Clinical features of asthma with connective tissue diseases

BACKGROUND: The clinical features of asthma with connective tissue diseases (CTDs) are not well‐known. This study therefore aimed to investigate the clinical characteristics of asthma with CTDs. METHODS: We retrospectively examined the records of adults (≥18 years old) with asthma followed up between January 2010 and December 2019. We then compared the clinical features of asthma with and without CTDs. RESULTS: Among 568 subjects with asthma, 42 subjects (7.4%) had CTDs. The most frequent concomitant CTD was rheumatoid arthritis (n = 23, 54.8%), followed by systemic lupus erythematosus (n = 6, 14.3%). The proportion of women (with vs. without CTDs, 85.7% vs. 56.5%, p < 0.001) and Global Initiative for Asthma step were higher (Step 4 or 5, with vs. without CTDs, 81.0% vs. 62.0%, p = 0.01) in asthma with CTDs, whereas frequency of allergic rhinitis was higher in asthma without CTDs (with vs. without CTDs, 7.1% vs. 26.1%, p = 0.005). Eosinophil ratio (with vs. without CTDs, 2.1% vs. 3.5%, p = 0.009) and total immunoglobulin E level (with vs. without CTDs, 43 IU/mL vs. 237 IU/mL, p = 0.002) were lower in asthma with CTDs. In terms of lung function, percentage predicted forced vital capacity (with vs. without CTDs, 86.7% vs. 99.7%, p = 0.008) and percentage predicted forced expiratory volume in 1 s (%FEV1) (with vs. without CTDs, 77.2% vs. 88.4%, p = 0.02) were all lower in asthma with CTDs. With multivariable analysis, CTDs (odds ratio [OR] 2.8, 95%CI 1.3–6.0; p = 0.008), chronic obstructive pulmonary disease (OR 3.8, 95%CI 2.1–6.7; p < 0.001) and asthma onset at <20 years old (OR 1.8, 95%CI 1.1–3.2; p = 0.03) were associated with low FEV1 (defined as %FEV1 < 80%) in asthma. CONCLUSIONS: Asthma with CTDs was related to lower lung function and low‐T2 inflammation asthma.