Letter to the Editor

Abstract

At 6 months of age, the right temporal muscle was swollen. Serum CK level was elevated (CK 735 IU/mL). MRI depicted an increased intensity in the right temporal muscle. The swelling mass gradually resolved after 1 month. At 8 months of age, swelling of the right forearm was observed. The swelling was found to be a firm mass measuring 2 cm in diameter, which disappeared spontaneously after 1 week without specific treatment. Shortly after the disappearance of the right forearm mass, a few swollen masses appeared on the bilateral soles. No biopsies of the affected muscles were performed because of the absence of consent from the parents. No signs of polymyositis and dermatomyositis (e.g. fever, skin rashes and muscle weakness) had developed throughout the patient's clinical course.FM localised frequently in the lower limb (thigh and lower leg), and in temporal muscles in a few cases. 6 The clinical course, the result of laboratory tests and the MRI findings of our patient were consistent with the diagnosis of recurrent FM.Treatment for recurrent FM has not been established. Several treatment options have been attempted, including non-steroidal anti-inflammatory drugs, methotrexate and methylprednisolone; however, no consistent results have been obtained thus far. 2,4The aetiology of recurrent FM remains unknown. Manganelli et al.2 reported a case of a 22-year-old man who developed bilateral recurrent FM of the gastrocnemius muscles 3 weeks after receiving BCG vaccination. Our patient was administered BCG vaccination 2 months prior to the swelling of the left temporal muscle. In Japan, BCG vaccination is given to more than 1 million infants annually. However, recurrent FM has not been reported in Japanese children thus far. Therefore, if BCG vaccination is a possible trigger for recurrent FM, then host defence mechanisms might be associated with the development of the disorder. Interestingly, FM was reported to have developed in monozygotic twins. Recurrent FM occurred in one of the identical twins, while the other twin developed nonrecurrent FM.3 Further studies are necessary to identify genetic and environmental factors associated with recurrent FM.