CRYSTALLOIDAL PARAPROTEIN DEPOSITS IN THE CORNEA - AN ULTRASTRUCTURAL-STUDY OF 2 NEW CASES WITH TUBULAR CRYSTALLOIDS THAT CONTAIN IGG-KAPPALIGHT-CHAINS AND IGG-GAMMA HEAVY-CHAINS

The fine structure and immunoprotein content of the crystalloids are d escribed in two cases of paraproteinemic crystalloidal keratopathy, bo th of which had clinical features thought by the referring ophthalmolo gists to be those of atypical lattice-type corneal dystrophy (presumab ly because of lattice-like lines). Most keratocytes in one case were s urrounded by a mantle of densely packed tubular crystalloids. Individu al tubules were annular in cross section with mean dimensions as follo ws: overall diameter, 29.32 nm (SD 1.26); internal diameter (core), 8. 53 nm (SD 1.12); wall thickness, 10.39 nm (SD 0.85) (n = 10). Crystall oids were extracellular and found only in the corneal stroma, with non e in Bowman's layer or Descemet's membrane. In the second case, the tu bules had a similar distribution but formed geometric arrays with no c lear relationship to, or envelopment of, the keratocytes. The tubules were thin-walled, with mean dimensions as follows: overall diameter, 2 6.12 nm (SD 1.12); internal diameter (core), 15.46 nm (So 1.12); wall thickness, 5.33 nm (SD 0) (n = 10). In both cases the tubules were kap pa-light chain- and gamma-chain-positive. Laboratory investigations re vealed the presence of two IgM-kappa paraproteins and an IgG-kappa par aprotein in the serum of the first patient. The second patient had an IgG-kappa paraproteinemia and bone marrow changes consistent with low- grade non-Hodgkin's lymphoma. These cases emphasize and extend the mor phological range of corneal IgG crystalloids; the second case also dem onstrates that corneal IgG crystalloids may be an early indicator of a n underlying immunoproliferative disease.