Certain red cell genetic factors and prevalence of chloroquine-induced pruritus.

The hypothesis that chloroquine-induced pruritus (CIP) may be determined by certain genetic factors was tested by investigating the epidemiology of CIP with respect to certain genetic red cell markers namely, haemoglobin genotype, glucose-6-phosphate dehydrogenase (G6PD) deficiency and the ABO blood groups. Three hundred consecutive patients treated for malaria with chloroquine at the University College Hospital, Ibadan, Nigeria were recruited into the study. They were observed over 3 days for presence of CIP. ABO blood groups, G6PD and Hb genotypes were determined appropriately for each patient. One hundred and twenty four (41.3%) of the patients responded positively to CIP. There was a reduced frequency of the sickle cell trait (HbAS) among itchers relative to non-itchers. This suggests that the trait may be protective against CIP. G6PD deficiency was also found to be relatively more common among itchers than non-itchers. This indicates that G6PD deficiency may increase susceptibility to CIP. There was however no difference in the distribution of itchers among the different ABO blood groups. It was concluded that CIP may be associated with certain genetic red cell markers particularly Hb and G6PD types which are known malaria markers but not ABO blood groups.