sentences:  Defects in orotate phosphoribosyltransferase have been implicated in numerous medical conditions.Defects in the orotate phosphoribosyltransferase domain of UMPS cause orotic aciduria in humans, which is a rare hereditary metabolic disease resulting from problems with pyrimidine metabolism.It can lead to megaloblastic anemia and orotic acid crystalluria, which is associated with physical and mental impairments.