A Case of Distal Hereditary Motor Neuropathy with HSPB1 Mutation in Coexistence with Myotonia and Myopathy

Distal hereditary motor neuropathies (dHMNs), also named as distal spinal muscular atrophy, are a group of disorders that cause degeneration of motor nerves. Currently, only 15% to 32.5% of patients with dHMN have been genetically identified. The most common cause of dHMNs gene mutations is HSPB1 mutation. In HSPB1 mutation, which is also one of the myopathogens via satellite cell pathology, dHMNS may coexist with neuromuscular junction disorder, motor neuron disease, satellite cell dysfunction and therefore myopathic findings. No case of myopathy and myotonia with HSPB1 mutation has been reported in the literature yet. We present a case with electrophysiologic findings in HSPB1 mutation by discussing the possible mechanisms underlying myotonic discharges and myopathic findings.