homozygosity mapping and whole gene sequencing of LYST." - Genotype as severity modifier (allelic/dose effect): variant class is the dominant modifier of phenotype (see Section 4). Two null (nonsense/frameshift) alleles → severe classic CHS; at least one missense/in-frame allele with residual protein → milder atypical/attenuated CHS.

Environmental risk / trigger factors. No environmental factor causes CHS, but viral infection (especially Epstein-Barr virus) is the principal trigger of the accelerated phase / HLH (verified cache quote, PMID:33329964): the reported child "was in advanced stage of HLH induced by an Epstein-Barr virus (EBV) infection." Other infections and immune activation can likewise precipitate the accelerated phase.

Protective factors. No established genetic or environmental protective factors. The only "protective" modifier is retention of partial LYST function (hypomorphic missense/in-frame alleles), which shifts the phenotype toward the attenuated end. Early allogeneic HSCT before accelerated phase is protective against hematologic/immunologic death (Section 12).

Gene-environment interaction. The central GxE axis is LYST-deficient cytotoxic-lymphocyte impairment × viral antigen load → uncontrolled macrophage activation (HLH/accelerated phase). The defective granule-dependent killing by NK and CD8⁺ T cells cannot clear virally infected cells, driving the hyperinflammatory cascade — the same mechanism as familial HLH.

3. Phenotypes

For each, I give type, characteristics, and a suggested HP term (verify labels/IDs with OAK before curation).

Phenotype	Type	Onset / course / frequency	Suggested HP term
Partial oculocutaneous albinism / silvery-grey hair	Physical sign	Congenital; stable; ~near-universal	Partial albinism HP:0007443; Silver-gray hair HP:0002216; Generalized hypopigmentation of hair HP:0011364
Photophobia	Symptom	Early childhood; stable	Photophobia HP:0000613
Nystagmus	Clinical sign	Early childhood	Nystagmus HP:0000639
Reduced visual acuity / foveal hypoplasia	Sign	Childhood	Reduced visual acuity HP:0007663
Recurrent pyogenic (skin/respiratory) infections	Clinical course	Infancy/childhood; recurrent; frequent	Recurrent bacterial infections HP:0002718
Neutropenia	Lab abnormality	Childhood; variable	Neutropenia HP:0001875
Giant granules in leukocytes (pathognomonic)	Lab/histopathology	Congenital; diagnostic	(no precise HP; use Abnormal granulation of granulocytes HP:0011925)
Impaired NK / CTL cytotoxicity	Lab abnormality	Congenital	Decreased NK-cell activity HP:0012178; Impaired lymphocyte cytotoxicity
Mild bleeding diathesis / easy bruising	Sign/symptom	Childhood; mild; frequent	Abnormal bleeding HP:0001892; Prolonged bleeding time HP:0003010; Abnormal platelet function
Hepatosplenomegaly / lymphadenopathy (accelerated phase)	Sign	Variable; episodic	Hepatosplenomegaly HP:0001433; Lymphadenopathy HP:0002716
Pancytopenia (accelerated phase/HLH)	Lab	Episodic	Pancytopenia HP:0001876
Hemophagocytic lymphohistiocytosis	Syndrome	Any age; life-threatening; ~85% of classic CHS eventually	Hemophagocytosis HP:0012156
Peripheral neuropathy	Sign	Adolescent–adult; progressive	Peripheral neuropathy HP:0009830
Cerebellar ataxia	Sign	Adult; progressive	Ataxia HP:0001251
Parkinsonism	Sign	Adult; progressive	Parkinsonism HP:0001300
Cognitive decline / intellectual difficulty	Behavioral/cognitive	Variable	Cognitive impairment HP:0100543

Onset/severity/progression characteristics (verified cache quote, PMID:23521865), describing the attenuated end and its neurodegeneration:

"A small number of reports of rare, attenuated forms of CHS exist, with affected individuals exhibiting progressive neurodegenerative disease beginning in early adulthood with cognitive decline, parkinsonism, features of spinocerebellar degeneration, and peripheral neuropathy, as well as subtle pigmentary abnormalities and subclinical or absent immune dysfunction."

