USMLE Step 1 Question 311

Question:

A 25 year old from Massachusetts complains of increasing fatigue and pre-syncope. Upon further questioning, he admits to having had a rash on his arm a couple of months ago. He denies joint pain, photophobia or a stiff neck.
An EKG is taken which shows 3rd degree heart block (complete heart block). His laboratory tests are within normal limits. Blood cultures are pending.
What is the most appropriate treatment?

Correct Answer: A.  Ceftriaxone

This patient is suffering from Lyme disease which is endemic to the North-East of the United States. It is borne by a tick and caused by the spirochete Borrelia burgdorferi. After the tick infects the patient, many patients experience a rash that has a target appearance (erythema migrans). Lyme disease in later stages can cause meningitis, arthritis and heart block. The most appropriate treatment is ceftriaxone, which is the drug of choice when the patient develops advanced signs of lyme disease, that include Complete heart block or CNS involvement.
Doxycycline (Choice B), a tetracycline which is the primary treatment for stage 1 of Lyme disease.

Although this patient is found to be in heart block, the most appropriate treat at this moment is doxycycline rather than an implantable defibrillator (Choice C) since the heart block will improve with treatment.

Penicillin G (Choice D) given in high doses can be use in the treatment for cardiac complications of Lyme Disease.

Rifampin (Choice E) is part of TB treatment.