T-cell prolymphocytic leukaemia (T-PLL) is a rare, aggressive neoplasm of mature T lymphocytes. The small cell variant occurs in approximately 20% of T-PLL patients. The skin findings of leukaemia consist of leukaemia-specific skin lesions, which are infiltrated by leukaemia cells, and non-specific lesions. The former type of lesion signifies leukaemia cutis. Leukaemia cutis presents clinically as tumours, nodules, or patches on the scalp, face and trunk. We report here an 82-year-old Korean male patient who presented with erythema, erosion, vesicles, and scales on his entire body with no clear underlying cause. He had been treated with oral retinoids, steroids, and phototherapy for the diagnoses of drug eruption, pityriasis rubra pilaris, and exfoliative dermatitis at other hospitals. We suspected a hidden malignancy and diagnosed small cell variant T-PLL through blood and bone marrow examination. A skin biopsy specimen showed dense infiltration of small lymphocytes in the dermis. Most of the atypical lymphocytes stained positively with CD markers such as CD2, CD3, CD4, CD5, CD7 and CD8, thereby confirming the presence of leukaemia cells. To our knowledge, this is the first case of generalized leukaemia cutis from small cell variant of T-PLL presenting with exfoliative dermatitis over the whole body.