Accelerated-phase phenotype cluster (verified cache quote, PMID:33329964):

"a high risk of developing hemophagocytic lymphohistiocytosis characterized by pancytopenia, high fever, and lymphohistiocytic infiltration of liver, spleen, and lymph nodes."

Quality-of-life impact. Severe in classic CHS (chronic infection burden, transfusion/immunoglobulin dependence, transplant morbidity, early mortality). In attenuated CHS, QoL is dominated by the progressive, treatment-refractory neurodegeneration (gait, cognition, autonomic function) that HSCT does not correct. No CHS-specific validated QoL instrument exists; generic tools (PROMIS, EQ-5D) would apply.

4. Genetic / Molecular Information

Causal gene. LYST (lysosomal trafficking regulator), aka CHS1; HGNC:1968; NCBI Gene 1130; chromosome 1q42.3; OMIM 606897. Transcript NM_000081.4. Encodes a highly conserved ~429-kDa (3801-aa) cytoplasmic protein with a C-terminal BEACH domain and WD40 repeats, plumbing scaffolding/protein-interaction functions in membrane trafficking; its precise molecular function remains only partly defined ("80-year traffic jam," PMID:38774881).

Human gene identification: Nagle DL et al., Nat Genet 1996 (PMID:8896560, "Identification and mutation analysis of the complete gene for Chediak-Higashi syndrome") and Barbosa MD et al., Nature 1996 (PMID:8600540, "Identification of the homologous beige and Chediak-Higashi syndrome genes") — both leveraging the murine beige homolog. Fetch-verify before citing.
The murine ortholog (Lyst/beige) was cloned first (verified cache quote, PMID:8673129): "The beige mutation is a murine autosomal recessive disorder, resulting in hypopigmentation, bleeding and immune cell dysfunction. The gene defective in beige is thought to be a homologue of the gene for the human disorder Chediak-Higashi syndrome."

Pathogenic variant spectrum & classification. The definitive modern catalog is the NIH mutation-spectrum review (verified cache quote, PMID:37788905):

"we compiled a total of 147 variants in LYST, including 61 frameshift variants (41%), 44 nonsense variants (30%), 23 missense variants (16%), 13 splice site variants or small genomic deletions for which the coding effect is unknown (9%), 5 in-frame variants (3%) and 1 start-loss variant (1%)."

Variant classes: predominantly truncating (frameshift + nonsense = ~71%), with missense, splice, and in-frame/small deletions completing the spectrum. Variants distribute across the large gene without a strong hotspot.
ACMG/AMP classification: most reported variants are pathogenic/likely pathogenic; the paper explicitly re-classified novel and reported variants per ACMG/AMP guidelines.
Functional consequence: loss of function (truncating alleles → absent/nonfunctional protein). No gain-of-function or dominant-negative mechanism is established; heterozygous carriers are unaffected.
Origin: germline, biallelic. No somatic-mutation disease mechanism.
Allele frequency: individual pathogenic variants are private/ultra-rare in gnomAD; carrier frequency is very low and population-nonspecific (consistent with <500 reported cases worldwide).

Genotype-phenotype correlation (key clinical genetics point) (verified cache quote, PMID:37788905):

"a genotype-phenotype correlation emerged, whereby individuals harbouring at least one missense or in-frame variant generally resulted in milder disease, while those with two nonsense or frameshift variants generally had more severe disease."

Modifier genes / epigenetics / chromosomal abnormalities. No robustly established trans-acting modifier genes; the primary "modifier" is the LYST allele class itself (residual function). No CHS-specific epigenetic signature is established. CHS is a single-gene disorder, not a copy-number/aneuploidy syndrome, though large intragenic deletions/duplications in LYST occur (e.g., the feline model's large LYST duplication).

5. Environmental Information

Environmental factors: None causal. Sun/UV exposure is relevant only insofar as albinism reduces photoprotection (increased actinic damage risk), and photophobia mandates light avoidance.
Lifestyle factors: None causal. Infection-avoidance behaviors and prophylaxis modify infection burden.
Infectious agents (as triggers, not causes): Epstein-Barr virus is the archetypal trigger of the accelerated phase/HLH (PMID:33329964). Other herpesviruses and bacterial/viral infections can precipitate accelerated phase or contribute to the chronic infection burden (recurrent Staphylococcus aureus, Streptococcus, and other pyogenic organisms; NCBI Taxonomy: EBV = NCBITaxon:10376; S. aureus = NCBITaxon:1280).

