How Should These Itchy Bumps Be Identified?

A 79-year-old male presented with a 2-week history of itchy bumps on his chest. He denies any recent exposure, new medications, or recent illnesses.

Your approach would be:

A. Bacterial culture
B. Fungal culture
C. Prescribe a trial of antibacterial oral antibiotics such as doxycycline
D. Skin biopsy for diagnosis
E. Ketoconazole 2% cream to the affected area twice a day for 10 days

(Answer and discussion on next page)

Answer: Perform a skin biopsy for diagnosis then prescribe a trial of antibacterial oral antibiotics such doxycycline  

Clinical diagnosis rules out related mutations such as pityrosporon or fungal folliculitis, which can be itchy, but is usually more monophorous and less inflamed than the eruption seen here. Bacterial folliculitis is usually tender, and cultures would have been negative.

Suspicion of myriad other differential diagnosis could be confirmed by performing a skin biopsy; in this case, a potassium hydroxide preparation test (KOH test) of a pustule found numerous Demodex mites, supporting the clinical diagnosis of Demodex folliculitis.
___________________________________________________________________________________________________________________________________________________________________

RELATED CONTENT
Demodicidosis
What is causing episodes of pruritic facial erythema?
___________________________________________________________________________________________________________________________________________________________________

Demodex mites are present in healthy individuals and may have a pathogenic role only when present in high densities. It remains unknown if Demodex is the underlying cause of this condition or if Demodex mite density increases due to inflammation of affected follicles.

Fortunately, this patient responded well to oral doxycycline and a sulfur/sulfacetamide daily cleanser over a 2-week period. A skin biopsy will typically show multiple mites per follicle.