Actinomycosis of bilateral psoas muscle: a case report

Abstract

Actinomycosis is an underreported chronic invasive disease caused by Actinomyces spp. In that group of diseases, pelvic actinomycosis is very rare and most of the cases reported in the literature have shown unilateral psoas muscle involvement. We report a 35-year-old woman with a retroperitoneal mass located in the left psoas muscle that makes abdominal tenderness and difficulty in walking. She had a 7-year history of intrauterine device which had been removed one month just before this event. After undergoing two laparotomies to perform a biopsy with undetermined results, she developed a new mass in the right psoas muscle which was similar to the left one. On the third attempt, the histopathology revealed yellow sulfur granules of Actinomyces which reacted positively with periodic acid Schiff and Grocott’s dye. After three months of treatment with Amoxicillin plus Clavulanic acid, her abscesses were completely resolved. Actinomycosis should always be included in the diagnostic list in patients with a pelvic mass and a history of intrauterine device.