Dermatophytic infections are common in adults. Tinea incognito is one such infection which has lost its characteristic features due to the use of topical and systemic immunosuppressive agents. This poses a challenge for the clinician as tinea incognito can mimic many other dermatoses. We report one such case of tinea incognito masquerading as psoriasis.

Introduction

Dermatophytes are a group of fungi that can infect the skin, hair and nails. Skin lesions typically begin as erythematous plaques with raised borders that extend in all directions. Tinea incognito is a dermatophytic infection which has lost its clinical features due to the use of topical and systemic immunosuppressive agents. The lesions may look different with the absence of typical raised borders. The fungus flourishes as there is suppression of local immune response. Tinea incognito remains a challenge to the clinicians and at times misdiagnosed leading to a prolonged disease course. We report one case of tinea incognito masquerading as psoriasis.

Case presentation

A 28-year-old healthy male patient presented with multiple itchy reddish lesions over face, back, neck, both upper and lower extremities for the last 3 years. He was treated with topical steroids, emollients and oral antihistamines elsewhere during these 3 years. His lesions showed improvement initially with the treatment given, only to recur. During the past 4-5 months the lesions showed extensive involvement of his body. Physical examination revealed multiple lichenified well-defined scaly plaques distributed over face, neck, back, trunk, both upper and lower extremities. Differential diagnosis of chronic eczematous dermatosis and psoriasis were considered. His routine hematological investigations were within normal limits. Histopathological examination of skin sample from the lesion showed features suggestiveof psoriasis (Fig. 1).

The patient was treated with oral antibiotics, antihistamines and topical steroids. On subsequent visit, the patient showed a different clinical picture of erythematous plaques with scaly borders distributed all over the body, which made us consider the diagnosis of tinea incognito (Fig. 2a, 2b). A 10% potassium hydroxide examination of the lesions revealed numerous branching septate hyphae, which confirmed the diagnosis of tinea incognito. The patient was treated with oral itraconazole and topical antifungal for 2 weeks, with dramatic improvement (Fig. 3a and 3b).

Discussion

The term tinea incognito was coined by Ive and Marks in 1968 for cases of dermatomycosis, erroneously treated with topical steroids, having clinical manifestations that mimicked other skin conditions.1 Topical steroids modify the local immune response and allow the fungus to grow easily. As a result, the fungal infection may have an altered clinical picture.2 Tinea incognito is difficult to diagnose in the absence of its classical clinical picture of ringworm appearance, i.e, concentric erythematous rings with central clearing.2,3 Tinea incognito may mimic eczema, psoriasis, pityriasis rosea and atopic dermatitis.2,4 Only mycological examination can aid in correct diagnosis in these conditions.

Topical potent steroids and other immunosuppressive agents have been very effective in treating several dermatological conditions in the recent years. These benefits are mainly due to their anti-inflammatory and antimitotic actions. However, their efficiency has resulted in their misuse. These agents are often misused as over the counter drugs by the patients and also are frequently prescribed by practitioners.

The diagnosis of tinea incognito is simple. It includes a microscopic visualization of branching septate hyphae and fungal culture. Treatment requires cessation of steroid use and implementation of appropriate antifungals. However, the patient must be instructed not to reinstitute the steroids.

Conclusion

This case report highlights the importance of mycological examination in chronic inflammatory dermatoses to rule out tinea incognito.

References

1. Kedia S K, Mathur M. Tinea incognito: Report of two cases. J Coll Med Sci-Nepal 2010;6(3):46-9.
2. Ebtisam Elghblawi (2013), Extensive ‘Tinea incognito’ due to topical steroid, a case report. JMED Research 2013;2013:599265.
3. Yu C, Zhou J, Liu J. Tinea incognito due to microsporum gypseum. J Biomed Res 2010;24:81-3.
4. Rallis E, Koumantaki-Mathioudaki E. Pimecrolimus induced tinea incognito masquerading as intertriginous psoriasis. Mycoses 2008;51:71-3.