A Rare Presentation of Cutaneous Pseudolymphoma as a Preleukaemic State

A patient presented with progressive and unresponsive erythematous rash affecting his trunk and limbs over a period of 5 years. His systemic examination and extensive relevant investigations were normal throughout this period. Skin biopsies at different times showed features of annular erythema, cutaneous pseudolymphoma and sub-acute dermatitis. Five years after the initial presentation, he developed erythroderma, leonine facies, lymphadenopathy and peripheral lymphocytosis. CT chest and abdomen revealed generalised lymphadenopathy. Skin biopsy and immunophenotyping was suggestive of Sezary syndrome. However, peripheral blood smear examination was highly suggestive of T-cell prolymphocytic leukaemia (TPLL). Subsequent molecular genetic analysis was consistent with TPLL. To the best of our knowledge, there are no reports of cutaneous pseudolymphoma transforming to TPLL in the literature. The long indolent course of apparently benign skin disease before transforming into TPLL appears to be unique in our case. An analogy can be made with cutaneous T-Cell lymphoma both in terms of the difficulty in proving the diagnosis-needing multiple skin biopsies, and in the possible link between cutaneous and systemic disease. TPLL should be considered as a rare cause of erythroderma, which may clinically and histologically mimic Sezary syndrome.