This group included the individual with the largest within-person percentage change in Hb concentration (−23%; this person had the A variant of G6PD deficiency); this man had a Hb concentration of 147 g/L at baseline and 113 g/L 9 days following PQ administration, was positive for P. falciparum malaria at baseline by PCR, was positive by blood smear on days 1 and 3–7, and received a symptomatic malaria diagnosis on days 6–9 following treatment with PQ. Here, GSTM1 is linked to G6PD deficiency.