Serum transaminases are frequently elevated at time of diagnosis of idiopathic inflammatory myopathy and normalize with creatine kinase.

INTRODUCTION: Despite multiple reports of elevated transaminases in muscle injury, aspartate aminotransferase (AST) and alanine aminotransferase (ALT) are not always considered indicators of muscle damage. The purpose of this study was to examine the relationship between serum AST, ALT, and creatine kinase (CK) levels at time of diagnosis of idiopathic inflammatory myopathy (IIM) and at the time of CK normalization.
METHODS: We conducted a retrospective chart review of all adult patients attending rheumatology clinics at a county hospital with a diagnosis of IIM. Data collected included patient demographics, serial CK measurements, and serial serum transaminase measurements.
RESULTS: We identified 85 patients with IIM. At myositis presentation, 75 (88%) had CK above the upper limit of normal (ULN), 72 (85%) had AST above the ULN, and 68 (80%) had ALT above the ULN. The average CK was 5302 U/L (range, 23-38,461 U/L [SD, 7096]), average AST 215 U/L (range, 16-1270 [SD, 227]), and average ALT 137 U/L (range, 10-621 [SD, 137]). The average AST and ALT at first available normalized CK was 26 U/L (range, 9-139 [SD, 18]) and 26 U/L (range, 5-96 [SD, 19]). We found a strong correlation between CK and AST (r= 0.832; P < 0.001) and ALT (r = 0.775; P < 0.001) at initial presentation and also at the time of peak CK levels (r = 0.874 [P < 0.001] and r = 0.842 [P < 0.001], respectively).
CONCLUSIONS: In our series, we found a strong correlation between CK and serum transaminases. Serum transaminases were elevated in 80% of patients at the time of presentation and normalized in 85% of the patients at the time of CK normalization. Appropriate recognition of these laboratory changes in IIM may help reduce unnecessary hepatic evaluation, delayed diagnosis, unnecessary avoidance of second line immunosuppressants, and misdiagnosis of primary liver disease.