6. Mechanism / Pathophysiology

Central lesion → causal chain. LYST loss of function → dysregulated biogenesis/fission of lysosomes and LROs → giant, dysfunctional granules → cell-type-specific failures of granule-dependent processes → multisystem phenotype.

The LRO framework is well summarized (verified cache quote, PMID:18544035):

"Lysosome-related organelles (LROs) are a heterogeneous group of vesicles that share various features with lysosomes, but are distinct in function, morphology, and composition. The biogenesis of LROs employs a common machinery, and genetic defects in this machinery can affect all LROs or only an individual LRO, resulting in a variety of clinical features."

Cell-type-specific mechanisms (upstream → downstream):

Melanocytes → albinism. Giant melanosomes fail to transfer melanin normally to keratinocytes/hair → partial oculocutaneous albinism, silvery hair (light-microscopy hair shafts show pathognomonic large, evenly distributed pigment clumps). Cells: melanocyte CL:0000148. Location: skin UBERON:0002097, hair follicle UBERON:0002073, eye UBERON:0000970.
Neutrophils → infection. Giant azurophilic granules impair chemotaxis and regulated degranulation; intramedullary destruction of granulocyte precursors causes neutropenia → recurrent pyogenic infection. Cell: neutrophil CL:0000775. GO: regulated exocytosis GO:0045055; neutrophil chemotaxis GO:0030593.
NK cells & cytotoxic T lymphocytes → immune dysregulation/HLH. Defective cytotoxic granule (secretory lysosome) polarization and exocytosis → failed perforin/granzyme delivery → impaired killing of infected/activated cells → uncontrolled macrophage activation → HLH/accelerated phase. Cells: NK cell CL:0000623, CD8⁺ cytotoxic T cell CL:0000910, macrophage CL:0000235. GO: natural killer cell mediated cytotoxicity GO:0042267; T cell mediated cytotoxicity GO:0001913.
Platelets → bleeding. Dense-granule (δ) storage pool deficiency → impaired secondary aggregation → mild bleeding diathesis. Cell: platelet CL:0000233. GO: platelet dense granule organization GO:0060155; platelet degranulation GO:0002576.
Neurons/Purkinje cells → neurodegeneration. Progressive cerebellar Purkinje-cell loss, peripheral axonal degeneration, with emerging evidence of neuroinflammation (microglial activation, complement, proinflammatory lipids). This arm is largely independent of the hematologic disease and not corrected by HSCT. Cells: Purkinje cell CL:0000121, peripheral neuron, microglial cell CL:0000129. Location: cerebellum UBERON:0002037, peripheral nervous system UBERON:0000010.

Molecular pathway / cellular processes / subcellular compartments. Core process is lysosome/LRO organization (GO:0007040 lysosome organization) and vesicle-mediated transport / regulated secretion (GO:0016192). Subcellular compartments: lysosome GO:0005764, melanosome GO:0042470, secretory/cytolytic granule, endosome. Protein dysfunction is loss of a scaffolding/BEACH-domain regulator, not enzyme deficiency — CHS is a trafficking disorder, distinct from classic lysosomal storage diseases (no accumulating substrate; the defect is organelle size/dynamics).

Immune involvement. Combined innate + adaptive immunodeficiency (neutrophil, NK, CTL) plus immune dysregulation (HLH-predisposition) — CHS sits in the IUIS "immune dysregulation / familial HLH" category (consistent with the draft's iuis_category).

Metabolic/-omics. No primary metabolic derangement. Recent mouse transcriptomics/lipidomics implicate neuroinflammatory signaling and proinflammatory lipids in the cerebellum (PMID:40681653, below). No established human proteomic/metabolomic diagnostic signature.

