Myopathy related to systemic sclerosis (Myo-SSc) is a disabling and unpredictable complication of SSc. We assessed the predictive value of serum aldolase, creatine kinase (CK), alanine transaminase (ALT), aspartate transaminase (AST) and C-reactive protein (CRP) to estimate the risk of developing Myo-SSc.
We enrolled 137 SSc patients without proximal muscle weakness in a prospective monocentric study to follow them longitudinally over a four-year period. The risk of occurrence of Myo-SSc was ascertained according to the European NeuroMuscular Centre criteria and was analyzed according to levels of plasma aldolase, CK, transaminase enzymes and CRP at inclusion. Performance of each parameter to predict Myo-SSc occurrence was assessed and compared with the others.
The area under the receiver operating characteristic curves (ROC) of plasma aldolase for Myo-SSc occurrence prediction was 0.80 (95% CI: 0.67 to 0.94, P < 0.001), which was higher than that of plasma CK (0.75, P = 0.01), and that of ALT (0.63, P = 0.04). AST and CRP had no predictive value for Myo-SSc occurrence. The best cut-off of aldolase for prediction of Myo-SSc occurrence within three years after inclusion was 9 U/L and higher than the upper normality limit (7 U/L), unlike that of CK and ALT. Myo-SSc occurred more frequently in patients whose plasma aldolase was higher than 9 U/L. Adjusted Hazard Ratio for patients with aldolase > 9 U/L was 10.3 (95% CI: 2.3 to 45.5), P < 0.001.
Increased plasma aldolase level accurately identified SSc patients with high risk to develop subsequent Myo-SSc. This could help initiate appropriate treatment when the disabling muscle damage is still in a reversible stage.