G6PD and G6PD deficiency: Although there are now more than 200 different G6PD deficiency genotypes described, usually resulting in an unstable enzyme, there is substantial phenotypic variability within genotypes, so severe haemolysis can still occur with so called “mild variants.” Amongst the more common G6PD variants globally, the African A-genotype is at the mild end of the spectrum, and the Mediterranean variant is at the severe end.