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Generalized syringotropic mycosis fungoides responsive to extracorporeal photopheresis

DEAR EDITOR, Syringotropic mycosis fungoides (STMF), a rare variant of mycosis fungoides (MF) and a subtype of follicular MF based on current classification, classically presents with punctate erythematous papules or plaques on the trunk or limbs, often with alopecia or anhidrosis, and typically follows an indolent clinical course. Because of the perieccrine localization of the dermal infiltrates, STMF is often less responsive to skin-targeted therapies than classic MF, and given the rarity of the disease there is no accepted treatment approach, especially for those with generalized disease. A 72-year-old white man presented with a 10-year history of generalized severe pruritus, scored as 10/10 on the numerical rating scale (NRS), with erythematous papules and plaques on his trunk and extremities, associated with generalized patchy hair loss. He reported no improvement with topical corticosteroids or emollients. Clinical examination revealed erythematous plaques, folliculotropic papules with perifollicular erythema (Fig. 1a) and large, open comedones on his upper mid-back, flanks and thighs, amounting to a body surface area involvement of 15%. There was focal alopecia of the frontal and temporal scalp, without loss of follicular orifices, and diffuse thinning of the eyebrows and body hair. There was no evidence of organomegaly or lymphadenopathy on clinical examination. Routine laboratory testing, lactic dehydrogenase and flow-cytometric analysis of circulating T-cell subsets were normal. Several skin biopsies were performed, sampling the most prominent erythematous plaques on his back, a large comedone on his forearm and an area of alopecia on the temporal scalp. The unifying features in all biopsies were the presence of a moderate to dense perieccrine atypical lymphocytic infiltrate with exocytosis into the eccrine structures (Fig. 2a,b). In addition, a biopsy taken from an area with follicular prominence and perifollicular erythema revealed superficial perifollicular lymphocytic infiltrates. There was no evidence of scarring. Immunohistochemical stains revealed a CD3+ infiltrate, the majority of which was CD4+ admixed with few CD8+ cells. T-cell receptor (TCR) rearrangement studies revealed a clonal population of T lymphocytes. Based on clinical presentation, the histopathological findings and TCR studies, a diagnosis of STMF stage 1b (T2N0M0) was made. The treatment options for generalized STMF were discussed with the patient. Phototherapy [narrowband ultraviolet (UV) B] and photochemotherapy [psoralen plus UVA (PUVA)] were considered, but deemed unlikely to be effective given the location of the deep dermal syringotropic infiltrates. The patient was also unable to commit to the frequency of phototherapy treatment sessions. Given its systemic treatment approach, excellent tolerability and very low rate of adverse events, extracorporeal photopheresis (ECP) was started for two consecutive days every 4 weeks, while continuing application of topical steroids. After cycle three, the patient demonstrated