Glucose-6-phosphate dehydrogenase (G6PD) deficiency is the most common red cell enzymopathy among humans. In India, G6PD Mediterranean, G6PD Orissa, and G6PD Kerala–Kalyan are the three common mutations which account almost 90% of G6PD deficiency. Here we describe G6PD Coimbra, an unreported variant from India, and a novel 593 G → A mutation in exon 6 with an amino acid change of Arg 198 His, among the tribal groups of the Nilgiris in Southern India. Further, this novel mutation was structurally characterized and it was found that the mutation is located at the end of the coenzyme domain, which may cause enzyme instability. [ABSTRACT FROM AUTHOR]