Mycosis on mycosis fungoides: zoophilic dermatophytosis selectively superimposed on pre-existing cutaneous T-cell lymphoma (mycosis fungoides) plaques.

We report a case of tinea corporis caused by a cattle-derived strain of Trichophyton mentagrophytes in a 44-year-old male affected by cutaneous T-cell lymphoma (CTCL, so-called mycosis fungoides). Fungal colonization of glabrous skin was strictly confined within pre-existing lymphomatous plaques. Either oral itraconazole or griseofulvin, or topical terbinafine were ineffective until the patient, who was treated with systemic retinoids and interferon-alpha for his CTCL, was shifted from leucocyte to lymphoblastoid interferon. The hypothesis that a local immunodisturbance could be responsible for the selective superimposition of tinea on CTCL lesions ('mycosis on mycosis'), and that such an immunodisturbance could be partially corrected by the interferon switch is discussed.