A 7-year-old boy is examined by his pediatrician because of complaints of severe cramping pain in his legs whenever he rides his bike. In addition, he experiences nausea and vomiting during these attacks. The child has noted that the severity of the cramps is most intense after dinners that include baked potatoes or pasta and sometimes bread. Clinical studies undertaken following a treadmill test demonstrate myoglobinuria, hyperuricemia, and increased serum bilirubin. Which of the following enzyme deficiencies is associated with these clinical findings?

Question

Quizplus · Accepted Answer

The symptoms and clinical findings suggest a deficiency in muscle phosphofructokinase (PFK1), which is associated with glycogen storage disease type VII (Tarui's disease). This condition leads to exercise intolerance, muscle cramps, and myoglobinuria, especially after consuming high-carbohydrate meals.  This patient is exhibiting symptoms of Tarui disease (GSD7) due to mutation in the gene encoding muscle and erythrocyte PFK1. The symptoms of this disease are very similar to those observed in patients suffering from McArdle disease (GSDV), in particular the presentation of exercise-induced pain and myoglobinuria. However, since Tarui disease also involves a defect in erythrocyte PFK1, there are associated mild forms of jaundice, resulting from accelerated destruction of erythrocytes.

A 7-Year-Old Boy Is Examined by His Pediatrician Because of Complaints