Paramyotonia Congenita

Paramyotonia congenita is an inherited disorder that affects skeletal muscles (muscles used for movement). Beginning in infancy or childhood, affected individuals experience frequent episodes of myotonia (muscle tensing that fail to relax normally after contracting), especially after exercise or exposure to cold.

Features

• Myotonia (muscle stiffness) mainly affects muscles in the face, neck, arms and hands. It can also affect muscles in the legs and muscles used for breathing.
• Myotonia tends to worsen with repeated movement or exercise
• Exposure to cold causes myotonia, and prolonged cold exposure also leads to episodes of muscle weakness.
• A few patients may experience periodic paralysis and sudden “floppy” weakness of limbs that can last minutes or hours. These episodes can be brought on by certain foods or drinks rich in potassium, resting after exercise, missing meals or an infection.
• Older affected individuals may develop permanent muscle weakness that affect the motor ability.

Cause

Here the defect is in so-called sodium ion channels in the muscle membrane. The condition is inherited as an autosomal dominant trait.