USMLE · Question #558
A 23-year-old woman comes to the physician for genetic counseling prior to conception. Her brother and maternal uncle had Duchenne muscular dystrophy (DMD) and died at the ages of 28 and 17 years…
The correct answer is E. The patient's DMD carrier status is uncertain because of random X inactivation. See the full explanation below for the reasoning.
Question
A 23-year-old woman comes to the physician for genetic counseling prior to conception. Her brother and maternal uncle had Duchenne muscular dystrophy (DMD) and died at the ages of 28 and 17 years, respectively. Genetic analysis was not performed on either relative prior to death. Serum studies show a muscle creatine kinase concentration of 120 U/L (N = 22 `" 198). The patient's 50-year-old mother has a serum muscle creatine kinase concentration of 300 U/L. Which of the following is the most appropriate assessment of this patient's carrier status for this disease?
Options
- AThe patient has a 50% risk for developing DMD
- BThe patient has a 50% risk of having a child with DMD
- CThe patient is a carrier of the disease based on her family history of DMD
- DThe patient is not a carrier of the DMD based on her normal creatine kinase concentration
- EThe patient's DMD carrier status is uncertain because of random X inactivation
How the community answered
(35 responses)- A6% (2)
- B11% (4)
- C3% (1)
- D3% (1)
- E77% (27)
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