Have just joined the forum and asked the same question myself!  I've had KC for 35 years and have always understood that no-one knows for sure the cause.  My daughter was diagnosed with Sjogren's Syndrome last week and all the symptoms were gone through.  To my surprise, one of them was corneal ulcers - which I had even before my KC was diagnosed.  Another was dry eyes - well, I've always put that down to my KC, but I'm beginning to wonder now.  Her specialist also pointed out a goitre on her neck, which is typical of Sjogren's Syndrome ... and I had the same a couple of years ago.  I know that S's Syndrome is likely to be genetic and, with the similarities of some of the symptoms, I'm wondering too if it's somehow related/connected to KC.

Search on "Pub Med"

http://www.ncbi.nlm.nih.gov/pubmed

(The public medicine website where many of the research papers are at)

I was reading that KC is associated with several hundred conditions, so don't worry too much, but it may cluster as well as be sporadic. Its still very much a mystery.

Also, don't be too worried in the content you read from research studies unless the results has been reproduced by various research groups and as well as been peer reviewed.