Meesmann Corneal Dystrophy Misdiagnosed as Refractory Dry Eye Disease: A case Report

Background Meesmann epithelial corneal dystrophy (MECD) is a well-recognized autosomal-dominant epithelial disorder caused by keratin mutations and classically characterized by diffuse intraepithelial microcysts. However, when these microcysts are subtle on routine slit-lamp examination, the condition may closely mimic chronic dry eye disease, leading to delayed diagnosis and prolonged ineffective therapy. We report a familial case initially managed as refractory dry eye disease in which multimodal imaging and genetic analysis established the correct diagnosis and identified a previously unreported keratin 3 variant. Case presentation: A 55-year-old Chinese man with well-controlled type 2 diabetes presented with six months of bilateral ocular discomfort and progressive visual blur. Slit-lamp examination demonstrated a narrow tear meniscus and diffuse punctate epithelial erosions without obvious dystrophic features, and he was treated for presumed dry eye disease with lubricants, anti-inflammatory agents, and epithelial trophic therapy over several months without meaningful improvement. The persistence of epithelial irregularity despite therapy prompted re-evaluation, and pre-fluorescein retroillumination revealed numerous glistening intraepithelial microcysts across the interpalpebral cornea. In vivo confocal microscopy confirmed dense, sharply demarcated microcysts involving superficial and basal epithelial layers. Examination of his asymptomatic 30-year-old son disclosed similar bilateral microcystic changes. Targeted next-generation sequencing identified a heterozygous keratin 3 missense variant (c.1525G > C, p.Glu509Gln) in both individuals, with Sanger sequencing confirming familial segregation. The variant is absent from population databases and predicted to be deleterious by computational analysis, supporting the diagnosis of Meesmann epithelial corneal dystrophy. Conclusions MECD may masquerade as therapy-refractory dry eye disease when microcysts are inconspicuous on standard examination. Persistent epithelial changes despite optimized tear management should prompt retroillumination, in vivo confocal microscopy, and consideration of genetic testing. Early recognition prevents prolonged misdirected treatment and enables appropriate family counseling.