Systemic Sclerosis - Skin and Vascular Features
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Direct answer
Systemic sclerosis is an autoimmune disease marked by fibrosis of the skin and internal organs, with Raynaud phenomenon often preceding skin change. Skin involvement is limited or diffuse, with thickening confined to the distal limbs and face in limited disease but extending proximal to the elbows and knees and onto the trunk in diffuse disease. Anticentromere antibodies are typical of limited disease, whereas anti-topoisomerase I antibodies mark diffuse disease.
What you must remember
- Limited cutaneous: skin thickening confined to the face and the limbs distal to the elbows and knees, with a long Raynaud history.
- CREST features: calcinosis, Raynaud phenomenon, oesophageal dysmotility, sclerodactyly and telangiectasia, typical of limited disease.
- Diffuse cutaneous: thickening spreads proximal to the elbows and knees and may involve the trunk, with early visceral disease.
- Autoantibodies: anticentromere in limited disease, and anti-topoisomerase I (Scl-70) or anti-RNA polymerase III in diffuse disease.
- Raynaud: triphasic colour change of white pallor, blue cyanosis and red reactive hyperaemia on rewarming.
- Digital complications: pitting scars, digital ulcers, sclerodactyly and subcutaneous calcinosis.
- Assessment: the modified Rodnan skin score grades skin thickening, and nailfold capillaroscopy shows giant capillaries with capillary loss.
- Renal crisis: abrupt hypertension and oliguria, a medical emergency in which ACE inhibitors are the key therapy.
Limited versus diffuse disease in practice
Limited and diffuse disease are separated by how far the skin thickening extends, and that boundary predicts which organs are at risk. The table sets out the differences examiners test most often, row by row.
| Feature | Limited cutaneous | Diffuse cutaneous |
|---|---|---|
| Skin extent | Fingers, face and distal limbs | Proximal to elbows and knees, trunk involved |
| Raynaud history | Often precedes skin change by years | Usually a shorter lead time |
| Typical antibody | Anticentromere | Anti-topoisomerase I, anti-RNA polymerase III |
| Visceral disease | Late, notably pulmonary hypertension | Early, including renal crisis and lung fibrosis |
| Usual course | Slower, often milder | Faster, more organ-threatening |
Lung and renal involvement carry most of the mortality, so the extent of skin disease guides how intensively organs are screened. Pulmonary hypertension in limited disease can appear long after the skin changes, which is why echocardiography is repeated during follow-up. Antibody status is therefore recorded at diagnosis, because it helps predict which organ complications to screen for.
Where candidates lose marks
Questions on this topic test whether candidates recognise the early Raynaud clue and screen the organs that matter.
- Trap: calling any Raynaud phenomenon in a young woman systemic sclerosis without further evaluation Correct: primary Raynaud is far commoner, and sclerosis is suspected with digital ulcers, capillary changes or antibodies.
- Trap: treating scleroderma renal crisis with routine antihypertensives alone Correct: ACE inhibitors are the key therapy, and early treatment prevents irreversible renal failure.
- Trap: judging severity from skin thickening alone Correct: the modified Rodnan skin score measures skin extent, and internal organs need separate screening such as lung function and echocardiography.
Frequently asked questions
What distinguishes limited from diffuse systemic sclerosis?
Limited cutaneous systemic sclerosis involves the face and skin distal to the elbows and knees, while diffuse cutaneous disease extends proximal to the elbows and knees and may involve the trunk. Anticentromere antibodies are typical of the limited form.
Which antibody is characteristic of limited systemic sclerosis?
Anticentromere antibodies are characteristic of limited cutaneous systemic sclerosis and are associated with a long Raynaud history and later pulmonary hypertension. Anti-topoisomerase I antibodies, by contrast, mark diffuse disease with early visceral involvement.
What is the modified Rodnan skin score used for?
The modified Rodnan skin score grades skin thickening across 17 body areas, giving a semi-quantitative measure of skin involvement. It is used in trials and follow-up to track disease extent over time.
Why is scleroderma renal crisis treated as an emergency?
Scleroderma renal crisis presents with sudden hypertension, oliguria and rising creatinine, and early ACE inhibitor therapy can prevent irreversible renal failure. It is most typical of early diffuse cutaneous disease.
What does nailfold capillaroscopy show in systemic sclerosis?
Nailfold capillaroscopy shows giant capillaries, microhaemorrhages and capillary loss, which support systemic sclerosis over primary Raynaud phenomenon. Primary Raynaud phenomenon typically shows a normal capillary pattern.