Pyomyositis following respiratory viral infections in children: A case series

Introduction: Pyomyositis is a suppurative infection of striated muscle. Historically endemic to tropical countries, it occurs at much lower incidence in the temperate zone. Outside of the tropics it most commonly occurs in adult patients. The pathogenesis is thought to involve secondary bacterial infection of injured muscle. Injury is most often the result of direct trauma or vigorous exercise. An alternative route is highlighted by our cases. Cases: We present two cases of pyomyositis in the setting of respiratory viral infection in children under the age of two. An 11-month-old male with Influenza A infection developed fever, abdominal distention and a right abdominal wall mass. WBC was normal but CRP and CPK were elevated. Pyomyositis was identified with ultrasound and characterized with CT and MRI. The abscess reaccumulated after treatment with antibiotics and aspiration but resolved with catheter drainage. Culture was positive for Staphylococcus aureus. A 20-month-old male with Enterovirus/Rhinovirus infection developed fever, and erythema and tenderness around the left scapula. WBC and CRP were elevated. Pyomyositis was identified by ultrasound and characterized by CT. The abscess resolved with aspiration and antibiotics. Culture was positive for Streptococcus pyogenes (group A streptococcus). Conclusion: Pyomyositis is a relatively rare pathology of skeletal muscle in non-tropical countries. We suggest the pathogenesis of pyomyositis in the context of a viral respiratory infection involves secondary bacterial infection of a viral-associated myositis.