Copy number variation found to cause rare kidney disease

So far, the disease, which the researchers have named CFHR5 nephropathy, has been identified in over one hundred people, all of whom are of Cypriot descent, including some living in the UK. Symptoms include blood in the urine -- both microscopic and, occasionally, visible -- and progressive kidney malfunction.

Under current guidelines, the presence of blood in the urine, when not accompanied by traces of protein, urinary tract abnormalities or impairment to the kidneys, is considered benign and is not investigated further. However, in a study published in The Lancet, researchers from Imperial College London and UCL (University College London) show that in rare cases, it can be symptom of this progressive, chronic kidney disease.

The researchers, working with colleagues in Cyprus, identified an inherited kidney disorder caused by a copy number variation of the gene CFHR5. Copy number variations are large chunks of DNA either duplicated or deleted from our genes when passed down to children. CFHR5 is involved in the production of proteins used by the complement system, a key component of the body's innate immune response.

The mutation was found in twenty-six individuals from eleven families. All were of Cypriot ancestry. The researchers believe the mutation dates back to a single common ancestor over sixteen generations ago.

"We believe this mutation accounts for a significant proportion of kidney disease in the Cypriot population, both on the island itself and worldwide," says Dr Matthew Pickering, a Wellcome Trust Senior Fellow at Imperial College London. "It is a potentially serious disease, but easily detectable from a simple DNA or blood test."

Although scientists do not yet fully understand how the mutation leads to disease, the researchers believe that the findings should help them provide effective genetic counselling to families affected by the condition.

"People who carry just one copy of the genetic mutation will almost certainly develop the condition," says Professor Patrick Maxwell from UCL. "Now that we know the mutation responsible, we are in a position to offer genetic counselling to parents considering having children."

No evidence-based treatments currently exist for the condition, so the researchers are now focusing their research efforts on the development of therapies for CFHR5 nephropathy.