Spinal muscular atrophy with lower extremity predominance 2B

Spinal Muscular Atrophy with Lower Extremity Predominance 2B (SMA-LED2B) is a rare neuromuscular disorder characterized by muscle weakness and wasting (atrophy), predominantly affecting the lower limbs. This condition is part of a broader group of disorders known as spinal muscular atrophies (SMAs), which are genetic diseases that cause weakness and wasting of the voluntary muscles in the arms and legs of affected individuals.

Causes

SMA-LED2B is caused by mutations in the DYNC1H1 gene, which encodes for a protein that is essential for the proper functioning of motor neurons. Motor neurons are nerve cells that send electrical signals from the brain to the muscles, directing them to contract. The mutations in the DYNC1H1 gene disrupt the normal function of these neurons, leading to the symptoms associated with SMA-LED2B.

Symptoms

The primary symptom of SMA-LED2B is progressive muscle weakness and atrophy, particularly in the lower extremities. This can lead to difficulty walking, frequent falls, and in severe cases, the need for wheelchair assistance. Some individuals may also experience mild upper limb involvement, though this is less common. Symptoms typically begin in childhood or adolescence.

Diagnosis

Diagnosis of SMA-LED2B involves a combination of clinical examination, family history, genetic testing, and sometimes electromyography (EMG) to assess the electrical activity of muscles. Genetic testing is crucial for confirming the diagnosis, as it can identify mutations in the DYNC1H1 gene.

Treatment

There is currently no cure for SMA-LED2B, and treatment focuses on managing symptoms and improving quality of life. Physical therapy and occupational therapy can help maintain muscle strength and flexibility, and assistive devices may be used to aid mobility. In some cases, orthopedic surgery may be necessary to correct skeletal deformities resulting from muscle weakness.

Prognosis

The prognosis for individuals with SMA-LED2B varies. While the condition can significantly impact mobility and daily activities, it does not typically affect life expectancy. Early intervention with physical and occupational therapy can improve outcomes and help individuals lead active lives.

NIH genetic and rare disease info

• NIH info on Spinal muscular atrophy with lower extremity predominance 2B

Spinal muscular atrophy with lower extremity predominance 2B is a rare disease.