The analysis of clinical phenotypes and autoantibodies in juvenile dermatomyositis

Abstract

Objective: To elucidate the relationship between the myositis autoantibodies and clinical phenotypes of juvenile dermatomyositis (JDM). Methods: A total of 76 JDM patients admitted to the Children's Hospital of Chongqing Medical University from January 2017 to May 2020 were tested for myositis autoantibodies, including myositis-specific autoantibodies (MSAs) and myositis-associated autoantibodies (MAAs). Kruskal-Wallis test and logistic regression were used to analyze the relationship between the antibodies and clinical characteristics. Results: In the 76 cases, 37 were females and 39 males. Forty-three cases (53%) were MSAs positive, among which the most common subtypes were autoantibodies against nuclear matrix protein 2 (NXP2) (15/76, 20%), melanoma differentiation-associated protein 5 (MDA5) (13/76, 17%) and transcription intermediary factor 1 gamma (9/76, 11%). While 20 cases (26%) were positive for MAAs, among which anti-Ro-52 antibody (17/76, 22%) was the most common subtype. Sixteen patients (21%) had both MAAs and MSAs. The incidences of arthritis (9 cases), fever (8 cases), skin ulcers (5 cases) and macrophage activation syndrome (MAS) (1 case) were significantly higher in the patients with anti-MDA5 antibody among the antibody groups. Dysphasia (6 cases) and edema (8 cases) mainly occurred in patients with anti-NXP2 antibody. Children with anti-MDA5 antibody were more likely to develop arthritis (OR=10.636, 95%CI: 2.770-40.844, P=0.001), skin ulcers (OR=12.500, 95%CI: 2.498-62.522, P=0.002), fever (OR=5.600, 95%CI: 1.580-19.849, P=0.008) and interstitial lung disease (ILD) (OR=23.333, 95%CI: 4.750-114.616, P<0.01). In the patients with different subtypes of MSAs, the creatine kinase value was significantly lower in the anti-MDA5 group than those in the anti-aminoacyl-tRNA synthetase (P=0.03), anti-NXP2 (P<0.01), and MSAs-negative group (P=0.013). Conclusions: Most children with JDM have positive myositis autoantibodies, and will present with different clinical phenotypes based on different autoantibodies. And children with anti-MDA5 antibodies are likely to develop ILD and MAS. Therefore the detection of myositis-specific autoantibodies is important.