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Chediak-Higashi syndrome

 Chediak-Higashi syndrome



Overview

Chediak-Higashi syndrome is a rare genetic disorder that impairs immune cells, leading to recurrent infections, and also affects pigment in the skin, hair, and eyes, causing a form of albinism. Key symptoms include recurrent bacterial infections, oculocutaneous albinism (light skin and hair, sometimes with a metallic sheen), and vision problems. Over time, neurological problems such as weakness, clumsiness, and difficulty walking can develop

Symptoms

Recurrent infections: Due to damaged immune cells, individuals are prone to serious and frequent bacterial and viral infections. 

Oculocutaneous albinism: This is characterized by pale skin, light-colored hair that may have a metallic sheen, and possible vision problems like reduced sharpness, rapid eye movements (nystagmus), and sensitivity to light. 

Neurological problems: These typically appear later and can include peripheral neuropathy, poor coordination (ataxia), and progressive motor dysfunction. 

Bleeding and bruising: Problems with blood clotting can cause easy bruising and abnormal bleeding. 

Accelerated phase: Many patients develop a life-threatening "accelerated phase" characterized by symptoms like fever, jaundice, enlarged liver and spleen, and lymphadenopathy. 

causes

Impaired Immune Function: The primary defect in CHS is caused by enlarged lysosomes in immune cells. These abnormally large lysosomes prevent immune cells from fusing with and destroying bacteria, leading to recurrent and severe infections. 

Albinism: Mutations in the LYST gene also affect melanocytes, the cells responsible for producing pigment. This results in melanosomes (related to lysosomes) being abnormally large, causing reduced pigmentation in the skin, hair, and eyes, a condition known as oculocutaneous albinism. 

Neurological Problems: Over time, the disease can also lead to neurological issues, including progressive neuropathy. 

Bleeding Tendencies: There is also a bleeding tendency caused by defects in platelet function, even though platelet counts are typically normal. 

Diagnosis

Clinical and laboratory diagnosis

Blood smear analysis: The primary diagnostic finding is the presence of abnormally large, fused granules in cells like neutrophils, eosinophils, and lymphocytes in a peripheral blood smear.

Bone marrow examination: Microscopic examination of bone marrow also reveals these giant inclusion bodies in leukocyte precursor cells.

Other cellular examination: Diagnosis can be supported by finding giant melanosomes in melanocytes (pigment cells) in skin, hair, and eye samples.

Fluorescence cytometric analysis: This technique can offer additional diagnostic information by analyzing cellular granularity. 

Genetic diagnosis

Molecular genetic testing: This is the definitive way to confirm the diagnosis. 

Gene tested: The test identifies biallelic pathogenic variants (mutations) in the LYST gene. 

Gene function: The LYST gene provides instructions for making the lysosomal trafficking regulator (LYST) protein, which is essential for the proper formation of lysosomes and other vesicles. 

Inheritance pattern: CHS is an autosomal recessive disorder, meaning an individual must inherit a mutated copy of the gene from both parents to have the condition. 

Treatment

Curative treatment

Allogeneic HSCT: This is the only treatment that can cure the hematologic and immunologic defects of CHS. 

Timing is critical: The best outcomes are achieved when HSCT is performed before the development of the accelerated phase. 

Treatment for accelerated phase: If the accelerated phase is present, chemotherapy (like etoposide, dexamethasone, and cyclosporine A) is used to bring the condition into remission before HSCT can be performed. 

Management of symptoms and complications

Infection prevention: Prophylactic antibiotics can be used, and strict hygiene practices are recommended, such as daily washing with disinfectant soap. 

Bleeding prevention: Avoid drugs that interfere with platelet function, like aspirin and other NSAIDs. Avoid intramuscular injections. 

Interferon gamma: Can help restore some immune function. 

Corticosteroids: Pulse doses of corticosteroids can help induce a transient remission of the accelerated phase. 

Splenectomy: Can also induce a temporary remission. 

Ophthalmologic care: Corrective lenses can be used for refractive errors, and sunglasses are recommended to protect from UV light.

Type of Doctor Department : A hematologist, neurologist, immunologist, dermatologist, and ophthalmologist

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