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A 14-year-old boy presents to his family physician with complaints of muscle weakness...

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asked Oct 6, 2017 in Pediatrics by Rajesh Bahara

 

A 14-year-old boy presents to his family physician with complaints of muscle weakness affecting his ability to play on his soccer team. Physical examination reveals pseudohypertrophy of his calf muscles. The boy’s family history is positive for similar symptoms in a maternal uncle, whose condition progressed to a wheelchair-bound state by the age of 30 years. 

 

Which of the following is the etiology of this disorder?

(A) Autosomal dominant
(B) Autosomal recessive
(C) Mitochondrial inheritance
(D) Somatic mutation
(E) X-linked dominant
(F) X-linked recessive 

 

1 Answer

+1 vote
 
Best answer
The correct answer is F. X-linked recessive inheritance shows affected male individuals inheriting a defective copy of the X chromo- some from heterozygous (asymptomatic) mothers. There is no male-to-male transmission. Heterozygous females may be affected, but usually not as severely as males. Becker’s muscular dystrophy is a milder, slower-developing form of dystrophinopathy with manifestations similar to those of Duchenne’s muscular dystrophy.

Answer A is incorrect. Autosomal dominant inheritance shows disease in many generations, with both males and females affected. It is possible for a male or a female to transmit the defective gene to their offspring. Becker’s muscular dystrophy is not inherited in this manner.

Answer B is incorrect. In autosomal recessive inheritance, a defective gene from each carrier parent is transmitted to the offspring. Disease is often seen in only one generation. Males and females are equally likely to be affected. Becker’s muscular dystrophy is not inherited in this manner.

Answer C is incorrect. In mitochondrial inheritance, all children (male and female) of an affected mother exhibit the disease. The dis- ease is not transmitted from fathers to any of their children (only maternal transmission). Becker’s muscular dystrophy is not inherited in this manner.

Answer D is incorrect. Somatic mutations occur in the somatic (non-germ) tissues; they are unable to be transmitted to offspring and often occur in isolated individuals within a family. Males and females are equally susceptible to somatic mutations. Becker’s muscular dystrophy is not inherited in this manner.

Answer E is incorrect. X-linked dominant inheritance shows disease in any offspring who inherit the affected X chromosome. It is transmitted from fathers to all their daughters but none of their sons, and from mothers to sons or daughters. Becker’s muscular dystrophy is not inherited in this manner.
answered Oct 6, 2017 by Rajesh Bahara

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