A Case of Multifocal Primary Pyomyositis Complicated With Toxic Shock Syndrome in a Non-tropical Region

Primary pyomyositis, also known as tropical pyomyositis, is a primary bacterial infection of skeletal muscle following hematogenous infections. It is primarily caused by Staphylococcus aureus or Group A Streptococcus and predominantly affects children and young adults. Although rarely observed in temperate climates, its prevalence appears to be increasing. Here, we present the case of a 36-year-old male patient who manifested with persistent fever and inflammatory signs in multiple skeletal muscle locations following acute pharyngitis, further complicated by toxic shock syndrome within 48 h of admission. The blood cultures were positive for Streptococcus pyogenes and ultrasound evaluation demonstrated muscle tissue heterogeneity, associated with areas of liquid collection and subcutaneous edema, in the right pectoral muscles and bilaterally in the fibularis longus and extensor digitorum longus muscles, confirming the diagnosis of primary pyomyositis. After treatment with a prolonged course of antibiotics, the patient showed substantial clinical improvement and was completely asymptomatic at 6-month follow-up. This case illustrates the possible risks associated with primary pyomyositis and the importance of its early recognition and treatment, regardless of geographic location.