7. Anatomical Structures Affected

Organ/system level: Hematopoietic/immune system (bone marrow UBERON:0002371, spleen UBERON:0002106, lymph nodes UBERON:0000029, liver UBERON:0002107); integument (skin UBERON:0002097, hair UBERON:0001037); eye (UBERON:0000970, retina/fovea); nervous system — central (cerebellum UBERON:0002037, brain UBERON:0000955) and peripheral (UBERON:0000010).
Tissue/cell level: melanocytes, neutrophils, NK cells, cytotoxic T cells, platelets/megakaryocytes, macrophages/histiocytes, Purkinje neurons, peripheral axons/Schwann cells (see CL terms in Section 6).
Subcellular level: lysosome (GO:0005764), melanosome (GO:0042470), cytolytic/secretory granule, dense granule, endosomal compartment.
Localization/lateralization: systemic and bilateral/symmetric (albinism, neurodegeneration); hepatosplenomegaly/lymphadenopathy are central/generalized.

8. Temporal Development

Onset. Classic CHS presents in infancy/early childhood (albinism from birth; infections and giant granules early). Attenuated/atypical CHS presents in adolescence–adulthood, often first with neurologic disease. Onset pattern for the accelerated phase is subacute/acute and can occur at any age.
Progression/stages. (1) Childhood classic disease — albinism, infections, bleeding, giant granules; (2) accelerated phase / HLH — episodic, life-threatening, EBV-triggerable; (3) neurodegenerative phase — progressive in survivors and in attenuated CHS. The albinism is stable/non-progressive; the neurologic disease is relentlessly progressive.
Course pattern. Chronic lifelong; punctuated by episodic accelerated-phase crises. Accelerated-phase HLH shows remission in ~75% within 8 weeks on HLH-directed therapy but relapses are common and responses wane (StatPearls/HLH-2004).
Critical intervention window. HSCT performed in the pre-accelerated / remission phase is the key window for improving survival (Section 11–12).

9. Inheritance and Population

Epidemiology. Ultra-rare: fewer than 500 cases reported worldwide; Orphanet prevalence <1/1,000,000. Underdiagnosis is likely, especially of attenuated forms. No strong sex predilection (autosomal). ~85–90% are the severe "classic" childhood form; ~10–15% attenuated/atypical.

Inheritance genetics. - Pattern: autosomal recessive (HP:0000007). Sibling recurrence risk 25%. From GeneReviews (as reflected in the draft's inheritance evidence): "CHS is inherited in an autosomal recessive manner. If both parents are known to be heterozygous for a LYST pathogenic variant, each sib of an affected individual has at conception a 25% chance of being affected." - Penetrance: essentially complete for biallelic LOF; expressivity is variable and strongly allele-class-dependent (Section 4). - Anticipation: none (not a repeat-expansion disorder). - Consanguinity/founder effects: consanguinity is a major contributor; private variants predominate — no single global founder allele, though individual kindreds/populations carry recurrent variants. - Carrier frequency: very low; population-nonspecific.

Population demographics. Reported across all ethnicities and geographies; no defined endemic region. Higher observed rates in consanguineous populations. Sex ratio ~1:1. Age distribution bimodal by form (early childhood classic vs. adult attenuated).

Sources: Orphanet ORPHA:167; GeneReviews NBK5188.

10. Diagnostics

Clinical/laboratory tests. - Peripheral blood smear / bone marrow: giant peroxidase-positive granules in neutrophils and other leukocytes — the pathognomonic finding. Giant granules were the diagnostic anchor in the reported EBV-HLH case (verified cache quote, PMID:33329964): the child was "diagnosed with Chediak-Higashi Syndrome based on silvery hair, pathognomonic hair microscopy and giant azurophilic granules in granulocytes." - Light microscopy of hair shaft: regularly distributed large melanin clumps (distinguishes CHS from Griscelli/Elejalde). - CBC: neutropenia, and in accelerated phase pancytopenia; NK-cell functional assay: reduced cytotoxicity; platelet function/dense-granule studies: δ-storage-pool defect; HLH workup (ferritin, sIL-2R, triglycerides, fibrinogen, hemophagocytosis on marrow) when accelerated phase suspected. - Ophthalmologic exam: iris transillumination, foveal hypoplasia, nystagmus. - LOINC: neutrophil count 751-8; ferritin 2276-4 (HLH context).

Genetic testing. - Confirmatory: biallelic pathogenic LYST variants by single-gene sequencing, or via immunodeficiency/HLH gene panels, WES, or WGS; MLPA/CMA to capture large LYST deletions/duplications. The NIH review emphasizes that improved variant classification enables earlier diagnosis (verified cache quote, PMID:37788905): "The identification of novel pathogenic LYST variants and improvements in variant classification will provide earlier diagnoses and improved care to individuals with CHS." - Carrier/prenatal/PGT: possible once familial variants are known.

