Schnyder's Corneal Dystrophy

A Rare Genetic Disease Affecting People of Swedish-Finn Ancestry

by Joelle Steele

Schnyder's Crystalline Corneal Dystrophy (SCCD) is a rare, inherited eye disease which is found in populations of Swede-Finns, as well as people of other ethnicities. First identified in research literature in 1924, SCCD occurs when there are abnormal deposits of cholesterol and lipids (fats) in the cornea. The condition is difficult to diagnose in its early stages, and eventually leads to clouding of the cornea and loss of vision with age. Treatment at this time is corneal transplant surgery, if the vision is markedly reduced from the cholesterol deposits.

Most individuals with SCCD who have been studied to date are Swede-Finns. Dr. Jayne S. Weiss was the Director of the Cornea Service at the University of Massachusetts Medical Center in 1987, when she first began encountering people with SCCD. Upon closer investigation, Dr. Weiss discovered that three "unrelated" people with SCCD had the surname Johnson in their families and were of Swede-Finn descent. She was able to identify four family pedigrees with SCCD in the central Massachusetts area, all of which were traced to families living within a 100 km radius of southwest Finland on the Bay of Bothnia.

As of the early 2000s, Dr. Weiss examined more than 60 people with SCCD in the Swede-Finn population, the largest number of SCCD patients ever reported in the world. Having this identifiable population directed Dr. Weiss and her research group towards genetic research. In addition to Dr. Helena Kuivaniemi and Dr. Gerard Tromp at Wayne State University, Dr. Weiss' team includes researchers at Children's Hospital in Philadelphia, the National Institutes of Health in Maryland, Massachusetts Institute of Technology in Boston, and the University of Sweden in Helsinki. In 2001, Weiss, Kuivaniemi, and Tromp received a $750,000 grant from the National Institute of Health to isolate the gene responsible for SCCD.

Once the gene is isolated, Dr. Weiss plans future studies to study its function, which will hopefully lead to a medical treatment that may be able to save patients' vision by preventing the  accumulation of the cholesterol and lipids in the cornea. In addition, there are broad implications for sufferers of atherosclerosis and hypercholesterolaemia, diseases becoming more common in our overweight and fatty foods‑consuming society. Microscopic changes found in the corneas of patients with SCCD resemble those seen with atherosclerosis. Many patients in SCCD families have elevated levels of blood cholesterol, and it could be that a gene located near the SCCD gene is the cause. So genetic research done on SCCD could be a link to greater knowledge of genes' roles in relation to cholesterol in the body.

For more information, contact Jayne S. Weiss, MD, Professor of Ophthalmology, Pathology and Pharmacology, LSU Eye Center at LSU Health Sciences Center, New Orleans, 533 Bolivar Street/CSRB 459, New Orleans, LA 70112.