Warburg micro syndrome

Warburg Micro syndrome-1 (WARBM1) is a rare autosomal recessive syndrome characterized by microcephaly, microphthalmia, microcornea, congenital cataracts, optic atrophy, cortical dysplasia, in particular corpus callosum hypoplasia, severe mental retardation, spastic diplegia, and hypogonadism (summary by Morris-Rosendahl et al., 2010). Genetic Heterogeneity of Warburg Micro Syndrome Warburg Micro syndrome-2 (WARBM2; 614225) is caused by mutation in the RAB3GAP2 gene (609275) on chromosome 1q41. WARBM3 (614222) is caused by mutation in the RAB18 gene (602207) on chromosome 10p12. WARBM4 (615663) is caused by mutation in the TBC1D20 gene (611663) on chromosome 20p13. Handley et al. (2013) provided an overview of the disease variants identified in the RAB3GAP1, RAB3GAP2, and RAB18 genes, noting that a total of 144 families with WARBM and 9 families with Martsolf syndrome had been studied. Mutations were identified in RAB3GAP1 in 41% of cases, in RAB3GAP2 in 7% of cases, and in RAB18 in 5% of cases. Although RAB18 had not been linked to RAB3 pathways, Handley et al. (2013) stated that mutations in all 3 genes cause an indistinguishable phenotype, making it likely that there is some functional overlap. [from OMIM]