Intraepithelial corneal immunoglobulin crystals in IgG-kappa multiple myeloma.

A 52-year-old man was first examined because of bilateral superficial punctate keratitis. Slit-lamp examination disclosed numerous intraepithelial minute opacities in both corneas. A corneal biopsy revealed intraepithelial rhomboidal or rectangular crystals that immunohistochemically stained only for IgG-kappa. Serum immunoelectrophoresis demonstrated an IgG-kappa monoclonal gammopathy. Over the ensuing 6 years, the clinical appearance of the crystals changed from small dot-like opacities to polychromatic crystals. At this time, bone marrow examination established the diagnosis of multiple myeloma. Ophthalmologists should be aware of this entity and carefully monitor these patients; the corneal lesions may be the initial manifestation of an asymptomatic monoclonal gammopathy preceding the development of multiple myeloma.