A 35-year-old returning traveler from Northeast India presents with fever, hepatosplenomegaly, and pancytopenia. Peripheral smear shows intraerythrocytic parasites with a characteristic 'Maltese cross' (tetrad) appearance. The MOST likely Plasmodium species responsible is:

• A Plasmodium falciparum
• B Plasmodium knowlesi ✓
• C Plasmodium malariae
• D Plasmodium vivax

Explanation

The 'Maltese cross' or tetrad (Schuffner's dot arrangement of 4 merozoites within a single RBC) is the hallmark of Babesia species, but among Plasmodium species, P. knowlesi — a zoonotic primate malaria transmitted in Southeast and South Asia — can occasionally show similar tetrad forms and importantly has a quotidian (24-hour) fever cycle causing rapid severe disease. The clinical context plus the tetrad appearance points to P. knowlesi. P. falciparum shows multiple ring forms and banana-shaped gametocytes; P. malariae shows band-form trophozoites; P. vivax shows enlarged RBCs with Schüffner's dots.

Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.