Question
A 6-year-old boy is brought to the pediatric clinic with progressive difficulty in running and climbing stairs. His parents report that he frequently falls and has difficulty rising from the floor. On examination, he uses his hands to “climb up” his thighs while standing up from a squatting position (Gowers’ sign). He also has enlargement of the calf muscles and mild exertional dyspnea.
What is the most likely diagnosis?
| A. |
Duchenne Muscular Dystrophy (DMD)
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| B. |
Tay–Sachs Disease (GM2 Gangliosidosis due to Hexosaminidase A deficiency)
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| C. |
Gaucher Disease (Glucocerebrosidase deficiency)
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| D. |
Fabry Disease (α-Galactosidase A deficiency)
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Show Answer
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Correct Answer » A
Explanation
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The key clues in this question are:
- Young boy
- Progressive proximal muscle weakness
- Difficulty running and climbing stairs
- Inability to rise from squatting position
- Positive Gowers’ sign
- Calf pseudohypertrophy
- Exertional breathing difficulty
These findings are classic for Duchenne Muscular Dystrophy (DMD).
Gowers’ Sign
When proximal muscles of the pelvic girdle are weak, the child cannot stand directly from a sitting or squatting position.
Instead, he:
- Gets onto hands and knees.
- Places hands on thighs.
- “Climbs up” his own body using his hands.
This is called Gowers’ sign and is a hallmark of Duchenne Muscular Dystrophy.
Why Duchenne Muscular Dystrophy Occurs
Genetics
- X-linked recessive inheritance
- Mutation of the Dystrophin gene (Xp21)
Pathogenesis
Dystrophin stabilizes muscle cell membranes.
Absence of dystrophin causes:
- Muscle fiber degeneration
- Progressive muscle weakness
- Replacement by fat and connective tissue
Clinical Features of Duchenne Muscular Dystrophy
Early Features (2–5 years)
- Delayed motor milestones
- Frequent falls
- Difficulty running
- Difficulty climbing stairs
- Gowers’ sign
Characteristic Features
- Calf pseudohypertrophy
- Waddling gait
- Lumbar lordosis
- Toe walking
Late Features
- Respiratory muscle weakness
- Dilated cardiomyopathy
- Scoliosis
Most patients become wheelchair-bound during adolescence.
Why the Other Options are Incorrect
B. Tay–Sachs Disease
Deficiency: Hexosaminidase A
Clinical Features
- Developmental regression
- Exaggerated startle response
- Cherry-red spot in macula
- Neurodegeneration
- No hepatosplenomegaly
Does not cause Gowers’ sign or calf pseudohypertrophy.
C. Gaucher Disease
Deficiency: Glucocerebrosidase
Clinical Features
- Hepatosplenomegaly
- Pancytopenia
- Bone pain
- Erlenmeyer flask deformity
Does not present with proximal muscular weakness and Gowers’ sign.
D. Fabry Disease
Deficiency: α-Galactosidase A
Clinical Features
- Angiokeratomas
- Acroparesthesias
- Renal failure
- Hypertrophic cardiomyopathy
Not associated with calf pseudohypertrophy or Gowers’ sign.
