Erythrodermic cutaneous T-cell lymphoma: how to differentiate this rare disease from atopic dermatitis.

Sézary syndrome and erythrodermic mycosis fungoides have been recognized as part of a broader spectrum of erythrodermic cutaneous T-cell lymphoma (E-CTCL). Atopic dermatitis (AD) is the most common, chronic inflammatory skin disease and can, in its most severe form, manifest as erythroderma. It is often difficult to clinically distinguish E-CTCL from various common and benign diseases presenting as erythroderma, including AD. Differentiating E-CTCL from benign inflammatory diseases is important to ensure proper disease management, and to provide accurate prognostic information. Clinical and laboratory features, including pruritus and serum levels of soluble interleukin-2 receptor, lactate dehydrogenase (LDH), immunoglobulin E (IgE), and several chemokines, do not differentiate E-CTCL from AD. In contrast, low serum allergen-specific IgE levels, presence of Sézary cells in peripheral blood, histological findings, and high CD4/CD8 ratio and CCR10 positivity in lesional skin are helpful in reaching a correct diagnosis. Patients with E-CTCL have been treated with oral etretinate, intravenous or subcutaneous interferon, bexarotene, extracorporeal photopheresis, total body surface electron beam, chemotherapy, or any combination of these modalities. Older patients, high serum LDH levels, and high number of circulating atypical lymphocytes are associated with poor prognosis.