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Duchenne & Becker Muscular Dystrophy

Quick Summary

Definition: X-linked dystrophinopathies caused by DMD variants (absent dystrophin in Duchenne, reduced or altered in Becker), causing progressive skeletal myopathy and a dilated cardiomyopathy.[1]

  • Prevalence: DMD 1 in 3,500 male births (most common MD), BMD 1 in 18,000[3]
  • Key gene: DMD (dystrophin), X-linked recessive - males affected, females carriers (30% develop DCM)
  • Hallmark: Progressive skeletal muscle weakness + DCM (posterolateral wall first) + respiratory failure (DMD severe, BMD milder)
  • High-risk markers: LVEF <35%, NSVT, extensive LGE, respiratory failure, late gadolinium enhancement
  • First-line Mx: ACE-I/ARB early (before LVEF drops), beta-blockers, corticosteroids (DMD), ICD if LVEF <35%, transplant consideration

Aetiology

Monogenic (Mendelian): 100%, DMD-gene mutations affecting dystrophin (~1/3 de novo)[3]

Genetics

Inheritance: X-linked recessive (DMD gene, dystrophin)

Males: Affected (hemizygous); out-of-frame mutations → absent dystrophin (DMD); in-frame mutations → truncated, partially functional dystrophin (BMD, milder)

Female carriers: ~10–30% develop dilated cardiomyopathy (often later onset, age 30–50); baseline echocardiogram essential before pregnancy

Mutation-specific cardiac risk (Landfeldt et al 2024[7]):

  • Mutations in exons 51 and 52 are significantly associated with lower risk of cardiomyopathy
  • Deletions treatable by exon 53 skipping and mutations in the Dp116 coding region are associated with improved LVEF and prolonged cardiac dysfunction-free survival
  • Mutations in exons 45–50 and 52 associated with earlier left ventricular systolic dysfunction
  • Genetic modifiers (LTBP4, ACTN3) also influence LVEF and cardiomyopathy risk

Prevalence

Duchenne: 1 in 3,500 male births (most common muscular dystrophy)[3]

Becker: 1 in 18,000 male births[3]

Diagnosis

Duchenne (severe):

  • Onset <5 years, wheelchair-bound by teens
  • Cardiomyopathy universal by late teens
  • Death typically 20s-30s (respiratory/cardiac failure)

Becker (milder):

  • Later onset, slower progression
  • Cardiac involvement variable - can be predominant feature
  • Longer survival (40s-60s)

Cardiac features: Dilated cardiomyopathy (posterolateral wall first), arrhythmias, conduction disease

Investigations

CK: Markedly elevated (10-100x normal)

Genetic testing: DMD gene deletion/duplication analysis, then sequencing

Cardiac MRI: Early detection of fibrosis (inferolateral wall) - before EF drops

ECG: Tall R in V1, deep Q laterally, short PR

Treatments

Skeletal muscle: Corticosteroids, deflazacort (preferred in UK; high-quality evidence for preserved LVEF and improved fractional shortening vs no corticosteroid[7]); prednisone/prednisolone also associated with improved EF and lower risk of cardiomyopathy (low-quality evidence[7]); physiotherapy; respiratory support as disease advances

Cardiac, early and proactive GDMT (BSH/ESC consensus[1][2]):

1. ACE inhibitor, START EARLY (even if LVEF normal)

  • Perindopril (most evidence in DMD, PERDU trial[4]):
    • Start from age 10 (DMD) or at diagnosis (BMD) regardless of LVEF[4]
    • 2 mg once daily → target 4–8 mg once daily
    • RCT evidence: proportion with LVEF <45% at 60 months was 4% (treated) vs 28% (untreated), p=0.02[7]
    • Also associated with slower myocardial fibrosis progression on CMR (moderate-quality evidence[7])
  • Ramipril (alternative): 1.25–2.5 mg once daily → target 5–10 mg once daily
  • Switch to ARNI (sacubitril/valsartan 24/26 → 97/103 mg twice daily) if LVEF drops to ≤40%

