AKT · Neurology/Cord & peripheral

Muscular dystrophies (Duchenne & Becker)

X-linked dystrophin gene mutation (Duchenne = absent, Becker = reduced)

Overview

X-linked recessive disorders of the dystrophin gene. Duchenne (dystrophin ABSENT) is severe and presents in early childhood; Becker (dystrophin REDUCED) is milder and later. Boys present with proximal weakness, calf PSEUDOHYPERTROPHY and Gowers sign, with a markedly raised creatine kinase.

Recognise

Boys; Duchenne: delayed walking, proximal weakness, GOWERS sign (climbing up the legs to stand), calf PSEUDOHYPERTROPHY, age 3–5
Markedly raised creatine kinase; later cardiomyopathy and respiratory failure
Becker: same features but milder and later onset

Red flags

Cardiomyopathy and respiratory failure (the causes of death); a boy not walking by 18 months → check CK

Differentials & how to tell them apart

Spinal muscular atrophyLMN/anterior-horn, tongue fasciculation, normal CK

Other limb-girdle dystrophiesgenetics/biopsy distinguish

Inflammatory myopathyacquired, raised inflammatory markers

Cerebral palsynon-progressive, perinatal, normal CK

Investigations

Markedly raised serum creatine kinase (screening) → genetic testing (dystrophin gene) ± muscle biopsy (absent/reduced dystrophin); echocardiogram + respiratory function for surveillance.

Management

Corticosteroids (Duchenne) + multidisciplinary cardiac/respiratory surveillance

1Raised CK in a boy with proximal weakness/Gowers → genetic testing. Duchenne: corticosteroids to slow progression + MDT care.Gate: A boy who is late to walk or uses Gowers manoeuvre → check creatine kinase BEFORE attributing it to simple developmental delay (the screening step for muscular dystrophy)
2Cardiac surveillance (cardiomyopathy → ACE-i/beta-blocker) and respiratory support (NIV); physiotherapy, orthotics; genetic counselling (X-linked).

Corticosteroids — slow loss of muscle function in Duchenne

MDT supportive care — physio, cardiac (ACE-i/beta-blocker for cardiomyopathy), respiratory (NIV)

Key points

Boy + proximal weakness + Gowers + calf pseudohypertrophy + very high CK = Duchenne; milder/later = Becker. CK is the screening test; cardiomyopathy/respiratory failure determine prognosis. (Cross-reference: child_health developmental milestones.)

Monitor & prognosis

Motor function, cardiac (echo) and respiratory function, steroid effects.

Duchenne: wheelchair by ~12, death from cardiorespiratory failure in 20s–30s; Becker much milder.

Source: NICE; neuromuscular guidance