Duchenne Muscular Dystrophy Inheritance Pattern
Duchenne muscular dystrophy (DMD) is inherited as an X-linked recessive disorder, meaning the disease-causing mutation is located on the X chromosome and primarily affects males. 1
Key Inheritance Characteristics
Males (Affected Individuals)
- Males are predominantly affected because they have only one X chromosome (XY), so a single mutated dystrophin gene results in disease manifestation 1
- The incidence is approximately 1 in 3,000 to 1 in 5,000 live male births 1
- One-third of cases result from de novo (new) mutations with no prior family history 2
Females (Carriers and Rare Manifestations)
- Female carriers (heterozygotes) typically do not manifest the disease because they possess a second, normal X chromosome 1
- When female carriers do develop symptoms, they tend to present with mild to moderate dilated cardiomyopathy in the fifth decade of life, with slowly progressive disease 1
- Symptomatic females are extremely rare and occur through specific mechanisms 3, 4, 5:
Mutation Origin Patterns
- In isolated female dystrophinopathy cases, paternal transmission of new mutations occurs approximately 10-fold more frequently than maternal transmission 4
- This represents a 30-fold variance from expected Bayesian predictions and suggests mechanistic interaction between new dystrophin mutations, paternal inheritance, and skewed X-inactivation 4
Clinical Implications for Genetic Counseling
- Genetic testing should identify the specific mutation type (large deletions/duplications in 70-80% of cases, point mutations in 20-30%) to enable accurate family counseling 2
- Family screening is essential as approximately 30-50% of dilated cardiomyopathy cases in DMD families show inherited patterns 1
- Female carriers require cardiac surveillance given their risk of late-onset cardiomyopathy 1