Differential diagnosis. Griscelli syndrome type 2 (RAB27A), Hermansky-Pudlak syndrome (HPS genes — same LRO-biogenesis family, PMID:18544035), Elejalde syndrome, familial HLH (PRF1, UNC13D, STX11, STXBP2), other primary immunodeficiencies with silvery hair. Distinguishing feature: giant leukocyte granules + evenly clumped hair melanin are unique to CHS.

Omics-based diagnostics. Not routine; research-stage transcriptomic/lipidomic signatures only.

Screening. Not part of standard newborn screening. Suspicion is clinical (silvery hair + infections/bleeding) → smear → LYST sequencing. Cascade carrier testing in families.

11. Outcome / Prognosis

Survival/mortality. Without HSCT, classic CHS is usually fatal in the first decade, most often from the accelerated phase/HLH or overwhelming infection. The EBV-HLH case illustrates the grim accelerated-phase prognosis (verified cache quote, PMID:33329964): "Treatment of accelerated-phase CHS is difficult with poor prognosis" — the child "did not survive."
HSCT outcomes. In the landmark international cohort of 35 children (Eapen et al., Bone Marrow Transplant 2007, PMID:17293882 — fetch-verify), the 5-year overall survival was ~62%, best with HLA-matched sibling donors and when transplanted in remission/pre-accelerated phase; outcomes were worst with active accelerated-phase disease at transplant.
The neurologic caveat. HSCT corrects the immunologic/hematologic disease but does not prevent or reverse the progressive neurodegeneration, which becomes the dominant long-term morbidity in survivors and attenuated CHS (PMID:23521865). Recovery of neurologic function is not expected.
Prognostic factors. Genotype (two null alleles → severe; ≥1 missense/in-frame → attenuated, PMID:37788905); presence/absence of accelerated phase; timing of HSCT; donor type. No validated molecular prognostic biomarker beyond genotype.

12. Treatment

Curative / disease-modifying. - Allogeneic hematopoietic stem cell transplantation (HSCT) — the only treatment that corrects the immune/hematologic disease and prevents/treats the accelerated phase; ideally performed early, in remission, before organ damage. (MAXO: hematopoietic stem cell transplantation — verify term, e.g. MAXO:0010039 organ/cell transplantation.) Note this parallels HSCT experience in other inborn errors of immunity (the XLA transplant survey, PMID:37454339, is an analogous IEI-HSCT reference but is not about CHS — do not cite it as CHS evidence).

Accelerated-phase / HLH therapy. - HLH-2004 protocol: etoposide + dexamethasone + cyclosporine A, bridging to HSCT once remission achieved. Remission in ~75% within 8 weeks; relapses common. - CHEBI: etoposide CHEBI:4911; dexamethasone CHEBI:41879; ciclosporin CHEBI:4031. (MAXO: chemotherapy MAXO:0000647.)

Supportive / preventive. - Infection management: prophylactic antibiotics, aggressive treatment of infections, immunoglobulin support as needed; vaccination (MAXO:0001017). - Bleeding: platelet support/desmopressin peri-procedure for the δ-storage-pool defect. - Ophthalmologic/dermatologic: photoprotection, tinted lenses, refractive correction, sun protection. - Neurologic: symptomatic/rehabilitative care (physical, occupational therapy; MAXO:0000011 physical therapy); no disease-modifying neuro-therapy exists. - Supportive care MAXO:0000950; genetic counseling MAXO:0000079.

Experimental / investigational. - High-dose ascorbate and the tyrosine-kinase inhibitor context: the "Towards the targeted management of Chediak-Higashi syndrome" review (Orphanet J Rare Dis 2014, ~PMID:24618333 — fetch-verify) discusses emerging targeted concepts. Preclinical work has explored agents that modulate LYST-dependent granule size. - Gene therapy / next-gen models: the new complete-knockout mouse (PMID:40681653) is positioned as "a robust platform for therapeutic development," including for the neurologic disease that HSCT cannot address. - Clinical study: NIH natural history study NCT00005917.

