Bogovič et al.
Elevated levels of serum muscle enzymes in the initial phase of tick-borne encephalitis. Infect. Dis. 2024; 56:6,504-509. doi:1080/23744235.2024.2335349

In the initial phase of TBE virus infection, clinical signs and symptoms are nonspecific, and TBE antibodies have yet not been produced. Virus RNA can principally be demonstrated in blood, but this is not a routine approach.

Since some patients have pronounced myalgias early during TBE virus infection, a study has been carried out to assess abnormalities of muscle enzymes in the early phase of disease (in the first phase of the biphasic course of disease).

Among 24 patients with confirmed TBE virus infection, 33% had elevated creatine kinase serum activity, 26% had elevated myoglobin levels, and 22% had elevated troponin levels. At least one of the muscle enzymes was elevated in 42% of the patients. Although most of these abnormalities were mild to moderate, some were quite pronounced.

The mechanisms of muscle involvement in viral infections are unclear. One can assume an immune mediated damage: The presence of TBE virus in blood triggers the secretion of immune mediators, that damage bone marrow, liver and muscles resulting in transient leukopenia, thrombocytopenia, increased activity of some liver and muscle enzymes.

The authors concluded that clinicians in TBE endemic areas should consider a TBE virus infection not only in the case of unspecific fever, associated with leukopenia, thrombocytopenia and/or abnormal liver tests, but also in the presence of elevated muscle enzymes.

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