Spontaneous regression of a presumed orbitocranial eosinophilic granuloma in an adult patient: illustrative case

BACKGROUND: Eosinophilic granuloma (EG) is a localized subtype of Langerhans cell histiocytosis (LCH) that involves infiltration of tissues by a clonal proliferation of Langerhans cells. EG is a rare tumor of the orbit and most commonly presents in childhood. This tumor is known to regress after minimal intervention (including biopsy), and management includes curettage and intralesional corticosteroids. The natural history of EG is not well understood, and true spontaneous regression of the lesion without intervention has rarely been described. OBSERVATIONS: Herein, the authors present a unique case of an adult patient with presumed orbitocranial EG with true spontaneous regression over a 4-month period. Biopsy of the residual mass revealed reactive changes and no evidence of neoplasia, consistent with resolved EG. LESSONS: Adult patients with EG may experience regression of the lesion without intervention. https://thejns.org/doi/10.3171/CASE25426.