Two point mutations are responsible for G6PD polymorphism in Sardinia.

The human X-linked gene encoding glucose 6-phosphate dehydrogenase (G6PD) is highly polymorphic; more than 300 G6PD variants have been identified.
G6PD deficiency in different geographical areas appears to have arisen through independent mutational events, but within the same population it may also be heterogeneous.
One example is the island of Sardinia, where careful clinical and biochemical studies have identified four different G6PD variants.
We cloned and sequenced the four G6PD variants from Sardinia and found that only two mutations are responsible for G6PD deficiency in this area  one mutation is the cause of the G6PD Seattle-like phenotype, a milder form of G6PD deficiency; the other mutation is responsible for all forms of very severe G6PD deficiency in Sardinia and, possibly, in the Mediterranean.. 
