# Redefining Systemic Sclerosis Classification: Anti-Topoisomerase Antibody as a Superior Predictor of Interstitial Lung Disease and Skin Progression Compared to Limited Cutaneous Systemic Sclerosis Subset

## TL;DR

This study shows that anti-topoisomerase antibody-positive limited cutaneous systemic sclerosis has a similar risk of lung disease and skin progression as diffuse cutaneous systemic sclerosis but better outcomes than antibody-negative cases.

## Contribution

The study identifies anti-topoisomerase antibody as a better predictor of disease progression than the limited cutaneous classification in systemic sclerosis.

## Key findings

- ATA-positive lcSSc patients developed interstitial lung disease faster than dcSSc-negATA patients.
- Time to reach max-mRSS was shorter in lcSSc-posATA compared to dcSSc-negATA.
- ATA-positive lcSSc had a better prognosis than dcSSc-posATA.

## Abstract

Background: Currently, no information exists on the clinical course of anti-topoisomerase I antibody (ATA)-positive limited cutaneous systemic sclerosis (lcSSc). We aimed to evaluate the incidence of and time to the development of interstitial lung disease (ILD), pulmonary hypertension (PHT), scleroderma renal crisis (SRC), and maximal modified Rodnan skin score (max-mRSS) in patients with lcSSc and dcSSc, with and without ATA. Methods: This cohort study included 522 patients with systemic sclerosis (SSc). The incidence of and time to the development of ILD, PHT, SRC, and max-mRSS were assessed. Results: ATA-positive dcSSc (dcSSc-posATA) was the most common presentation among Thai patients (321 cases; 61.5%). The median time to the development of ILD was shorter than that in lcSSc-posATA, comparable to that in dcSSc-posATA (1.0 vs. 1.8 years, p = 0.21), and shorter than that in ATA-negative dcSSc (dcSSc-negATA) (1.0 vs. 4.8 years, p = 0.001). The time to max-mRSS in lcSSc-posATA was comparable to that in dcSSc-posATA (p = 0.17) but shorter than that in dcSSc-negATA (p < 0.001). Conclusions: Patients with lcSSc-posATA had a similar risk of ILD development and time to reach max-mRSS as those with dcSSc, regardless of the presence of ATA, but had earlier ILD development and max-mRSS compared to those with dcSSc-negATA. Their prognosis appeared to be better than that of dcSSc-posATA.