Babesiosis masquerading as recurrent immune thrombocytopenic purpura in a splenectomized patient

Abstract

Dear Editor, Splenectomy is a clinically effective therapeutic intervention against chronic immune thrombocytopenic purpura (ITP) [1]. Severe, potentially life-threatening infections are a major long-term complication of splenectomy [2]. Certain infections may present with thrombocytopenia, which, in the case of splenectomized patients with a history of ITP, may be mistaken for ITP recurrence. We report what is, to the best of our knowledge, the first case of babesiosis in a patient with stable chronic ITP who had previously undergone splenectomy. The patient was a 66-year-old woman from Nantucket Island, MA, USA, with a known diagnosis of ITP, who was treated with prednisone, intravenous immunoglobulin, and rituximab before eventually undergoing splenectomy. Her postsplenectomy platelet count remained stable in the 60,000–70,000 range, without treatment. Two years following splenectomy, she presented with fever (temperature 101°F), chills, myalgias, and arthralgias. She denied any bleeding or bruising. Physical examination was unremarkable. Complete blood count demonstrated a hematocrit of 45.5 vol%, a white blood cell count of 4,600 cells/μL, and a platelet count of 10,000 platelets/μL. Liver function tests were notable for a slightly elevated alanine transaminase of 64 and aspartate transaminase of 49. Peripheral smear showed characteristic Howell-Jolly bodies and rare intraerythrocytic parasite ring forms in normal-sized red blood cells (Fig. 1). Babesiosis was confirmed by extremely high IgG and IgM titers to Babesia of 1:1,024 and 1:1,280, respectively, and a positive polymerase chain reaction (PCR). Importantly, there were no detectable antibodies for Lyme disease and ehrlichiosis. The patient was started on azithromycin and atovaquone and on a tapering dose of prednisone. She received 4 weeks of antibiotic therapy and her platelet count increased to 325,000 platelets/μL. Four weeks after completing the course of antibiotics, the platelet count dropped again to 24,000 platelets/μL. She continued to have circulating intracellular parasites on peripheral smear, and Babesia PCR and serologies were still positive. Atovaquone, azithromycin, and prednisone treatments were restarted. Her platelet count steadily improved, and only after 4 months of antibiotic therapy did the PCR for Babesia normalize. Steroids were discontinued. Her platelet count returned to her baseline value of 60,000–70,000, off immunosuppressive and anti-infective therapies. The approach to thrombocytopenia should always include an accurate history, physical examination, and examination of the peripheral blood smear. Splenectomy predisposes to infections that may present with thrombocytopenia, including ehrlichiosis, Colorado tick fever, Rocky Mountain spotted fever, babesiosis, and malaria. While patients can have a recurrence of ITP, other causes of thrombocytopenia need to be excluded. Babesiosis is a worldwide tick-borne disease caused by the intraerythrocytic protozoan Babesia [3]. Humans are infected by various tick vectors (Ixodes scapularis and Ixodes ricinus) and rarely by transfusions. In the USA, endemic areas include the islands off the coasts of MA and NY [4]. Symptoms include fever, chills, weakness, and myalgias. Babesiosis may present with hemolytic anemia, lymphopenia, and thrombocytopenia. Splenectomized patients may develop a fulminant infection with massive intravascular hemolysis [5]. The peripheral blood smear reveals small coccoid and dumbbell-shaped organisms. The trophozoites are small rings similar to those of Plasmodium falciparum. The parasites can be pyriform (pear shaped). Babesia microti is associated with Maltese cross forms and ring forms. IgM or P. A. Konstantinopoulos . K. B. Miller . B. J. Dezube (*) Division of Hematology/Oncology, Beth Israel Deaconess Medical Center, Harvard Medical School, 330 Brookline Avenue, Boston, MA 02215, USA e-mail: bdezube@bidmc.harvard.edu Tel.: +1-617-6677082 Fax: +1-617-9758030