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OverviewAetiologyPathophysiologyClinical features and red flagsInvestigationsDifferential diagnosisManagementComplicationsMonitoring and follow-upSpecial situationsCommon pitfallsQuestionsSources
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Educational draft · awaiting clinical reviewThe full textbook explains uncertainty but does not replace live national or local guidance, specialist advice, or current prescribing information.

Neuromuscular weakness and Duchenne muscular dystrophy

Paediatrics and child health · UK scope · Sources checked 27 Aug 2026 · Clinical review pending

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Neuromuscular respiratory or bulbar failure

Weak cough, drooling, choking, inability to count or speak normally, orthopnoea, morning headache, paradoxical breathing or rapid loss of mobility can precede hypoxaemia and requires urgent ventilatory assessment.

Action: Use ABCDE, measure serial respiratory function when feasible, avoid excessive oxygen without ventilation assessment, involve paediatric intensive care and neuromuscular teams and protect swallowing and airway clearance.

Overview

Localise childhood weakness, identify respiratory and bulbar emergencies, recognise Duchenne muscular dystrophy early and organise creatine kinase, genetic confirmation, corticosteroid, cardiac, respiratory and family care.

Ask when milestones were acquired and whether abilities are being lost. Observe floor rise, running, jumping, stairs, gait, scapular winging and facial movement. Test neck, shoulder and hip power, reflexes, sensation, fatigability, coordination and spine. A child using hands on thighs to rise demonstrates proximal compensation, not a diagnostic sign unique to Duchenne.

Respiratory assessment cannot rely on saturation. Nocturnal hypoventilation first causes restless sleep, morning headache, daytime fatigue and concentration change while oxygen saturation may be normal awake. Weak cough and recurrent lower respiratory infection indicate airway-clearance failure. Bulbar weakness produces prolonged meals, nasal speech, cough with drink and aspiration.

In suspected Duchenne, CK is often tens of times above the upper reference limit. AST and ALT can also be muscle-derived; check CK before launching a liver-only investigation in a weak child. Molecular testing establishes the reading-frame variant, enables carrier testing and determines eligibility for mutation-specific therapies. ECG and cardiac imaging begin at diagnosis.

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Paediatrics and child healthOriginal SBA

Preschool proximal weakness

A four-year-old boy has frequent falls, calf enlargement and climbs up his thighs to stand. What is the best first-line diagnostic blood test?

Choose one answer, then submit
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Sources and review status4 sources · checked 27 Aug 2026 · clinical review pending+
Sources

Sources and review status

National guidance is shown before implementation-dependent detail. Typical adult dose examples remain subject to patient factors, contraindications and the live BNF or specialist protocol. Source check completed 27 Aug 2026; clinical approval remains outstanding.

  • NICE NG127 Neurological RecognitionReferral for motor regression, weakness and creatine kinase testing in boys.
  • NHS Muscular Dystrophy OverviewPresentation, diagnosis and multidisciplinary management.
  • Muscular Dystrophy UK DuchenneUK family information on diagnosis, progression and care.
  • DMD Care UK StandardsUK consensus care pathways for Duchenne multidisciplinary management.

Editorial contact: Doctor’s Passport editorial team. Source-check date is separate from clinical approval. Report a content problem · Content changes

Authoring stateComplete draftClinical stateAwaiting reviewJurisdictionUnited Kingdom

Multidisciplinary care changes natural history. Daily stretching and appropriately timed orthoses maintain comfort but excessive eccentric exercise can injure muscle. Regular submaximal activity is encouraged. Corticosteroids can prolong walking and respiratory function; treatment choice incorporates behaviour, weight, growth, bone and adrenal risks. Never stop chronic steroids abruptly, especially during illness or surgery.

Cardiomyopathy is often silent. Regular ECG and echocardiography or cardiac MRI detect fibrosis and dysfunction before symptoms, allowing ACE inhibitor, angiotensin-receptor blocker, mineralocorticoid antagonist or beta-blocker therapy through cardiology. Respiratory teams track forced vital capacity, cough flow and sleep gas exchange and introduce lung-volume recruitment, assisted cough and non-invasive ventilation.

Bone health requires vitamin D and calcium assessment, fracture vigilance and steroid-aware endocrine input. Loss of ambulation must not end active care: upper-limb function, accessible technology, supported standing, pressure care, spinal monitoring, sexuality and transition remain important. Advance care planning is an offer to improve choices, not withdrawal of disease-directed treatment.

