Presymptomatic diagnosis: metachromatic leukodystrophy or pseudo arylsulphatase A deficiency?

Diagnosis of metachromatic leukodystrophy (MLD) was established in the proband at age 27 months. An examination of the family arylsulphatase A profile revealed that the father and younger sibling, age 2 months, had very low enzyme activities like the proband. The father, in all likelihood, had the pseudo arylsulphatase A deficiency trait, but the sibling could be either pseudodeficient or affected with MLD. The fibroblast cerebroside sulphate loading test confirmed that the father had pseudo arylsulphatase A deficiency. The test also indicated that the sibling was affected with MLD. This was confirmed by clinical evidence of neurological degeneration by 18 months.