Introduction:
Mycosis fungoides (MF) is the most common variant of primary skin T-cell lymphoma, affecting nearly half of the cases of skin T-cell lymphoma. It is most prevalent among the middle aged and elderly adults of all races1. MF typically manifests as an indolent cutaneous eruption with erythematous scaly patches or plaques and may progress to a generalized erythroderma and/or cutaneous tumors or invade the extra-cutaneous tissues, and in the early stages it usually mimics other common skin disorders including psoriasis and eczema2. Diagnosis of MF is challenging due to the nonspecific clinical and pathological findings especially at the early stages, making it highly possible to get misdiagnosed for years3. Final diagnosis is confirmed through pathological findings of skin biopsy, and treatment is available with desirable therapeutic outcome in many cases3. Several treatment options are available for the treatment of MF including skin-directed therapy consisting of topical corticosteroids, phototherapy, topical chemotherapy, topical retinoids and radiotherapy for the early stages and systemic therapy including interferone-alpha, oral retinoids including bexarotine, acitretin, histone deacetylase inhibitors, fusion toxin denileukin diftitox, and chemotherapy drugs for more advanced stages. The prognosis is highly depended on the type and extent of skin involvement the presence of extracutaneous involvement, while most patients have an indolent and incurable course4,5. Psoriasis is one of the most prevalent chronic inflammatory disorders of the skin with an auto-immune origin. Manifestations include erythematous scaly plaques that are clinically similar to psoriasiform MF. Psoriatic patients are at increased risk of skin malignancies. A diagnosis of psoriasis is usually made clinically and treatment options mainly include immunosuppressants and biologic agents6,7.
In this article we report an uncommon presentation of psoriasiform MF in a patient who was diagnosed with psoriasis and managed accordingly for a long time as well as the diagnostic and therapeutic challenges encountered with a review of the literature on similar cases and their clinic-pathological findings.