A 2-year-old boy is brought to the pediatrician for a routine health maintenance examination. He has a condition characterized by joint contractures, coarse facial features, and recurrent ear infections. The liver edge is palpated 3cm inferior to the right costal margin. Biochemical studies show a deficiency of N-acetylglucosamine-phosphotransferase. Serum studies show elevated levels of numerous lysosomal enzymes. A photomicrograph of the patient’s lymphocytes is shown.
Which of the following processes is most likely impaired in this patient?
Phosphoribosyl pyrophosphate synthesis
Phosphoribosylation of acetylglucosamine
Phosphorylation of GM2 ganglioside
Phosphorylation of lysosomal target membrane
Phosphorylation of 6th position on mannose
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Cut-to-the-chase Answer (0:46):
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HY USMLE Answer (7:48):
