A 48-year-old man comes to the hospital due to 10 days of persistent fever, chills, fatigue, and dyspnea. He had a splenectomy at age 28 after a motor vehicle accident and received the appropriate vaccines. The patient does not use tobacco, alcohol, or illicit drugs. He recently traveled from New York City to Connecticut for a family wedding. His temperature is 38.6 C (101.5 F), blood pressure is 118/70 mm Hg, and pulse is 108/min. Lung examination reveals coarse crackles. Laboratory studies are as follows: Chest x-ray reveals bilateral infiltrates. A peripheral blood smear shows normocytic, normochromic anemia with ring- and cross-shaped intraerythrocytic inclusions. The vector responsible for this patient's current condition can also transmit which of the following organisms?

Question

A 48-year-old man comes to the hospital due to 10 days of persistent fever, chills, fatigue, and dyspnea.  He had a splenectomy at age 28 after a motor vehicle accident and received the appropriate vaccines.  The patient does not use tobacco, alcohol, or illicit drugs.  He recently traveled from New York City to Connecticut for a family wedding.  His temperature is 38.6 C (101.5 F), blood pressure is 118/70 mm Hg, and pulse is 108/min.  Lung examination reveals coarse crackles.  Laboratory studies are as follows:  Chest x-ray reveals bilateral infiltrates.  A peripheral blood smear shows normocytic, normochromic anemia with ring- and cross-shaped intraerythrocytic inclusions.  The vector responsible for this patient's current condition can also transmit which of the following organisms?

Quizplus · Accepted Answer

This patient with an acute febrile illness, thrombocytopenia, hemolytic anemia (indirect hyperbilirubinemia, elevated lactate dehydrogenase, low haptoglobin), abnormal liver function tests, and intraerythrocytic inclusions (ring-shaped and "Maltese cross" forms) has babesiosis, a tick-borne infection. A definitive diagnosis can be made from a Giemsa-stained blood smear showing intraerythrocytic parasites. Splenectomy places patients at increased risk for severe babesiosis, which can manifest as acute respiratory distress syndrome (dyspnea, coarse crackles, bilateral infiltrates on chest x-ray). Babesiosis (caused by Babesia microti) and Lyme disease (caused by Borrelia burgdorferi) are both transmitted by the Ixodes tick and occur in similar geographic regions. Coinfection is common and could be considered in the appropriate epidemiologic setting (eg, patients who present with babesiosis in a region endemic for Lyme disease and who do not improve despite appropriate treatment). (Choices B and F) Dengue virus is transmitted by Aedes mosquitos, and Plasmodium falciparum is transmitted by Anopheles mosquitos. Dengue fever and malaria may present as acute febrile illnesses, but both infections occur mainly in tropical regions. Malaria is characterized by intravascular hemolysis, anemia, and abnormal liver function tests (similar to babesiosis), but the blood smear frequently shows ring-shaped (not cross-shaped) erythrocyte inclusions. (Choices C and E) Asplenic patients are at increased risk for life-threatening infections with encapsulated organisms (eg, Streptococcus pneumoniae, Haemophilus influenzae, Neisseria meningitidis) and therefore receive protective vaccines. Intraerythrocytic inclusions are also not seen in H influenzae and N meningitidis infections. (Choice D) Histoplasmosis is a common mycotic infection that is most commonly found in the Ohio and Mississippi river basins and is associated with activities involving exposure to bird or bat droppings (eg, caving). Educational objective: Babesiosis and Lyme disease are transmitted by the Ixodes tick and occur in similar geographic regions. Coinfection is common. __________ References: Coinfections acquired from Ixodes ticks. (http://www.ncbi.nlm.nih.gov/pubmed/17041141) Human babesiosis. (http://www.ncbi.nlm.nih.gov/pubmed/18755385) Tick-borne disease. (http://www.ncbi.nlm.nih.gov/pubmed/15999870)

A 48-Year-Old Man Comes to the Hospital Due to 10