engleski

Juvenile myasthenia gravis associated with autoimmune channelopathy and mixed connective

Ion channels are crucial elements in neuronal signaling and synaptic transmission. Autoantibodies against voltage-gated ion channels couse disorder in peripheral neuromuscular transmission. Autoantibodies against voltage-gated potassium channels (VGKC-Abs) are associated with acquired neuromyotonia (NMT) and related disorders such as Morvan's syndrome and limbic encephalitis. The symptoms of myasthenia gravis (MG) reflect the disfunction of neuromuscular transmission. We present a girl at age of 15 years with ptosis, proxymal muscle weakness, neuromyotonia hyperhidrosis, short memory loss and confusion. Anti-AChR antibodie were found. Electromyography showed neuromyotonic discharges. Cerebrospinal fluid analysis revealed oligoclonal bands. The plasma VGKC-Abs titer was elevated (176 pM, controls 100 pM), positive antiganglioside abs (GM1, asialo GM1, GM2, GD1a, b) and SS-A 211 U/ml, SS-B 157, U1-RNP 188 U/m, DNA-topo 128 U/ml (control>120). Brain MRI was normal. The girl was treated with pyridostigmine, steroids, intravenous immunoglobulins and azantioprine and repetitive plasma exchanges. Neurological impairment and myasthenic crisis occured in periods of 5-21 days. The neuromyotonia and some of the dysautonomic features are likely to be directly related to the VGKC abs on peripheral nervous system. The central nervous sistem symptoms are very likely due to the direct effects of VGKC abs, although there can be some other autoantibodies. A severe clinical course might be related to myasthenia gravis associated with autoimmune disease of central and peripheral nervous system overlapping probably with mixed connective tissue disease.

Keywords: myasthenia gravis; neuromyotonia; Morvan's syndrome; autoimmune channelopathy; voltage-gated potassium channel autoantibodies

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