Tinea lucidum or dermatophytosis of the stratum lucidum: is the epidermal location of dermatophyte infection evolving?

Dermatophyte infections are traditionally localized to the stratum corneum. The advent of immunosuppressants and topical steroid/antifungal preparations, however, has created a new phenomenon: dermatophytosis in the stratum lucidum. This atypical presentation manifests in 3 clinical scenarios: oral immunosuppression and/or medical comorbidities, lesions/body sites with lichenification, and sites on/near acral skin. In each setting, superficial potassium hydroxide (KOH) preparations have proved ineffective in diagnosis, despite high indices of suspicion for dermatophytosis. It is only under histologic examination that florid hyphal elements are identified. The authors propose a modified KOH technique requiring a sample of deeper, pathological scale-containing fungal elements to be used in scenarios where tinea lucidum or dermatophyte infection of the stratum lucidum may be present.