AKT · Dermatology/Reactive & systemic signs

Purpura and petechiae

Extravasated blood in the skin (non-blanching)

Overview

Non-blanching skin discolouration from extravasated blood: petechiae (1 cm). The two questions are: is it PALPABLE (vasculitis) or flat (thrombocytopenia/clotting), and is the child/adult systemically unwell (meningococcal sepsis is the emergency).

Recognise

NON-BLANCHING red-purple macules/papules (the glass/tumbler test does not blanch them)
Palpable purpura = small-vessel vasculitis (e.g. Henoch-Schönlein/IgA vasculitis, leukocytoclastic vasculitis); flat purpura/petechiae = platelet or clotting problem
Distribution clues — dependent/buttocks-and-legs in IgA vasculitis; widespread in thrombocytopenia

Red flags

A non-blanching rash in an unwell/febrile patient (especially a child) = MENINGOCOCCAL SEPSIS until proven otherwise → immediate benzylpenicillin and emergency transfer

Differentials & how to tell them apart

Meningococcal septicaemiathe must-not-miss — non-blanching purpura + fever/unwell → emergency antibiotics, do not wait

Immune thrombocytopenia (ITP)flat petechiae/purpura, isolated low platelets, otherwise well

Henoch-Schönlein purpura (IgA vasculitis)palpable purpura on buttocks/legs + arthralgia + abdominal pain + nephritis in a child

Senile/steroid purpurafragile vessels, dorsal hands/forearms in the elderly or on steroids — non-palpable

Clinical image

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Purpura and petechiae — clinical imagesDermNet

Investigations

Urgent: FBC (platelets), coagulation screen, blood film, CRP and septic screen if unwell. Palpable purpura → vasculitis work-up (urinalysis for renal involvement, ANCA, complement); IgA vasculitis is clinical.

Management

Exclude/treat meningococcal sepsis first; then investigate and treat the underlying cause

1Confirm non-blanching (glass test). If the patient is febrile/unwell → treat as MENINGOCOCCAL SEPSIS: immediate benzylpenicillin and emergency transfer.Gate: A non-blanching rash in an unwell or febrile patient is meningococcal sepsis until proven otherwise — give benzylpenicillin and transfer NOW; do not wait for investigations
2Well patient → classify palpable (vasculitis — check urine/renal function, IgA vasculitis is usually self-limiting) vs flat (FBC/film/clotting → ITP, clotting disorder, anticoagulant, senile purpura) and treat accordingly.

IM/IV benzylpenicillin — immediately if meningococcal sepsis is suspected — before transfer

Treat the underlying cause — ITP, vasculitis, anticoagulant effect, etc.

Key points

Two reflexes: do the glass test, and in any unwell patient with non-blanching spots assume meningococcus and give penicillin. Palpable vs flat splits vasculitis from a platelet/clotting cause.

Monitor & prognosis

Platelets/clotting, renal involvement (vasculitis), sepsis parameters.

Depends entirely on the cause — from benign senile purpura to life-threatening sepsis.

Source: NICE CKS; NICE NG51 (sepsis)