# Muscular Dystrophies > Muscular dystrophies for NEET-PG Medicine covering Duchenne, Becker and myotonic dystrophy genetics, Gowers sign, anticipation, heart disease and anaesthesia. - Canonical URL: https://prepelephant.com/topics/neet-pg/medicine/muscular-dystrophies - Exam / course: NEET-PG · Subject: Medicine - Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team - First published: 2026-10-08 - Last updated: 2026-10-08 - Reference basis: Bradley's Neurology in Clinical Practice; Adams and Victor's Principles of Neurology; Harrison's Principles of Internal Medicine - How to cite: "Muscular Dystrophies", PrepElephant, https://prepelephant.com/topics/neet-pg/medicine/muscular-dystrophies ## Direct answer Muscular dystrophies are inherited myopathies in which progressive muscle degeneration results from defects in structural proteins such as dystrophin or from repeat expansions in other genes. Duchenne muscular dystrophy is X-linked recessive, caused by out-of-frame deletions in the DMD gene, and presents in early childhood with proximal weakness, Gowers sign and cardiomyopathy. Becker dystrophy results from in-frame deletions and runs a milder course, while myotonic dystrophy type 1 is caused by a CTG repeat expansion with myotonia and anticipation. ## What you must remember - **Duchenne:** X-linked recessive, onset before five years, toe walking, calf pseudohypertrophy and very high serum creatine kinase, with loss of ambulation usually by about 12 years without steroids. - **Becker:** in-frame DMD deletion, later onset and slower progression, sometimes presenting with cramps or exercise intolerance. - **Diagnosis:** genetic testing usually confirms Duchenne or Becker; muscle biopsy shows absent dystrophin in Duchenne and reduced or abnormal dystrophin in Becker. - **Myotonic dystrophy type 1:** autosomal dominant CTG repeat in the DMPK gene, with myotonia, frontal balding, cataract, insulin resistance and conduction defects. - **Anticipation:** congenital myotonic dystrophy usually follows maternal transmission, with hypotonia and respiratory failure at birth. - **Facioscapulohumeral dystrophy:** D4Z4 deletion on chromosome 4q35, causing facial weakness and scapular winging. - **Anaesthesia:** succinylcholine is avoided in Duchenne because of hyperkalaemia and rhabdomyolysis, and in myotonic dystrophy because it can provoke sustained myotonic contracture; specialist planning is needed. ## A clinical route for a boy who cannot climb stairs A four-year-old boy is slow to walk, toe-walks and has calf enlargement. 1. **Look for proximal weakness:** Gowers sign, in which the child climbs up his own thighs with his hands to rise from the floor, points to proximal pelvic girdle weakness. 2. **Measure creatine kinase:** Serum creatine kinase is markedly raised. Genetic testing for deletions or duplications in the DMD gene is ordered, with counselling for the mother and wider family. 3. **Screen the heart:** An ECG and echocardiogram are done at diagnosis, because cardiomyopathy begins in childhood and needs monitoring even before symptoms. 4. **Start steroids and physiotherapy:** Prednisolone or deflazacort is considered, since they slow the loss of function, with physiotherapy and orthopaedic review to prevent contractures. 5. **Monitor breathing:** Respiratory function is measured by spirometry, and night-time non-invasive ventilation is introduced when the vital capacity falls. 6. **Add cardiac drugs:** ACE inhibitors and beta-blockers are added when cardiomyopathy develops. Each step aims to preserve function over the child's life. ## Where examiners test the reading frame and the myotonia Four rules recur in muscular dystrophy questions. - **Trap:** treating all dystrophin deletions alike. — **Correct:** out-of-frame deletions give Duchenne and in-frame deletions give Becker, so name both genes and the protein difference. - **Trap:** confusing myotonia with weakness. — **Correct:** myotonia is delayed muscle relaxation after contraction, a separate phenomenon from weakness, and it is absent in Duchenne. - **Trap:** pelvic girdle weakness as the sign of facioscapulohumeral dystrophy. — **Correct:** it is distinguished by facial weakness and scapular winging rather than pelvic girdle weakness. - **Trap:** a routine anaesthetic in myotonic dystrophy. — **Correct:** succinylcholine is avoided in Duchenne (hyperkalaemia, rhabdomyolysis) and in myotonic dystrophy (sustained myotonic contracture), and specialist anaesthetic planning is needed. Myotonic dystrophy is tested through frontal balding, cataract, heart block and insulin resistance, and the congenital form usually follows maternal transmission. ## Frequently asked questions ### What genetic defect separates Duchenne from Becker muscular dystrophy? Duchenne and Becker muscular dystrophy both involve the dystrophin gene on the X chromosome. Duchenne results from out-of-frame deletions that abolish dystrophin, while Becker results from in-frame deletions that leave a shorter but partly functional protein, which explains its milder course. ### What is Gowers sign in muscular dystrophy? Gowers sign is the child using the hands to climb up the thighs when rising from the floor, a sign of proximal pelvic girdle weakness. It is classic in Duchenne muscular dystrophy but also occurs in other proximal myopathies. ### Why must succinylcholine be avoided in myotonic dystrophy? Succinylcholine is avoided in myotonic dystrophy because it can provoke a sustained myotonic contracture that makes ventilation and intubation difficult. In Duchenne the concern is hyperkalaemia and rhabdomyolysis. Anaesthetic planning in myotonic dystrophy needs specialist input and careful monitoring. ### Which cardiac problem is common in myotonic dystrophy? Conduction disease is common in myotonic dystrophy, with progressive atrioventricular block and arrhythmias, so ECG monitoring and rhythm review are essential. Pacemaker or defibrillator decisions follow cardiology assessment.