Sickle cell anemia is a public health concern worldwide, proven by approximately 300,000 newborns carrying such conditions, and 100,000 American adults suffering from this disease. It is a genetic disorder that causes red blood cells to have a sickle shape. The heredity pattern of sickle cell anemia does not entirely follow the law of dominance, which was spearheaded by Mendel. Instead, the deformed hemoglobin characteristics are inherited as a codominant trait.
A codominant allele is an allele that can be expressed simultaneously with its homologous allele that signifies the same phenotype. Sickle cell anemia can be concluded as a codominantly-inherited disease as the two alleles of hemoglobin deformities, termed as HbS and HbC (can be coinherited as HbSC). The difference between these two deformity alleles resides in the replacing amino acids; in HbS, a single base mutation occurs, which results in the replacement of glutamic acid with valine. HbC also results from a single base mutation, except lysine is the replacing amino acid in this case. However, if any of those two alleles are inherited along with the normal human hemoglobin allele (HbA), it would not cause any observable symptoms. A similar trend is also known in the case of the homozygous HbC genotype, in which the patient exhibits only a few symptoms aside from mild haemolytic anemia. Meanwhile, HbSC patients exert similar but different clinical signs as those who bear HbSS genotypes. For instance, HbSC is signified by the inability of HbC to solubilize in the red blood cells, while HbS is characterized by the formation of sickle-shaped and rigid hemoglobins. In addition, HbSs is thought to be more severe compared to HbSc as HbSc patients suffer from milder symptoms and are less likely to have a complication compared to HbSS patients.
Sickle cell anemia has different symptoms in every case, and it usually appears at around six months of age. Red blood cells in sickle cell anemia often die within 10 to 20 days. This creates a lack of red blood cells compared to normal red blood cells, which typically have a lifespan of around 120 days before they need to be replaced. Therefore, the main symptom of this disease is anemia itself. Other than that, periodic episodes of extreme pain, swelling of hands and feet, frequent infections, delayed growth or puberty, and vision problems are also primary symptoms of sickle cell anemia. However, several treatments can be done to treat the disease, such as blood transfusion and stem cell or bone marrow transplant, which involves replacing stem cells or bone marrow affected by sickle cell anemia with healthy counterparts from a donor.