Distinctly different purpura on different arms

Abstract

A 44-year-old woman, with severe lupus-associated renal failure needing haemodialysis, was admitted with purpura on both arms. Only the eruptions on her left arm were painful. Blood test results showed low platelets (6×109 per L), reduced complement activity, and high concentrations of antibodies to double-stranded DNA and ribonucleotide protein. Examination showed purpura aff ecting both arms, with a distinctly asymmetric appearance. Closer inspection of the right arm showed fl at, painless confl uent ecchymosis (fi gure A). By contrast, the left arm showed haemorrhagic vesicular (fi gure B) eruptions in a dermatomal pattern (fi gure C). Histological examination of a sample from one of the vesicles revealed multinucleated giant cells supportive of herpes zoster. Both the left-sided arm pain and haemorrhagic vesicles responded well to valaciclovir treatment. Skin bruising (ecchymosis) can result from several mechanisms, giving rise to distinct patterns and terminology. Purpura refers broadly to the spectrum of patterns and mechanistic processes that arise from extravasation of blood into skin. When purpuric eruptions are diminutive or pinpoint in size, they are termed petechiae. Purpura can result from dangerously low platelet concentrations (eg, idiopathic thrombocytopenic purpura), impaired platelet function (eg, eff ect of aspirin), congenital or acquired clotting disorders (eg, haemophilia or disseminated intravascular coagulation), or from an intense infl ammatory or structural injury to the blood vessel wall (eg, vasculitis vs scurvy). Various patterns include palpable purpura overlying the buttocks and legs (eg, Henoch-Schonlein purpura), involvement of palms and soles (eg, disseminated meningococcal or gonococcal infection), and a dermatomal distribution arising from concomitant herpes zoster infection and profound thrombocytopenia (fi gure C). Lancet 2009; 374: 1010