Outbreak of Influenza B related to Benign Acute Childhood Myositis

Abstract

Outbreak of Influenza B related to Benign Acute Childhood Myositis Purpose: Benign acute childhood myositis (BACM) is a rare syndrome caused by a viral infection and is characterized by gait disturbance with calf pain in children. I investigated whether BACM is related to the incidences of seasonal influenza and of specific influenza subtypes in Korea. Methods: Patients diagnosed with BACM between March, 2010 and December, 2014 were investigated retrospectively. The occurrence of BACM was compared with the incidence of influenza for each influenza season, as obtained from the Korea Centers for Disease Control and Prevention. Results: All patients had previous infection preceding calf muscle pain or gait disturbance. Laboratory findings showed elevated levels of creatine kinase (median, 1243 U/L) and leukopenia (<4500/µL). Patients exhibited benign courses that resolved within a few days without any complications. The rate of influenza B was correlated with BACM occurrence (P=0.05) although this relationship was not statistically significant. Neither the rate of total influenza nor the rate of influenza subtype A was associated with BACM occurrence. Conclusion: The outbreak of influenza B was correlated with the occurrence of BACM. We should recognize the occurrence of this disease and avoid unnecessary evaluation to diagnose BACM when an outbreak of influenza B is expected.