Authors describe clinical, pathological, imaging and genetic findings in the first Irish family with Laing distal myopathy in whom a novel mutation in the human slow β-myosin heavy chain (MYH7) gene has been identified. A kindred of 14 over 6 generations included 6 individuals with childhood onset distal lower limb weakness in a scapula-peroneal distribution with subsequent proximal upper and lower limb weakness. Finger extensor weakness especially in the 3rd-5th fingers was present in each and two patients had "hanging big toe" sign. Three patients were non-ambulatory by middle-age. One patient developed cardiomyopathy and two patients had respiratory muscle impairment. Intriguingly, brain white matter lesions and epilepsy were present in three patients. Muscle biopsy revealed fibre-size variation, rimmed vacuoles, mild-extensive central nucleation, redundant and folded sarcolemmal membrane and Z band streaming. Genetic analysis revealed a novel heterozygous mutation in the MYH7 gene in one patient which co-segregated perfectly in the remaining 5 affected members and was absent in six unaffected members.
Keywords: Brain white matter disease; Epilepsy; Laing distal myopathy; MYH7.
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