2. Beta-blocker, add once LVEF <55% or LV dilatation

  • Carvedilol (preferred, additional antioxidant properties):
    • Start 3.125 mg twice daily → target 12.5–25 mg twice daily (uptitrate every 2 weeks)
  • Bisoprolol (alternative): 1.25 mg once daily → 5–10 mg once daily
  • Caution: respiratory muscle weakness, monitor SpO₂; avoid in significant respiratory compromise

3. MRA, add if LVEF <45%

  • Eplerenone: 25 mg once daily → 50 mg once daily (preferred over spironolactone in males, avoids gynaecomastia)
    • RCT evidence: eplerenone significantly reduced LVEF decline at 12 months (median change −1.8% treated vs −3.7% untreated, p=0.032) and attenuated LVESV progression[7]
  • Monitor K⁺ and eGFR; hold if K⁺ >5.5 mmol/L

4. SGLT2 inhibitor, consider if LVEF <40%

  • Dapagliflozin 10 mg or empagliflozin 10 mg once daily
  • Limited DMD-specific data but consistent HF benefit in HFrEF (DAPA-HF, EMPEROR-Reduced)

Device therapy:

  • ICD if LVEF ≤35% after GDMT optimisation (apply standard HFrEF criteria; consider life expectancy and functional status)
  • CRT-D if LVEF ≤35% + LBBB + QRS ≥130 ms
  • Wearable cardioverter defibrillator (LifeVest) may bridge to ICD in acute LV dysfunction

Emerging:

  • Exon-skipping therapy (eteplirsen, golodirsen), limited to specific mutation types; modest dystrophin restoration
  • Microdystrophin gene therapy, phase 1/2 trials showing promising results
Related Resources

Complications

  • Progressive dilated cardiomyopathy: leading to heart failure, now a leading cause of death as respiratory care has improved, and can be severe and disproportionate in Becker (transplant candidacy)[1]
  • Arrhythmia and conduction disease: atrial and ventricular
  • Anaesthetic hazard: volatile agents and suxamethonium can trigger rhabdomyolysis and hyperkalaemia (TIVA preferred), which is not classic malignant hyperthermia
  • Female carriers: carry an under-recognised DCM risk warranting surveillance

Risk Stratification

Cardiac disease major cause of death (especially as respiratory support improves survival)

Pregnancy Management

Pregnancy in DMD/BMD Female Carriers (mWHO Class II-III)

Pregnancy in FEMALE CARRIERS of DMD/BMD mutations

Affected males rarely reach reproductive age (especially DMD) due to severe skeletal muscle disease

PRECONCEPTION COUNSELLING:

  • Female carrier status and cardiac risk:
    • 20-30% of female DMD carriers develop dilated cardiomyopathy (often later onset, age 30-50)
    • 10-15% of BMD carriers develop cardiomyopathy
    • Cardiac involvement can occur WITHOUT skeletal muscle weakness
    • X-inactivation pattern determines phenotype (skewed inactivation → symptomatic carriers)
    • Pregnancy may UNMASK previously asymptomatic carrier state (volume load reveals subclinical dysfunction)
  • Risk stratification:
    • Normal LVEF, no LV dilatation: mWHO II (low-moderate risk)
    • LVEF 40-50%, mild LV dilatation: mWHO II-III (moderate risk)
    • LVEF <40%, NYHA II-III: mWHO III-IV (high risk, pregnancy discouraged)
    • Unknown carrier status but family history: Screen with echo + genetic testing BEFORE pregnancy
  • X-linked inheritance counselling:
    • Female carrier:
      • 50% of sons will be affected (severe DMD or milder BMD)
      • 50% of daughters will be carriers (risk of cardiomyopathy)
    • Prenatal testing: CVS (10-12 weeks), amniocentesis (15-18 weeks)
    • Preimplantation genetic diagnosis (PGD): Option for unaffected pregnancy
    • Fetal sex determination: Cell-free DNA from 10 weeks (if male → affected vs unaffected 50:50; if female → carrier vs non-carrier 50:50)
    • Many carriers opt for PGD or prenatal testing given severity of DMD in affected males
  • Baseline cardiac assessment - ESSENTIAL:
    • Echo (LVEF, LV dimensions, regional wall motion)
    • ECG (conduction abnormalities, Q waves)
    • Consider cardiac MRI if echo suboptimal or abnormal (LGE pattern predicts events)
    • NT-proBNP (baseline)
    • If LVEF <50% or LV dilatation: Start ACE-I BEFORE conception (stop when pregnant, but establishes treatment)
  • Medications:
    • ACE-I/ARBs: STOP pre-conception (teratogenic)
    • Beta-blockers: Continue if on (metoprolol, bisoprolol, carvedilol safe)

