An unusual homozygous arylsulfatase: a pseudodeficiency in a metachromatic leukodystrophy Tunisian patient.

Metachromatic leukodystrophy is an autosomal recessive neurodegenerative lysosomal disease characterized by a deficiency of the lysosomal enzyme arylsulfatase A and the subsequent accumulation of sulfatide in neuronal and visceral tissues. Clinical diagnosis is usually confirmed by in vitro analysis of arylsulfatase A activity but may be complicated in cases of arylsulfatase A pseudodeficiency and sphingolipid activators protein deficiency. We report the case of a 3-year-old boy who presented a severe form of late infantile metachromatic leukodystrophy. This patient was found to be homozygous for the arylsulfatase A pseudodeficiency. This condition is rare and can lead to a severe disease. Prenatal diagnosis was performed in this family, and the fetus was healthy.