Tinea incognito

Tinea incognito (often mislabeled as “tinea incognita”) is a fungal infection modified and exacerbated by the inappropriate use of topical steroids, leading to an altered clinical appearance.

The clinical features may become masked with attenuated scale and erythema, as well as a less well-defined border

The infection may also be exacerbated as the dermatophytes invade the dermis or subcutaneous tissue causing deep-seated folliculitis, also referred to as Majocchi’s granuloma.

• Cause:
  • Primary cause is dermatophyte infection, commonly by Trichophyton rubrum.
  • Exacerbated by the use of anti-inflammatory treatments like topical steroids, tacrolimus ointment, and pimecrolimus cream.
  • Systemic steroids can also induce tinea incognito.
• Risk Factors:
  • Use of immune suppressive drugs.
  • Conditions like HIV infection and diabetes mellitus.
  • Environmental factors such as sweating, abrasion, and maceration.

Clinical Features of Tinea Incognito

• Compared to Untreated Tinea Corporis:
  • Less raised margins.
  • Less scaliness.
  • More pustular.
  • More extensive and irritable.
• Secondary Changes Due to Long-Term Steroid Use:
  • Skin atrophy and stretch marks.
  • Bruising (purpura) and visible broken blood vessels (telangiectasia).

Diagnosis of Tinea Incognito

• Initial Steps:
  • Take skin scrapings for microscopy and culture, ideally a few days after stopping all creams.
  • Laboratory may report negative results if there is little surface scale.
• Post-Steroid Presentation:
  • Becomes highly inflamed after stopping steroids, with more visible fungal elements on microscopy.
  • The fungus typically grows promptly in culture.
• Biopsy:
  • If performed, pathology will reveal the fungal organisms.

Treatment of Tinea Incognito

• Discontinuation of Cause:
  • Stop any topical steroids or calcineurin inhibitors.
• Management:
  • Apply bland antipruritic lotions.
  • Use standard antifungal treatments, likely requiring oral antifungals such as terbinafine or itraconazole for effective management.

Prevention of Tinea Incognito

• Avoidance:
  • Do not use topical steroids for undiagnosed skin conditions.
  • Healthcare providers should consider a dermatophyte infection in the diagnosis of any scaly or pustular rash with a prominent and irregular border, especially if unilateral or asymmetrical.
  • Perform mycology to confirm diagnosis in doubtful cases of scaly or pustular rashes.