Master the board step 3

Infectious Diseases
Lymphogranuloma venereum (LGV)
Large tender nodes are present in addition to the ulcer. The enlarged nodes,
sometimes called “buboes,” may develop a suppurating, draining sinus tract.
Diagnostic Testing
Diagnose with serology for Chlamydia trachomatis.
Treatment
Aspirate the bubo. Treat with doxycycline or azithromycin.
Basic Science Correlate
Mechanism of Erythromycin Adverse Effects
Why don’t we use erythromycin for chlamydia? First, its efficacy is less than
that of azithromycin. Second it causes severe nausea, vomiting, and diarrhea.
Erythromycin increases the release of motilin, a hormone that increases GI
motility between meals. Erythromycin abnormally increases it to where there
is excess GI motility. This is why it works for hypomotility disorders such as
diabetic gastroparesis.
Herpes Simplex Virus Type 2 (HSV2) (Genital Herpes)
A 34-year-old man comes to the clinic with multiple vesicles on his penis. There is
enlarged adenopathy in the inguinal area. What is the next step in management?
a. Tzanck prep
b. Viral culture
c. Valacyclovir
d. Valganciclovir
Answer: C. When there are clear vesicular lesions present, there is no need to do a specific
diagnostic test for herpes. If the question describes multiple vesicles, then treatment
with acyclovir, valacyclovir, or famciclovir for 7–10 days is the next best step in management.
Daily suppressive therapy can be prescribed for recurrent genital herpes. If the roofs
come off the vesicles and the lesion becomes an ulcer of unclear etiology, then the best
initial diagnostic test is a Tzanck prep. The most accurate test for herpes is a viral culture.
If there are clear vesicles, this is not necessary; go straight to treatment. Valganciclovir is
therapy for cytomegalovirus (CMV). Patients with frequent recurrence should be placed
on chronic suppressive therapy. Acyclovir resistant herpes is treated with foscarnet.
Acyclovir is safe in
pregnancy. Use acyclovir
in pregnancy if there is
evidence of active lesions
at 36 weeks.
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