PREGNANCY MANAGEMENT:

  • Monitoring frequency:
    • Known carrier, normal baseline cardiac function: Echo each trimester
    • Known carrier, LVEF 40-50%: Monthly cardiology review, echo each trimester + if symptoms
    • Known carrier, LVEF <40%: As per DCM pregnancy protocol (see DCM section)
    • NT-proBNP each trimester (trend important - rising suggests decompensation)
  • Unmasking of carrier state:
    • Pregnancy volume load may reveal previously subclinical LV dysfunction
    • Low threshold for echo if dyspnea, fatigue, palpitations
    • If new LV dysfunction detected: Treat as DCM (hydralazine + nitrates, beta-blockers, diuretics, close monitoring)
  • Medical therapy if LV dysfunction:
    • Hydralazine 75-300mg/day + isosorbide dinitrate 60-120mg/day (replace ACE-I)
    • Beta-blockers: Metoprolol 100-200mg/day (uptitrate to maximum tolerated)
    • Diuretics if fluid overload (furosemide safe)
    • No data on SGLT2 inhibitors in pregnancy - avoid
  • Activity:
    • Normal activity if LVEF preserved
    • Avoid strenuous exercise if LVEF <50%
    • Rest/reduce activity if symptomatic

LABOUR & DELIVERY:

  • Delivery planning:
    • Tertiary centre if LVEF <50%
    • Standard obstetric unit acceptable if normal LVEF and asymptomatic
  • Mode of delivery:
    • Vaginal delivery preferred if LVEF >40%
    • Elective caesarean if LVEF <40% or NYHA III
    • Assisted second stage if LVEF <50% (reduce maternal effort)
  • Anaesthesia:
    • Epidural safe and preferred
    • GA if caesarean: Standard precautions for LV dysfunction
    • Anaesthetic caution: dystrophinopathy is not classic (RYR1-mediated) malignant hyperthermia, but volatile agents and depolarising muscle relaxants (e.g. suxamethonium) can trigger rhabdomyolysis and life-threatening hyperkalaemia in affected individuals, so these are generally avoided and total intravenous anaesthesia is preferred; manifesting carriers should be assessed individually
  • Intrapartum monitoring:
    • Continuous ECG if LVEF <50%
    • Standard monitoring otherwise

POSTPARTUM:

  • Peripartum cardiomyopathy (PPCM) phenocopy:
    • DMD/BMD carriers can present with "PPCM-like" deterioration postpartum
    • Actually unmasking of underlying genetic cardiomyopathy, NOT true PPCM
    • If new/worsening LV dysfunction postpartum in carrier:
      • Treat as heart failure (ACE-I, beta-blockers, diuretics, aldosterone antagonist)
      • Bromocriptine NOT indicated (this is genetic DCM, not PPCM)
      • Recovery possible but may have persistent dysfunction
  • Restart medications:
    • ACE-I (enalapril 5-20mg BD, safe with breastfeeding)
    • Continue/start beta-blockers if LV dysfunction
    • Standard GDMT as per heart failure guidelines
  • Follow-up:
    • Echo at 6 weeks (assess recovery)
    • If new LV dysfunction in pregnancy/postpartum: Echo 3, 6, 12 months (assess trajectory)
    • LIFELONG cardiac surveillance even if LVEF recovers - carriers remain at risk
  • Breastfeeding: Safe; ACE-I (enalapril, captopril) and beta-blockers compatible
  • Contraception: All methods safe; LARC if heart failure (avoid pregnancy until stable)
  • Genetic testing of offspring:
    • Male infants: Creatine kinase (CK) at birth (elevated if affected); confirm with genetic testing
    • Female infants: Genetic testing to determine carrier status (enables lifelong cardiac surveillance)
    • Early diagnosis in males allows early cardiac surveillance, steroids (improve outcomes), family planning

IMPORTANT DATA:

