Anti-Scl-70 (anti-topoisomerase I) antibody
An autoantibody that is highly specific for systemic sclerosis (scleroderma). A positive result in someone with skin thickening and Raynaud's strongly supports the diagnosis and flags a higher risk of lung and kidney involvement, so it helps guide monitoring.
What it measures
Anti-Scl-70, also called anti-topoisomerase I, is an autoantibody against the enzyme topoisomerase I, and it is one of the antibodies checked after a positive ANA when a connective-tissue disease is suspected. Its importance is that it is highly specific for systemic sclerosis (scleroderma) — a disease in which the immune system drives excess collagen and scarring (fibrosis), thickening and tightening the skin and, importantly, sometimes affecting internal organs. A positive anti-Scl-70 rarely appears outside scleroderma, so in someone with the right features — skin thickening, Raynaud's phenomenon, puffy fingers — it strongly supports the diagnosis. It is particularly associated with the diffuse form of the disease (more widespread skin involvement) and, clinically most important, with a higher risk of scarring of the lungs (interstitial lung disease) and of a kidney complication (scleroderma renal crisis). That prognostic link is why the antibody matters: identifying it prompts closer monitoring of the lungs and kidneys. It is not a measure of disease activity over time, but a marker that helps classify the disease and its risks, interpreted by a rheumatologist.
What a high value can mean
- Systemic sclerosis (scleroderma) — highly specific; a positive result strongly supports the diagnosis in someone with typical features.
- Diffuse cutaneous scleroderma — particularly associated with the more widespread skin form.
- Higher risk of lung scarring (interstitial lung disease) — an important reason to monitor.
- Higher risk of scleroderma renal crisis — a kidney complication to watch for.
High Anti-Scl-70 (anti-topoisomerase I) antibody: full guide
What a low value can mean
- Negative — the expected result; makes anti-Scl-70-associated scleroderma unlikely, though other scleroderma antibodies (such as anticentromere) can still be positive.
When to discuss with a doctor
Anti-Scl-70 is tested when systemic sclerosis is suspected — for example with Raynaud's phenomenon, skin thickening or puffy fingers and a positive ANA. A positive result is highly specific and strongly supports scleroderma in the right clinical setting, and because it flags a higher risk of lung and kidney involvement, it prompts a rheumatologist to arrange closer monitoring (such as lung function tests and blood-pressure and kidney checks). The diagnosis and the monitoring plan are made by the specialist, using the whole picture rather than the antibody alone. Mediora.AI can surface a positive anti-Scl-70 alongside ANA so the scleroderma pattern is visible in your results, but confirming the diagnosis and managing the organ risks belongs with your doctor and rheumatologist.