Leukocytes adhere to blood vessels as a mechanism to enter tissue where there is inflammation. Inadvertently, they pile up sickle cell red blood cells.
Mutations in the hemoglobin gene can render a person to a lifetime of sickle cell disease (SCD). While otherwise healthy individuals with one allele (gene copy) of the sickle hemoglobin (HbS) gene are carriers, the disease is seen in those with two HbS alleles – one inherited from each carrier parent. A single HbS allele can also cause SCD in a person who inherits other defects in the second hemoglobin allele.