A 32-year-old man comes to the emergency department due to 5 days of intermittent high fever, chills, and drenching sweats. He also has malaise, fatigue, and dark urine. The patient has no medical history other than a splenectomy after a motor vehicle collision 10 years ago. He drinks alcohol on social occasions and does not use tobacco or illicit drugs. He is married and in a monogamous relationship with his wife. The patient lives on Long Island, New York, and works in Manhattan as a software programmer. He has not traveled outside the country but likes to hike and explore the woods. He recently camped in New England and found 2 ticks on his legs when he returned home. Temperature is 39.5 C (103 F), blood pressure is 110/70 mm Hg, and pulse is 116/min. Mild scleral icterus is present. There are no enlarged lymph nodes or skin rash. A mildly tender liver edge is palpable 3 cm below the right costal margin. Laboratory results are as follows: Which of the following is most likely to yield the diagnosis in this patient?

Question

A 32-year-old man comes to the emergency department due to 5 days of intermittent high fever, chills, and drenching sweats.  He also has malaise, fatigue, and dark urine.  The patient has no medical history other than a splenectomy after a motor vehicle collision 10 years ago.  He drinks alcohol on social occasions and does not use tobacco or illicit drugs.  He is married and in a monogamous relationship with his wife.  The patient lives on Long Island, New York, and works in Manhattan as a software programmer.  He has not traveled outside the country but likes to hike and explore the woods.  He recently camped in New England and found 2 ticks on his legs when he returned home.  Temperature is 39.5 C (103 F), blood pressure is 110/70 mm Hg, and pulse is 116/min.  Mild scleral icterus is present.  There are no enlarged lymph nodes or skin rash.  A mildly tender liver edge is palpable 3 cm below the right costal margin.  Laboratory results are as follows:  Which of the following is most likely to yield the diagnosis in this patient?

Quizplus · Accepted Answer

11ec25c8_d43e_1d29_bc81_83e5e17251cf_MD0003_00 Babesiosis is a tick-borne protozoal illness endemic to the northeastern United States. Human transmission occurs via Ixodes scapularis approximately 48-72 hours after attachment. I scapularis also may transmit Borrelia burgdorferi (Lyme disease) and Anaplasma phagocytophilum (human granulocytic anaplasmosis); therefore, coinfection with multiple organisms is possible. Peak prevalence is in July and August, when tick populations are at their highest. Ixodes scapularis Infection is often asymptomatic or mild, but patients with immunocompromise, age >50, or a history of splenectomy are at higher risk for severe illness. Symptoms typically include the gradual onset of fatigue, malaise, weakness, chills, and fever. The organism multiplies in red blood cells, so patients may develop anemia with signs of intravascular hemolysis (jaundice, dark urine, indirect hyperbilirubinemia, reticulocytosis, elevations of aminotransferases and lactate dehydrogenase). Thrombocytopenia is common and mild hepatosplenomegaly may occur. Diagnosis is made by identifying organisms on peripheral blood smear ("Maltese cross"). Treatment includes 7-10 days of atovaquone plus azithromycin or quinine plus clindamycin (for severe illness). Symptoms may take up to 3 months to fully resolve. blood smear (Choice A) Rocky Mountain spotted fever is the most prevalent rickettsial illness in the United States. Symptoms often include fever, headache, myalgias, and a prominent rash (macular/petechial) that spreads centripetally and includes the palms and soles. Hemolytic anemia is uncommon. (Choice C) Lyme disease is also transmitted by I scapularis. Early disease is usually characterized by erythema migrans (a punched out, spreading rash), fever, myalgias, headache, and/or lymphadenopathy. Anemia with intravascular hemolysis is uncommon. (Choice D) Ehrlichiosis is a tick-borne (Amblyomma americanum) illness that causes nonspecific symptoms (eg, fever, myalgias, headache) and leukopenia/thrombocytopenia. This patient with leukocytosis and signs of intravascular hemolysis is more likely to have babesiosis. (Choice E) The diagnosis of dengue fever can be aided by using the tourniquet test. This illness is often asymptomatic, but some patients develop fever and severe myalgias/headache ("breakbone fever"). Leukopenia (not leukocytosis) and thrombocytopenia are common. Intravascular hemolysis is atypical. (Choice F) Acute viral hepatitis is usually characterized by fever, vomiting, jaundice, abdominal pain, and dramatic elevations in aminotransferases (>1000 U/L). Educational objective: Babesiosis is a tick-borne protozoal illness found primarily in the northeastern United States. Transmission occurs via Ixodes scapularis, and coinfection with other microbes (eg, Borrelia burgdorferi, Anaplasma phagocytophilum) is possible. Symptoms are often flu-like (fever, chills, malaise), and laboratory studies usually show anemia with signs of intravascular hemolysis and thrombocytopenia. Diagnosis is made primarily by identifying organisms on peripheral blood smear ("Maltese cross").

A 32-Year-Old Man Comes to the Emergency Department Due to 5