Pigmented purpuric dermatosis: Ten years of experience in a tertiary hospital and awareness of mycosis fungoides in differential diagnosis

Background: Pigmented purpuric dermatoses (PPD) can clinically mimic many diseases. Histopathology provides a definitive diagnosis. The aim of the study is to reveal the features of patients with PPD and to determine the disease frequency in the differential diagnosis, especially mycosis fungoides (MF). Methods: We retrospectively reviewed records of patients with PPD admitted to our hospital from January 2010 to May 2019. We studied the histopathological features of 127 patients, and performed pattern analysis on cases with a confirmed histopathologic diagnosis of PPD. Among the cases presenting with clinical features of PPD, but displaying different histopathological diagnoses, we focused on MF and tried to clarify the features of PPD-like MF. Results: Overall, 389 patients were admitted to our hospital with PPD symptoms. Of them, 262 patients were diagnosed clinically and a histopathological examination was performed in 127 patients. Of 127, 87 were diagnosed with PPD, and in the remaining 40, non-specific features (9.4%), vasculitis (6.2%), pityriasis rosea (4.7%), MF (3.9%), suspected-MF (1.5%), and other dermatoses (%5.5) were detected. The biopsy findings of two patients showed PPD, but during follow-up, the diagnosis of MF was established. Conclusions: MF should be included in the differential diagnosis of PPD cases presenting with longstanding and widespread involvement.