Background/Purpose:

Anti-Th/To antibody is an autoantibody associated with systemic sclerosis (SSc), occurring in 5-10% of patients. To date, only relatively small case series have described the clinical associations of this autoantibody, as commercial testing has not been readily available. Thus, the long-term clinical features and outcomes of patients with anti-Th/To antibody is not known. The objective of this study was to further characterize the clinical associations and mortality risk of SSc patients who are anti-Th/To positive.

Methods:

We performed a case-control study. Eligible patients were identified from consecutive new SSc patietns seen at a large US SSc Center between 1980-2015. Cases were found to be anti-Th/To antibody positive by immunoprecipitation. Each case was matched to the next two consecutive SSc patients seen in clinic (2:1 match). Descriptive statistics, Kaplan-Meier and Cox proportional hazards was performed using SAS 9.4.

Results:

199 Th/To-positive SSc patients were identified and matched to 398 controls. The mean age of the entire population was 51.6 ± 14.1 years, 78% female and 92% Caucasian. Th/To positive patients were more frequently Caucasian, had long disease duration at evaluation and more often presented with SSC sine scleroderma (see Table 1). At baseline Th/To patients were more frequently found to have pulmonary hypertension, but less frequent joint involvement. There was no difference in rate of interstitial lung disease (ILD) found on radiographic imaging (Table 1).

As of last follow-up 41 (21%) of Th/To positive patients had developed PAH compared to 43 (11%; p=0.001). Twenty-five (13%) Th/To positive patients had developed PH secondary to ILD compared to 33 (8%) controls (p= 0.10), with no difference in frequency of ILD. Despite the greater frequency of PH in cases, 5-year cumulative survival was not any different between Th/To positive patients (29%) and controls (28%; p=0.90), even after adjustment for age and gender.

Conclusion:

This is the largest cohort of Th/To antibody positive SSc patients for which there is long-term follow-up for clinical features and survival data available. Compared to other SSc patients, anti-Th/To patients develop higher rates of PAH. Cumulative 5-year survival is not reduced in Th/To patients, likely reflecting advances in PAH management. SSc patients should be routinely screened for the Th/To antibody, with consideration of appropriate screening for PAH.

Table 1: Characteristics of Anti-Th/To Positive Patients and Controls at First SSc Center Visit

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/long-term-survival-and-follow-up-of-anti-thto-antibody-positive-systemic-sclerosis-patients/