[Benign infant myositis associated to influenza B]

Benign childhood myositis is a self-limiting inflammatory condition that primarily affects schoolaged boys during the winter months. It is associated with respiratory viral infections, such as influenza A and B viruses, respiratory syncytial virus (RSV), and Mycoplasma pneumoniae, among others. In September 2022, an epidemiological alert was raised due to a high number of reported cases in the metropolitan area of Buenos Aires. We present two cases of female adolescents, aged 10 and 14 years, who developed this condition in association with influenza B virus infection. Their treatment and follow-up differed based on their clinical presentation and laboratory findings. This entity should be considered in the differential diagnosis of lower limb myalgia, difficulty walking, and functional impotence. It is necessary to establish management guidelines according to the clinic and laboratory. The search for respiratory viruses, mainly influenza, should be done taking into account the local epidemiology.