Clinical Pathology: General Principles, Hematology & Coagulation

398) A 54-year-old man with ulcerative colitis was recently being tapered off steroids. While traveling to New Haven, Conn., to drop his son off at college, he developed worsening of his abdominal pain and diarrhea. When he returned home, his physician increased his dose of prednisone to 40 mg per day. Five days later, the patient developed severe fatigue, dizziness, and shortness of breath. A complete blood cell count (CBC) sample was sent to the laboratory. The peripheral blood film is shown in the figure. Which one of the following is the most likely cause of his symptoms?

Babesia microti is a parasite transmitted to humans through bites of the Ixodes species of ticks. These ticks are the same vector for Lyme disease and ehrlichiosis. The intermediate hosts are deer and rodents.

Babesia sporozoites are transferred while the tick is feeding. They invade erythrocytes and multiply. Babesia can also be transfusion-transmitted from a blood donor with a subclinical infection.

• Clinical symptoms can be mild and unnoticed, or they can be more severe, with fever, chills, and severe hemolytic anemia. Very young, elderly, and immunocompromised patients are more susceptible to severe infection.

• Peripheral blood smear shows intraerythrocytic rings forms. These forms can be mistaken for malaria. The appearance of Maltese crosses is essentially diagnostic for Babesia.

• Often, the clinical history is helpful in distinguishing malaria from Babesia. Malaria will be found in patients traveling to endemic malarial regions (e.g., sub-Saharan Africa, Asia), whereas patients with Babesia will more likely have a travel history to Long Island, New York, or Connecticut.

• The hemolytic anemia can be treated with antibiotics. If the parasitemia is very high and the patient has severe disease, red cell exchange can be performed.

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