There are over 30 genetic sub-types (forms) of LGMD and all these rare muscular dystrophies cause weakness of the ’limb-girdle’ muscles — the muscles surrounding the shoulders and hips. The severity, age of onset, and features of limb-girdle muscle dystrophy vary among the many sub-types of this condition and may be inconsistent even within the same family. Signs and symptoms may first appear at any age and generally worsen with time, although in some cases they remain mild.
In the early stages of limb-girdle muscular dystrophy, affected individuals may have an unusual walking gait, such as waddling or walking on the balls of their feet, and may also have difficulty running. They may need to use their arms to press themselves up from a squatting position because of their weak thigh muscles. As the condition progresses, people with limb-girdle muscular dystrophy may eventually require wheelchair assistance.
Muscle wasting may cause changes in posture or in the appearance of the shoulder, back, and arm. In particular, weak shoulder muscles tend to make the shoulder blades (scapulae) “stick out” from the back, a sign known as scapular winging. Affected individuals may also have an abnormally curved lower back (lordosis) or a spine that curves to the side (scoliosis). Some develop joint stiffness (contractures) that can restrict movement in their hips, knees, ankles, or elbows. Overgrowth (hypertrophy) of the calf muscles occurs in some people with limb-girdle muscular dystrophy.
The weakening of the heart muscle (cardiomyopathy) occurs in some forms of limb-girdle muscular dystrophy. Some affected individuals experience mild to severe breathing problems related to the weakness of muscles needed for breathing.
Intelligence is generally unaffected by limb-girdle muscular dystrophy; however, developmental delay and intellectual disability have been reported in rare forms of the disorder.
There are many sub-types of LGMD, in fact, more than 30 sub-types have been identified and more are being discovered each year. The different subtypes of LGMD are classified according to the inheritance pattern of the gene mutation responsible for the disease. LGMD either has an autosomal dominant inheritance pattern or an autosomal recessive inheritance pattern. In 2017, the naming system (nomenclature) of limb girdle muscular dystrophies was changed. Patient information leaflet on new names for LGMD (PDF Document)
Autosomal dominant inheritance pattern: In autosomal dominant inheritance, only one parent needs to transmit the mutated gene for the disorder to be inherited. Even though the matching gene from the other parent is unaffected, the faulty gene dominates. Autosomal dominant disorders typically appear in every generation without skips.
Autosomal recessive inheritance pattern: In autosomal recessive inheritance, both parents must be carriers of the faulty gene for their child to inherit the condition. A carrier harbors the faulty gene, but usually shows no symptoms. When a mutation is recessive, it can exist in a person without showing any symptoms so long as their other copy of the same gene is healthy. Autosomal recessive disorders typically appear when there is no known family history of the disorder.