Orotic Aciduria

Orotic aciduria is a rare inherited condition that affects the body's ability to make DNA and RNA, which are essential for cell growth and function. It primarily impacts the metabolic system by disrupting the production of pyrimidines, the building blocks of genetic material. This leads to a buildup of orotic acid in the urine and causes problems like slow growth, anemia, and difficulty gaining weight. The condition usually appears in infancy or early childhood and can cause symptoms such as fatigue, poor appetite, and developmental delays. Because it affects how cells grow and divide, it can have widespread effects on overall health.

Orotic aciduria is an autosomal recessive disorder caused by a deficiency of the bifunctional enzyme UMP synthase, which catalyzes the conversion of orotic acid to uridine monophosphate in the de novo pyrimidine synthesis pathway. This enzymatic defect leads to the accumulation and excessive excretion of orotic acid in urine and a deficiency of pyrimidine nucleotides, impairing DNA and RNA synthesis. Clinically, it presents with megaloblastic anemia unresponsive to vitamin B12 or folate, failure to thrive, and developmental delay. The disorder is distinct from other causes of orotic aciduria such as urea cycle defects because it lacks hyperammonemia. Early diagnosis is critical due to the potential for effective treatment with uridine supplementation.