Different entities of proximal spinal muscular atrophy within one family |
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Authors: | B Wirth D Tessarolo E Hahnen S Rudnik-Schöneborn H Raschke M Liguori M Giacanelli K Zerres |
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Institution: | (1) Institute of Human Genetics, Wilhelmstrasse 31, D-53111 Bonn, Germany Tel.: +49-228-2872344; Fax: +49-228-2872380; e-mail: bwirth@uni-bonn.de, DE;(2) S. Camilio Hospital, Department of Neuroscience, Service of Neuromuscular Diseases, I-00149 Rome, Italy, IT |
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Abstract: | The molecular analysis of the survival motor neuron (SMN) gene and several closely flanking polymorphic markers in an atypical
pedigree with four patients suffering from spinal muscular atrophy (SMA) over two generations has raised new aspects concerning
the etiology and the molecular spectrum of autosomal recessive SMA. Three patients in two generations show homozygous deletions
of exons 7 and 8 of the telomeric copy of SMN (telSMN), thus confirming the presence of autosomal recessive SMA, with localisation
on chromosome 5q12. The fourth SMA patient with mild neurogenic atrophy (confirmed by muscle biopsy and electromyography)
shows no homozygous deletion of telSMN but carries a heterozygous deletion of telSMN, as can be deduced from her two affected
homozygously deleted children. No intragenic mutation has been identified in the remaining telSMN. In addition, she shares
only one SMA chromosome with her affected brother, is haploidentical with two healthy brothers, and has a 31-year-old healthy
son, who has inherited an SMN-deleted paternal chromosome and the SMN non-deleted maternal chromosome. These results suggest
that this patient either has a neurogenic atrophy of a different origin or exhibits an unusual heterozygous manifestation
of SMA 5q12. Interestingly, the two haploidentical telSMN-deleted affected sibs in the second generation show a strikingly
discordant clinical picture indicating that, in addition to telSMN mutations, other factors influence the phenotype of SMA
in the reported pedigree.
Received: 20 March 1997 / Accepted: 4 June 1997 |
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