Polycythemia vera in identical twins

The occurrence of polycythemia vera in family members has been a rare event, with little or no documentation in the literature to suggest a common genetic defect. We report here on the first case of polycythemia vera documented in identical twins. No chromosomal abnormalities have yet been detected in these patients. The criteria for the diagnosis of polycythemia vera are reviewed, and the possible implications of our findings are discussed.