kappa-Immunoglobulin corneal deposits associated with monoclonal gammopathy. Immunohistochemical and electron microscopic findings.

A 62-year-old man had a 1-year history of bilaterally decreased visual acuity associated with irregular, patchy, grayish-white stromal infiltrates involving both corneas. As visualized by light microscopy, the keratectomy specimen showed numerous homogeneous, eosinophilic deposits located mostly within keratocytes in the posterior one-third of the stroma. The deposits stained reddish-brown with Masson's trichrome but were periodic acid/Schiff-negative. As visualized by electron microscopy, the intracytoplasmic deposits were located within dilated cisternae of rough-surfaced endoplasmic reticulum of keratocytes and disclosed a 10-nm periodicity with a distinct lattice pattern. Immunoperoxidase strains confirmed that the deposits contained immunoglobulin (IgG-kappa). At 2 weeks following a histopathologic examination of the keratectomy specimen, serum protein analysis and immunoelectrophoresis with quantitation of immunoglobulins demonstrated an IgG-kappa monoclonal gammopathy. The abnormal corneal deposits may be the first clinical sign of a malignant lymphoproliferative process that may be associated with a monoclonal gammopathy.