Confocal microscopy in a case of crystalline keratopathy in a patient with smouldering multiple myeloma

We report the clinical and confocal microscopic findings of the cornea in a patient with smouldering multiple myeloma (SMM) using in vivo scanning laser confocal microscopy. A 72-year-old female underwent a complete ophthalmological examination including slit-lamp biomicroscopy with digital photography, HRT II laser scanning in vivo confocal microscopy and haematological laboratory assessment. Corneal biomicroscopy revealed the presence of bilateral diffuse microgranular tiny grey opacities. In vivo confocal microscopy showed randomly oriented hyper-reflective needle-shaped crystals throughout all levels of the stroma, sparing epithelium and endothelium. In vivo confocal microscopy was very helpful in the differential diagnosis by allowing the nature of the corneal deposits to be established, revealing the typical aspect of the crystals, and excluding granular dystrophy, leading to a suspected diagnosis of SMM. Crystalline corneal deposits may easily be confused as crumb-like opacities typical of granular dystrophy on slit-lamp examination even by experienced ophthalmologists.