Background/Purpose Antisynthetase syndrome (aSS) corresponds to an overlapping inflammatory myopathy identified by different myositis specific autoantibodies (directed against tRNA-synthetases). Myocardial involvement in this condition is poorly described.

Methods From a 342 aSS patient registry, nine cases of myocarditis were identified on the basis of an unexplained increased in cardiac troponin I levels associated with either suggestive cardiac magnetic resonance imaging (MRI) findings, normal coronary artery explorations, and/or positive endomyocardial biopsy.

Results The prevalence of myocarditis in aSS is 2.6% (n=9) and was not linked to any autoantibody specificity: anti-Jo1 (n=5), anti-PL7 (n=3) and anti-PL12 (n=1). Myocarditis was an inaugural presentation in 44% of the cases and was asymptomatic (n=1) or revealed by an acute (n=4) or subacute (n=4) cardiac failure. Of note, myocarditis was always associated with an active myositis. When performed (n=8), cardiac MRI revealed a late hypersignal in the T₁-images in 87% of the cases (n=7). Four patients (44%) required intensive care. Seven patients (78%) received dedicated cardiotropic drugs. Steroids and at least one immunosuppressive drug were given in all cases. After a median follow-up of 23 months (range 2-51), six (67%) patients recovered whereas three (33%) developed chronic cardiac insufficiency. No patient died.

Conclusion The prevalence of myocarditis in aSS is similar to that reported in other inflammatory myopathies. Although it has a relatively good prognosis, myocarditis is a severe condition and should be carrefully explored in active aSS patients.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/myocarditis-in-antisynthetase-syndrome/