An unusual form of galactosemia is described in a 7‐month‐old boy, characterized by a late onset of the clinical symptoms. A high apparent residual activity of erythrocyte galactose‐1‐phosphate uridyl transferase (GT) was measured with the spectrophotometric UDP‐Glucose consumption test (±25% of normal). The residual activity in erythrocyte lysates, determined when the patient was 7, 16 and 22 months old, significantly decreased upon storage and after preincubation with NAD‐ase. The radiochemical measurement of GT activity demonstrated a severe deficiency: only a level of ± 1% of normal activity was observed, and no effects of storage or NAD‐ase could be demonstrated.
GT and galactokinase (GK) activities were measured radiochemically in lysates from hair roots obtained from the human scalp, and it was found that the GT/GK activity ratio is a useful index for the detection of heterozygotes. Erythrocyte and hair root lysates from the heterozygous parents of the patient displayed GT/GK ratios which were intermediate between mutant and normal. Because they offer a simple and fast way to obtain biopsy material, hair roots might become of increasing importance for carrier detection studies.