Associations between nailfold capillaroscopy findings and interstitial lung disease in patients with mixed connective tissue disease

Introduction: Mixed connective tissue disease (MCTD) is a chronic immune-mediated disorder defined by the combined presence of serum anti-RNP antibodies and distinct clinical features including progressive lung fibrosis. The aim of this study was to evaluate potential associations between lung fibrosis in MCTD and specific clinical and laboratory findings including results of nailfold capillaroscopy (NFC) examination. Material and methods: Patients with MCTD who were admitted to the Departments of Allergy and Immunology or Dermatology at the University Hospital of Krakow (Poland) in 2015-2018 were identified based on comprehensive individual record review. Diagnosis of MCTD required fulfilment of at least one of the four widely accepted sets of diagnostic criteria. Clinical and laboratory data were collected, and statistical analysis was performed to identify potential predictors of interstitial lung disease (ILD). Results: Thirty patients (90% females) aged 22-81 years met the study inclusion criteria. The mean duration of symptoms associated with MCTD was 7.3 months. Photosensitivity and Raynaud's phenomenon were the most common clinical manifestations (90% and 70%, respectively). Hand oedema, sclerodactyly and the presence of giant capillaries in NFC correlated significantly with the risk of lung involvement. In multivariate analysis, the presence of enlarged loops in NFC (giant capillaries) was identified as an independent factor for ILD (R-2 = 0.82, p < 0.0000001). Conclusions: The NFC examination should be considered in all patients with a diagnosis of MCTD. The presence of giant capillaries may be a promising marker for interstitial lung disease in these patients, especially among those with a short duration of disease (i.e. < 1 year).