Distal spinal muscular atrophy with vocal cord paralysis (dSMA-VII) is not linked to the MPD2 locus on chromosome 5q31.

Distal spinal muscular atrophy with vocal cord paralysis (dSMA-VII) is not linked to the MPD2 locus on chromosome 5q31 EDITOR—Hereditary distal limb weakness and atrophy is a heterogeneous condition that may be neurogenic or myopathic in origin. Hereditary motor and sensory neuropathy (HMSN) I and II (also known as Charcot-Marie-Tooth (CMT) 1 and 2), distal spinal muscular atrophy (dSMA), and the distal myopathies may all present with this clinical picture. Traditionally, these disorders were diVerentiated according to electrophysiological and histopathological characteristics, with subtypes of each group identified on the basis of inheritance pattern, age of onset, and associated clinical features. The localisation of several genes that confer susceptibility to these disorders has necessitated the re-evaluation of current classification systems, as conditions that were clinically classified as distinct are now known to be allelic at the genetic level. Vocal cord weakness/paralysis is occasionally associated with distal muscular atrophy. This association was first described by Young and Harper 1 in a Welsh family in which the disorder segregated in an autosomal dominant fashion. The presentation was one of progressive distal muscle wasting and weakness together with a dysphonic or hoarse voice. Motor and sensory nerve conduction was normal with the exception of one patient who showed mild motor slowing. Spontaneous fibrillation was detected on EMG. Unilateral or bilateral vocal cord palsy was present in all aVected subjects. The findings were consistent with anterior horn cell disease and the condition was assumed to be a form of dSMA associated with vocal cord paralysis. In a subsequent classification of the proximal and distal spinal muscular atrophies the disorder was designated dSMA type VII. 2 Recently, a family with vocal cord and pharyngeal weakness associated with a distal myopathy was reported. 3 This family has many clinical similarities with the pedigree presented by Young and Harper. 1 Both families exhibit auto-somal dominant inheritance; in both families distal wasting and weakness is observed, with particularly severe involvement of the abductor pollicis brevis; laryngeal involvement was present in the majority of subjects from both pedigrees and was the presenting symptom in some cases. In contrast to the Young-Harper family, the family presented by Feit et al 3 showed both neurogenic and myopathic muscle potentials on EMG. Following evaluation of electrophysiology and histopathology data, the disorder was judged to be myopathic in origin and distinct from previously described distal myopathies. The condition was designated vocal cord and pharyngeal …