We describe a patient with a familial form of amyotrophic lateral sclerosis (ALS) in which a heterozygous G>A exchange at position 1087 in the SOD1 gene was detected. This mutation results in an amino acid substitution of aspartate for glycine at position 93 (G93D). The patient had a five-year history of fasciculations in all four limbs, with no clear evidence of muscular atrophy or weakness at last follow-up. However, electrophysiological examination revealed lower and upper motor neuron involvement. His mother and a cousin had died of ALS after prolonged disease. This report shows that G93D may cause a form of ALS with slow progression, long-lasting paucisymptomatic phase and both lower and upper motor neuron involvement.