These less severe but disabling dystrophies. There are many other varieties of muscular dystrophy. Most are associated with a sarcoglycan deficiency.
Genes for various limb girdle muscular dystrophies (LGMD) have been located; some of the proteins for which they code, e.g. calpain, are known. These diseases are progressive and may involve other muscles over a period of time.
Type 1 LGMD is a rare autosomal dominant condition.
Type 2 LGMD includes all recessive varieties, further subdivided, e.g. LGMD2A (calpain III deficiency), LGMD2C.
Causes of Limb girdle muscular dystrophy
There are many different genetic faults associated with limb girdle 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).
LGMD2C-2F is caused by mutations in the sarcoglycan genes.
Symptoms of Limb girdle muscular dystrophy
Frequently, the first reported symptoms are difficulty climbing stairs, standing from a squatting position, or raising arms above the head. Muscle weakness in pelvis, hips, upper legs, shoulders. Palpitations or passing out spells can be caused by abnormal heart rhythms.
Diagnosis of Limb girdle muscular dystrophy
LGMD is not normally a fatal disease. The greatest danger comes from weakening heart muscles or respiratory muscles. Monitoring for heart or breathing complications is recommended for the later stages of the disorder, but these cases are rare. Other tests are:
- Needle electromyography (EMG) and nerve conduction studies (NCSs)
- These will include a selection of blood tests, electrical tests and very importantly a muscle biopsy.
- In most situations the muscle biopsy gives the best chance of reaching a precise diagnosis.
- Cardiac involvement is common in the autosomal dominant syndromes of LGMD1A and 1B (50-65%). Cardiomyopathy of both and cardiac arrhythmias in LGMD1B may cause clinically significant morbidity.
Treatment of Limb girdle muscular dystrophy
No specific treatment is available for any of the LGMD syndromes, though aggressive supportive care is essential to preserve muscle function, maximize functional ability, and prolong life expectancy.
Gene therapy may become available in the future. Supportive treatment can decrease the complications of the disease.
In some cases, joint deformities may be prevented through exercises, physiotherapy, orthoses, and surgery.
One very important reason for knowing exactly which type of limb girdle muscular dystrophy someone has is to make sure that people are getting the right follow up and management.