Key points

  • Localise weakness by onset, proximal or distal distribution, symmetry, fatigability, reflexes, sensation, cranial and bulbar signs and upper motor-neurone features.
  • Duchenne muscular dystrophy usually becomes apparent between two and five years with delayed milestones, Gowers manoeuvre, waddling, toe walking, falls and calf pseudohypertrophy.
  • First-line testing for a boy with unexplained motor delay or proximal weakness is serum creatine kinase; a very high result demands urgent neuromuscular referral, not repeated observation.
  • Confirm dystrophinopathy with molecular genetic testing, starting with methods that detect exon deletions or duplications and then sequencing when required; biopsy is reserved for unresolved cases.
  • A normal newborn period does not exclude Duchenne, and language or learning difficulty may precede obvious weakness because dystrophin isoforms are expressed in brain.
  • Corticosteroids prolong ambulation and preserve respiratory and upper-limb function; the neuromuscular team selects daily or intermittent prednisolone or deflazacort and monitors toxicity.
  • Cardiac surveillance begins before symptoms and uses ECG plus echocardiography or cardiac MRI; cardioprotective therapy is introduced through the specialist protocol.
  • Serial forced vital capacity, sleep study when indicated, cough assessment, vaccination and assisted cough or non-invasive ventilation prevent crisis better than waiting for resting hypoxaemia.
  • Avoid succinylcholine and alert anaesthesia to dystrophinopathy because hyperkalaemic arrest and anaesthesia-associated rhabdomyolysis can occur.
  • Offer genetic counselling, carrier testing through clinical genetics, education support, bone protection, physiotherapy, psychosocial care and timely transition as one coordinated pathway.

Aetiology

01

Dystrophin gene variant

X-linked pathogenic DMD variants abolish or severely reduce dystrophin, usually causing Duchenne disease in boys and occasionally symptomatic females.

02

Other inherited myopathy

Limb-girdle dystrophy, congenital myopathy, spinal muscular atrophy and metabolic muscle disease produce different distributions, ages and systemic risks.

03

Peripheral nerve or junction disease

Guillain-Barré syndrome, hereditary neuropathy, myasthenia and botulism impair motor transmission with characteristic reflex, sensory, autonomic or fatigability findings.

04

Acquired muscle injury

Inflammation, endocrine disease, electrolyte disorder, infection, toxin and corticosteroid exposure can cause potentially reversible childhood muscle weakness.

Pathophysiology

  1. 1
    Dystrophin membrane instability

    Without functional dystrophin, contraction damages the muscle-cell membrane, allowing calcium injury, fibre necrosis and creatine kinase leakage.

  2. 2
    Fibrofatty replacement

    Repeated degeneration exceeds regeneration, replacing skeletal and cardiac muscle with fat and fibrosis while calves appear enlarged but weak.

  3. 3
    Biomechanical compensation

    Proximal hip weakness produces lumbar lordosis, waddling, toe walking and hand climbing up the thighs during Gowers manoeuvre.

  4. 4
    Cardiorespiratory progression

    Diaphragm and expiratory weakness impair ventilation and cough, while dystrophin-deficient myocardium develops dilated cardiomyopathy and arrhythmia.

Clinical features and red flags

Gowers manoeuvre

The child rolls prone, widens stance and pushes hands up the thighs to compensate for hip and trunk weakness.

Calf pseudohypertrophy

Calves appear enlarged from fat and connective tissue replacement despite progressive loss of contractile muscle strength.

Proximal gait pattern

Lumbar lordosis, pelvic waddling, toe walking, poor running and difficulty with stairs reflect hip-girdle weakness and contracture.

Respiratory weakness

Weak cough, orthopnoea, morning headache, sleep disturbance and recurrent infection can precede daytime hypoxaemia.

Cardiac involvement

Asymptomatic ventricular fibrosis, tachycardia, palpitations or heart-failure features require lifelong dystrophinopathy cardiac surveillance.

