Orbital Abscess in an Infant With STAT3 Hyper-IgE Syndrome.

Orbital cellulitis (OC) is a rare diagnosis in infants, with limited numbers of cases reported in the literature to date. We report a 34‑day‑old female who presented with severe left-sided periorbital swelling and proptosis. Imaging confirmed a large orbital abscess with associated ethmoid sinusitis, and she underwent urgent exploration and drainage and initiation of broad‑spectrum intravenous antibiotics. Cultures grew methicillin‑sensitive Staphylococcus aureus. Postoperatively, she developed leukocytosis, eosinophilia, and recurrent skin abscesses, prompting immunologic evaluation. Genetic testing identified a novel STAT3 mutation in the SH2 domain consistent with Hyper‑IgE syndrome. This case highlights both the importance of prompt surgical and medical intervention in infantile orbital cellulitis and the need to consider underlying immune dysregulation when atypical clinical or laboratory findings are present. To our knowledge, this is the first reported case of infantile orbital cellulitis associated with Hyper-IgE syndrome, and the first report of this specific STAT3 variant causing hyper‑IgE syndrome.