This study retrospectively analyzed the laboratory data and chest images of patients with amyopathic dermatomyositis associated with interstitial lung disease (ADM-ILD) and patients with other connective tissue disease-related ILDs (CTD-ILDs) to find a characteristic index for the early recognition of ADM-ILD and help clinicians consider the possibility of ADM-ILD as soon as possible.
In our cohort study, the records of 128 Chinese patients with CTD-ILD, including 33 ADM-ILD patients, 37 rheumatoid arthritis (RA)-ILD patients, 33 primary Sjogren’s syndrome (pSS)-ILD patients, 14 systemic sclerosis (SSc)-ILD patients and 11 systemic lupus erythematosus (SLE)-ILD patients. The patients’ clinical features, laboratory parameters, and chest HRCT findings were analyzed.
ADM-ILD patients generally had significantly higher LDH (333.52±160.21 U/L), AST (66.21±83.66 U/L), and CK-MB (18.23±8.28 U/L) levels than other CTD-ILD patients. A total of 90.91% (30/33) of ADM-ILD patients had elevated LDH. Patients with ADM-ILD were more prone to organizing pneumonia radiologic patterns on chest HRCT scans than patients with other CTD-ILDs ( χ2
=37.39, p < 0.001) and were found in 18 of 33 ADM-ILD patients. Anti-MDA5 (45.45%) was the most commonly detected autoantibody in ADM-ILD patients, followed by anti-PL-7 (21.21%), anti-Jo-1 (12.12%), and anti-PL-12 (9.09%), and levels of ALT (96.93±119.79 vs. 17.50±6.218 U/L), AST (113.00±106.13 vs. 23.56±6.91 U/L), LDH (415.00±198.51 vs. 261.94±67.75 U/L) and CK-MB (22.57±5.91 vs. 14.61±8.36 U/L) were significantly higher in anti-MDA5-positive patients, but these patients had significantly lower WBC counts (4.82±2.61 vs. 7.14±3.00 × 10 9 /L), lymphocyte counts (0.72±0.20 vs. 1.23±0.53 × 10 9 /L), and ALB levels (31.90±4.76 vs. 35.49±4.71 g/L).
ADM-ILD patients have higher serum LDH, AST and CK-MB levels, especially serum LDH levels, and are more prone to organizing pneumonia radiologic patterns on chest HRCT scans than other CTD-ILD patients. A high level of serum LDH with ILD may be a useful characteristic index for recognizing ADM-ILD.
Idiopathic inflammatory myopathies (IIMs) are a heterogeneous group of autoimmune diseases characterized by inflammation of the skeletal muscles. The most common subgroups in adults are dermatomyositis (DM), polymyositis (PM) and inclusion body myositis (IBM).
The clinical manifestations of IIM are diverse and are characterized by various degrees of muscle, skin, and lung involvement. Interstitial lung disease (ILD) is a common complication of IIMs that results in high mortality, with an estimated prevalence of 30%. With the widespread awareness of myositis-specific autoantibodies (MSAs) and the myositis-associated autoantibody (MAA) spectrum, an increasing number of amyopathic dermatomyositis (ADM) cases have been diagnosed, especially with anti-melanoma differentiation-associated gene 5 (MDA5) antibodies. ADM is defined as a subset of DM characterized by typical cutaneous manifestations of classic DM lasting 6 months or longer with no clinical evidence of muscular manifestations and no elevation in serum creatine kinase (CK). There is a strong correlation between the incidence of ILD in IIM patients and myositis-specific autoantibodies. The incidence of ILD in MDA5-positive ADM patients is more than 90%, and ADM-ILD with MDA5 positivity is characterized by a risk of rapidly progressive ILD (RP-ILD), which has an estimated prevalence of 26.8–62.5%, especially in East Asia, and is often resistant to intensive therapy, such as high-dose corticosteroids combined with cyclosporine A (CsA), tacrolimus, or cyclophosphamide agents. The result is acute fatal respiratory failure, and the 6-month mortality rate is as high as 45.0–64.3%. , , Previous studies showed that patients who were treated intensively with combination immunosuppressive therapy upon diagnosis with ADM-ILD had better survival outcomes than those who received immunosuppressive therapy using a sequential approach after failure of the initial treatment. ,
Therefore, early diagnoses and timely treatment are very important for reducing the mortality of ADM-ILD.
However, ADM diagnosis has embraced the use of overlapping syndromes to account for clinical heterogeneity and the lack of muscular manifestations and elevated CK, making the diagnosis even more difficult. This study retrospectively analyzed the laboratory data and chest images of 128 patients with CTD-ILD, including 33 ADM-ILD patients, to establish a characteristic index for the early recognition of ADM-ILD and alert clinicians to the possibility of ADM-ILD as early as possible.