Griscelli syndrome

Griscelli syndrome (GS) is a rare autosomal recessive disorder characterized by hypopigmentation of the skin and hair (silvery-gray hair) combined with variable immunological and neurological impairment. The condition results from defective melanosome transport, leading to characteristic large clumps of pigment in the hair shaft and an accumulation of melanosomes in melanocytes. Three subtypes have been identified based on the underlying genetic cause: GS type 1 (MYO5A gene) presents primarily with hypopigmentation and severe primary neurological impairment; GS type 2 (RAB27A gene) is the most common form and features hypopigmentation with a severe primary immunodeficiency leading to uncontrolled T-lymphocyte and macrophage activation, known as hemophagocytic lymphohistiocytosis (HLH); and GS type 3 (MLPH gene) presents with isolated hypopigmentation without immunological or neurological involvement. The syndrome primarily affects the immune system, the nervous system, and the integumentary system (skin and hair). GS type 2, the most clinically significant form, is characterized by recurrent and often life-threatening episodes of HLH, which manifests as fever, hepatosplenomegaly, pancytopenia, and multi-organ dysfunction. Without treatment, HLH episodes in GS type 2 are typically fatal in early childhood. GS type 1 is associated with severe neurological dysfunction including hypotonia, intellectual disability, and seizures. The only curative treatment for GS type 2 is hematopoietic stem cell transplantation (HSCT), which corrects the immunological defect but does not reverse the pigmentary dilution. Acute HLH episodes are managed with immunosuppressive and chemotherapeutic protocols. GS type 1 has no specific curative treatment, and management is supportive. GS type 3, being limited to hypopigmentation, generally has a benign course and requires no specific treatment. Early diagnosis through microscopic examination of hair shafts and genetic testing is critical for appropriate management, particularly to distinguish GS type 2 from other forms.

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