Monoclonal gammopathy presenting with paraproteinemic keratopathy documented with anterior segment OCT: a case report

Paraproteinemic keratopathy (PPK) is a rare ocular manifestation of monoclonal gammopathies such as monoclonal gammopathy of undetermined significance (MGUS), smoldering multiple myeloma (SMM), and multiple myeloma (MM). Although these hematologic conditions are relatively common in older adults, their ocular presentations remain underrecognized or misdiagnosed. We report a case of PPK where anterior segment optical coherence tomography (AS-OCT) revealed a unique mixed-layer deposition pattern, contributing new imaging insights to the clinical spectrum of PPK and underscoring the importance of ophthalmic findings in prompting systemic evaluation.

A 52 -year-old man with no prior medical or family history presented with incidental discovery of bilateral corneal white lesions. Visual acuity was 20/20 in both eyes. Slit-lamp examination showed bilateral peripheral white nummular stromal opacities with limbal sparing. AS-OCT revealed mid-peripheral hyperreflective lesions affecting Bowman's layer, anterior and posterior stroma, and endothelium, with a clear intermediate stroma separating the lesions, an imaging feature not previously documented in PPK. Hematologic workup revealed an IgG kappa monoclonal gammopathy, and bone marrow biopsy confirmed smoldering multiple myeloma without systemic symptoms. The patient received nine courses of chemotherapy leading to hematologic remission and progressive improvement of corneal changes on slit-lamp examination and AS-OCT.

This case illustrates the potential of AS-OCT to identify subtle and layered patterns of corneal paraprotein deposition in PPK. While findings are limited to a single patient, the imaging features expand current understanding of the disease and support the integration of AS-OCT into diagnostic and follow-up strategies. Ophthalmologists should consider monoclonal gammopathies in unexplained bilateral interstitial keratitis, as timely diagnosis may influence both ocular and systemic outcomes.