Hemophagocytic lymphohistiocytosis of the ocular adnexal mimicking orbital cellulitis in a patient with unknown X-linked lymphoproliferative syndrome type 1 (XLP1): Case report and literature review.

A 5-year-old boy presented with severe acute bilateral periorbital edema. Initial misdiagnosis was made as preseptal orbital cellulitis, and he failed to respond to conventional antibiotic therapy. Magnetic resonance imaging revealed thickening of the anterior orbital adipose tissue bilaterally, with hyperintensity on T2-weighted imaging. The biopsy unveiled lymphoma-associated hemophagocytic syndrome, specifically Epstein-Barr virus related. The patient was administered rituximab, resulting in a significant amelioration. A family history, coupled with genetic investigation, ultimately led to the diagnosis of X-linked lymphoproliferative syndrome type 1 due to a large deletion of exons 2-4 of *SH2D. Reported ocular manifestation of XLP1 includes retinal hemorrhages, disc edema, acute posterior multifocal placoid pigment epitheliopathy, and macular edema. No ocular adnexal involvement has been previously reported. This case documents a case of XLP1 syndrome affecting the ocular adnexa and emphasizes the critical need to consider underlying immunodeficiencies in patients who do not respond to conventional therapies.