• Clinical science

Progressive muscular dystrophies


Muscular dystrophies are a group of progressive diseases that affect the musculoskeletal system. Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD) are X-linked recessive diseases, whereas limb-girdle muscular dystrophy (LGMD) may be either autosomal dominant or recessive. Muscular dystrophies are commonly due to mutations involving muscular genes (e.g., dystrophin-protein coding gene). Patients typically present with muscular complaints affecting specific muscle groups, particularly the pelvic girdle musculature. DMD is the most severe form of muscular dystrophy, with disease onset typically occurring at two to three years of age. BMD usually does not become evident before the age of 15. DMD progresses rapidly and typically leads to ambulatory inability by age 12. Diagnosis of DMD and BMD is established based on blood tests that show increased creatinine kinase, whereas diagnosis of LGMD is mainly based on genetic analysis. Treatment of muscular dystrophies is usually supportive and includes physiotherapy, assistive devices (e.g., wheelchair), and psychological support. The life expectancy for patients with DMD is approx. 30 years, whereas patients with BMD and LGMD have a longer life expectancy.


  • Incidence
    • DMD: 1/3500
    • BMD: 1/30,000
  • Sex
    • DMD and BMD: only males affected
    • LGMD: affects both genders equally
  • Age of onset
    • DMD: 2–5 years
    • BMD: usually not earlier than 15 years of age


Epidemiological data refers to the US, unless otherwise specified.




  • The dystrophin protein anchors the cytoskeleton of a muscular cell to the extracellular matrix by connecting cytoskeletal actin filaments to membrane-bound dystroglycan that is, in turn, connected to extracellular laminin.
  • Dystrophin gene
    • Largest known protein-coding gene in the human DNA. Therefore, there is an increased risk of spontaneous mutations.
    • Mutations and subsequent alterations of the dystrophin proteinpartial (BMD) or almost complete impairment (DMD) of the protein → disturbance of numerous cellular signaling pathways → necrosis of affected muscle cells and subsequent replacement with connective and fat tissue → muscle appears larger (“pseudohypertrophy”)

Duchenne is caused by Deleted Dystrophin.


Clinical features

Duchenne muscular dystrophy (DMD)

Becker muscular dystrophy (BMD)

  • Symptoms identical to those of DMD
  • Slower progression (patients often remain ambulatory into adult life) and milder symptoms
  • Heart involvement is more common compared to DMD.



  • Blood tests:
    • ↑↑ creatine kinase in serum of almost all affected individuals (also, in > 50% of female carriers)
    • ↑ serum aldolase
  • Genetic analysis (confirmatory test): detect dystrophin gene mutation
  • Muscle biopsy
    • Only performed if genetic analysis is inconclusive
    • All dystrophies: muscle fibers diameter changes, later in the disease course, necrosis and replacement with adipose tissue
    • DMD: absent dystrophin
    • BMD: reduced dystrophin


Differential diagnoses

The differential diagnoses listed here are not exhaustive.


Currently there is no curative treatment for muscular dystrophies!

  • Medical therapy
  • Supportive therapy
    • Physiotherapy
    • Orthopedic assistive devices (wheelchair, walkers)
    • Psychological support
    • Ventilation support



  • DMD: Life expectancy for patients with DMD is approx. 30 years.
  • BMD: : Life expectancy for patients with BMD is 40–50 years.