An Elusive Case of Mycosis Fungoides: Case Report and Review of the Literature.

Erythroderma refers to a spectrum of skin diseases resulting in diffuse erythema and scaling encompassing ≥ 90% of the body surface area. The differential diagnosis ranges from primary dermatologic diseases such as atopic dermatitis and psoriasis to potentially deadly causes such as staphylococcal toxic shock syndrome, toxic epidermal necrolysis, and malignancy. Cutaneous T cell lymphoma (CTCL) is an uncommon but highly morbid cause of erythroderma. This non-Hodgkin lymphoma remains a diagnostic challenge due to its variable clinical presentation and varied histologic features. Mycosis fungoides (MF) is the most common form of CTCL. Making a timely diagnosis is challenging as it may mimic inflammatory diseases of the skin including eczema, psoriasis, lichen planus, and cutaneous lupus. We present a case of a 58-year-old man who presented with 5 years of cutaneous symptoms and several months of fevers and night sweats, ultimately diagnosed as MF. Owing to diffuse CD30 positivity, he was a candidate for brentuximab vedotin, an antibody-drug conjugate medication that selectively targets the CD30 antigen. This resulted in an excellent therapeutic response.