Limb-girdle muscular dystrophy (LGMD) is a diverse group of disorders with many subtypes categorised by disease gene and inheritance. LGMD usually manifests in the proximal muscles around the hips and shoulders. The proximal muscles are those closest to the center of the body; distal muscles are farther away from the center — for example, in the hands and feet.
The shoulder girdle is the bony structure that surrounds the shoulder area, and the pelvic girdle is the bony structure surrounding the hips. Collectively, these are called the limb girdles, and it is the observed weakness and atrophy (wasting) of the muscles connected to the limb girdles that has given this group of disorders its name.
The hallmark symptoms of LGMD include weakness and atrophy of the limb-girdle muscles. However, the age at which symptoms appear, and the speed and severity of disease progression, can vary. Individuals may first notice a problem when they begin to walk with a “waddling” gait because of weakness of the hip and leg muscles. They may have trouble getting out of chairs, rising from a toilet seat, or climbing stairs. As this weakness progresses, the person may require the use of assistive mobility devices. Additional symptoms include weakness of the heart muscle (cardiomyopathy) and/or abnormal transmission of signals that regulate the heartbeat (conduction abnormalities or arrhythmias). Some disease subtypes also involve the muscles used for breathing, and for that reason, respiratory function, along with cardiac function, should be monitored regularly. Other symptoms may be present in some of the different subtypes of LGMD, including muscle cramps, enlargement of calf muscles, and involvement of distal muscles of the body such as those controlling the hands and feet.
LGMD can arise through mutations in a large number of different genes, with mutations in certain genes linked to certain subtypes of diease. There are also many cases of LGMD for which the causative gene is not yet known (and people with these cases are not identified as having a subtype-specific form of LGMD).
Source: Muscular Dystrophy Association (United States)
