Orbital Waldenström Macroglobulinemia With Angiopathic Paraprotein Deposition: A Case Report.

Ocular manifestations of Waldenström macroglobulinemia (WM) are most frequently related to hyperviscosity-related retinopathy but may also include conjunctival infiltration and vitritis. Orbital and ocular adnexal lymphomatous deposition, including within the orbit, is exceedingly rare. We report a unique case of a 66-year-old female with orbital infiltration from WM presenting with recurrent episodes of transient vision loss secondary to angiopathic deposition of eosinophilic hyaline paraprotein in the absence of hyperviscosity syndrome. Right orbital biopsy demonstrated adipose tissue with deposition of eosinophilic hyaline material, outlining adipocytes and deposited within walls of blood vessels. The material was strongly PAS positive, weakly metachromatic with crystal violet but was negative for apple-green birefringence on Congo red staining. IgM immunohistochemistry strongly decorated the orbital eosinophilic material, suggesting macroglobulinosis paraprotein deposition and not amyloid. There was an associated patchy infiltrate of low-grade lymphoplasmacytic B-cell lymphoma with kappa light chain restriction demonstrated in the neoplastic plasma cell population, consistent with her known WM.