Purpuric Lesions

Abstract

Purpuric lesions, probably more than any other skin lesion morphology, carry a grave prognosis not shared by most other skin eruptions. The pathogenetic mechanisms of purpura may be divided based on various criteria: (1) systemic (immune complex vasculitis) versus cutaneous (solar purpura); (2) platelet related (ITP) versus coagulation abnormalities (proteins C and protein S, antiphospholipid antibody syndrome); (3) abnormalities inside the blood vessel (thrombosis) versus in the blood vessel wall (hyalinizing vasculitis) versus the vessel dermal supportive tissue (scurvy).

In the histological evaluation of a biopsy specimen from a purpuric lesion, attention is given to: (1) the type of infiltrate; (2) whether the pathology is limited to the superficial vascular plexus or in addition involves the deeper vascular plexus; (3) inflammation of blood vessel walls versus vascular occlusion; and (4) composition of the occluding material.