Streptococcus agalactiae pyomyositis in a patient with primary biliary cholangitis: A case report

Pyomyositis is an uncommon clinical scenario; it is usually associated with predisposing factors, including poorly controlled diabetes mellitus, trauma history, and immunocompromise. We discuss the case of an elderly woman with a 20-year history of diabetes mellitus and remissive breast cancer after modified radical mastectomy and subsequent chemotherapy 28 years previously. The patient presented with severe shoulder pain and gradual swelling. After examination, pyomyositis was diagnosed and debridement surgery was performed. Culture of the wound samples showed the growth of Streptococcus agalactiae. During hospitalization, primary biliary cholangitis (PBC) was diagnosed incidentally, accompanied by poor glycemic control. After treatment with antibiotics for pyomyositis and ursodeoxycholic acid for PBC, the infection resolved in 8 weeks, and her glycemic control was improved after PBC treatment. It is possible that the long-term untreated PBC worsened insulin resistance and aggravated diabetes mellitus in this patient. To the best of our knowledge, this is the first reported case of pyomyositis caused by an unusual pathogen, S. agalactiae, in a patient with newly diagnosed PBC.