  • 20-30% of female DMD carriers develop dilated cardiomyopathy (often late-onset, 30s-50s)
  • Pregnancy may unmask subclinical LV dysfunction in carriers
  • Cardiac MRI with LGE predicts cardiac events in carriers (even with normal LVEF)
  • Early ACE-I therapy in carriers with LV dysfunction may prevent progression

KEY POINTS:

  • ALL women with family history of DMD/BMD should have cardiac screening BEFORE pregnancy
  • 20-30% of carriers develop cardiomyopathy (can be unmasked by pregnancy)
  • 50% risk to male offspring (severely affected) - prenatal testing/PGD discussion essential
  • Pregnancy generally safe if normal LVEF; high-risk if LVEF <40%
  • Postpartum "PPCM" in carrier = unmasking of genetic DCM (treat with standard HF therapy)
  • Lifelong cardiac surveillance for all carriers, even if pregnancy uneventful

Follow-up

Based on the AHA scientific statement on neuromuscular cardiac care[2].

Advanced / complicated = established cardiomyopathy (LVEF decline or LGE), arrhythmia, or symptomatic heart failure.

Genotype-positive / phenotype-negative (G+/P−) = a confirmed pathogenic-variant carrier with no overt disease expression yet.

Genotype+ / Phenotype−Uncomplicated / StableAdvanced / Complicated
FrequencyFemale carriers: echo every ~5 yrs; pre-CM males: annualAnnual (from diagnosis)Every 6 months once cardiomyopathy present
Clinical reviewCardiac symptom reviewSymptoms (may be masked by immobility), HF signsAs above
ECGPeriodicAnnual 12-leadEach visit
Cardiac imaging (echo / CMR)Echo ± CMR periodicallyAnnual (CMR preferred for early fibrosis where feasible)6-monthly
Holter / ambulatoryAs indicatedAs indicated (arrhythmia, esp. BMD)Periodic
Carrier screening–Echo for female carriers every ~5 years–

Disclaimer: This table is general guidance based on published guidelines and does not replace clinical judgement. The responsible clinician is accountable for determining the appropriate, individualised follow-up plan for each patient.

Key Points

  • Annual cardiac screening from diagnosis (echo, ECG, Holter)[1]
  • Start ACEi/ARB early - delays cardiomyopathy even with normal EF[1]
  • Screen female carriers - 20-30% develop cardiomyopathy (often late-onset)[1]
  • PRECONCEPTION cardiac screening ESSENTIAL for all female carriers - pregnancy may unmask subclinical dysfunction
  • Pregnancy generally safe if normal LVEF (mWHO II); high-risk if LVEF <40% (mWHO III-IV)
  • 50% risk to male offspring - discuss prenatal testing/PGD
  • Multidisciplinary care essential (neurology, respiratory, cardiology)

References & Review Date

Last reviewed: June 2026

  1. Arbelo E, et al. 2023 ESC Guidelines for the management of cardiomyopathies. Eur Heart J. 2023;44(37):3503–3626. doi:10.1093/eurheartj/ehad194
  2. Feingold B, et al. Management of cardiac involvement associated with neuromuscular diseases: a scientific statement from the American Heart Association. Circulation. 2017;136(13):e200–e231. doi:10.1161/CIR.0000000000000456
  3. McNally EM, et al. Contemporary cardiac issues in Duchenne muscular dystrophy. Circulation. 2015;131(18):1590–1598. doi:10.1161/CIRCULATIONAHA.114.011887
  4. Duboc D, et al. Effect of perindopril on the onset and progression of left ventricular dysfunction in Duchenne muscular dystrophy (PERDU trial). J Am Coll Cardiol. 2005;45(6):855–857. doi:10.1016/j.jacc.2004.08.081
  5. McDonagh TA, et al. 2021 ESC Guidelines for the diagnosis and treatment of acute and chronic heart failure. Eur Heart J. 2021;42(36):3599–3726. doi:10.1093/eurheartj/ehab368
  6. Joint Formulary Committee. British National Formulary (BNF). bnf.nice.org.uk
  7. Landfeldt E, Alemán A, Abner S, et al. Predictors of cardiac disease in Duchenne muscular dystrophy: a systematic review and evidence grading. Orphanet J Rare Dis. 2024;19:359. doi:10.1186/s13023-024-03372-x