Simplify the following text for a Grade 12 native English-speaking person.
Original: Sickle-cell disease ( SCD ) , or sickle-cell anemia ( or anemia ; SCA ) or drepanocytosis , is an autosomal recessive genetic blood disorder , with overdominance , characterized by red blood cells that assume an abnormal , rigid , sickle shape .
Simplified: This is a life long disease and a life long blood disorder , sickle cell disease or sickle-cell anemia , characterized by red blood cells that have an abnormal , rigid , sickle shape .