Background
Epithelial basement membrane degeneration previously was classified as a type of corneal dystrophy. It historically was referred to as epithelial basement membrane dystrophy and also is known as map-dot-fingerprint dystrophy. [1] This name comes from the distinctive appearance observed in its characteristic slit-lamp findings. Other past names include Cogan microcystic epithelial dystrophy and anterior basement membrane dystrophy. [2, 3, 4, 5, 6]
Epithelial basement membrane degeneration is much more common than any corneal dystrophy. Unlike corneal dystrophies, epithelial basement membrane degeneration is sporadic, not hereditary, and is variable and fluctuating in its course rather than progressive. [7] It usually is bilateral, but can be unilateral or very asymmetric in presentation. [8]
Corneal dystrophies usually are described as hereditary, progressive, bilateral, and not associated with systemic or local disease. [9] The International Committee for Classification of Corneal Diseases (IC3D) classifies corneal dystrophies partly by anatomic layer of corneal involvement, but increasingly on a genetic basis. In the updated 2024 IC3D 3rd edition, the historical nomenclature epithelial basement membrane dystrophy is retained but noted to be "most likely degenerative and not hereditary." [9] It remains included as a class 3 dystrophy based on one report of two families with a presumed autosomal-dominant pattern attributed to the TGFBI gene, locus 5q31. [10, 11, 12, 13] ("Class 3: a well-defined corneal dystrophy in which the disorder has not yet been mapped to a chromosomal locus.") [9]
Pathophysiology
The corneal epithelium produces and adheres to its underlying basement membrane. Corneal abnormalities associated with epithelial basement membrane dystrophy are the result of a faulty basement membrane, which is thickened, multilaminar, and misdirected into the epithelium. [3, 8, 14] Deeper epithelial cells that normally migrate to the surface can become trapped. Epithelial cells anterior to aberrant basement membrane may have difficulty forming viable hemidesmosomes and basement membrane complexes, which attach to the underlying stroma, resulting in recurrent erosions. Irregular epithelium centrally can cause decreased vision.
Misdirected and reduplicated basement membrane into the epithelium in parallel or concentric rows may on slit lamp view appear as fingerprints. Sheetlike arrangements of intraepithelial multilamellar basement membrane may appear as maps or map outlines. Trapped epithelial cells may degenerate into microcysts containing cellular debris and apppear as dots or irregular grey-white patches. Small mounds of abnormal fibrillogranular material or thickened basement membrane located between the epithelium and Bowman layer may appear as blebs best seen in retroillumination. [15]
Epidemiology
Frequency
United States
Estimates of the prevalence of epithelial basement membrane degeneration range from 2% to 43% of the general population. [16] Of patients with epithelial basement membrane degeneration, 10% to 33% have recurrent corneal erosions. As many as 50% of patients with recurrent corneal erosions have epithelial basement membrane degeneration. [17, 18, 19, 20]
Mortality/Morbidity
Patients with epithelial basement membrane degeneration may be asymptomatic. Others experience painful recurrent erosions, decreased vision, or both. [20]
Sex
This condition is slightly more common in females than in males.
Age
This condition is uncommon in children.
Prognosis
Epithelial basement membrane degeneration findings may fluctuate but tend not to progress over time. Most patients are able to maintain sufficient vision and comfort for reading, driving, and other visual tasks, except during episodes of corneal erosions. [20] Most patients with visually disabling symptoms can be successfully treated with mechanical or laser keratectomy, or rigid contact lenses including scleral lenses.
Patient Education
Patients with epithelial basement membrane degeneration should be informed that refractions and best spectacle corrected vision may vary from visit to visit and even day to day, due to fluctuations in epithelilal and basement membrane involvement.