Anti-th/to-positivity in a cohort of patients with idiopathic pulmonary fibrosis.

Objective: To evaluate the presence and clinical relevance of anti-Th/To-positivity in patients with idiopathic pulmonary fibrosis (IPF).
Methods: Antinuclear antibody (ANA) testing was performed in 285 patients with a clinical diagnosis of IPF and surgical lung biopsy-proven usual interstitial pneumonia. Twenty-five subjects (8.8%) were found to have a positive ANA with a nucleolar-staining pattern and were followed for 10 years. Immunoprecipitation analysis indicated that 13 of the 25 subjects had autoantibodies against Th/To antigen.
Results: All subjects presented with worsening dyspnea. Pulmonary physiology and gas exchange did not differ between those with and those without a positive ANA, those with and without a nucleolar-staining ANA, and those with and without anti-Th/To antibody positivity. Retrospective review of the clinical record revealed that none of the 25 subjects with a nucleolar-staining ANA had the characteristic cutaneous features of systemic sclerosis (SSc). Four of the 13 Th/To-positive subjects had 3 of 5 criteria of limited cutaneous SSc (CREST variant), and 9 met proposed criteria for SSc sine scleroderma. None of the 12 Th/To-negative subjects had 3 or more criteria of limited cutaneous SSc (CREST variant), and only one met proposed criteria for SSc sine scleroderma. Of the 25 subjects with nucleolar-staining ANA, cumulative survival was similar between those who were Th/To-positive and those who were Th/To-negative (log-rank test, p = 0.73). Cumulative survival was similar between the 13 Th/To-positive subjects and all other 272 IPF subjects (log-rank test, p = 0.34).
Conclusion: Our findings indicate that a nucleolar-staining ANA is a common finding in patients with IPF, and that antibodies against Th/To are responsible for the majority of these. Given the high specificity of Th/To-positivity for SSc, our data suggest that these subjects may have SSc sine scleroderma, and that their prognosis is no different from those with IPF.