Folliculotropic mycosis fungoides

Folliculotropic mycosis fungoides (FMF), also known as folliculotropic MF or pilotropic mycosis fungoides, is a distinct variant of mycosis fungoides, which is the most common type of cutaneous T-cell lymphoma (CTCL). In this condition, malignant T-lymphocytes preferentially infiltrate the hair follicles rather than the epidermis, which distinguishes it from classic mycosis fungoides. FMF is generally considered a more aggressive subtype with a less favorable prognosis compared to classic early-stage mycosis fungoides. The disease primarily affects the skin, with a predilection for the head and neck region, though it can involve other body areas. Key clinical features include grouped follicular papules, acneiform lesions, areas of alopecia (hair loss), and mucinorrhea (mucin discharge from affected follicles). Patients frequently experience intense pruritus (itching), which can significantly impair quality of life. The lesions may appear as comedone-like plugs, cysts, or indurated plaques. Secondary bacterial infections of affected follicles are common. In some cases, eyebrow loss (madarosis) is an early and characteristic sign. Treatment depends on the extent and stage of disease. Localized disease may be managed with skin-directed therapies including topical corticosteroids, phototherapy (PUVA or narrowband UVB), localized radiotherapy, or total skin electron beam therapy. More widespread or refractory disease may require systemic treatments such as retinoids (bexarotene), interferon-alpha, histone deacetylase inhibitors, or combination chemotherapy. Due to the follicular tropism, FMF can be less responsive to superficial skin-directed therapies compared to classic mycosis fungoides, and deeper-penetrating treatments are often needed. Allogeneic stem cell transplantation may be considered in advanced or refractory cases. Long-term follow-up is essential as the disease can progress over time.

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