A review on potassium channel antibody disorders

Voltage gated potassium channels is a group of tetrameric signalling proteins with several functions which includes modulation of neuronal excitability and neurotransmitter release. Potassium channel antibody disorder was first described in acquired neuromyotonia condition which is a syndrome of spontaneous and continuous muscle fibre contraction resulting from hyperexcitability of motor nerves. A syndrome from antibodies to voltage gated potassium channel includes Neuromyotonia, Morvan’s syndrome, limbic encephalopathy. Neuromyotonia is a peripheral nerve hyperexcitability that causes spontaneous muscular activity resulting from repetitive motor unit action potential of peripheral origin with clinical presentations like Muscle cramps, Myotonia, Hyperhydrosis, Myokymia, Fasciculations, Fatigue, Exercise intolerance, Myoclonic jerks. Diagnosis includes needle electromyography, nerve conduction studies, chest CT, TSH, ESR, EEG. Morvan’s syndrome is rarely characterised by peripheral and central system involvement with neuropathic pain, stocking type sensory loss and areflexia. Pathogenesis includes Antibodies against the voltage gated potassium channels which are detectable in neuromyotonia have been implicated in Morvan’s syndrome. Raised serum level of antibodies to voltage gated potassium channels binding of these raised antibodies to the voltage gated potassium channel causes central nervous system dysfunction which may also leads to the nerve hyperexcitability. Diagnosis includes needle electromyography, nerve conduction studies, chest CT, TSH, ESR, EEG, increased levels of antibodies against LGI-1,CASPR2, or both, detection of m-RNA. Limbic encephalopathy is most commonly seen in children characteristic feature found as cognitive impairment and seizures in anti-LGI-1positive patients, and peripheral motor hyperexcitability in anti- CASPR2 positive patients. Diagnosis includes neurpathological or neuroradiolgical examination.