Mucolipidosis type IV
Mucolipidosis type IV Wikipedia is a rare but severe inherited lysosomal storage disease that is more common among Ashkenazi Jews than in other populations. About 1 in 100 individuals in this ethnic group is a carrier. Only a child who inherits two mutated copies of the mucolipin-1 (MCOLN1) gene will develop the disease; carriers are not affected. Children with this disorder are usually severely developmentally delayed.
23andMe tests for this variation using its own terminology, specifically i4000425 (risk genotype G;G; carrier genotype A;G).