Prenatal diagnosis of Tay-Sachs disease in cell-free amniotic fluid

The diagnosis of 6 known Tay-Sachs cases was confirmed by isoelectric focusing of the cell-free amniotic fluid. The presence of an additional--hitherto unknown--heatstable, acid hexosaminidase X in normal and pathological amniotic fluids must be taken into account especially when the heat denaturation method of detecting Tay-Sachs disease is applied. Hexosaminidase X shows some properties similar to those of hexosaminidase B.