How is orotic aciduria diagnosed?
Sarah Duran
Updated on February 21, 2026
How is orotic aciduria diagnosed?
A diagnosis of hereditary orotic aciduria is based upon identification of characteristic symptoms, a detailed patient and family history, a thorough clinical evaluation and examination of the urine. Examination of the urine (urinalysis) can reveal elevated levels of orotic acid.
What is orotic aciduria?
Orotic aciduria refers to an autosomal recessive condition characterized by excessive excretion of orotic acid in urine in the presence of normal levels of ammonia in the urine.
What causes orotic acid?
Orotic acid, first discovered in ruminant milk, is an intermediate in the pyrimidine biosynthesis pathway of animal cells. Its synthesis is initiated by the formation of carbamoyl phosphate (CP) in the cytoplasm, with ammonia derived from glutamine. For that, ammonia is derived from tissue fluid.
How does OTC deficiency cause orotic aciduria?
In OTC deficiency, carbamoyl phosphate accumulates and is alternatively metabolized to orotic acid. Allopurinol inhibits orotidine monophosphate decarboxylase and, when given to OTC carriers (who may have normal orotic acid excretion), can cause increased excretion of orotic acid.
Why is type 2 orotic aciduria caused?
Orotic aciduria is characterized by excessive excretion of orotic acid in urine because of the inability to convert orotic acid to UMP….
| Orotic aciduria | |
|---|---|
| Causes | Autosomal recessive mutation of the UMPS gene |
| Differential diagnosis | Mitochondrial disorders; Lysinuric protein intolerance; liver disease |
How does allopurinol cause orotic aciduria?
Treatment with allopurinol or 6-azauridine also produces orotic aciduria as a result of inhibition of orotidine-5′-phosphate decarboxylase by their metabolic products.
What enzymes are deficient in orotic aciduria?
The disease is caused by deficiency of the enzymes orotidylic pyrophosphorylase and orotidylic decarboxylase, or by deficiency only of the latter. These enzymes normally catalyze the formation of uridine monophosphate from orotic acid during pyrimidine synthesis.
Is orotic acid harmful?
Orotic acid has a low acute toxicity. In repeated doses orotic acid induces fatty livers in the rat, but not in other species tested.
What enzyme is deficient in orotic aciduria?
2 Uridine Monophosphate Synthase (UMPS) Deficiency. Hereditary orotic aciduria is caused by the deficiency of uridine monophosphate synthase (UMPS). UMPS is a bifunctional enzyme consisting of orotate phosphoribosyltransferase and orotidine-5-monophosphate decarboxylase.
What is OTD disorder?
Ornithine transcarbamylase deficiency is an inherited disorder that causes ammonia to accumulate in the blood. Ammonia, which is formed when proteins are broken down in the body, is toxic if the levels become too high. The nervous system is especially sensitive to the effects of excess ammonia.
Why is type 1 orotic aciduria caused?
Orotic aciduria (AKA hereditary orotic aciduria) is a disease caused by an enzyme deficiency resulting in a decreased ability to synthesize pyrimidines….
| Orotic aciduria | |
|---|---|
| Causes | Autosomal recessive mutation of the UMPS gene |
| Differential diagnosis | Mitochondrial disorders; Lysinuric protein intolerance; liver disease |
How are allopurinol and 6 Azauridine involved in the pathophysiology of orotic aciduria?
Both allopurinol and 6- azauridine cause increased orotic acid excretion (1). The mechanisms of these effects are not clear but appear to involve actions by metabolites of the drugs on pyrimidine synthesis, distal to the formation of orotic acid.
