Sanfilippo B of bomozygous and in tbree families disease: Serum assays for detection beteroz ygous individuals

Three assays [or the determination o[ N-acetyl-a-D-glucosaminidase activity in the serum are described. In three [amilies with patients suffering [rom SanfiIippo B disease, the affected individuals had a residual enzyme activity in the range o[ 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 o[ these [amilies had enzyme activities lowered to the same extent and were there[ore considered to be heterozygous carriers o[ the Sanfilippo B gene.