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Recently characterized as an immune-mediated channelopaty, Isaacs' syndrome (also known as acquired neuromyotonia) was first described in 1961 in two men with persistent, generalized muscle stiffness, in addition to spontaneous, rapid discharges of motor-unit potentials on electromyography. In the peripheral nervous system, antibodies targeted to voltage-gated potassium channels induce hyperexcitability of motor axons, resulting in signs of muscle stiffness or of pseudomyotonia. A spontaneous burst of single motor-unit activity, and myokymic and neuromyotonic discharges, are the most characteristic features found in electromyography studies. This report describes Isaacs' syndrome in a child, in whom the diagnosis was made by clinical features of acquired, spontaneous muscle overactivity and typical electromyographic findings.

Bilateral segmental neurofibromatosis is a rare condition characterized by the occurrence of neurofibromas and/or café-au-lait spots limited to an area or segment of the body bilaterally. It is caused by a postzygotic mutation in the neurofibromatosis type I gene, resulting in a phenotype of genetic mosaicism. This report describes a case of bilateral segmental neurofibromatosis with multiple nodules sitting on a café-au-lait spot.