[Erdheim Chester Histiocytosis as a Diagnostic Challenge in a Systemic Presentation: A Case Report]

Histiocytosis are caused by pathogenic myeloid cells, and can be classified as Langerhans cell histiocytosis (LCH) and non-LCH. Erdheim-Chester disease (ECD) is a non-LCH, characterized by multi-organ involvement, typical imaging findings, and confirmatory histological studies. A case with multi-organ involvement and histological confirmation is presented. A male patient, 50 years old, presented muscle weakness associated with elevated inflammatory parameters, visual disturbances, and exophthalmos. Imaging studies revealed a non-specific retro-orbital mass and retroperitoneal fibrotic mass with perivascular, myocardial, and perirenal infiltration and bone hypermetabolism. Systemic corticosteroids were started, and a biopsy of the retroperitoneal mass informed foamy histiocytes, positive for CD68, negative for CD1a, and positive for BRAFV600 mutation. Treatment with Vemurafenib was started with a good response. Less than 500 cases of ECD have been reported in the literature. It has been described to present with multi-organ involvement, including bone, orbital, renal, and endocrinological involvement, among others. Its diagnostic criteria include imaging and histological alterations, consistent with those described in this patient. The first line of treatment is interferon alpha, which has been shown to improve survival but is associated with adverse effects. As a second line, it has been proposed Vemurafenib when BRAFV600 mutation is present.