Understanding the enigmatic association between mycosis fungoides and psoriasis: Report of two cases and review of the literature.

Psoriatic patients present an increased risk for developing lymphoma, particularly cutaneous T-cell lymphoma (CTCL). To what degree psoriasis itself through chronic immune stimulation, or the immunosuppressive medications used for its treatment or comorbidities (obesity, diabetes mellitus, etc), or lifestyle (smoking, alcohol, diet, etc) may play a role in the onset of MF is not yet clear. Psoriasis and Mycosis Fungoides (MF), the most common variant of CTCL, represent two distinct entities sharing common pathogenetic mechanisms and a wide spectrum of common clinical features associated with the abnormal activation of T-cells. The aim of this study is to explore the relationship between MF and psoriasis by presenting two cases with clinical and histopathologic features of both psoriasis and MF with a particular emphasis on the time of presentation of both disorders, the use of previous immunosuppressive drugs as well as the therapeutic management of patients. Biopsy of the cutaneous lesions before the introduction of biologics should be incorporated in clinical practice. Biopsy of the cutaneous lesion should also be performed in the case of appearance of psoriasiform lesions during biologic treatment for autoimmune disorders because this may represent an indolent form of MF. Psoriatic patients with poor or no-response to treatment should be examined thoroughly for MF using immunochemistry and, if necessary, molecular biology techniques. In concomitant MF and psoriasis, combination treatment may be beneficial for both entities. Finally, a large multicentric registry of MF patients who were treated for benign dermatoses (i.e. eczema, psoriasis) with classic immunosuppressive drugs and/or biologics is needed to collect data and further clarify the enigmatic relationship between psoriasis, MF and immunosuppressive treatment.