Background Interstitial lung disease (ILD) is a common complication and is associated with the prognosis of dermatomyositis (DM). The respiratory function deteriorate quickly and leads to poor prognoses in some individuals, a condition known as rapidly progressive ILD (RP-ILD). Some patients with DM associated RP-ILD present characteristic cutaneous rash of DM but have not clinically significant muscle weakness, a subgroup of DM designated as clinically amyopathic dermatomyositis (CADM) . Recent studies have demonstrated that most patients with DM and RP-ILD are positive for anti-melanoma differentiation-associated gene 5 (MDA5). Spontaneous pneumomediastinum (PNM) is a rare but devastating illness in DM-ILD. Albeit that previous studies have revealed that some patients with DM and PNM have mild muscle involvement and are anti-MDA5 positive , the clinical and serological features of this severe entity have not been fully elucidated.
Objectives To explore the clinical and serological features of patients with DM and PNM.
Methods A total of 93 (68 classic DM and 25 CADM) patients were recruited. Anti-MDA5 antibodies were detected using ELISA . Variables were compared between patients with and without PNM. Multivariate analysis was performed using a multivariate logistic regression model. The following variables were assessed as potential factors associated with spontaneous PNM in DM: presence of RP-ILD, DM subgroup (classic DM or CADM), presence of skin ulcers and presence of anti-MDA5 antibodies.
Results A total of 11 patients (7 man and 4 women) developed PNM. Seven patients were diagnosed with CADM while 4 patients were diagnosed with classic DM. Despite being treated with the combination of glucocorticoids and immunosuppressants, during the follow-up period, 6 patients died of respiratory failure, with a varied interval after the occurrence of PNM ranged from 3 to 48 weeks. Compared with DM patients without PNM, DM patients with PNM had significantly higher frequencies of RP-ILD (63.6% vs 24.4%, P =0.01), anti-MDA5 antibodies (90.9% vs 52.4%, P =0.02), CADM diagnoses (63.6% vs 22.0%, P =0.007) and cutaneous ulcers (36.4% vs 10.2%, P =0.04), but significantly lower creatine kinase (CK) levels (58.5 vs 284 ng/ml, P =0.04). The logistic multivariate analysis indicated that cutaneous ulcer was the only independent risk factor for the occurrence of PNM in DM (OR =5.98, 95% CI 1.12–31.98, P=0.037).
Conclusions Spontaneous PNM is a refractory complication and tends to occur in DM patients with RP-ILD, anti-MDA5 antibody, CADM diagnosis and low CK level, especially in patients with cutaneous ulcers.
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Disclosure of Interest None declared