Sample presentation
-Intertriginous rash affecting his groin, axilla, etc
DDx of intertriginous rash:
-It is itchy but not painful and does not affect his ADLs.
-antifungal creams haven’t worked.
On examination you find well-demarcated, dark red patches in the inguinal region bilaterally.
Under Wood’s light the area fluoresces coral-red.
“Coral-red fluorescence on Wood’s light examination is typical of infection with Corynebacterium minutissimum, a condition known as erythrasma. This organism commonly complicates intertrigo, often in the groin or interdigital spaces.
Erythromycin is the most effective treatment for this bacterial infection.”ABFM
Janniger CK, Schwartz RA, Szepietowski JC, Reich A: Intertrigo and common secondary skin infections. Am Fam Physician 2005;72(5):833-838. 2) Binic I, Jankovic A: Coral-red fluorescence. N Engl J Med 2011;364(13):e25.
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A 45-year-old male is seen for a well-demarcated, nonpruritic rash in the right axilla. It is fine-scaled with a cigarette-paper appearance. The rash has a coral-red fluorescence under a Wood’s light. Which one of the following is the most likely diagnosis?
Candidiasis
Tinea cruris
Erythrasma
Inverse psoriasis
Rationale:
All of the diagnoses listed are intertriginous rashes but only erythrasma fluoresces with Wood’s light. Erythrasma is a superficial gram-positive bacterial infection caused by Corynebacterium minutissimum. The fluorescence is caused by porphyrins. Erythrasma is most often seen between the toe web spaces, followed by the groin and axillae. There are multiple treatments, including topical and oral erythromycins and clindamycins (level of evidence 3, strength of evidence 1).
Vary JC, O’Connor KM: Common dermatologic conditions. Med Clin North Am 2014;98(3):445-485.”ABFM