Benign Acute Childhood Myositis: A Benign Disease that Mimics More Severe Neuromuscular Disorder

Proximal lower limb weakness presenting acutely with or without preceding fever is a strong mimic of Guillain-Barré syndrome (GBS). Benign acute childhood myositis (BACM) forms an important differential diagnosis in such cases.

To characterize the clinical and laboratory findings of patients with BACM for better understanding of the disease.

This prospective longitudinal study was conducted in a tertiary care hospital of northern India.

Thirty-two patients presenting in the outpatient or emergency clinic of the hospital with severe myalgia that exacerbated with straight leg raising test and fever from July 2016 to July 2017 were included in the study.

All the continuous data were expressed as number and percentage or mean ± standard deviation/median. Non-parametric continuous data between groups were analyzed by Friedman's test.

The mean age of the patients was 14.3 (±8.7) years and they presented after a nonspecific febrile illness in most of the cases (53.1%). The symptoms resolved after a mean of 5.7 (±1.6) days. Myalgia was present in 21 (65%) cases, whereas proximal weakness was the prominent finding in 14 (43%) cases. Electrolyte abnormality (hypokalemia) was present in four (12.5%) cases. In all patients, the muscle enzymes (creatine phosphokinase, serum glutamic oxaloacetic transaminase, serum glutamic pyruvic transaminase, and lactate dehydrogenase) were elevated at presentation, and electromyography showed myopathic pattern. A significant recovery took place in the next 5-7 days.

BACM should be actively looked for in cases of painful acute proximal limb weakness in the adolescents.