Discussion
Mycosis fungoides shares similar manifestation and overlapping pathophysiology with psoriasis. It is yet unknown whether a shared pathophysiology of psoriasis and the immunosuppressant medications prescribed for these patients causes the disease progression to MF or a diagnosis of MF was missing since the onset of the manifestations. This is proved that psoriatic patients are at risk for developing lymphoma, particularly cutaneous T-cell lymphoma. One example is the administration of cyclosporine by psoriatic patients, which is a highly effective treatment for psoriatic plaques while significantly worsens the course of MF or may be a possible underlying cause for progression to MF 8,9. In most cases pathological findings are not supportive for a diagnosis of psoriasis, while non-specific histopathological findings of MF in the early stages may get misdiagnosed with psoriasis. Studies have also highlighted the frequent development of MF later in the course of psoriasis and other autoimmune disorders and following the administration of immunosuppressive and biologic agents. Similarly, our case was either a case of psoriasis who progressed to MF following long-term immunosuppressive treatment, or a pure case of misdiagnosed MF10. This case, besides several cases that have been reported earlier, highlights the importance of consideration of MF especially in cases with psoriatiform plaques and those who are ot responsive to psoriasis treatment or refractory cases. In these cases, skin biopsy is required as soon as possible. It is also highly recommended to consider skin biopsy before administration of biologics for treatment of autoimmune disorders in clinical practice. Refractory cases of psoriatiform plaques with poor therapeutic responses are required to receive thorough examination for MF using immunochemistry and molecular biology techniques, as well10. Interestingly, combination treatment has proved efficacy in cases of concomitant MF and psoriasis and may be considered when a diagnosis is not confidently confirmed10. In this case, after histopathological confirmation of MF, combination therapy was initiated. Topical treatment consisted of two mixture ointments inclduing 90% ucerin and 10% urea once daily, and another with 50% clobetasol and 50% ucerin once every night and systemic treatment included weekly methotrexate injection and oral prednisolone. PUVA therapy was also initiated with high efficacy for MF. Our case also shows the significant efficacy of PUVA besides combination therapy for complete resolution of MF lesions and the underlying systemic inflammation. Previous studies highly recommend initiating PUVA therapy in MF cases as soon as a diagnosis is confirmed. In refractory cases, low-dose methotrexate is also highly recommended and a combination of topical medications is often required. A retrospective study, investigated the occurrence and time of relapse in patients with early MF treated with narrowband UVB phototherapy. Of 31 patients, who were followed-up for a mean of 56.5 ± 30.2 months (median 55 months, range 20-120 months), relapse was observed in 11 (35.5%) patients, within a mean of 28.8 ± 18.2 months (median 33 months, range 4-59 months), whereas 20 (64.5%) patients stayed relapse-free for a mean of 54.2 ± 28.8 months (median 55.5 months, range 20-119 months). Patients received maintenance phototherapy with a median duration of 12 months (range 1-30 months) after achieving complete response11. Results indicate that narrow band UVB phototherapy may induce low relapse rates and long relapse-free intervals for early MF. Another retrospective study aimed to review the response rate of methotrexate in the treatment of MF. Sixty-nine MF patients with patch/plaque and tumor stage, with a follow-up period of 201 months were studied. The greatest number of patients (60) had patch/plaque stage T2 disease (≥10% skin involved). Of these, 7 (12%) achieved complete remission and 13 (22%) achieved partial remission, with a total response rate of 20 of 60 (33%). The median time of treatment failure was 15 months. Side effects caused treatment failure in 6 of 69 patients (9%). Accordingly low-dose methotrexate may be valuable for treating a subset of MF patients with patch/plaque, whom are resistant to other therapies12. Moreover, a large prospective non-randomized study investigated the efficacy of mechlorethamine hydrochloride and topical betamethasone in the treatment of early-stage MF patients. Sixty-four consecutive patients with newly diagnosed early-stage MF (stage IA, n = 33; stage IB, n = 26; stage IIA, n = 5) were enrolled in the study. Patients were treated with application of 0.02% aqueous solution of mechlorethamine followed by application of betamethasone cream, twice-weekly for 6 months. They concluded that topical anti-inflammatory agents alone are highly effective treatment for early-stage of MF13.