T-cell prolymphocytic leukemia (T-PLL) is a rare and aggressive post-thymic malignancy that is characterized by the proliferation of small- to medium- sized prolymphocytes. The classic clinical features of T-PLL are lymphocytosis, lymphadenopathy, hepatosplenomegaly, and skin lesions. Skin involvement varies clinically from diffuse infiltrated erythema. Infiltration is localized to the face and ears, nodules, and erythroderma. We present a case of small cell variant of T-PLL in a patient who presented with unusual cutaneous manifestations of acquired palmoplantar keratoderma (PPK) followed by diffuse erythematous infiltrated papules and plaques involving the trunk. When the etiology of acquired PPK is not clear, the physician should consider the possibility of an underlying malignant disease. In this case, the diagnosis of T-PLL was subsequently confirmed by laboratory and cytological findings, as well as by the immunophenotyping of leukemic cells in skin biopsy. Since paraneoplastic acquired PPK may be the initial evident sign of malignancy, the physician's awareness of this manifestation may be crucial for early diagnosis and treatment. Our case emphasizes the importance of accurate evaluation of skin lesions and early skin biopsy in the diagnosis of some hematological malignancies.