Neuromytonia (NMT) (also known as Isaac's syndrome, Isaac-Mertens syndrome, continuous muscle fiber activity syndrome, and quantal squander syndrome) is a condition affecting adults which causes spontaneous muscle contractions and cramps due to peripheral nerve hyperexcitability.
It can affect any muscle group, but is usually found in the legs, trunk, face and neck.
About 40% of patients have detectable levels of antibodies to their own voltage-gated potassium-channel (VGKC) proteins - crucial compounds for nerve impulse transmission. The antibodies are generated by the patient's own immune system, so NMT is currently thought-of as an auto-immune condition.
The exact causes are presently unclear, though it's known that in some cases it can be inherited. It's a rare disease, but the prevalence of the disease in society is also currently unknown.
Further info.:Neuromytonia, Clinical Neurophysiology, Volume 117, Issue 10,