Tinea incognita

Tinea incognita or Tinea incognito[1] is a fungal infection of the skin masked and often exacerbated by application of a topical immunosuppressive agent.[2] The usual agent is a topical corticosteroid.[3] As the skin fungal infection has lost some of the characteristic features due to suppression of inflammation, it may have a poorly defined border and florid growth. Occasionally, secondary infection with bacteria occurs with concurrent pustules and impetigo.[4]

Tinea incognita
Tinea incognita in the forearm of a child being treated for contact dermatitis
SpecialtyDermatology

Cause

The use of a topical steroid is the most common cause. Frequently, a combination topical steroid and antifungal cream is prescribed by a physician. These combinations include betamethasone dipropionate and clotrimazole (trade name Lotrisone) and triamcinolone acetonide and clotrimazole. In areas of open skin, these combinations are acceptable in treating fungal infection of the skin. In areas where the skin is occluded (groin, buttock crease, armpit), the immunosuppression by the topical steroid might be significant enough to cause tinea incognita to occur even in the presence of an effective antifungal.

Diagnosis

Clinical suspicion arises especially if the eruption is on the face, ankle, legs, or groin. A history of topical steroid or immunosuppressive agent is noted. Confirmation is with a skin scraping and either fungal culture or microscopic exam with potassium hydroxide solution. Characteristic hyphae are seen running through the squamous epithelial cells.

Treatment

The removal of the offending topical steroid or immunosuppressive agent and treatment with a topical antifungal is often adequate. If the tinea incognita is extensive or involves hair bearing areas, treatment with a systemic antifungal may be indicated.

References
  1. This is a common misspelling according to "What is tinea incognita?". DermNet NZ. Archived from the original on April 30, 2019.
  2. Chander, Jagdish (2018). Textbook of Medical Mycology (4th ed.). New Delhi: Jaypee Brothers Medical Publishers Ltd. p. 172. ISBN 978-93-86261-83-0.
  3. James, William D.; Elston, Dirk; Treat, James R.; Rosenbach, Misha A.; Neuhaus, Isaac (2020). "15. Diseases resulting from fungi and yeasts". Andrews' Diseases of the Skin: Clinical Dermatology (13th ed.). Elsevier. p. 296. ISBN 978-0-323-54753-6.
  4. Habif, T. P. (1995) Clinical Dermatology. Mosby, 3rd ed.; pp. 41-42.
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