Genetic diversity in hemoglobins. Disease and nondisease.

Recent mass screening programs for sickle cell trait have been the first large-scale efforts to detect potentially deleterious genes and to provide genetic counseling to healthy carriers. In these programs, the expected prevalence of sickle hemoglobin and hemoglobin C has been found, and other mutant hemoglobin genes have also been uncovered. Many of these are not associated with disease, but simply reflect normal genetic diversity. A paradox of this finding is illustrated when, in counseling, many persons demonstrate difficulty in understanding that though they have an abnormal hemoglobin gene, they themselves are not ill or abnormal. The problem's solution lies in educating both health professionals and the public so that the normal existence of considerable genetic diversity is recognized. Since every person may carry mutant genes, whether potentially deleterious or innocuous, our definition of normal must be revised.