RÉSUMÉ
We report here a familial observation of metachromatic leukodystrophy (MLD) in 2 sisters. The very beginning, with only psychiatric manifestations at adolescence, could be precisely established. The evolution towards a dementia, and the evidence of a pyramidal syndrome oriented later towards a clearly organic disease. A very wide bilateral and symmetrical demyelination was shown by Magnetic Resonance imaging. The deficiency in arylsulfatase A activity oriented towards MLD which was confirmed by metachromatic deposits in the nerve biopsy. Molecular biology evidenced in the two, compound heterozygoty with both the classical mutation of the infantile form with loss of a splicing site at the level of intron 2, and the ileu > Ser 179 mutation frequent in adult forms.