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Vasculitis is the term to describe heterogeneous disorders with presence of inflammation of blood vessel walls. Patients with vasculitis can present with various clinical findings based on the size of affected vessels. Vasculitis is suggested by a spectrum of clinical and laboratory features.

When to suspect vasculitis

  • Constitutional symptoms (e.g., fever, weight loss, persistent fatigue).
  • Multiple organ involvement.
  • Pathognomonic signs of vasculitis (e.g., Mononeuritis multiplex, brain infarction, hypertension, pulmonary hemorrhage, stroke in the young, palpable purpura, livedo reticularis).

Step by step approach to suspected primary vasculitis.

Step 1: Exclude vasculitis mimics (e.g., infective endocarditis, anti-phospholipid syndrome, thrombotic thrombocytopenic purpura, paraneoplastic syndrome).

Step 2: Exclude secondary vasculitis. 

  • Infections: hepatitis, HIV, CMV, mycobacteria, mycoplasma, COVID-19
  • Autoimmune: SLE, inflammatory bowel disease, juvenile dermatomyositis 
  • Malignancies: lymphoma, lymphoproliferative syndrome
  • Medication: serum sickness, amphetamines, cocaine 

Step 3: Defining the primary vasculitis syndrome.

Step 4: Classify type of vasculitis based on clinical phenotypes and size of affected vessels (Small/Medium/Large) as described in the Table below:

Large blood vessels

Medium sized blood vessels

Small blood vessels


Subcutaneous nodules

Palpable purpura

Pulse absence/unequal

Deep ulcers

Infiltrated erythema


Livedo reticularis

Urticarial vasculitis

Asymmetric blood pressure

Digital gangrene

Superficial ulcers


Mononeuritis multiplex



Erythema nodules

Pulmonary haemorrhage



Gastric colic


Classification of primary childhood vasculitis

Large vessel vasculitis

Takayasu arteritis

Medium-sized vessel vasculitis

Polyarteritis nodosa


Kawasaki disease*

Small-sized vessel vasculitis


ANCA-associated vasculitis


-        Granulomatous

Granulomatosis with polyangiitis (GPA); former name: Wegener’s granulomatosis

Eosinophilic granulomatosis with polyangiitis (EGPA); former name: Churg-Strauss syndrome

-        Non-granulomatous

Microscopic polyangiitis (MPA)

Other small-sized vessel vasculitis

IgA vasculitis (Henoch Schönlein purpura)*

Variable-sized vessel vasculitis

Behcet’s disease 

*Most common vasculitis in children

Abnormal laboratory features may include:

  • Increased acute-phase reactants (ESR, CRP).
  • Anaemia, Leukocytosis, Eosinophilia (EGPA).
  • Antineutrophil cytoplasmic antibodies (ANCA).
    • Most  (75-95%) patients with GPA are c-ANCA or anti-proteinase 3 Antibodies positive
    • Many (40-80%) patients with EGPA, MPA are p-ANCA or anti-myeloperoxidase antibodies positive
  • Elevated factor VIII - related antigen (von Willebrand factor).
  • Haematuria and active urine sediment.
  • Histopathology can be performed in medium or small-sized vessel vasculitis. 
  • Imaging study (e.g., MRAngiogram, CTAngiogram) may be useful to diagnose medium or large-sized vessel vasculitis. US or CT abdomen may be performed in complicated cases of HSP.

Useful resources to demonstrate skin lesions in vasculitis: 

Welcome to Skin Deep - Skin Deep (dftbskindeep.com)


The photograph below shows a 'target lesion' of skin vasculitis 

The photograph below shows ischaemic fingers in vasculitis with antiphospholipid syndrome