SNP Shot: Genomic Insights

Limb-girdle muscular dystrophy (LGMD) is a group of genetic muscle disorders. These conditions primarily cause weakness and wasting (atrophy) in the muscles of the arms and legs. The muscles closest to the center of the body, called proximal muscles, are most commonly affected. This includes muscles around the shoulders, upper arms, hips, and thighs.

The symptoms, severity, and age of onset of LGMD vary greatly. These differences can be seen across different types of LGMD, and even within the same family. Symptoms can start at any age and typically get worse over time. However, some people with LGMD may only have mild symptoms.

Early warning signs of LGMD might include an abnormal walking style, like waddling or walking on tiptoes, and trouble running. People might also need to use their arms for support when standing up from a squatting position because of weakness in their thigh muscles. As the disease progresses, some people with LGMD may eventually need to use a wheelchair.

As muscles waste away, this can alter posture and change the appearance of the shoulders, back, and arms. Weak shoulder muscles can cause the shoulder blades to stick out from the back, known as scapular winging. People affected might also develop an exaggerated curve in the lower back (lordosis) or a sideways curve in the spine (scoliosis). Some develop stiff joints (contractures) that limit movement in the hips, knees, ankles, or elbows. In some types of LGMD, the calf muscles may become larger (hypertrophy).

Certain forms of LGMD can affect the heart muscle, leading to a condition called cardiomyopathy. In addition, some people with LGMD may experience mild to severe breathing problems because of weakness in the muscles used for breathing. In severe situations, they might need a machine to help them breathe (mechanical ventilation).

Generally, LGMD does not affect a person's thinking abilities. However, in rare cases, some people with LGMD have been reported to have developmental delays or intellectual disabilities.

Inheritance:

LGMD can be passed down through families in several ways. The most common pattern is autosomal recessive inheritance. This means that a person must inherit two copies of a mutated gene (one from each parent) to develop the condition. In autosomal recessive inheritance, each parent carries one copy of the faulty gene but usually doesn't have any symptoms themselves. Less often, LGMD is inherited in an autosomal dominant pattern, where only one copy of the altered gene in each cell is sufficient to cause the disorder.