Connective Tissue Diseases and Vasculitis
Connective tissue disease patterns
Learn the pattern, not the single antibody. Systemic lupus erythematosus is a multisystem disease with mucocutaneous, articular, renal, haematological and neurological features; anti-dsDNA and anti-Smith are specific, and complement falls during active disease. Systemic sclerosis divides into limited (CREST: calcinosis, Raynaud, oesophageal dysmotility, sclerodactyly, telangiectasia; anti-centromere) and diffuse (anti-topoisomerase/Scl-70, early lung fibrosis, renal crisis). Sjögren syndrome causes sicca symptoms with anti-Ro/La and carries lymphoma risk. Polymyositis and dermatomyositis cause proximal weakness with raised creatine kinase; dermatomyositis has a characteristic rash (Gottron papules, heliotrope) and is paraneoplastic in adults. Mixed connective tissue disease has anti-U1-RNP with overlapping features and pulmonary hypertension risk.
Vasculitis by vessel size
- Large: giant cell arteritis (age over 50, headache, jaw claudication, visual loss; give steroids immediately, biopsy does not wait) and Takayasu arteritis (young women, pulseless upper limbs).
- Medium: polyarteritis nodosa (microaneurysms, hepatitis B association) and Kawasaki disease in children.
- Small: ANCA-associated (granulomatosis with polyangiitis, microscopic polyangiitis, eosinophilic granulomatosis with polyangiitis), IgA vasculitis (palpable purpura, abdominal pain, nephritis), cryoglobulinaemic vasculitis.
Traps
- A positive ANA alone is not lupus.
- Suspected giant cell arteritis with visual symptoms is an emergency: treat first, investigate after.
- Raynaud phenomenon with puffy fingers and positive ANA should prompt assessment for scleroderma spectrum disease.
Rule of thumb
Localise the vessel size and organ pattern first; the antibody panel confirms, it does not diagnose.