Noun
a congenital form of anemia occurring mostly in blacks; characterized by abnormal blood cells having a crescent shape
Source: WordNetsickle cell disease
Reducing the instance of sickle-cell disease genes in Africa where malaria is a common and deadly disease could indeed have extremely negative net consequences. Source: Internet
Some diseases such as sickle-cell disease and cystic fibrosis respectively confer immunity to malaria and resistance to cholera when a single copy of the recessive allele is contained within the genotype of the individual. Source: Internet