Clinical characteristics and prognosis of amyopathic dermatomyositis patients with interstitial lung disease: insights from a retrospective cohort

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IntroductionThe diagnosis of amyopathic dermatomyositis with interstitial lung disease (ADM-ILD) is challenging due to the lack of typical skin features and overlapping syndromes. We aimed to determine the characteristics and prognosis of patients with ADM-ILD to further guide their clinical management.MethodsA retrospective cohort study comprising 190 Chinese patients diagnosed with interstitial lung disease (ILD) was conducted. Patients were stratified into four groups using the Sontheimer criteria and predominant high-resolution computed tomography (HRCT) patterns. Demographic features, clinical presentation, laboratory parameters, duration of ILD, and follow-up data were analysed.ResultsThere were significant differences in the clinical parameters among the 190 patients with ILD in the amyopathic dermatomyositis (ADM, n = 69) and control (n = 121) groups. The ADM with nonspecific interstitial pneumonia (NSIP) group (n = 46) presented increased haemoglobin (125.93 ± 12.91 g/L, p = 0.005), creatine kinase-MB (15.19 ± 8.58 U/L, p < 0.001), and partial pressure of oxygen (93.08 ± 26.20 mmHg, p = 0.003) levels and decreased β2-microglobulin (2.61 ± 1.21 mg/L, p = 0.039) levels compared to the control-NSIP group (n = 92). The ADM with organizing pneumonia (OP) group (n = 23) had a greater percentage of females (7/16, p = 0.023) and higher alanine aminotransferase (30.30 ± 20.67 U/L, p = 0.039) and aspartate aminotransferase (53.35 ± 65.86 U/L, p = 0.003) levels than the control-OP group (n = 29). Both the ADM-NSIP and OP groups presented elevated lactate dehydrogenase (LDH) levels (290.61 ± 86.49 U/L, p = 0.009; 317.35 ± 181.32 U/L, p = 0.003, respectively) and increased anti-nuclear antibody (ANA) positivity rates (82.61%, p = 0.01; 73.91%, p < 0.001, respectively). Notably, 81.26% of patients with ADM-NSIP/OP had LDH levels above normal. The serum LDH levels could be used to distinguish patients with ADM-NSIP/OP (sensitivity: 73.91%, specificity: 82.64%). Survival was shorter among patients with ADM-OP than among control patients (p = 0.002). Cox multivariate analysis revealed that age (p = 0.002), smoking status (p = 0.011), anti-melanoma differentiation-associated gene 5 (MDA5) antibody (p = 0.017), and white blood cell count (p = 0.004) were independent predictors of shorter survival.ConclusionsElevated serum LDH levels in patients predominantly presenting with NSIP or OP patterns may indicate the presence of ADM-ILD. The identified prognostic factors underscore the importance of early detection and personalized management strategies for optimizing outcomes in patients with ADM-ILD.