# Sezary Syndrome > Sezary syndrome for NEET-PG Dermatology covers erythroderma, Sezary cells, blood staging, photopheresis and mogamulizumab in this leukaemic lymphoma. - Canonical URL: https://prepelephant.com/topics/neet-pg/dermatology/sezary-syndrome - Exam / course: NEET-PG · Subject: Dermatology - Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team - First published: 2026-10-14 - Last updated: 2026-10-14 - Reference basis: Fitzpatrick's Dermatology; IADVL Textbook of Dermatology - How to cite: "Sezary Syndrome", PrepElephant, https://prepelephant.com/topics/neet-pg/dermatology/sezary-syndrome ## Direct answer Sezary syndrome is the leukaemic variant of cutaneous T-cell lymphoma, defined by generalised erythroderma, a clonal population of Sezary cells in the blood and intense pruritus. Staging uses a blood threshold of at least 1000 Sezary cells per microlitre with a matching T-cell clone. Unlike mycosis fungoides, which starts as patches and plaques, it presents with diffuse red, scaly skin and carries a worse prognosis. ## What you must remember - **Defining feature:** erythroderma, meaning redness over more than 80 per cent of the body surface, together with circulating malignant T cells. - **Sezary cell:** a small to medium atypical CD4-positive T lymphocyte with a cerebriform, folded nucleus, visible on a peripheral blood smear and the morphology examiners expect you to name. - **Immunophenotype:** CD4-positive cells that often lose CD7 and CD26 on flow cytometry, with a clonal T-cell receptor gene rearrangement. - **Clinical features:** erythroderma, generalised lymphadenopathy, palmoplantar hyperkeratosis, alopecia, ectropion and nail dystrophy. - **Staging:** blood involvement at the B2 level places the patient in stage IV of the TNMB system, which governs prognosis and therapy. - **Skin biopsy:** histology in established erythroderma can be nonspecific, so blood and nodal findings usually carry the diagnosis. - **Treatment:** extracorporeal photopheresis, mogamulizumab (an anti-CCR4 antibody), methotrexate and, in selected cases, total skin electron beam therapy. - **Prognosis:** survival is poor compared with mycosis fungoides and falls further with advanced nodal or visceral disease. ## A staged work-up from red skin to diagnosis A patient with long-standing red, itchy skin and no obvious trigger needs systematic exclusion before lymphoma is named. The sequence moves from skin to blood to lymph nodes, and each step narrows the differential. 1. **Exclude benign causes:** take a full drug history and consider psoriasis, atopic dermatitis and pityriasis rubra pilaris as the usual mimics. 2. **Examine the blood:** a Wright-stained smear and flow cytometry look for Sezary cells and an aberrant CD4-positive phenotype. 3. **Count the cells:** at least 1000 Sezary cells per microlitre with a matching clone places the patient in the B2 category. 4. **Assess the nodes:** palpate for lymphadenopathy and biopsy any enlarged node to assign the N category. 5. **Image for visceral disease:** CT of the chest, abdomen and pelvis stages organ involvement before therapy is chosen. 6. **Stage and treat:** combine the T, N, M and B categories to choose between skin-directed therapy and systemic agents. ## Where the exam tries to catch you Stems hinge on separating the leukaemic variant from look-alike erythrodermas and from early mycosis fungoides. - **Trap:** calling every red, scaly body erythroderma of psoriasis. **Correct:** suspect Sezary syndrome when erythroderma comes with lymphadenopathy, a clonal T-cell population and Sezary cells, so ask for a blood smear and flow cytometry. - **Trap:** choosing a skin biopsy as the only test. **Correct:** biopsy alone is often nonspecific in erythroderma; the blood and node findings carry the diagnosis. - **Trap:** treating Sezary syndrome like early mycosis fungoides with topical steroids. **Correct:** it is a systemic leukaemic disease that needs systemic therapy or photopheresis. ## Frequently asked questions ### Which blood finding defines Sezary syndrome in staging? Blood involvement at the B2 level defines Sezary syndrome in the TNMB staging system. It means at least 1000 Sezary cells per microlitre with a matching T-cell clone, and that threshold separates Sezary syndrome from mycosis fungoides, where circulating malignant cells are scant. ### What is the immunophenotype of Sezary cells? Sezary cells are typically CD4-positive helper T cells. Flow cytometry often shows loss of CD7 and CD26 within an aberrant clonal population, and this supports the diagnosis of Sezary syndrome, although the phenotype alone is not enough. ### What is mogamulizumab used for in Sezary syndrome? Mogamulizumab is an anti-CCR4 monoclonal antibody that targets the chemokine receptor expressed on malignant T cells in Sezary syndrome. It is a systemic option for advanced disease when skin-directed treatments are insufficient. ### How does extracorporeal photopheresis work in Sezary syndrome? Extracorporeal photopheresis removes part of the patient's blood, exposes the white cells to a photosensitising drug and UVA light, and returns them to the circulation. The benefit is thought to come from an immune response against the malignant clone, and the therapy is a standard option in specialist centres. ### How does Sezary syndrome differ from psoriatic erythroderma? Sezary syndrome shows a clonal population of atypical T lymphocytes in the blood and often in lymph nodes. Psoriatic erythroderma is a clinical diagnosis that usually has a history of plaque psoriasis and no circulating clone, so a blood smear and flow cytometry settle an unclear case.