Red flags requiring action

  • Loss of previously acquired motor skills, rapid progression or weakness after a normal early course requires urgent neurological assessment.
  • Weak cough, recurrent aspiration, sleep-disordered breathing, morning headache or inability to lie flat suggests respiratory muscle failure even with normal oxygen saturation.
  • Duchenne clues include delayed walking, Gowers manoeuvre, frequent falls, waddling gait, toe walking and calf enlargement in a preschool boy.
  • Markedly raised transaminases with no liver explanation should prompt creatine kinase because muscle releases AST and ALT.
  • Weakness with areflexia progressing over days suggests Guillain-Barré syndrome, while bladder change, sensory level or brisk reflexes suggests spinal cord disease.
  • Children with dystrophinopathy have anaesthetic-associated rhabdomyolysis and hyperkalaemia risk; avoid succinylcholine and ensure specialist anaesthetic planning.

Investigations

  1. 01
    First-line serum creatine kinaseFirst stepFirst line
    Why
    Detect muscle-fibre injury in a child with objective weakness, Gowers manoeuvre or delayed motor milestones.
    Interpretation and limitations
    A markedly raised value supports muscular dystrophy and needs urgent referral; a normal value makes Duchenne very unlikely.
  2. 02
    DMD molecular genetic testing
    Why
    Confirm dystrophinopathy, define the variant and enable carrier and mutation-specific treatment assessment.
    Interpretation and limitations
    Deletion or duplication analysis is followed by sequencing when needed; specialist interpretation distinguishes Duchenne from Becker phenotype.
  3. 03
    ECG and cardiac imaging
    Why
    Identify conduction abnormality, myocardial fibrosis and ventricular dysfunction before clinical heart failure.
    Interpretation and limitations
    Normal early studies do not end surveillance; frequency increases with age and abnormal findings under the neuromuscular cardiac plan.
  4. 04
    Serial respiratory function and sleep assessment
    Why
    Detect declining forced vital capacity, cough weakness and nocturnal hypoventilation before acute respiratory failure.
    Interpretation and limitations
    Trend values sitting and supine with symptoms; sleep carbon dioxide and oximetry guide non-invasive ventilation.
  5. 05
    Muscle biopsy only selectively
    Why
    Assess dystrophin expression or alternative myopathy when modern genetic testing does not resolve a convincing phenotype.
    Interpretation and limitations
    It is not the first investigation for typical suspected Duchenne and should be directed by a neuromuscular centre.

Differential diagnosis

01

Spinal muscular atrophy

Symmetrical proximal weakness, hypotonia, tongue fasciculation and reduced reflexes with preserved sensation suggests anterior horn cell disease.

02

Becker muscular dystrophy

Partially functional dystrophin produces a later, milder course, although cardiomyopathy may be substantial despite better mobility.

03

Cerebral palsy

Upper motor-neurone signs, hyperreflexia and a non-progressive early pattern distinguish cerebral palsy from progressive primary muscle disease.

04

Inflammatory myositis

Subacute weakness with pain, rash or systemic inflammation suggests juvenile dermatomyositis and needs muscle enzymes and rheumatological assessment.

05

Developmental coordination disorder

Clumsiness without objective weakness, Gowers manoeuvre, calf hypertrophy or raised creatine kinase follows a neurodevelopmental rather than myopathic pathway.

Additional chapter-specific clues

Alternative neuropathic pattern

Distal weakness, sensory loss and reduced reflexes suggests peripheral nerve disease rather than primary dystrophin muscle degeneration.

Management

01LocaliseConfirm genuine weaknessFirst stepA child has delayed motor skills, falls or loss of function.+
  1. 1Observe play, floor rise, run and stairs before formal power, reflex and sensory examination.
  2. 2Screen bulbar, respiratory, cardiac and bladder symptoms to identify emergency localisation.
  3. 3Request creatine kinase promptly for objective proximal weakness or Gowers manoeuvre.
02ConfirmEstablish dystrophin diagnosisClinical pattern and creatine kinase suggest Duchenne muscular dystrophy.+
  1. 1Refer urgently to the regional paediatric neuromuscular service and clinical genetics.
  2. 2Perform deletion or duplication analysis and sequencing according to the molecular pathway.
  3. 3Begin baseline cardiac, respiratory, developmental, bone and therapy assessment without waiting for advanced weakness.
03PreserveUse anticipatory multidisciplinary careDuchenne or another progressive neuromuscular disorder is confirmed.+
  1. 1Discuss corticosteroids, activity, stretching, orthoses, nutrition, bone and adrenal safety.
  2. 2Institute scheduled cardiac imaging, lung function, cough and sleep surveillance with preventive treatment.
  3. 3Provide genetic counselling, school access, psychosocial support and mutation-specific review.
04DeteriorationEscalate breathing and swallowingEscalationCough, sleep, bulbar or respiratory symptoms worsen acutely or progressively.+
  1. 1Measure serial ventilatory function and obtain blood gas or sleep assessment according to urgency.
  2. 2Use airway clearance, assisted cough and non-invasive ventilation through the respiratory plan.
  3. 3Admit rapidly progressive weakness or aspiration and involve intensive care before exhaustion.
Key medicines and prescribing safety2 treatments · regimens, roles and cautions+
Disease-modifying corticosteroid that prolongs ambulation and supports respiratory and upper-limb function in Duchenne muscular dystrophy.

