Make the Diagnosis: Smear Savvy

Presentation

Case Findings: A 45-year old male patient with no significant past medical history presents with recurrent fevers, fatigue, arthralgias, and general malaise that have persisted for the past two months. He denies any weight loss, nausea, vomiting, abdominal pain, or headaches. He is a Boy Scout leader who spent the summer chaperoning at a Boy Scout camp.

A physical examination shows fever, scleral icterus, and mild hepatosplenomegaly. Laboratory studies reveal anemia, elevated lactate dehydrogenase, thrombocytopenia, elevated total bilirubin, low haptoglobin, reticulocytosis, elevated liver enzymes, and normal white blood cell counts. Imaging studies are unremarkable. The patient was diagnosed with Babesiosis.

Which features on the peripheral smear below describe the microscopic appearance of this disease?

Learnings

Correct Answer:

A. Babesiosis is an infectious, tick-borne illness caused by Babesia protozoa infection and subsequent lysis of host red blood cells. The most commonly implicated protozoan, B. microti, generally appears as a ring-shaped intra-erythrocytic microorganism with pale blue cytoplasm and one or two red chromatic dots.

The merozoites are often arranged in tetrads, known as the “Maltese Cross” formation. Notably, these microorganisms lack the brownish, hemozoin deposits, schizonts, and gametocyte forms usually seen in malarial infections. Babesial infection also may coexist with Lyme disease or human granulocytic anaplasmosis infection, so patients should be evaluated for these conditions as well, and treated as necessary.

Citation: Gelfand, Jeffery A., and Edouard Vannier. “Clinical Manifestations, Diagnosis, Treatment, and Prevention of Babesiosis.” Clinical Manifestations, Diagnosis, Treatment, and Prevention of Babesiosis. UpToDate, 21 Sept. 2012. Web. 07 Dec. 2012.

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Make the Diagnosis: Smear Savvy