ABIM Exam Review Practice Question of the Week: Infectious Organism causing Elevated LDH level

Here’s a question directly from the Knowmedge ABIM (Internal Medicine Board) Exam QVault.


Which of the following organisms is most likely to cause an elevated LDH level?


A. Babesia microti

B. Rickettsia rickettsia

C. Borrelia burgdorferi

D. Cardiobacterium

E. Klebsiella pneumoniae





The intracellular parasite Babesia microti causes the disease babesiosis. It is the organsim most likely to cause an elevated LDH. The organism is endemic to the northeastern United States including Long Island, Nantucket Island, Martha’s Vineyard and Cape Cod areas. The parasite may take residence inside rodents and cattle. Transmission to humans occurs when the Ixodes scapularis tick bites the host, taking up the babesia parasite, which it then delivers to a person by way of a bite.


Usually the infection is subclinical. However, in some patients, fevers, chills, sweats, myalgia, and arthralgia may develop. A febrile hemolytic anemia reaction may ensue in which labs will reveal increased reticulocyte count, increased indirect bilirubin and increased LDH level. Diagnosis of babesiosis is with peripheral blood smear revealing the parasite within RBCs. Treatment is with atovaquone and azithromycin.


You can see all the previous ABIM Exam Review Questions of the Week at the Knowmedge Blog. You can find also additional topics and questions directly from the Knowmedge Internal Medicine ABIM Board Exam Review Questions QVault.

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