We report the case of a 12-year-old child who was admitted to our Department, with 7 days’ history of high fever and splenomegaly. His father had similar symptoms starting on the same day. A rapid test and microscopy for malaria yielded a positive result for Plasmodium vivax. Antimalarial therapy was initiated. He developed methemoglobinemia treated with ascorbic acid and had uneventful recovery.