A detailed analysis of the distribution, morphology, and histopathology of complex purpura in hospitalized patients: A case series of 68 patients

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 during a 4-year period with a dermatologic consultation for purpura and biopsy findings of vasculitis or microvascular occlusion.

Results: Key features of complex purpura are nonbranching (round) versus branching (retiform) morphology, dependent versus acral or generalized distribution, and leukocytoclastic vasculitis versus microvascular occlusion (with emphasis on depth of involvement). Dependent nonbranching purpura with only superficial vessels involved by leukocytoclastic vasculitis was most often due to IgA vasculitis or cutaneous single-organ small-vessel vasculitis. In contrast, deeper involvement by leukocytoclastic vasculitis was suggestive of systemic disease (eg, antineutrophil cytoplasmic antibody-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: Nonbranching dependent purpura corresponded to leukocytoclastic vasculitis, with the most common diagnoses being IgA vasculitis or skin-limited small-vessel vasculitis; patients with deep involvement often had systemic diseases. In this series, branching purpura was due to microvascular occlusion rather than medium-vessel vasculitis, and had associated high mortality.