Rapid-onset group A streptococcal pyomyositis after minor blunt leg trauma in an immunocompetent adult: a case report

<p><strong>Background: </strong>Pyomyositis is uncommon in temperate regions and is usually caused by Staphylococcus aureus. Infections due to group A Streptococcus (GAS) are rare but can progress rapidly.</p> <p><strong>Case Presentation: </strong>A healthy 50-year-old man presented with a three-day history of left-calf pain and swelling two days after minor blunt trauma. He was tachycardic but normothermic. Work-up for thrombosis and cellulitis showed leukocytosis (24.9 × 10^9/L) and C-reactive protein 436 mg/L; Doppler leg ultrasonography and chest computed tomography (CT) were unremarkable. Within 18 hours, the limb became tense with new blisters and systemic instability. Urgent limb CT revealed extensive subcutaneous edema and fascial fluid. Fasciotomy identified intramuscular abscesses without necrotizing fasciitis. Cultures grew GAS sensitive to penicillin. Broad-spectrum intravenous antibiotics were streamlined to benzyl-penicillin, meropenem, and metronidazole; two weeks of intravenous therapy followed by two weeks of oral co-amoxiclav achieved near complete recovery.</p> <p><strong>Conclusions: </strong>GAS pyomyositis can transform mild limb discomfort into sepsis within hours, even in immunocompetent adults. Disproportionate tachycardia, rapidly spreading swelling or blistering, and escalating inflammatory markers warrant early cross-sectional imaging, multidisciplinary review, and prompt operative exploration. Vigilant reassessment and decisive intervention were critical to the favorable outcome in this case and may reduce morbidity in similar rapidly progressive infections.</p>