[Diagnostic trap and difficulties of genetic counseling in a family with neuromuscular disease carriers].

BACKGROUND

Recent advances in the field of molecular genetics have provided useful tools for the diagnosis of neuromuscular disorders. Genetic counselling for many of these conditions may, however, be fraught with difficulties.

CASE REPORT: The patient, two paternal uncles and a paternal aunt presented with clinical and electromyographic evidence of type III spinal muscular atrophy despite an autosomal dominant-like pedigree. The diagnosis was confirmed by genetic testing for the SMN deletion. As the proband's mother was pregnant at the time of presentation of the affected child, a prenatal diagnostic test was performed. The deletion was not found in the DNA extracted from the trophoblast and the pregnancy proceeded to full term, and a normal child. At the same time, a first cousin of the proband was found to have a clinically similar condition. He had not the SMN deletion. He presented with electrophysiological and pathological features of limb-girdle muscular dystrophy. Genetic testing revealed a homozygote del T521 mutation of the gama-sarcoglycan gene.

CONCLUSION

To provide accurate genetic counselling, it is essential to get precise data on family background and diagnostic confirmation for each affected relative to avoid missing the possibility, albeit rare, of several neuromuscular disorders within a family.