Issacs' syndrome in pediatric patient and voltage-gated potassium channels antibodies

Isaacs’ syndrome (IS), also known as acquired neuromyotonia, is a rare neuromuscular disease, manifested by involuntary continuous motor activity.1 Although there are reports in children,2,3 IS is more frequent in adults.1 The clinical presentation can include muscle cramps, fasciculations, myokymia, and pseudomyotonia. Electromyography (EMG) remains the gold standard for diagnosis.1,4 Dysfunction of peripheral nerve voltage-gated potassium channels (VGKC) appears to be related to the development of the disease.1,3,4,5 Paraneoplastic factors also play an important role in IS.5 Anticonvulsants are the first therapeutic option.1,4,5

Disorders of Increased Muscle Stiffness or Overactivity

Increased muscle stiffness or overactivity (which differs from parkinsonian rigidity or dystonia) can be caused by a variety of disorders of central or peripheral nervous system origin and genetic, autoimmune, or infectious etiology. Increased muscle stiffness may be the cause of some joint movements, particularly when such stiffness is associated with stimulus sensitivity that causes involuntary movements. The conditions discussed in this chapter include stiff person syndrome, progressive encephalomyelitis with rigidity and myoclonus (PERM), acquired neuromyotonia (Isaacs syndrome), hereditary neuromyotonia, tetanus (which has an infectious etiology), Satoyoshi disease, neuromyotonia, and rippling muscle disease. Many of these cases are caused by decreased synaptic inhibition through an autoimmune mechanism.