Benign acute childhood myositis. Physician’s and parent’s perception

Introduction
Benign acute childhood myositis (BACM) is a rare syndrome occurring in children during the convalescent phase after influenza B. It is characterized by the sudden onset of calf pain, which causes difficulty to walk. Symptoms were relieved in one week. In epidemic season 2015/2016, influenza type B predominated in Poland. It could cause a high incidence of BACM in the whole country. Objective: To evaluate parents' and doctors' disease perception and diagnostic and therapeutic methods used in the practice. To describe the clinical features of benign acute childhood myositis and recommend investigations.

Materials and methods
We performed a search of electronic database (PubMed) to identify information about BACM. We analyzed questionnaires obtained from the whole of Poland after an information campaign. We evaluated disease progression, patient-management, and parents' attitude to influenza vaccination.

Results
We analyzed 68 questionnaires. Among all the reported cases of BACM, 70% occurred in boys; the average age was 6 years. Almost all children had flu-like symptoms in the period prece¬ding the occurrence of BACM. Almost all patients (98.5%) complained about calf pain, some feet pain (12%), or thigh pain (6%). In all children, abnormal gait was noticed, and almost half refused to walk. 85.3% of children were examined by the physician; 31% of them had laboratory tests. In 19% of cases, the doctor suspected flu as the cause of the disease. Symptoms usually resolved after two or three days. No child was vaccinated against influenza.

Conclusions
Polish physicians are insufficiently familiar with the symptoms and causes of BACM. Every child with this diagnosis should be examined by a doctor and should have laboratory tests performed. This allows differentiating BACM from other diseases with poor prognosis. In the flu season, physicians need to consider BACM as a cause of altered gait. Pediatricians should recommend vaccination against influenza to their patients.