A 50-year-old Portuguese man presented initially with myalgia, headache, and fever (39ºC) at the end of May 2023, approximately one week after returning from a tour across Africa. A peripheral blood smear identified multiple ring-form inclusions in erythrocytes, compatible with Plasmodium falciparum infection (parasitemia 5%) (Fig. 1-A). The patient was admitted to the Infectious Diseases ward due to severe malaria. He was treated with artemether-lumefantrine (AL) 480/80 mg twice a day for 4 days, an antimalarial combination therapy effective in malaria due to any species [1], and was discharged asymptomatic and with undetectable parasitemia.
Fig. 1.
Peripheral blood smear (May Grunwald-Giemsa stain, 1000x); A, multiple thin ring form inclusions (trophozoites) in erythrocytes, suggestive of P. falciparum infection (arrow); B, ring form inclusion in smaller erythrocytes resembling a “basket-form” (top arrow) and schizont with 8 merozoites and brown pigment near the top of the erythrocyte (bottom arrow), suggestive of P. malariae infection
One month after discharge, with no recent travel to an endemic area nor possibility of re-exposure, the patient returned to the Hospital following fever peaks every 72 h for 9 days. A new peripheral blood smear was performed, where trophozoites and schizonts in erythrocytes compatible with P. malariae infection could now be observed (Fig. 1-B).
Following this, the initial diagnosis was challenged. Similar to previously reported cases [2], a Plasmodium co-infection with P. malariae in its pre-erythrocytic stage was the likeliest explanation as to why it remained undetectable during the initial episode—in addition, AL does not treat this stage of Plasmodium [2]. The new diagnosis was confirmed through PCR testing.
Author Contributions
MAQF collected clinical data. DN and FL collected the laboratory data. DN, FL and MAQF wrote the initial draft. CR, CVC and JMC critically reviewed and finished writing the paper. All authors contributed equally to research and analysis of the case.
Declarations
Competing Interests
The authors have no competing interests. No conflicts of interest declared.
Footnotes
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References
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