Sézary syndrome

**Definition:** A generalised peripheral (mature) T-cell neoplasm characterised by the presence of erythroderma, lymphadenopathy, and neoplastic, cerebriform T-lymphocytes in the blood. Sézary syndrome is an aggressive disease.

**Long definition:** Sézary syndrome is a rare variant of cutaneous T-cell lymphoma characterized by erythroderma, blood involvement and a poor prognosis. Neoplastic lymphocytes are typically mature T-helper cells with cerebriform nuclei. Criteria for the diagnosis of Sézary syndrome include the demonstration of a peripheral blood T-cell clone by molecular or cytogenetic methods; an expanded CD4+ population resulting in a CD4:CD8 ratio > 10, and immunophenotypic abnormalities such as absent expression of T-cell antigens (CD2, CD3, CD4 and/or CD5). Sézary syndrome is distinguished from erythrodermic mycosis fungoides by the presence of a clonal T-cell population in the peripheral blood, a criterion which also distinguishes it from reactive disorders that exhibit erythroderma and circulating cells with cerebriform nuclei.