Why is this inframammary rash not responding to over-the-counter creams?

Case 1:

After 1 month of scratching a worsening inframammary rash, a 68-year-old woman seeks medical evaluation. She has tried over-the-counter hydrocortisone followed by clotrimazole, but to no avail.

Your differential includes which of the following diseases?

A. Intertrigo.

B. Candidiasis.

C. Erythrasma.

D. Contact dermatitis.

E. Dermatophyte infection.

In this setting, the first diagnostic procedure you need to perform is:

F. Fungal culture.

G. Bacterial culture.

H. Patch test.

I. Potassium hydroxide (KOH) evaluation.

J. Wood’s light examination.

Case 1: Candidiasis

All of the diseases included in the differential are reasonable possibilities, given the location and appearance of the eruption. A KOH evaluation, I, is the first of the diagnostic procedures to be performed, since it is the easiest and simplest, and yields quick results. Here, the KOH examination confirmed the diagnosis of candidiasis, B.

The patient’s applications of an over-the-counter antifungal preparation probably failed because she did not use the agent for an adequate period. Occasionally, a strain of fungus is resistant to antifungal medications and the infection persists.
A 7- to 10-day course of prescription-strength imidazole cream cured
the infection.