Abstract

Pigmented purpuric dermatosis (PPD) is a rare condition characterized by purpuric and rust-colored macules, patches, and thin plaques on the lower extremities, with biopsy findings of a lymphocytic infiltrate involving the post capillary venules, red blood cell extravasation, and hemosiderin deposition. Variants are distinguished by spongiotic and lichenoid histopathologic features and/or clinical morphology, such as annular lesions or pinpoint macules simulating cayenne pepper. PPD typically involves the lower legs. Widespread lesions or lesions prominently above the legs have rarely shown histopathologic features of mycosis fungoides (MF). The progression of PPD to MF is rare and unpredictable. Because PPD may be monoclonal, it is considered a T-cell dyscrasia, reflecting the relationship with MF. Much overlap exists between PPD and MF. However identical clones, cerebriform atypia, upper spinous lymphocytes, CD4 phenotype, and widespread lesions favor MF and drug-induced pseudolymphoma should be excluded. A 72-year-old woman with several years of a non-pruritic rash on her thighs, which eventually progressed to her abdomen. The rash was steroid-responsive, although she was non-compliant. Examination revealed broad purpuric, violaceous, and rust-colored patches on her thighs and abdomen. Biopsies from the thigh and abdomen revealed an atrophic epidermis and a band-like lymphocytic infiltrate demonstrating epidermotropism characterized by beading of the base of the epidermis and peppering of the epidermis. Focal interface changes were also noted. The dermis showed papillary dermal fibroplasia, red blood cell extravasation, hemosiderin dispersion and the lymphocytes were CD4 predominant. PCR documented T-cell receptor monoclonal rearrangements, confirming MF. After combining all histopathological, clinical and laboratory findings, she was eventually diagnosed as PPDMF. She has responded to UV treatment given recently.

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