Potassium-aggravated myotonia

Potassium-aggravated myotonia is a rare genetic disorder characterized by muscle stiffness (myotonia) and sometimes mild muscle weakness. This condition is one of a group of genetic disorders known as the non-dystrophic myotonias. The severity and specific symptoms associated with potassium-aggravated myotonia can vary greatly from one person to another, even among members of the same family.

Signs and Symptoms

The primary symptom of potassium-aggravated myotonia is muscle stiffness, particularly in the skeletal muscles. This stiffness is usually triggered by rest after exercise or by consumption of potassium-rich foods. Some affected individuals may also experience mild muscle weakness, particularly in the face and hands.

Causes

Potassium-aggravated myotonia is caused by mutations in the SCN4A gene. This gene provides instructions for making a protein that plays a critical role in muscles used for movement (skeletal muscles). Mutations in the SCN4A gene alter the usual structure and function of these channels, leading to the signs and symptoms of potassium-aggravated myotonia.

Diagnosis

Diagnosis of potassium-aggravated myotonia is based on the presence of characteristic signs and symptoms, a detailed patient history, a thorough clinical evaluation, and a variety of specialized tests. These tests may include electromyography (EMG), which measures the electrical activity of muscles, and genetic testing, which can identify mutations in the SCN4A gene.

Treatment

There is currently no cure for potassium-aggravated myotonia. Treatment is symptomatic and supportive and may include medications to help manage muscle stiffness and weakness. Physical therapy may also be beneficial for some individuals.

See Also

• Myotonia
• SCN4A
• Non-dystrophic myotonias

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