Potassium-aggravated myotonia

Also known as: PAM, sodium channel myotonia


Genetics Home Reference

Potassium-aggravated myotonia is a disorder that affects muscles used for movement (skeletal muscles). Beginning in childhood or adolescence, people with this condition experience bouts of sustained muscle tensing (myotonia) that prevent muscles from relaxing normally. Myotonia causes muscle stiffness that worsens after exercise and may be aggravated by eating potassium-rich foods such as bananas and potatoes. Stiffness occurs in skeletal muscles throughout the body. Potassium-aggravated myotonia ranges in severity from mild episodes of muscle stiffness to severe, disabling disease with frequent attacks. Unlike some other forms of myotonia, potassium-aggravated myotonia is not associated with episodes of muscle weakness.

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Potassium-aggravated myotonia (PAM) is a muscular channelopathy presenting with a pure myotonia dramatically aggravated by potassium ingestion, with variable cold sensitivity and no episodic weakness. This group includes three forms: myotonia fluctuans, myotonia permanens, and acetazolamide-responsive myotonia (see these terms).

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Medical Term Other Names Description
Myotonia Delayed relaxation of muscle fibers after contraction An involuntary and painless delay in the relaxation of skeletal muscle following contraction or electrical stimulation.
Muscle stiffness A condition in which muscles cannot be moved quickly without accompanying pain or spasm.

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