As a result of carrier protection against malaria, the inherited hemoglobin disorders are the commonest diseases attributable to single defective genes. Approximately 7 percent of the world's population is a carrier, and 300,000 to 500,000 babies with severe forms of such disorders are born each year (WHO 1989). Although these disorders are most frequent in tropical regions, they are now encountered in most countries because of migrations of populations.
Copyright © 2006, The International Bank for Reconstruction and Development/The World Bank Group.