Unusual Midline Chest Wall Cellulitis in an Infant Without Trauma or Skin Barrier Disruption.

Cellulitis in children usually develops on the extremities or face following minor trauma or skin barrier disruption, and involvement of the trunk is uncommon. We report a one-year-old previously healthy boy who presented with fever and a rapidly enlarging anterior chest wall mass. Laboratory tests revealed elevated inflammatory markers without evidence of immunological abnormality. Ultrasonography showed a 12-mm swelling beneath the lower sternum with increased blood flow but no abscess. Cellulitis was diagnosed, and intravenous cefazolin was initiated. Blood culture obtained on admission grew methicillin-susceptible Staphylococcus aureus. On hospital day nine, contrast-enhanced magnetic resonance imaging demonstrated cellulitis localized to the xiphoid process without evidence of osteomyelitis. The patient completed two weeks of intravenous cefazolin and was discharged without complications. In this case, the absence of trauma, skin barrier disruption, or underlying disease raises the possibility of hematogenous dissemination of S. aureus as the cause of infection. Although rare, hematogenous cellulitis should be considered in pediatric patients presenting with soft-tissue infection at unusual sites. Imaging and microbiological evaluation may be helpful in atypical cases to support diagnosis and guide management.