Neutral lipid storage myopathy

Neutral Lipid Storage Myopathy (NLSM) is a rare genetic disorder characterized by the abnormal accumulation of neutral lipids in the muscle cells and other tissues of the body. This condition is part of a group of disorders known as lipid storage diseases, which affect the body's ability to metabolize fats properly, leading to their accumulation in various tissues.

Causes

NLSM is caused by mutations in specific genes that are involved in the breakdown and utilization of fats. The most commonly implicated genes are PNPLA2, which encodes the enzyme adipose triglyceride lipase (ATGL), and ABHD5, which encodes a co-activator of ATGL. Mutations in these genes disrupt the normal breakdown of triglycerides, leading to their accumulation in cells.

Symptoms

The symptoms of NLSM can vary widely among affected individuals but generally include progressive muscle weakness, myalgia (muscle pain), and sometimes hepatomegaly (enlarged liver) or hepatosteatosis (fatty liver). In some cases, individuals may also develop cardiomyopathy (disease of the heart muscle), leading to heart failure. The accumulation of lipids in the retina can also cause vision problems in some patients.

Diagnosis

Diagnosis of NLSM typically involves a combination of clinical evaluation, muscle biopsy, and genetic testing. Muscle biopsy can reveal the characteristic lipid droplets within muscle cells, while genetic testing can identify mutations in the PNPLA2 or ABHD5 genes.

Treatment

There is currently no cure for NLSM, and treatment focuses on managing symptoms and preventing complications. This may include physical therapy to maintain muscle strength and mobility, medications to manage heart problems if they arise, and dietary modifications to control lipid levels. In some cases, individuals may benefit from enzyme replacement therapy or other experimental treatments under clinical trials.

Prognosis

The prognosis for individuals with NLSM varies depending on the severity of symptoms and the presence of complications such as cardiomyopathy. While the disorder can significantly impact quality of life, with appropriate management, many individuals can lead active lives.

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