This is a recessive deficiency of the enzyme orotidylate decarboxylase, encoded at human chromosome 3q13 or a deficiency of orotate phosphoribosyl transferase. Rare human diseases have their counterparts in other higher eukaryotes. The clinical symptoms include anemia with large immature erythrocytes and urinary excretion of orotic acid (see Fig. O24). The administration of uridylate and cytidylate alleviates the symptoms. Homologous mutations have been detected in cattle. orotic acid
