Inheritance of the enzyme deficiency in three neurolipidoses: variant 0 of Tay-Sachs disease (Sandhoff's disease), classic tay-sachs disease, and metachromatic leukodystrophy. Identification of the heterozygous carriers

The recessive inheritance of the enzyme deficiencies (total hexosaminidase, hexosaminidase A, arylsulfatase A) in nine families with neurolipidoses (variant 0 of Tay-Sachs disease=“Sandhoffs disease”, classic Tay-Sachs disease, metachromatic leukodystrophy) has been studied. 62 family members were identified as: genotypically normals, phenotypically normal heterozygous carriers, or patients, according to the enzyme levels (normal, about half normal or low) in the leukocytes. The activities of the lysosomal enzymes involved in the diseases are related to the mean relative activity of three or four lysosomal reference enzymes thereby identifying the heterozygous carrier state by the enzyme level about half the normal enzyme. It cannot be completely excluded that the heterozygous state or total enzyme deficiency occur more frequently than would be expected according to Mendel's laws. This problem is discussed.