Prednisolone in Duchenne

A common specialist daily regimen is 0.75 mg/kg orally once daily, with dose or intermittent schedule adjusted to response and adverse effects; provide a written steroid sick-day and perioperative plan and never stop abruptly.

Monitor weight, height, blood pressure, behaviour, glucose, cataract, infection, puberty, bone strength and adrenal suppression; give stress dosing during significant illness or surgery as directed.

Alternative disease-modifying corticosteroid when its weight, behavioural or availability profile better suits the individual child.

Deflazacort in Duchenne

A common specialist daily regimen is 0.9 mg/kg orally once daily, adjusted by the neuromuscular team for benefit, growth and toxicity, with the same adrenal emergency precautions as other chronic glucocorticoids.

Cushingoid effects, cataract, growth and pubertal suppression, hypertension, infection, osteoporosis and adrenal crisis remain important despite differing weight effects from prednisolone.

Complications

01

Respiratory failure

Weak inspiratory muscles, ineffective cough, scoliosis and sleep hypoventilation progress to infection vulnerability and ventilatory dependence.

02

Dilated cardiomyopathy

Myocardial fibrosis causes ventricular dysfunction and arrhythmia that may be clinically silent until advanced without regular surveillance.

03

Contracture and scoliosis

Muscle imbalance, reduced mobility and growth cause ankle, knee and hip contractures and spinal curvature affecting comfort and breathing.

04

Glucocorticoid toxicity

Weight gain, growth suppression, cataract, hypertension, adrenal suppression and low bone strength require proactive prevention and monitoring.

05

Family genetic risk

Carrier relatives may have reproductive and cardiac implications, so a molecular diagnosis should trigger counselling and cascade testing.

Monitoring and follow-up

  • Measure functional milestones, timed floor rise, walking or upper-limb ability with consistent age-appropriate tools.
  • Record weight, height or arm span, blood pressure, puberty, cataract and adrenal plan during corticosteroid treatment.
  • Perform scheduled ECG and echocardiography or cardiac MRI even when there are no cardiac symptoms.
  • Trend forced vital capacity, cough strength, respiratory infections and sleep symptoms and introduce support before daytime failure.
  • Review joint range, spine, pain, fractures, vitamin D, calcium intake and weight-bearing opportunities.
  • Reassess swallowing, meal duration, nutrition and aspiration as weakness progresses.
  • Update genetic counselling, carrier cardiac screening, emergency card, anaesthetic alert and transition plan.

Special situations

Transaminases can be muscle

AST and ALT may prompt extensive liver tests unless a simple creatine kinase reveals ongoing muscle-fibre injury.

Big calves are weak

Pseudohypertrophy reflects fat and fibrosis, so calf size should never be interpreted as preserved muscle power.

Saturation falls late

Ventilatory weakness first raises carbon dioxide during sleep while daytime oxygen saturation can remain deceptively normal.

Genotype directs family care

A molecular result confirms diagnosis, enables carrier testing and may open a mutation-specific treatment pathway.

Anaesthesia needs advance warning

Dystrophinopathy creates severe hyperkalaemia and rhabdomyolysis risk with specific agents even before cardiomyopathy is symptomatic.

Common pitfalls

  1. 01

    Calling Gowers manoeuvre ordinary clumsiness.

  2. 02

    Investigating raised transaminases without checking creatine kinase.

  3. 03

    Waiting for hypoxaemia before assessing ventilation.

  4. 04

    Stopping chronic corticosteroids abruptly during illness.

  5. 05

    Using succinylcholine in known or possible dystrophinopathy.

  6. 06

    Assuming good mobility excludes cardiomyopathy.

  7. 07

    Delaying genetic counselling until the child loses ambulation.