Sanfilippo B disease: Serum assays for detection of homozygous and heterozygous individuals in three families

Three assays for the determination of N-acetyl-α- -D-glucosaminidase activity in the serum are described. In three families with patients suffering from Sanfilippo B disease, the affected individuals had a residual enzyme activity in the range of 2 to 16 per cent that of normal control subjects. Their obligate heterozygous parents had an activity diminished to 26 to 35 per cent. Nine other members of these families had enzyme activities lowered to the same extent and were therefore considered to be heterozygous carriers of the Sanfilippo B gene.