Letter to the Editor

Abstract

Focal myositis (FM) is a benign inflammatory pseudo-tumour of skeletal muscle. Focal enlargement is usually self-limiting without recurrence. Very few recurrent FM cases have been reported in adults. [1][2][3] In addition, three paediatric cases of recurrent FM (9-year-old boy, 4 12-year-old boy 5 and 15-year-old boy 1 ) have been reported thus far. We describe here a 5-monthold girl who developed recurrent FM originating from the left temporal muscle. To our knowledge, this is the first report of recurrent FM in an infant.The patient was born to healthy parents via Caesarean section at the gestational age of 38 weeks and 5 days because of fetal distress. The patient had no siblings. At the age of 3 months, she received a Bacille de Calmette et Guerin (BCG) vaccination. At the age of 5 months, the mother observed a painful swelling in the left temporal region of the infant. There was no previous history of trauma. Physical examination revealed a firm mass measuring 5 cm in diameter over the left temporal bone. No neurological deficit was observed. Otitis media was excluded. Blood chemistry showed a marked elevation in creatine kinase (CK) (633 IU/mL, reference value 13-33) and a mild increase in aspartate aminotransferase (AST) (48 IU/mL, reference value 6-27). C-reactive protein was slightly elevated. Anti-nuclear antibody, angiotensin-converting enzyme and anti-Jo-1 antibody levels were within their normal ranges. Complete blood count analysis did not reveal significant changes. Eosinophilia was not seen. Contrast-enhanced T1-weighted magnetic resonance imaging (MRI) with fat suppression showed an enlarged muscle of the left temporal region and increased signal intensity within the left temporal muscle (Fig. 1). The left temporal swelling resolved after 1 week of treatment with a cephem antibiotic, Cefazolin (Astellas Pharma Inc., Tokyo, Japan).