Keratopathy of multiple myeloma masquerading as corneal crystals of ocular cystinosis.

We describe a 49-year-old woman in whom ocular cystinosis was diagnosed on the basis of a routine eye examination 12 years previously. Conjunctival biopsy was reported to support the diagnosis. The patient described photophobia for the past 5 years and reported a 2-fold increase in her serum IgG level for the past 12 years. On ophthalmic examination, corneal crystals were evident in the epithelium and superficial stromal layers, rather than throughout the corneal epithelium and the entire stroma as in ocular cystinosis. The patient's serum protein level was elevated at 8.7 g/dL; protein electrophoresis showed an elevated gamma-globulin peak, and the IgG level was twice that of normal at 2820 mg/dL. Bone marrow biopsy confirmed the diagnosis of multiple myeloma. This case illustrates that multiple myeloma can mimic corneal findings of cystinosis.