Unilateral 'cheetah-like' endotheliopathy: A rare endothelial phenotype regressing after phacoemulsification.

Purpose: To report an exceptional case of unilateral endothelial corneal disease with unique specular microscopy findings and a regressive course following cataract surgery. Methods: We present a 60-year-old patient with a unilateral corneal anomaly discovered during a routine slit-lamp examination. Specular microscopy, retro-illumination (innovative prototype) were used for imaging. Endothelial cell density (ECD) was assessed, and genetic testing for TCF4 gene mutations was performed. During the follow-up, the patient underwent phacoemulsification for cataract surgery. Results: Retroillumination images showed numerous vesicular-like lesions in the center of the cornea that were not confluent. Specular microscopy revealed a cheetah-like pattern of dark spots centered in endothelial cells with normal ECD. Post-surgery, most vesicular-like lesions disappeared, replaced by regular pigment deposits, which diminished over time. ECD decreased by 49% one year post-surgery, but corneal transparency and normal thickness were maintained. Genetic testing for TCF4 triplet repeat expansions was negative. Conclusion: These findings reveal a previously uncharacterized endothelial anomaly, representing a diagnostic challenge given its strictly unilateral presentation and sudden resolution after phacoemulsification. The disappearance of vesicular-like lesions and subsequent pigment deposition suggest a possible relationship with membrane structures, such as macrovesicles or primary cilia. The findings highlight the value of retro-illumination imaging, which we have recently reintroduced using an innovative prototype. This technique proved crucial in detecting subtle and widespread endothelial abnormalities that were otherwise difficult to observe with a slit lamp, offering a valuable diagnostic tool for diagnosing and monitoring endothelial disorders.