Benign acute childhood myositis as a complication of influenza B and its differential diagnosis]

Study aim: Analysis of the course of benign acute childhood myosistis during the influenza epidemic of 2012/2013, with a focus on the clinical specificities, laboratory findings, diagnostic and therapeutic approaches, and prognosis. Methods: A retrospective study was conducted of 10 patients with myositis during influenza infection. The haematological and biochemistry parameters were analysed. A direct real time-PCR assay was used to detect the virus from nasopharyngeal swabs. Results: Eight of 10 patients were males of an average age of 7.1 years. Muscle disorders emerged during recovery from influenza. They were characterized by a sudden onset of severe pain in the calf muscles with the consequent inability to walk in nine patients. Toe walking was reported in six children and wide-base gait in one patient. The full blood count showed leukopenia (eight cases) and thrombocytopenia (five cases). Blood biochemistry typically detected elevated muscle enzymes (creatine kinase and aspartate aminotransferase) and elevated myoglobin in all patients. Influenza B was confirmed in all study patients. They all recovered spontaneously within two to four days. Conclusions: Benign acute childhood myositis presents with the clinical picture of transient muscle disorders resulting in difficulty walking and very rarely can be complicated by rhabdomyolysis and kidney failure. It is most often associated with influenza B and affects school age children, mostly males. Good awareness of the condition facilitates the differential diagnosis and enables to rule out other more serious causes of difficulty walking. Symptomatic therapy is an adequate option and the patient recovers spontaneously within a couple of days. Early recognition of the disease avoids unnecessary diagnostic and therapeutic interventions.