A 55-year-old man has progressive erythroderma, generalised pruritus, and circulating atypical lymphocytes with convoluted cerebriform nuclei. Skin biopsy shows epidermotropism of atypical T cells forming intraepidermal collections. Blood shows more than 1000 atypical (Sézary) cells per cubic millimetre with an altered CD4:CD8 ratio and loss of CD7. Which diagnosis fits these findings best?

• A Sézary syndrome, the leukemic variant of mycosis fungoides ✓
• B Adult T-cell leukemia/lymphoma with HTLV-1 seropositivity expected
• C Peripheral T-cell lymphoma, NOS, with secondary skin involvement
• D T-cell prolymphocytic leukaemia with marked lymphocytosis

Explanation

Sézary syndrome represents the erythrodermic, leukemic form of cutaneous T-cell lymphoma. Diagnostic features include erythroderma, Pautrier microabscesses on biopsy, and blood involvement defined by a Sézary count above 1000 per cubic millimetre with a raised CD4:CD8 ratio above 10 or CD7 loss. Adult T-cell leukemia/lymphoma requires clonal HTLV-1 proviral integration and shows lobulated rather than cerebriform nuclei. T-cell prolymphocytic leukaemia lacks epidermotropic skin infiltrates and Pautrier microabscesses.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

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Written and medically reviewed by the StethoPrep medical team.