Obturator pyomyositis and labium majus cellulitis: A case report and literature review

Pyomyositis is a rare, subacute, deep bacterial infection of the skeletal muscle. When treatment is delayed, pyomyositis causes abscess formation and progresses to sepsis; therefore, its early diagnosis is important. However, the clinical presentation and laboratory findings of pyomyositis are not specific; hence, diagnosis often takes time. We encountered the case of a girl with obturator pyomyositis and redness and swelling of the labium majus, which we considered as potentially important symptoms for distinguishing obturator pyomyositis from septic hip arthritis. An 8-year-old Japanese girl presented to our hospital with fever and right hip pain. On physical examination, she had redness and swelling of the right labium majus and a right limp. She was diagnosed with obturator pyomyositis and labium majus cellulitis with magnetic resonance imaging. Her clinical presentation markedly improved after starting antibiotic therapy with intravenous cefazolin for 2 weeks and oral cefaclor for 1 week. Improvement in the inflammation of the obturator muscle and labium majus was confirmed with follow-up magnetic resonance imaging. She recovered fully with no long-term sequelae. In conclusion, obturator pyomyositis rather than septic hip arthritis should be considered in children with a limp and hip and perineal pain, particularly girls with redness and swelling of the labium majus. In addition, imaging studies, including magnetic resonance imaging, should be performed for early diagnosis.