Limb-girdle muscular dystrophy

Limb-girdle muscular dystrophy or Erb's muscular dystrophy is an autosomal class of muscular dystrophy that is similar but distinct from Duchenne muscular dystrophy and Becker's muscular dystrophy. Limb-girdle muscular dystrophy encompasses a large number of rare disorders.

Presentation
The term "limb-girdle" is used to describe these disorders because the muscles most severely affected are generally those of the hips and shoulders -- the limb girdle muscles.

Common symptoms of limb-girdle muscular dystrophy are muscle weakness, myoglobinuria, pain, myotonia, cardiomyopathy, elevated serum CK, and rippling muscles.

The muscle weakness is generally symmetric, proximal, and slowly progressive.

In most cases, pain is not present with LGMD, and mental function is not affected.

LGMD can begin in childhood, adolescence, young adulthood or even later. The age of onset is usually between 10 and 30. Both genders are affected equally. When limb-girdle muscular dystrophy begins in childhood the progression appears to be faster and the disease more disabling. When the disorder begins in adolescence or adulthood the disease is generally not as severe and progresses more slowly.

There is no sensory neuropathy or autonomic or visceral disfunction at presentation.the specific dermatomes affected can be demonstrated clinically,and although lower limb deep tendon reflexes and plantar reflex are lost, abdominal reflexes are preserved

Prognosis
The distal muscles are affected late in LGMD, if at all. Over time (usually many years), the person with LGMD loses muscle bulk and strength. Eventually, s/he may need a power wheelchair or scooter, especially for long distances. The various forms of LGMD are highly variable, and can be variable even among persons with the same form of LGMD. In its most severe form, LGMD2C, the symptoms are usually similar to Duchenne Muscular Dystrophy, with individuals losing the ability to walk between ages 10 and 12.

While LGMD isn't typically a fatal disease, it may eventually weaken the heart and respiratory muscles, leading to illness or death due to secondary disorders. In its most severe form, LGMD2C, lifespans are typically limited to the 20s or early 30s.

Genetics
LGMD is typically an inherited disorder, though it may be inherited as a dominant, recessive, or X-linked genetic defect. The result of the defect is that the muscles cannot properly form the proteins needed for normal muscle function. Several different proteins can be affected, and the specific protein that is absent or defective identifies the specific type of muscular dystrophy. Among the proteins affected are α, β, γ and δ sarcoglycans. The sarcoglycanopathies could be possibly amenable to gene therapy.

Treatment
Treatment for LGMD is primarily supportive. Exercise and physical therapy are advised to maintain as much muscle strength and joint flexibility as possible. Calipers may be used to maintain mobility and quality of life. Careful attention to lung and heart health is also required. IVIg may increase strength in some forms and prevent progression in others, possibly through the prevention of fibrosis and inflammation without the secondary weakening caused by corticosteroids.

Research
There is currently not an effective treatment or cure to address the underlying genetic defects that cause LGMD. There is a variety of research underway targeted at various forms of LGMD. Methods thought to hold significant promise for an effective treatment include "exon skipping" and gene therapy. Several clinical trials are underway and seeking to apply these methodologies to various limb girdly dystrophies.

List of limb-girdle muscular dystrophies
The "LGMD1" family is autosomal dominant, and the "LGMD2" family is autosomal recessive.