Table 1.

Hexosaminidase A (HexA) activity both pre- and post-HSCT

	Diagnosis (age 14 years)	HSCT + 6 years	HSCT + 8 years	Reference range	Comments
Hexosaminidase A Plasma nmol/mg/h	5	14	15	50–250	Post-HSCT – Reduced to ~30% of lower limit of normal
Hexosaminidase A Leucocytes nmol/mg/h	Not measured	191	187	N/A normal controls 187 + 362	Post-HSCT – Activity comparable to normal controls
Graft status (QF-PCR)	N/A	100% donor?	100% donor	N/A	Full engraftment
Plasma GA2, Lc3, GM2 Plasma GA2	145, 24, 253	N/A	45, 16, 180	22–59, 6–12, 35–90	Decreased by 69, 33 and 29%, respectively Returned to normal levels

The deficiency of HexA measured in plasma pre-HSCT is consistent with a biochemical diagnosis of Tay-Sachs disease (TSD). HexA activity in leucocytes post-HSCT is comparable to normal controls, consistent with DNA analysis showing successful engraftment. The circulating HexA activity in plasma has not normalised. This is likely to reflect the contribution of HexA activity originating from the liver in normal individuals. GM2 GalNAc beta 1-4 [NeuAc alpha 2-3] Gal beta 1-4 Glc-ceramide, GA2 GalNAc beta1-4 Gal beta 1-4 Glc-ceramide, Lc3 GlcNAc beta1-3 Gal beta 1-4 Glc-ceramide. Plasma GA2, Lc3 and GM2 have been reduced by 69, 33 and 29%, respectively. GA2 has returned to normal levels