A Detailed Analysis of the Distribution, Morphology, and Histopathology of Complex Purpura in Hospitalized Patients: A Case Series of 68 Patients.

Abstract Background Purpura in inpatients commonly leads to dermatologic consultation. The differential diagnosis is broad and algorithms are intricate. Objective We evaluated inpatient consultations for complex purpura to document the most common diagnoses and to validate the true diagnostic utility of histopathology, clinical morphology, and distribution. Methods We reviewed a case series of 68 inpatients over a four-year period with a dermatologic consultation for purpura and biopsy findings of vasculitis or microvascular occlusion. Results Key features of complex purpura are non-branching vs. branching (retiform), morphology, dependent vs. acral/generalized distribution, and leukocytoclastic vasculitis (LCV) vs. microvascular occlusion (with emphasis on depth of involvement). Dependent non-branching purpura with only superficial vessels involved by LCV was most often due to IgA vasculitis or cutaneous single-organ small vessel vasculitis. In contrast, deeper involvement by LCV was suggestive of systemic disease (e.g. ANCA-associated vasculitis). Branching purpura was concerning, with greater than 90% sensitivity and specificity for microvascular occlusion and associated high mortality (∼50%). The majority of patients who died had acral branching lesions. Limitations Small sample size, inpatients at a tertiary care center, and retrospective nature are some limitations. Conclusion Non-branching, dependent purpura corresponded to LCV, with the most common diagnoses being IgA vasculitis or skin-limited small vessel vasculitis; cases with deep involvement often did have systemic diseases. In this series, branching purpura was due to microvascular occlusion, rather than medium-vessel vasculitis, and had associated high mortality.