Muscular dystrophy - limb-girdle type

Alternative names

Limb-girdle muscular dystrophies

Definition

Limb-girdle muscular dystrophies include at least 10 different inherited disorders that initially affect the muscles around the shoulder girdle and the hips. These diseases are progressive and may involve other muscles over a period of time.

Causes, incidence, and risk factors

This is a large group of genetic diseases featuring muscle weakness and wasting (muscular dystrophy). Most are inherited in an autosomal recessive manner (both parents must have the defective gene for a child to inherit it), but some are autosomal dominant (only one parent needs to carry the bad gene to affect the child). For some of these conditions, the defective gene has been discovered, but for others, the gene is not yet known.

Typically, onset of pelvic muscle weakness (difficulty standing from a sitting position without using arms, difficulty climbing stairs) starts in childhood to young adulthood. Later there is the onset of shoulder weakness with progression to significant loss of mobility or wheelchair dependence over the next 20-30 years.

An important risk factor is having a family member with muscular dystrophy.

Symptoms

• Muscle weakness in pelvis, hips, upper legs, shoulders
  
• Loss of muscle mass in the same areas, thinning of those body parts
  
• Low back pain
  
• Abnormal, sometimes waddling, gait while walking
  
• Later in disease, there can be facial muscle weakness
  
• Later in the disease, muscles of the lower legs, feet, lower arms, and hands can become weak
  
• Late in the disease, there can be contractures of joints (they become fixed in a contracted position)
  
• Palpitations or passing out spells can be caused by abnormal heart rhythms
  
• Sometimes the calves will look large and muscular (pseudohypertrophy), but they are actually not strong
  

Signs and tests

• Normal muscle biopsy for dystrophin (the protein that is defective in the more common Duchenne muscular dystrophy)
  
• Electromyogram (EMG) testing shows a pattern called myopathy, sick and dying muscle fibers
  
• High blood creatine kinase levels
  
• Muscle biopsy shows degenerating muscle with splitting of muscle fibers and presence of cells of the immune system (phagocytes), which are not normally present