Background: Several reports have shown that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection may trigger a vigorous immune response that could lead to the appearance of various autoantibodies such as antinuclear antibodies, antiphospholipid antibodies or anti-neutrophil cytoplasmic antibodies, among others. Moreover, the pulmonary involvement in SARS-CoV-2 may resemble that of patients with anti-MDA5 positive syndrome or acute form of antisynthetase syndrome.

Objectives: Our aim was to analyse the presence of anti-MDA5 and other myositis-specific autoantibodies such as the antisynthetase antibodies in patients diagnosed with severe acute respiratory syndrome caused by SARS-CoV-2.

Methods: Retrospective observational study performed in a tertiary care center. We included 28 patients admitted to the intensive care unit with severe acute respiratory syndrome, 14 at the onset of the disease (group A) and 14 after 30 days of being treated in an intensive care unit (group B). Chest CT was performed at the admission. We analyzed the presence of anti-MDA5 and antisynthetase antibodies by immunoblot (Euroimmune^®) and in those who were positive we performed a confirmatory test by immunoprecipitation.

Results: All chest CT showed bilateral ground glass pattern. Three out of 14 patients of group A (12 males, 86%, mean ± SD age 67.1 ± 12.2) were positive for antisynthetase antibodies (2 anti-PL7, 1 anti-Jo1), and 6 out of 14 patients of the group B (6 males, 48%, mean ± SD age 68.7 ± 8.1) were positive to antisynthetase antibodies (2 anti-PL7, 2 anti-PL-12, 1 anti-EJ, 1 anti-OJ+PL7). Immunoblots also show positivity for other myositis-specific or associated antibodies, such as anti-TIF1g, anti-PM75, anti-SAE and anti-SRP. All of these results found by immunoblotting were negative by immunoprecipitation. None of the 28 patients were positive for anti-MDA5 antibodies.

Conclusion: Severe SARS-CoV-2 pneumonia is characterized by ground glass pattern in chest CT, as it is found in anti-MDA5 or antisynthetase syndrome. The positivity of several myositis related autoantibodies showed in immunoblot appears to be more related to the vigorous immune response producing polyclonal immunoglobulins than triggering a real myositis-associated interstitial lung disease. Clinicians must be aware about these false positive results in patients with severe COVID-19 acute respiratory syndrome.

References: [1]Xu Q. MDA5 should be detected in severe COVID-19 patients. Med Hypotheses. 2020; 143:109890.

[2]Giannini M, Ohana M, Nespola B, Zanframundo G, Geny B, Meyer A. Similarities between COVID-19 and anti-MDA5 syndrome: what can we learn for better care? Eur Respir J. 2020; 56:2001618.

[3]Vlachoyiannopoulos PG, Magira E, Alexopoulos H, Jahaj E, Theophilopoulou K, Kotanidou A, Tzioufas AG. Autoantibodies related to systemic autoimmune rheumatic diseases in severely ill patients with COVID-19. Ann Rheum Dis. 2020 Dec;79(12):1661-1663

Disclosure of Interests: None declared