Cardiac troponin and beta-type myosin heavy chain concentrations in patients with polymyositis or dermatomyositis.

Cardiac troponin T (cTnT), cardiac troponin I (cTnI), myosin heavy chains (MHC), myoglobin, creatine kinase (CK), and creatine kinase isoenzyme MB (CKMB), were measured in blood samples from 39 polymyositis (PM) or dermatomyositis (DM) patients without clinical evidence for cardiac involvement to evaluate their clinical usefulness in this patient population. MHC, myoglobin, and CKMB were frequently elevated and correlated with each other and with disease severity. Undetectable cTnI in all but one patient indicated that MHC was released from skeletal muscle, thereby providing the first laboratory evidence of frequent slow-twitch muscle fibre-necrosis in patients with PM or DM. CKMB was elevated in 51%, cTnT in 41%, and cTnI in only 2.5% of patients. cTnI did not correlate with other markers or with disease severity scores. The close correlations found between cTnT and skeletal muscle damage markers and the relationship between cTnT with disease severity without clinical evidence for myocardial damage suggest a release of cTnT from skeletal muscle. The relationship of cTnT with disease severity indicates a possible role of the marker for risk stratification. However, the prognostic values of cardiac troponins and other muscle damage markers in PM/DM patients remain to be compared in prospective outcome trials.

Anti-endothelial cell antibody, thrombomodulin, and von Willebrand factor in idiopathic inflammatory myopathies.

Sera from 19 patients with idiopathic inflammatory myopathy (IIM) were examined for the presence of anti-endothelial cell antibodies (AECA) by an immunoglobulin G-specific cellular enzyme-linked immunosorbent assay. The mean binding index of AECA was found to be 37.7% +/- 26.5% for the patients, compared with a mean of 7.2% +/- 2.7% for normal controls (P < 0.04). Levels of thrombomodulin, von Willebrand factor antigen, and serum creatine kinase were also shown to be augmented. Interestingly, positive correlations between AECA on the one hand and Raynaud's phenomenon and interstitial lung disease on the other were demonstrated. Given that the pathogenesis of IIM remains uncertain, these findings may be of importance.

Elevated serum levels of neopterin in adult patients with polymyositis/dermatomyositis.

We determined serum concentrations of neopterin, soluble tumour necrosis factor (55 kDa) receptor (sTNF-R) and soluble interleukin-2 receptor (sIL-2R) in plasma of 44 patients with polymyositis (PM)/dermatomyositis (DM), including 15 patients with primary PM, 13 patients with primary DM, and 16 patients with myositis and systemic sclerosis in overlap. Concentrations of neopterin, sTNF-R and sIL-2R were measured using commercially available immunoassays. Serum neopterin was increased in 35 of 44 PM/DM patients (80%), sTNF-R in 14 (32%) and sIL-2R in 18 (41%) patients, respectively. There were significant correlations between serum neopterin and sTNF-R, sIL-2R and erythrocyte sedimentation rate (all P < 0.001). Neopterin, as well as sTNF-R and sIL-2R, did not correlate with clinical (neuromuscular and activities of daily living scores) and laboratory (creatine kinase levels) manifestations of myositis. Increased serum levels of neopterin were associated with non-muscular manifestations of PM/DM. In conclusion, serum neopterin appears to be a useful laboratory marker for ongoing immune activation and global disease activity in PM/DM.