Question

A boy presented with weakness in the lower limbs, calf hypertrophy, positive Gower's sign and an elevated CPK value of 10,000. The most likely diagnosis is:

• A. Duchenne muscular dystrophy
• B. Spinal muscular atrophy
• C. Myotonia congenita
• D. Myotonic dystrophy

Hint:

Boy plus calf pseudohypertrophy plus Gower's sign plus very high CPK equals Duchenne.

Answer 1

The Correct Option is A

Step 1: List the findings. A boy with proximal lower limb weakness, pseudohypertrophy of the calves, a positive Gower's sign (climbing up his own legs to stand because of proximal weakness), and a markedly raised creatine phosphokinase of about 10,000.

Step 2: Match the syndrome. This tetrad is the textbook presentation of Duchenne muscular dystrophy (DMD), an X linked recessive disorder of the dystrophin gene affecting boys, with onset in early childhood, calf pseudohypertrophy, and CPK levels in the thousands to tens of thousands.

Step 3: Eliminate the alternatives.
Spinal muscular atrophy is a lower motor neuron disorder with hypotonia, weakness, fasciculations, and tongue fasciculations, but it does not cause calf pseudohypertrophy, and CPK is normal or only mildly raised.
Myotonia congenita features muscle stiffness and difficulty relaxing (myotonia) often with muscle hypertrophy, but it lacks progressive proximal weakness and the very high CPK; it is a channelopathy.
Myotonic dystrophy shows myotonia, distal weakness, facial weakness, cataracts, and frontal balding, with only mild CPK elevation, and the classic age and pattern do not fit a young boy with calf pseudohypertrophy and CPK 10,000.

Step 4: The complete picture is Duchenne muscular dystrophy.

The correct answer is option A, Duchenne muscular dystrophy.