Paediatrics · Easy
This case is fictional and exists for study. It describes no real patient.
1 years · male
An 18-month-old boy is brought to the paediatric clinic by his mother due to concerns about his physical development. He learned to sit independently at 8 months, but he only started pulling himself up to stand at 16 months and cannot walk without support. When attempting to stand up from the floor, he places his hands on his knees and uses his arms to 'climb up' his legs. His mother reports he seems clumsy and falls frequently. Speech and social milestones are on track; he uses four words, points to objects, and interacts well. On examination, he has marked bilateral calf enlargement with a firm consistency and proximal muscle weakness in the lower extremities.
Vital signs
- HR
- 110 bpm
- BP
- 92/58 mmHg
- RR
- 24/min
- Temp
- 36.8 °C
- SpO₂
- 99%
Examination findings
- Inability to walk independently at 18 months
- Positive Gower's sign
- Bilateral calf pseudohypertrophy
- Symmetrical proximal lower limb weakness
Question 1 of 3
Which of the following is the most likely diagnosis?
The clinical presentation of gross motor delay (inability to walk independently by 18 months), proximal muscle weakness, Gower's sign (using hands on knees/thighs to stand up), and calf pseudohypertrophy in a young boy is classic for Duchenne muscular dystrophy (DMD). Cerebral palsy typically presents with hypertonia/spasticity and abnormal reflexes rather than calf pseudohypertrophy. Spinal muscular atrophy type 1 presents in infancy with severe generalized hypotonia, whereas DMD manifests later with proximal weakness. Normal variation does not account for weakness or calf enlargement.
Teaching point: Duchenne muscular dystrophy should be suspected in any boy with delayed walking, proximal weakness, Gower's sign, and calf pseudohypertrophy.
Question 2 of 3
Which of the following is the most appropriate initial investigation?
Serum creatine kinase (CK) is the single best initial screening test when muscular dystrophy is suspected. In Duchenne muscular dystrophy, CK levels are massively elevated (often >10,000 U/L), reflecting ongoing muscle membrane breakdown. MRI of the brain/spine is appropriate for suspected central nervous system lesions like cerebral palsy. Nerve conduction studies assess peripheral neuropathies rather than primary myopathies. Lumbar puncture is used to evaluate CNS infection or demyelinating conditions.
Teaching point: Serum creatine kinase is the primary screening investigation for suspected muscular dystrophies and will be markedly elevated in Duchenne muscular dystrophy.
Question 3 of 3
Following the discovery of a markedly elevated serum creatine kinase level, which of the following is the most appropriate next management step?
Once serum CK is confirmed to be high, genetic testing (e.g., multiplex ligation-dependent probe amplification or gene sequencing) for deletion/duplication mutations in the DMD gene is the gold standard diagnostic step. It avoids invasive muscle biopsy in the vast majority of cases. Corticosteroids are key in long-term management to slow functional decline, but they are initiated after genetic confirmation and specialist paediatric neurology assessment. Muscle biopsy is reserved for cases where genetic testing is negative or non-conclusive. Delayed review (reassurance) is inappropriate given the clinical findings.
Teaching point: Genetic testing for dystrophin gene mutations confirms the diagnosis of Duchenne muscular dystrophy non-invasively following an elevated serum creatine kinase level.
Key learning points
- Inability to walk independently by 18 months is a developmental red flag requiring clinical evaluation.
- Gower's sign combined with calf pseudohypertrophy in a young male is highly suggestive of Duchenne muscular dystrophy.
- Initial evaluation of suspected muscular dystrophy involves checking serum creatine kinase, followed by genetic testing for confirmation.
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