A 4-year-old recently returned from an endemic area develops pallor, high intermittent fever with rigors every 48 hours, and splenomegaly. Peripheral smear shows ring trophozoites with Maurer's clefts and multiple ring forms per RBC. Which plasmodium species is responsible?
- A Plasmodium vivax
- B Plasmodium malariae
- C Plasmodium falciparum ✓
- D Plasmodium ovale
Explanation
Plasmodium falciparum is the most virulent species and is identified on blood smear by: (1) ring trophozoites only (no mature trophozoites or schizonts in peripheral blood); (2) Maurer's clefts (irregular reddish dots in the RBC cytoplasm); (3) multiple ring forms per RBC; (4) appliqué/accolé forms (rings on the RBC rim); and (5) smaller delicate ring forms. The 48-hour erythrocytic cycle causes tertian periodicity but the fever pattern is often irregular. P. vivax also causes 48-hour tertian fever but shows Schüffner's dots (not Maurer's clefts), enlarged RBCs, and mature stages visible. P. malariae has 72-hour quartan fever with Ziemann's dots.
Reference: Ghai Essential Pediatrics, 10th ed.
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