A 57-year-old man underwent penetrating keratoplasty because of intractable symptoms caused by a corneal dystrophy. Which of the following statements is true regarding the disease depicted in the histopathology photos shown above?
Pathology and Tumors
Meesmann corneal dystrophy is a disease of the corneal epithelium and its basement membrane. Its onset is relatively early in life and can cause mild foreign body sensation and slightly-decreased visual acuity (though many patients remain asymptomatic for years). Recurrent erosions are rare compared to the other corneal dystrophies.
It is characterized on slit-lamp exam by punctate, blister-like, round-to-oval opacities present within the corneal epithelium ("epithelial vesicles"). These are best seen on retroillumination. On histopathology, one can see multiple cysts predominantly within the basal layer of the epithelium. However, much of the pathology is seen on PAS staining, where one can see a particularly thickened and coarse basement membrane as well as a fibrillogranular material within the epithelial cells and cysts, often referred to in the literature as “peculiar substance.” It is postulated that the deposition of this material in the epithelium leads to cell death and cyst formation.
Also, note that the stromal and endothelial layers are normal in Meesman corneal dystrophy, so it does not look similar to Fuchs endothelial dystrophy on histopathology.
Meesman is associated with a mutation in one of a pair of genes, KRT3 or KRT12 (corneal keratin). It is inherited in an autosomal dominant pattern.
(Editor's Note: yes, it would be very rare for a Meesmann's patient to undergo a penetrating keratoplasty for Meesmann's alone. But there is always an exception to any rule!)