It's been long known that patients with sickle cell disease have malformed, "sickle-shaped" red blood cells that can cause sudden painful episodes when they block small blood vessels.

Now, researchers at the University of North Carolina at Chapel Hill School of Medicine have shown blood from sickle cell patients also contains clumps of red and white blood cells.

The scientists said their finding marks the first time aggregates made up of red blood cells and white blood cells have been found in whole blood from sickle cell patients. The study also shows how the red and white blood cells adhere to one another.

"If the blockages are caused by these chunks of aggregates that are circulating in the blood, and we know how the aggregates are sticking together, we potentially could design drugs to disrupt the aggregates so that they pass through the blood vessel more freely," Assistant Professor Julia Brittain said.

The study was published on-line April 18 in the British Journal of Hematology.