Griscelli syndrome type 1 (GS1) is a rare autosomal recessive disorder that results in pigmentary dilution of the skin and hair, the presence of large clumps of pigment in hair shafts, and an accumulation of melanosomes in melanocytes. In addition to the characteristic silvery-gray appearance of hair and pigmentary defects of skin, GS1 is characterized by primary neurologic deficits that usually are apparent in early infancy and include hypotonia, developmental delay, intellectual disability, and seizures. Immune impairment is not present (summary by Abd Elmaksoud et al., 2020). Bahadoran et al. (2003) characterized GS1 as comprising hypomelanosis and severe central nervous system dysfunction, corresponding to the 'dilute' phenotype in the mouse, and GS2 as comprising hypomelanosis and lymphohistiocytic hemophagocytosis, corresponding to the 'ashen' phenotype in mouse. Anikster et al. (2002), Menasche et al. (2002), Huizing et al. (2002), and Bahadoran et al. (2003, 2003) suggested that Elejalde neuroectodermal melanolysosomal syndrome (256710) in some patients and GS1 represent the same entity. Genetic Heterogeneity of Griscelli Syndrome Griscelli syndrome type 2 (GS2; 607624), characterized by hypomelanosis with immunologic impairment, is caused by mutation in the RAB27A gene (603868). Griscelli syndrome type 3 (GS3; 609227), characterized by hypomelanosis with no immunologic or neurologic manifestations, is caused by mutation in the melanophilin (MLPH; 606526) gene.

Elejalde neuroectodermal melanolysosomal syndrome is a rare autosomal recessive disorder characterized by silvery-gray hair and severe dysfunction of the central nervous system, present from infancy or early childhood and consisting of severe hypotonia, seizures, and impaired intellectual development. Skin may be hypopigmented with bronzing after sun exposure. Microscopy of hair reveals large granules of melanin unevenly distributed in the hair shaft. Abnormal melanocytes and melanosomes and abnormal inclusion bodies in fibroblasts may be present (Elejalde et al., 1979; Duran-McKinster et al., 1999). It has been proposed that, in at least some cases, Elejalde neuroectodermal melanolysosomal syndrome and Griscelli syndrome type 1 (GS1; 214450) represent the same entity; see below. GS1 is caused by mutation in the MYO5A gene (160777).

Griscelli syndrome type 2 (GS2) is an autosomal recessive disorder characterized by pigmentary dilution of the skin and hair, the presence of large clumps of pigment in hair shafts, and an accumulation of melanosomes in melanocytes. Patients also have immunologic abnormalities with or without neurologic impairment (summary by Menasche et al., 2000). Some GS2 patients have been reported in whom central nervous system manifestations are the first presentation (Rajadhyax et al., 2007, Masri et al., 2008; Mishra et al., 2014; Lee et al., 2017). For a discussion of phenotypic and genetic heterogeneity of Griscelli syndrome, see Griscelli syndrome type 1 (GS1; 214450).