Orotic aciduria type II. Orotidine-5-prime-phosphate decarboxylase deficiency.
Incidence
Only 1 case has been identified, but recessive inheritance is strongly suspected.
Clinical Characteristics
This disorder differs from type I in that only one enzyme is defective: orotidine-5-prime-phosphate decarboxylase. Orotidine-5-prime-pyrophosphorylase (also known as orotate phosphoribosyl-transferase) activity is increased. Only 1 case has been identified, but recessive inheritance is supported by intermediate enzyme activity or urinary excretion of orotic acid in the patient's mother and brother and probably father. The clinical characteristics are the same as Orotic aciduria type I. Patients have megaloblastic anemia unresponsive to vitamin B12 and folate. Hypochromic, microcytic circulating erythrocytes persistent with administration of iron or pyridoxine. Predisposition to severe infections. There is cellular immune defect with normal humoral immunity. Mental retardation is present. There is Orotic aciduria. Orotic acid crystalluria. Anemia corrected by uridylic acid and cytidylic acid. Increased orotidine-5-prime-pyrophosphorylase. Orotidine-5-prime-phosphate decarboxylase defect.
Precipitants
No.
Provocation Tests
No.
Diagnostic Procedures
Orotic aciduria. Orotic acid crystalluria. Anemia corrected by uridylic acid and cytidylic acid. Increased orotidine-5-prime-pyrophosphorylase. Orotidine-5-prime-phosphate decarboxylase defect.