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. Orotic aciduria is associated with megaloblastic anemia due to decreased pyrimidine synthesis, which leads to decreased nucleotide-lipid cofactors needed for erythrocyte membrane synthesis in the bone marrow. In addition to the characteristic excessive orotic acid in the urine, patients typically have megaloblastic anemia (UMP synthase deficiency) which cannot be cured by administration of vitamin B12 or folic acid. Orotic aciduria can also cause inhibition of RNA and DNA synthesis and ultimately, failure to thrive.