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- distal spinal muscular atrophy
- distal hereditary motor neuronopathy
- spinal type of Charcot-Marie-Tooth
- new X linked distal spinal muscular atrophy
- linkage analysis
- CMT, Charcot-Marie-Tooth
- DHMN, distal hereditary motor neuronopathy
- DSMA, distal spinal muscular atrophy
Distal spinal muscular atrophy (DSMA, OMIM #182960),1 also known as distal hereditary motor neuronopathy (DHMN),2 Charcot-Marie-Tooth (CMT) spinal type,3 and neuronal motor neuropathy of peroneal muscular atrophy4,5 include a heterogeneous group of disorders. The primary defect responsible for these conditions lies in the lower motor neurone, with distal involvement of only lower or both lower and upper limbs.
DSMA is genetically heterogeneous. Four autosomal dominant and three autosomal recessive forms of the disease have already been mapped, including the Jerash type DHMN and congenital DSMA (table 1). However, the responsible genes were identified for only two of them: the glycil tRNA synthetase gene for DSMA type 56 and the immunoglobolin μ-binding protein 2 gene (IGHMBP2) for DSMA type 6.7
Although pedigrees with isolated male patients have been described,3 no confirmed X linked form has been reported to date. We examined a white Brazilian genealogy with 17 male patients who present a distal form of muscular atrophy affecting upper and lower limbs. The pedigree is consistent with recessive X linked inheritance. We present results of neurological and diagnostic tests in nine affected patients, which are consistent with the diagnosis of DSMA, in accordance with the criteria established in the Second European Neuromuscular Consortium.8 Genetic linkage analysis allowed mapping of the disease locus to Xq13–Xq21.
PATIENTS AND METHODS
The pedigree is depicted in fig 1. Nine affected males were examined. Diagnosis of DSMA was based on neurological examination and supported by electrophysiological and histopathological studies, according to the aforementioned guidelines.8 All studies were performed following informed consent.
In all affected patients, sensory nerve conduction studies were performed in the median, ulnar, superficial …