A new glucose 6-phosphate dehydrogenase variant (G-6-PD Verona) in a patient with myelodysplastic syndrome.

A 67-year-old woman investigated because of 'myelodysplastic syndrome' was found to have a 4-fold increase in G-6-PD activity in her erythrocytes. The enzyme was partially purified and characterized. On grounds of: (a) reduced electrophoretic mobility, (b) abnormal cathodic band(s) in isoelectrofocusing, (c) increased Michaelis constant for glucose 6-phosphate, (d) abnormal thermostability, and (e) abnormal interaction with the ligand NADPH, we conclude that this is a new structural variant which we designate G-6-PD Verona. G-6-PD Verona was the sole apparent source of G-6-PD activity in the patient's erythrocytes; by contrast, the patient's fibroblasts had only normal G-6-PH (type B). The patient's haematological course terminated into acute myeloid leukaemia. We believe G-6-PD Verona was the result of a somatic mutation in an X-chromosome which took place in a haemopoietic cell clone which subsequently underwent neoplastic transformation.