Abstract
Purpose:
To describe two novel ultrastructural patterns of corneal immunoglobulin deposition in monoclonal gammopathy of undetermined significance (MGUS).
Methods:
The corneal buttons of two patients with monoclonal gammopathy were studied. Histologic sections of corneal tissue were stained with hematoxylin and eosin, periodic acid-Schiff (PAS), Masson trichrome, and Congo red stains. Immunohistochemistry and in situ hybridization (ISH) studies for immunoglobulin heavy and light chains were performed on the histologic sections. Transmission electron microscopy (TEM) was also performed. Pertinent literature was reviewed.
Results:
Patient 1: A 76-year-old woman presented with bilateral corneal haze and vascularization believed to be secondary to old interstitial keratitis. Penetrating keratoplasty was performed. Histologic analysis revealed eosinophilic deposits within the corneal stroma which stained strongly with Masson trichrome. ISH failed to demonstrate the presence of light chains. TEM demonstrated extracellular electron-dense stromal scroll-like deposits ranging in size from 100-300 nm in diameter. Further clinical workup demonstrated MGUS.The patient is being monitored without treatment, with no recurrence noted at 16-month follow-up. Patient 2: A 53-year-old man presented with bilateral crystalline corneal opacities in the epithelium and superficial stroma in 2008. Serum protein electrophoresis (SPEP) was negative. The haze worsened in 2013 and repeat SPEP showed an M spike, presumed MGUS. Corneal biopsy demonstrated non-birefringent eosinophilic, PAS-positive, and Masson trichrome-positive deposits within the epithelium, Bowman layer, and superficial stroma. The deposits immunoreacted with antibodies to lambda light chains. TEM demonstrated round, electron-dense deposits consistent with immune complexes. Systemic workup including bone marrow biopsy is pending.
Conclusions:
To our knowledge, the ultrastructural patterns of large scroll-like deposits and immune complexes have not been previously described in the cornea but have been reported in the kidneys of patients with paraproteinemia. Our findings underscore the importance of careful clinical, histopathologic and ultrastructural evaluation of patients with corneal opacities suggestive of paraproteinemia.
Keywords: 597 microscopy: electron microscopy •
554 immunohistochemistry •
484 cornea: stroma and keratocytes