Benign acute childhood myositis: Case report

Background: Benign acute myositis of childhood typically affects boys. It is a disorder of midchildhood. An epidemiologic association with a viral infection like influenza virus has been reported although virologic analyses often remain negative. Prodromal signs of a viral illness may be present and clinical symptoms of benign childhood myositis occur suddenly after 2 to 5 days with severe calf pain and difficulty of walking. Usually it follows a benign and self-limiting cours, but cases have been reported with severe courses and life-threatening complications.

Case report: We report on a 10-year old boy who was presented to our outpatient clinic with a sudden appearing calf pain and difficulty of walking. Muscle tenderness was initially restricted to the gastrocnemius-soleus muscles and later spread on to the proximal muscles. It was his third episode of benign childhood myositis. Creatine kinase levels were elevated up to 180.000U/l and he developed myoglobinuria. Under supportive treatment the creatinin remained normal and he reached full recovery clinical and laboratory after 10 days. Serological blood investigations of common viruses were negative. Organic urin acids, carnitin levels and lactat were normal during the episode and afterwards. MRI of the calf muscles showed typical signs for a rhabdomyolysis of the gastrocnemius-soleus muscles on both sides. After 2 months the creatinin kinase level remained slightly elevated (412U/l) and the MRI stated improvement, but yet now the patient reached full recovery and had no physical restrictions.

Conclusion: We present a patient with three episodes of benign childhood myositis. Recurrent severe courses with rhabdomyolysis are rarely reported in this illness. Might the slight elevation of creatinin kinase in between the episodes be a sign of predisposition to develop BCM?