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A new locus for recessive distal spinal muscular atrophy at Xq13.1–q21
  1. R I Takata1,
  2. C E Speck Martins1,
  3. M R Passosbueno2,
  4. K T Abe2,
  5. A L Nishimura2,
  6. M Dorvalina Da Silva1,
  7. A Monteiro, Jr1,
  8. M I Lima1,
  9. F Kok3,
  10. M Zatz2
  1. 1Sarah Network of Hospitals for the Locomotor System, Brasília, DF, Brazil
  2. 2Human Genome Research Center, Departamento de Biologia, Instituto de Biociências, Universidade de São Paulo, São Paulo, SP, Brazil
  3. 3Department of Neurology, University of São Paulo School of Medicine, São Paulo, SP, Brazil
  1. Correspondence to:
 Dr M Zatz
 CP 11.461, CEP 05422-970; mayazatzusp.br

http://dx.doi.org/10.1136/jmg.2003.013201

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    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

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    Table 1

    Mapped loci and identified genes for distal spinal muscular atrophy conditions (DSMA)

    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

    Patients

    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.

    Figure 1

    Family pedigree. The individuals who had their DNA analysed are underlined.

    Eletrophysiological studies

    In all affected patients, sensory nerve conduction studies were performed in the median, ulnar, superficial …

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