What are common characteristics from all types of muscular dystrophy?

Updated: Aug 17, 2020
  • Author: Twee T Do, MD; Chief Editor: Jeffrey D Thomson, MD  more...
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Answer

Minor variations notwithstanding, all types of MD have in common progressive muscle weakness that tends to occur in a proximal-to-distal direction, though there are some rare distal myopathies that cause predominantly distal weakness. The decreasing muscle strength in those who are affected may compromise the patient's ambulation potential and, eventually, cardiopulmonary function.

In addition, structural soft-tissue contractures and spinal deformities may develop from poor posturing caused by the progressive muscle weakness and imbalance, all of which can further compromise function and longevity. Equinovarus contractures start as flexible dynamic deformities and advance to rigid contractures. This altered anatomy prevents normal ambulation, proper shoe wear, and transfers (how patients can be picked up to transfer out of their chair).

Once wheelchair-bound, patients with MDs tend to develop worsening contractures, osteopenia (initially, followed by osteoporosis), and rapidly progressive scoliosis. The change in bone mineral density (BMD) can lead to fractures of the long bones or vertebrae, which in turn lead to more immobilization, disuse demineralization, and exacerbation of scoliosis. On average, for each 10° of thoracic scoliosis curvature, forced vital capacity (FVC) decreases by 4%. [5] In a patient with an already weakened cardiopulmonary system, this decrease in FVC could rapidly become fatal.


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