Panstromal Schnyder corneal dystrophy. A clinical pathologic report with quantitative analysis of corneal lipid composition.

Background: The pathogenesis of Schnyder dystrophy is thought to be a primary abnormality of corneal lipid metabolism resulting in opacification secondary to lipid accumulation. Histochemical investigations have suggested the accumulated lipid includes unesterified cholesterol; however, quantitative analysis has not been done.
Methods: Quantitative biochemical analysis was performed on a corneal button obtained from a patient with clinically and pathologically proven Schnyder dystrophy. Results were compared with four age-, sex-, and size-matched corneal buttons obtained from cadaveric eyes.
Results: Corneal lipid accumulated in Schnyder dystrophy predominantly is composed of phospholipid, free cholesterol, and cholesterol ester. These constituents were markedly elevated in the Schnyder cornea when compared with cadaveric control corneas as follows: (1) phospholipid, 23.6 versus 4.05 mg/g; (2) unesterified cholesterol, 6.99 versus 0.52 mg/g; and (3) cholesterol ester, 3.16 versus 0.26 mg/g.
Conclusion: Phospholipid, unesterified cholesterol and cholesterol ester are the predominant lipids in Schnyder dystrophy. The pathogenesis may be a primary disorder of corneal lipid metabolism.