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|Limb-Girdle Muscular Dystrophy|
Limb-girdle muscular dystrophy (Limb-girdle MD) refers to more than a dozen inherited conditions marked by progressive loss of muscle bulk and symmetrical weakening of voluntary muscles, primarily those in the shoulders and around the hips. At least three forms of autosomal dominant limb-girdle MD (known as type 1) and eight forms of autosomal recessive limb-girdle MD (known as type 2) have been identified. Some autosomal recessive forms of the disorder are now known to be due to a deficiency of any of four dystrophin-glycoprotein complex proteins called the sarcoglycans.
The recessive limb-girdle muscular dystrophies occur more frequently than the dominant forms, usually begin in childhood or the teenage years, and show dramatically increased levels of serum creatine kinase. The dominant limb-girdle muscular dystrophies usually begin in adulthood. In general, the earlier the clinical signs appear, the more rapid the rate of disease progression. Limb-girdle MD affects both males and females. Some forms of the disease progress rapidly, resulting in serious muscle damage and loss of the ability to walk, while others advance very slowly over many years and cause minimal disability, allowing a normal life expectancy. In some cases, the disorder appears to halt temporarily, but symptoms then resume.
Weakness is typically noticed first around the hips before spreading to the shoulders, legs, and neck. Patients develop a waddling gait and have difficulty when rising from chairs, climbing stairs, or carrying heavy objects. Patients fall frequently and are unable to run. Contractures at the elbows and knees are rare but patients may develop contractures in the back muscles, which gives them the appearance of a rigid spine. Proximal reflexes (closest to the center of the body) are often impaired. Some patients also experience cardiomyopathy and respiratory complications. Intelligence remains normal. Most persons with limb-girdle MD become severely disabled within 20 years of disease onset.