Plasmodium vivax exhibits dormant
liver-stage
parasites, called hypnozoites, which can cause
relapse of
malaria. The only
drug currently used for eliminating hypnozoites is
primaquine. The
antimalarial properties of
primaquine are dependent on the
production of oxidized metabolites by the
cytochrome P450 isoenzyme 2D6 (
CYP2D6). Reduced
primaquine metabolism may be related to P. vivax
relapses. We describe a case of 4 episodes of
recurrence of
vivax malaria in a
patient with decreased
CYP2D6 function. The
patient was 52-year-old
male with
body weight of 52 kg. He received total
gastrectomy and
splenectomy 7 months before the first episode and was under
chemotherapy for the
gastric cancer. The first episode occurred in March 2019 and each episode had intervals of 34, 41, and 97 days, respectively. At the first and second episodes,
primaquine was administered as 15 mg for 14 days. The
primaquine dose was increased with 30 mg for 14 days at the third and fourth episodes. Seven
gene sequences of P. vivax were analyzed and revealed totally identical for all the 4 samples. The
CYP2D6 genotype was analyzed and intermediate metabolizer
phenotype with decreased function was identified.