ILD incidence rare in SLE patients, linked to death

Interstitial lung disease (ILD) rarely occurs in patients with systemic lupus erythematosus (SLE), but when it does, ILD is often associated with other systemic autoimmune disorders and may even significantly contribute to mortality, according to a study.

“ILD is rare, significantly associated with other systemic autoimmune disorders, and has a poor prognosis in SLE,” said the researchers, led by Arthur Mageau of the Service de Médecine Interne, Hôpital Bichat, Assistance Publique Hôpitaux de Paris, Paris, France.

Mageau and his team analysed the characteristics of all SLE inpatients admitted between 2011 and 2012 in France through the French medico-administrative database. They also examined the features associated with the presence of ILD.

The impact of ILD on survival from the first stay to 2020 was measured using Cox hazard model. Finally, the researchers estimated the incidence of ILD by analysing the onset of ILD from 2013 to 2020 in SLE patients who had no evidence of ILD in 2013.

A total of 10,460 SLE patients had at least one hospital stay between 2011 and 2012 that could be traced until 2020. Of these, 134 (1.2 percent) had a diagnosis of ILD at baseline. [Respirology 2022;27:630-634]

Patients who had a related autoimmune disease, such as Sjögren's syndrome or systemic sclerosis, had a higher frequency of ILD (29.9 percent vs 5.9 percent; p<0.0001). Notably, multivariable analysis revealed the association of ILD with an increased risk of death in SLE (hazard ratio [HR], 1.992, 95 percent confidence interval [CI], 1.420‒2.794; p<0.0001).

Among the 31,029 SLE patients with no evidence of ILD at baseline, 795 (2.6 percent) were diagnosed with ILD between 2013 and 2020. The incidence rate of ILD in SLE was 10.26 per 1,000 patient-years (95 percent CI, 10.24‒10.28).

“By using a nationwide healthcare database, we were able to analyse the burden of ILD in SLE and show that a very limited proportion of the SLE population admitted in hospital was affected by ILD (2.6 percent in a 7-year period),” the researchers said.

“Such rate is lower than the 3 percent to 13 percent of ILD prevalence previously reported in smaller clinical series of SLE patients,” they added. [Thorax 2000;55:159-166; Rev Mal Respir 2010;27:e66-78]

In a previous necropsy study, however, pulmonary fibrosis was detected in only four lung specimens from 120 patients with SLE. Consistent with the literature, ILD in SLE is associated with age and other comorbidities. [Arch Rheumatol 2020;35:239-246; Sci Rep 2019;9:7355; Am J Med 1981;71:791-798]

Earlier studies deemed that ILD has a limited effect on global outcome, but it is independently predictive of premature death in the present study. In addition, its HR is comparable to chronic kidney disease in SLE. [Semin Arthritis Rheum 1990;20:48-56; Autoimmun Rev 2019;18:733-737]

“SLE affects mostly women of childbearing age and involves multiple organs,” according to Mageau and colleagues. [Lancet 2014;384:1878-1888]

“Besides pleuritis—the most common thoracic manifestation of SLE—specific pulmonary manifestations mainly include acute pneumonitis, alveolar haemorrhage, organizing pneumonia, chronic ILD, shrinking lung syndrome, bronchiolitis obliterans, and pulmonary hypertension,” they added. [Thorax 2000;55:159-166; Arthritis Res Ther 2018;20:1-10]