Isaacs Syndrome

**Definition:** A rare neuromuscular disorder with onset usually in late childhood or early adulthood, characterized by intermittent or continuous widespread involuntary muscle contractions; FASCICULATION; hyporeflexia; MUSCLE CRAMP; MUSCLE WEAKNESS; HYPERHIDROSIS; TACHYCARDIA; and MYOKYMIA. Involvement of pharyngeal or laryngeal muscles may interfere with speech and breathing. The continuous motor activity persists during sleep and general anesthesia (distinguishing this condition from STIFF-PERSON SYNDROME). Familial and acquired (primarily autoimmune) forms have been reported. (From Ann NY Acad Sci 1998 May 13;841:482-496; Adams et al., Principles of Neurology, 6th ed, p1491)

**Tree numbers:** - C05.651.392 - C10.668.829.425

**Synonyms:** - Myokymia, Myotonia, Muscle Wasting, And Hyperhidrosis - Continuous Muscle Activity Syndrome - Gamstorp-Wohlfart Syndrome - Isaacs' Syndrome - Isaacs-Mertens Syndrome - Myokymia, Continuous - Neuromyotonia - Pseudomyotonia Syndrome of Isaacs - Quantal Squander - Syndrome of Continuous Muscle Activity