This is an extremely rare disorder identified in 14 cases widely distributed geographically, including Caucasians, Orientals, Polynesians, American Indians and negroes. It is due to an enzyme deficiency inherited in an autosomal recessive fashion. Hereditary orotic aciduria otherwise known as UMPS deficiency, results in the accumulation of orotic acid, which is excreted in quantity The clinical features are assumed to be related to pyrimidine nucleotide depletion. The onset of symptoms usually occurs in the first few months of life. All patients have a macrocytic hypochromic megaloblastic anaemia unresponsive to the usual forms of therapy (iron, folic acid and B12), and sometimes leucopenia. Failure to thrive, developmental retardation, cardiac malformations, bilateral strabismus, sparse hair, inability to sit unaided, and gross crystalluria, occasionally with ureteric obstruction, have been general findings.