Orotic aciduria


Orotic aciduria


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USMLE® Step 1 questions

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Orotic aciduria

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USMLE® Step 1 style questions USMLE

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A 7-month-old boy is brought by his parents for a wellness visit. According to the mother, the patient has had poor weight gain despite getting adequate nutrition via a combination of breastmilk and solid foods. In addition, the patient has difficulty rolling from a prone to supine position or sitting upright unassisted. Vitals are within normal limits The patient is at the 5th percentile for weight. Physical examination reveals a frail and pale infant. Enzymatic testing is performed and confirms an absence of uridine monophosphate synthase activity. Which of the following findings is likely to be found on further evaluation?  

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Failure to thrive p. 579

orotic aciduria p. 428

Megaloblastic anemia p. 425, 428

orotic aciduria p. 428

Orotic aciduria p. 428

in anemia taxonomy p. 425


Orotic aciduria refers to an autosomal genetic condition characterized by excessive excretion of orotic acid in urine. It is characterized by a deficiency in UMP (uridine monophosphate) synthase, an enzyme that normally converts orotic acid into another product called uridine monophosphate. People with orotic aciduria present with failure to thrive, poor physical and mental development, and megaloblastic anemia. The treatment may involve the replacement of uridine monophosphate.


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