A U.S. agency said it has found no environmental factors linking 38 cases of a rare blood cancer in northeastern Pennsylvania.

The Agency for Toxic Substances and Disease Registry confirmed 38 cases of polycythemia vera (PV) in Schuylkill, Luzerne and Carbon counties, using a recently discovered genetic marker known as JAK2. The agency, however, said the people diagnosed with PV did not share common occupations, water sources or other identifiable environmental exposures.

The cases were scattered throughout the area in no predictable pattern, the agency said Wednesday in a release.

PV is a rare blood disorder characterized by the overproduction of red blood cells. It is classified as a cancer because stem cells in the bone marrow do not respond to the normal signals to stop reproducing red blood cells.

"We will continue to monitor trends of PV and work with our partners to better understand the disease and its impact on residents in this area of the state," said Pennsylvania Health Secretary Dr. Calvin B. Johnson.

Copyright 2007 by United Press International