A 15-year-old boy is sent from gym class with a chief complaint of severe muscle aches. In class today he was competing with his friends and therefore engaged in weightlifting for the first time. A few hours later he was extremely sore and found that his urine was red when he went to urinate. This concerned him and he was sent to the emergency department for evaluation. Upon further questioning, you learn that since childhood he has always had muscle cramps with exercise. Physical exam was unremarkable. Upon testing, his creatine kinase level was elevated and his urinalysis was negative for blood and positive for myoglobin. Thinking back to biochemistry you suspect that he may be suffering from a hereditary glycogen disorder. Given this suspicion, what would you expect to find upon examination of his cells?
ANormal glycogen structure
BShort outer glycogen chains
CAccumulation of glycogen in lysosomes forming dense granules
DGlycogen without normal branching pattern
EAbsence of glycogen in muscles
A 23-year-old woman and her husband come to a genetic counselor because she is concerned about the chance of having an inherited defect if they had a child. Family history reveals no significant family history in her husband; however, her sister had a son who has seizures, failure to thrive, and neurodegeneration. She does not remember the name of the disease but remembers that her nephew had sparse, brittle hair that kinked in odd directions. She does not think that any other members of her family including her sister's husband have had this disorder. If this couple had a son, what is the most likely chance that he would have the same disorder that affected the patient's nephew?
A100%
B12.5%
C25%
D50%
EClose to 0%
A 3-month-old girl is brought to the emergency department by her parents after she appeared to have a seizure at home. On presentation, she no longer has convulsions though she is still noted to be lethargic. She was born through uncomplicated vaginal delivery and was not noted to have any abnormalities at the time of birth. Since then, she has been noted by her pediatrician to be falling behind in height and weight compared to similarly aged infants. Physical exam reveals an enlarged liver, and laboratory tests reveal a glucose of 38 mg/dL. Advanced testing shows that a storage molecule present in the cells of this patient has abnormally short outer chains. Which of the following enzymes is most likely defective in this patient?
ADebranching enzyme
BHepatic phosphorylase
CGlucose-6-phosphatase
DMuscle phosphorylase
EBranching enzyme
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