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Two new hereditary corneal disorders discovered

October 03, 2015

The story begins with a mother and daughter arriving at the eye clinic at the University Hospital in Link?ping. They both suffer from recurrent wounds on the cornea, causing pain, watery eyes, sensitivity to light and decreased vision. At the clinic they are seen by Professor Per Fagerholm and Specialist Consultant Bj?rn Hammar.

"They had been referred from a hospital in the county of Sm??land and their complaint did not match any previously diagnosed disorders. It transpired that many in their extended family suffered from the same problem", says Bj?rn Hammar, who now publishes the research results in his doctoral thesis at LiU.

He created a family tree, going back six generations with 171 individuals born 1854 and later. Of these 44 had suffered from the disorder and nine had undergone corneal grafting. Most had developed symptoms before the age of one. It soon became apparent this was a disorder with autosomal dominant inheritance, meaning you only need to get the abnormal gene from one parent in order for you to inherit the disorder.

Close clinical studies and genetic analyses showed this disorder was clearly demarcated from other disorders with similar symptoms. The disorder was named after the area of Sweden where this family had lived for generations, Dystrophia Smolandiensis.

The research led to data about a similar phenomenon in a different Swedish county, H?lsingland, being revisited and closer examined. This family tree included seven generations and 342 people, of which 84 had symptoms similar to that of the family from Sm??land, but the overall picture of the disorder deviated enough for a separate diagnosis. The onset in Dystrophia Helsinglandica was usually later, at the ages of 4-7, and the symptoms were worse but less frequent.

"Clinically we can determine that this is two similar but separate disorders. The next stage is to find the mutations in these families and then continue our research with ten further families we know of. This is likely to just be the tip of the iceberg" says Bj?rn Hammar.

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Dr. Christian Beckmann of Imperial College London, says it could be that the brain just wears itself out in some people as even when the volunteers carrying APOE4 weren't being asked to do anything, the memory part of their brain could be seen to be working harder than it was in the other volunteers.

Dr. Clare Mackay from the Department of Psychiatry and the Centre for Functional Magnetic Resonance Imaging of the Brain at the University of Oxford,who led the study, says these are the first steps towards a simple test that will be able to distinguish who will go on to develop Alzheimer's.

For the study the researchers used a type of real-time imaging called functional magnetic resonance imaging or fMRI to look at the brains of 36 volunteers aged 20 to 35, 18 who had at least one copy of APOE4 - none of whom were experiencing any memory problems and all performed normally on tasks designed to test their cognitive skills.

The researchers will now carry out a similar study of patients with mild cognitive impairment to explore how these differences in patterns of brain activity in young people may be associated with later changes.

The research is published in the journal Proceedings of the National Academy of Sciences.