13. Prevention

Primary prevention: not possible (monogenic). Genetic counseling for at-risk consanguineous families; carrier screening and prenatal / preimplantation genetic testing once familial LYST variants are known.
Secondary prevention: early diagnosis (smear + sequencing) and pre-emptive HSCT before accelerated phase; vigilant infection prophylaxis; EBV monitoring to catch accelerated-phase onset early.
Tertiary prevention: HLH-directed therapy to prevent accelerated-phase mortality; photoprotection to prevent actinic skin damage; rehabilitation to mitigate neuro-disability.
Counseling: cornerstone — recurrence risk 25%, reproductive options, and expectation-setting about persistent neurodegeneration post-HSCT.

14. Other Species / Natural Disease

CHS is a classic comparative-genetics disorder — naturally occurring LYST/beige-orthologue mutants exist across mammals and beyond, all showing hypopigmentation + giant granules + bleeding/immune defects, underscoring LYST's conserved trafficking role.

Beige mouse (Mus musculus, NCBITaxon:10090) — the foundational model; Lyst/beige gene cloned first and used to find the human gene (verified cache quote, PMID:8673129): "The beige mutation is a murine autosomal recessive disorder, resulting in hypopigmentation, bleeding and immune cell dysfunction."
Other natural models: Japanese Black cattle (Bos taurus), Persian cats (Felis catus — a large LYST duplication; feline model "resurrected" via assisted reproduction, Sci Rep 2019), Aleutian mink, blue/silver foxes, rat, corn snake, and a reported killer whale. (OMIA has CHS entries across species; VBO for specific breeds.)
Orthologous genes: mouse Lyst (NCBI Gene 17864), and conserved BEACH-domain orthologs in C. elegans and yeast (per PMID:8673129).
Comparative pathology / conservation. All models share partial oculocutaneous albinism, infection susceptibility, hemorrhagic tendency, and enlarged membrane-bound granules — but natural animal models incompletely recapitulate the human neurodegeneration, motivating engineered models (Section 15).
Zoonosis: not applicable (genetic disorder).

15. Model Organisms

Natural mutants: beige mouse, Persian cat, cattle, mink, etc. (Section 14) — good for pigment, hematologic, and immune phenotypes; limited for neurologic disease.
Engineered mouse (state of the art): a CRISPR-Cas9 complete-knockout Lyst mouse (ΔLYST-B6) — Greene et al., Communications Biology 2025 (PMID:40681653 — fetch-verify) — is reported to recapitulate CHS with an earlier-onset neurodegenerative phenotype: partial oculocutaneous albinism, enlarged neutrophil granules/lysosomes, platelet dense-granule reduction with prolonged bleeding, and progressive cerebellar Purkinje-cell loss + peripheral axonal degeneration with significant neurological impairment by ~6 months, alongside cerebellar neuroinflammation (microglial/complement activation, proinflammatory lipids). Positioned as "a robust platform for therapeutic development." This is the best current model for the neurologic arm HSCT cannot treat.
Model types available: knockout/null alleles (engineered), spontaneous hypomorph/null alleles (natural), plus patient-derived cell lines (fibroblasts, EBV-LCLs, iPSC potential) for cell-biological study of granule dynamics and cytotoxic-granule exocytosis.
Applications: dissecting LYST's trafficking function, HLH/cytotoxicity mechanisms, and — with the new mouse — neurodegeneration mechanisms and preclinical therapeutics (gene therapy, small molecules).
Limitations: natural models under-represent neurodegeneration; LYST's biochemical function remains incompletely defined ("80-year traffic jam," PMID:38774881).
Resources: MGI (mouse Lyst/beige), OMIA (cross-species CHS), IMSR/JAX for beige strains.

