What is Isaacs syndrome?
Isaacs syndrome (also known as myokymia with impaired muscle relaxation, neuromyotonia, pseudomyotonia, quantal squander, armadillo disease, and continuous muscle fiber activity) is a disorder characterized by muscle cramps, twitches, myokymia, weight loss, and hyperhidrosis.
If central nervous system dysfunction such as encephalitis is also present, then it is called Morvan’s fibrillary chorea .
Either myokymia or neuromyotonia can be observed on EMG. Antibodies against the voltage-gated potassium channel or neuronal ganglionic acetylcholine receptor are found in some patients.
Symptomatic treatment has been achieved with phenytoin (300 to 400 mg/day) or carbamazepine (200 mg, three or four times/day).
Some patients may respond favorably to plasma exchange or intravenous immunoglobulin. Isaacs’ syndrome can be associated with thymoma, small cell lung cancer, and Hodgkin’s lymphoma, or other autoimmune disorders.
