Elevated levels of serum muscle enzymes in the initial phase of tick-borne encephalitis

Abstract

Purpose

Since some patients with tick-borne encephalitis (TBE) have pronounced myalgias, and since myositis is reported in Flavivirus diseases such as dengue, we performed systematic search for abnormalities of muscle enzymes in a group of patients in whom the presence of tick-borne encephalitis virus (TBEV) RNA in the first phase of the disease was demonstrated and who developed second phase of TBE.

Methods

Total leukocyte and platelet blood counts were determined routinely at the initial examination during the first and the second phase of TBE. Activity of aspartate aminotransferase (AST), alanine aminotransferase (ALT), creatine kinase (CK), myoglobin and troponin was determined from the available stored serum specimens; the first and second phase disease specimens were tested simultaneously.

Results

Of 24 patients with biphasic course of TBE, 83% had leukopenia, 65% thrombocytopenia, 83% elevated AST and 4% elevated ALT level. Furthermore, 33% had elevated serum CK, 26% myoglobin and 22% troponin activity; at least one of the muscle enzymes was elevated in 42% of patients. Leukopenia, thrombocytopenia, elevated liver enzymes and elevations of CK and myoglobin were present in the initial phase but resolve later, while troponin abnormalities were also found in the second phase of TBE.

Conclusions

The present study exposes that in addition to previously known leukopenia, thrombocytopenia and increased liver enzymes activity, the initial phase of TBE is relatively often associated also with elevated muscle enzymes. Clinical relevance of these findings remains to be determined.

Keywords:

• Tick-borne encephalitis
• muscle enzymes
• creatine kinase
• myoglobin
• troponin

Author contributions

Conceptualization: PB and FS; methodology: PB, TAŽ, MK and ATB; validation: PB and FS; formal analysis: PB, KO, AK and FS; resources: PB and FS; writing original draft preparation: PB, KS and FS; writing review and editing: PB, SLF, KO, TAŽ, MK, AK, ATB, KS and FS; funding acquisition: PB and FS. All authors have read and agreed to the published version of the manuscript.

Disclosure statement

KS served as a consultant for T2 Biosystems, Roche, bioMerieux and NYS Biodefense Fund, for the development of a diagnostic assays in Lyme borreliosis. FS served on the scientific advisory board for Roche on Lyme disease serological diagnostics and on the scientific advisory board for Pfizer on Lyme disease vaccine and is an unpaid member of the steering committee of the ESCMID Study Group on Lyme Borreliosis/ESGBOR. Other authors report no conflict of interest.

Additional information

Funding

This work was supported by the Slovenian Agency for Research and Innovation (J3-3063 to PB and P3-0296 to FS).