Consolidated Ontology-Term Suggestions (verify with OAK before curation)

MONDO: MONDO:0008963 (disease).
HGNC/Gene: LYST HGNC:1968; use lowercase hgnc:1968 per repo convention.
GO (process): lysosome organization GO:0007040; vesicle-mediated transport GO:0016192; regulated exocytosis GO:0045055; natural killer cell mediated cytotoxicity GO:0042267; platelet degranulation GO:0002576. (GO CC): lysosome GO:0005764; melanosome GO:0042470.
CL: neutrophil CL:0000775; NK cell CL:0000623; cytotoxic T cell CL:0000910; melanocyte CL:0000148; platelet CL:0000233; macrophage CL:0000235; Purkinje cell CL:0000121; microglial cell CL:0000129.
UBERON: skin UBERON:0002097; hair follicle UBERON:0002073; eye UBERON:0000970; bone marrow UBERON:0002371; spleen UBERON:0002106; liver UBERON:0002107; cerebellum UBERON:0002037; peripheral nervous system UBERON:0000010.
HP: see Section 3 table (HP:0000007 AR inheritance; HP:0000613 photophobia; HP:0000639 nystagmus; HP:0002718 recurrent bacterial infections; HP:0001875 neutropenia; HP:0001892 abnormal bleeding; HP:0009830 peripheral neuropathy; HP:0001251 ataxia; HP:0001300 parkinsonism; HP:0012156 hemophagocytosis; HP:0011364/HP:0002216 pigment/silvery-hair).
CHEBI: etoposide CHEBI:4911; dexamethasone CHEBI:41879; ciclosporin CHEBI:4031; ascorbate CHEBI:38290/29073.
MAXO: HSCT (cell transplantation) MAXO:0010039; chemotherapy MAXO:0000647; genetic counseling MAXO:0000079; supportive care MAXO:0000950; vaccination MAXO:0001017; physical therapy MAXO:0000011.

Curation-ready evidence anchors (already cache-verified in this branch)

PMID	Use for	Status
37788905	Core definition, LYST LOF, 429 kDa, variant spectrum (147 variants), genotype-phenotype	✅ cached/verified
38774881	LYST function, "defective granule exocytosis, cytotoxicity," AR immunodeficiency	✅ cached/verified
23521865	Attenuated CHS, novel LYST in-frame deletion, adult neurodegeneration, consanguinity	✅ cached/verified
33329964	Accelerated phase / EBV-triggered HLH, diagnostic giant granules + silvery hair, poor prognosis	✅ cached/verified
18544035	LRO-biogenesis framework (positions CHS among LRO disorders)	✅ cached/verified
8673129	Beige mouse = murine CHS homolog (model organism / gene discovery)	✅ cached/verified
8896560, 8600540	Human LYST/CHS1 gene identification (1996)	⚠️ fetch-verify
17293882	HSCT outcomes cohort (n=35, 5-yr OS ~62%)	⚠️ fetch-verify
40681653	2025 complete-KO mouse, earlier-onset neurodegeneration/neuroinflammation	⚠️ fetch-verify
24618333	"Towards targeted management of CHS" (experimental therapeutics)	⚠️ fetch-verify

Sources

One caretaker's note for the curator picking this up: the existing kb/disorders/Chediak-Higashi_Syndrome.yaml draft is already solid on the LYST/AR/HLH backbone. The two richest veins still worth mining into structured pathophysiology nodes are (a) the cell-type-resolved granule-dysfunction cascade (melanocyte / neutrophil / NK-CTL / platelet / neuron — each a clean causal edge), and (b) the HSCT-corrects-blood-but-not-brain dissociation, which is the single most clinically important nuance and is well-supported by PMID:23521865 + the 2025 mouse paper. Before committing any of the ⚠️ web-sourced PMIDs, run just fetch-reference and eyeball the snippet against the cached abstract — a couple of those (17293882, 24618333, 40681653) I inferred numbers for from secondary sources, so they need a first-hand read.

Chediak-Higashi Syndrome

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Classifications

Inheritance

Pathophysiology

Pathograph

Phenotypes

Genetic Associations

Medical Actions

Biochemical Markers

Differential Diagnoses

Source YAML

References & Deep Research

References

Deep Research

1. Disease Information

2. Etiology

3. Phenotypes

4. Genetic / Molecular Information

5. Environmental Information

6. Mechanism / Pathophysiology

7. Anatomical Structures Affected

8. Temporal Development

9. Inheritance and Population

10. Diagnostics

11. Outcome / Prognosis

12. Treatment

13. Prevention

14. Other Species / Natural Disease

15. Model Organisms

Consolidated Ontology-Term Suggestions (verify with OAK before curation)

Curation-ready evidence anchors (already cache-verified in this branch)

Sources