Disorders Affecting Muscles

Inherited neuromuscular disorders are a group of rare genetic conditions that affect muscles, peripheral nerves, motor neurons and neuromuscular junctions. They are characterized by progressive muscle degeneration and weakness due to genetic changes that impair muscle function. Congenital myasthenic syndromes represent a group of inherited neuromuscular transmission disorders associated with muscle weakness and exercise intolerance. Motor neuron diseases, such as spinal muscular atrophy, can be associated with motor neuron degeneration and progressive muscle weakness. Multiple organs are often affected, necessitating a multidisciplinary approach to care.

Inherited neurodegenerative disorders comprise a group of rare genetic conditions caused by progressive damage and loss of nerve cells, which may be due to mutations in certain genes. These diseases often manifest later in life even though their underpinnings may begin in the earlier stages of the lifespan. Neurodegenerative multisystem diseases, such as spinocerebellar ataxia and ataxia-telangiectasia, can cause cerebellar ataxia and peripheral neuropathy, affecting gait stability, eye movement and speech.

Muscular dystrophies are a subgroup of genetic neuromuscular diseases associated with progressive skeletal muscle weakness and degeneration that often worsen over time. Some of these diseases can be congenital or appear in early childhood. They can progress to severe muscle weakness and atrophy, necessitating the use of a wheelchair by adolescence. Other organs, such as the heart, lung and gut muscles, can also be involved.

Myopathies are genetic diseases that affect skeletal muscle and are characterized by muscle weakness and joint stiffness. Congenital myopathies, such as nemaline myopathy or central core myopathy, are generally present at birth. Symptoms include muscle weakness and diminished muscle tone, weakness in breathing and swallowing, skeletal abnormalities and impaired speech. Metabolic myopathies are a group of rare disorders that affect glycogen and muscular lipid metabolism resulting in impaired energy production in skeletal muscle. They include primary mitochondrial myopathies and can be associated with muscle weakness or premature muscle fatigue with exercise.