THBS1 and Schnyder corneal dystrophy: Altered balance of proinflammatory and anti-inflammatory cytokines plays an important role in a painful crisis in SCD patients.23 Placenta growth factor is angiogenic growth factor released by immature erythrocytes and is elevated in SCD.24,25 Thrombospondin-1 is the major secretory product of activated platelets and is a key player in vascular biology that is increased in VOE.8,15