Crystalline keratopathy associated with monoclonal gammopathy of undetermined significance

Abstract

This otherwise healthy 81-year-old woman was noted at a routine ophthalmology appointment to have small crystalline deposits evenly distributed throughout the anterior corneal stroma of both eyes (image). She did not report any visual symptoms and her visual acuity remained unchanged at 6/9 in both eyes. The ocular examination was otherwise normal. She presented a year later to her general practitioner with fatigue. Serum electrophoresis demonstrated an IgG kappa paraprotein at a concentration of 17·2 g/l. She was referred to the haematology service and a bone marrow biopsy demonstrated a plasma cell infiltrate of 2%. As she had no myeloma-related organ or tissue impairment she was diagnosed with monoclonal gammopathy of undetermined significance (MGUS). She remains under surveillance by the haematology service. Crystalline keratopathy may be present in up to 1% of patients with MGUS and multiple myeloma. Crystals form as a result of immunoglobulin light chain deposition within cells in the epithelial and stromal layers of the cornea. Patients may report mild visual symptoms, such as photophobia, but their visual acuity is typically spared. Severe cases of paraproteinaemic crystalline keratopathy are rare but may result in corneal endothelial decompensation with progressive corneal thickening, stromal haze and visual loss. In symptomatic patients with paraproteinaemic crystalline keratopathy, treatment of the underlying disorder is the mainstay of management. Myeloma-associated crystalline keratopathy has been demonstrated to resolve as paraprotein levels fall in response to chemotherapy. Severe cases require a corneal graft but it is important to note that crystalline keratopathy can recur in the corneal graft if paraprotein levels remain high.