Chediak-Higashi Syndrome
Chediak-Higashi syndrome (CHS) is a rare autosomal recessive immune dysregulation disorder caused by mutations in the LYST gene, characterized by the triad of partial oculocutaneous albinism, recurrent pyogenic infections, and progressive neurological dysfunction—with diagnosis confirmed by identifying pathognomonic giant azurophilic granules in peripheral blood leukocytes. 1
Clinical Manifestations
Classic Triad
- Partial oculocutaneous albinism: Present from birth, affecting skin and hair pigmentation 1
- Recurrent pyogenic bacterial infections: Primarily affecting skin and respiratory tract 1
- Progressive neurological symptoms: Including cognitive impairment, photophobia, nystagmus, and cerebellar, spinal, and peripheral neuropathies 1
Additional Key Features
- Oral manifestations: Gingivitis, oral ulcerations, and periodontal disease occur frequently 1
- Bleeding diathesis: Mild coagulation defect that can become severe during the accelerated phase 1
- Hepatosplenomegaly: Often present, particularly as disease progresses 1
The Accelerated Phase (Critical Prognostic Factor)
Virtually all patients with CHS who do not die of infection will eventually develop hemophagocytic lymphohistiocytosis (HLH), termed the "accelerated phase"—this is usually fatal without aggressive treatment. 1 This phase presents with:
- High unremitting fever
- Hepatosplenomegaly
- Neurological deterioration (confusion, seizures, coma)
- Pancytopenia (anemia and thrombocytopenia)
- Hepatitis with elevated liver enzymes
- Hypertriglyceridemia
- Hypofibrinogenemia
- Hyponatremia
- Markedly elevated ferritin levels 1
Diagnostic Approach
First-Line Diagnostic Test
Examination of a peripheral blood smear should be the first diagnostic test for suspected CHS. 1 This reveals giant azurophilic lysosomal granules in all granulated cells, including hematopoietic cells and melanocytes—these findings are pathognomonic when combined with the clinical features described above 1
Confirmatory Testing
- Hair shaft examination: Shows evenly distributed melanin granules 2
- Genetic testing: Whole exome sequencing or targeted LYST gene analysis to identify mutations 2
- Bone marrow examination: May show similar giant granules and hemophagocytosis if accelerated phase is present 3
Important Diagnostic Pitfall
Some patients may have normal screening immunologic tests despite having infections 1. Do not exclude CHS based on normal initial immune workup—the peripheral blood smear showing giant granules is diagnostic.
Genetic Basis
CHS results from mutations in the lysosomal trafficking regulator (LYST) gene, which encodes a cytosolic protein involved in vesicle trafficking and lysosome fusion 1. Protein accumulation in lysosomes causes characteristic enlargement of organelles including melanosomes, platelet-dense bodies, and cytolytic granules 1. The location of mutations within LYST may correlate with disease severity and granule characteristics 4.
Management
Definitive Treatment
The only curative treatment is hematopoietic stem cell transplantation (HSCT), which must be performed before the accelerated phase develops to optimize survival. 1, 5
Critical limitation: HSCT corrects the hematologic and immunologic defects but does NOT correct the oculocutaneous albinism or neurological manifestations 1
Management of the Accelerated Phase
Treatment of HLH in patients with CHS is identical in principle to treatment of HLH in other contexts (familial hemophagocytic lymphohistiocytosis). 1 This requires:
- Aggressive chemotherapy protocols
- Immunosuppression
- Urgent consideration for HSCT if not previously performed 1
Supportive Care (Pre-transplant or if transplant not feasible)
- Aggressive treatment of bacterial infections with appropriate antibiotics
- Prophylactic antibiotics for recurrent infections
- Management of bleeding complications
- Neurological symptom management
- Regular monitoring for signs of accelerated phase development
Prognosis and Critical Timing
Without HSCT, most patients die in childhood either from overwhelming bacterial infections or from the accelerated phase of HLH. 1, 5 The key to improving outcomes is:
- Early diagnosis through recognition of the clinical triad and peripheral blood smear examination
- Prompt referral for HSCT before the accelerated phase develops
- Aggressive treatment of the accelerated phase if it occurs, followed by HSCT
The neurological manifestations are progressive and not corrected by transplantation, representing a major source of long-term morbidity even in successfully transplanted patients 1.