Background: Sickle cell diseases (SCDs) are inborn and catastrophic processes on vascular endothelium, particularly at the capillaries. Methods: All patients were included. Results: We studied 222 males and 212 females with similar mean ages (30.8 vs 30.3 years, p>0.05, respectively). Beside digital clubbing (14.8% vs 6.6%, p<0.001), smoking (23.8% vs 6.1%, p<0.001), alcohol (4.9% vs 0.4%, p<0.001), transfused red blood cells (RBCs) in their lives (48.1 vs 28.5 units, p=0.000), disseminated teeth losses (5.4% vs 1.4%, p<0.001), chronic obstructive pulmonary disease (COPD) (25.2% vs 7.0%, p<0.001), ileus (7.2% vs 1.4%, p<0.001), cirrhosis (8.1% vs 1.8%, p<0.001), leg ulcers (19.8% vs 7.0%, p<0.001), coronary heart disease (CHD) (18.0% vs 13.2%, p<0.05), chronic renal disease (CRD) (9.9% vs 6.1%, p<0.05), and stroke (12.1% vs 7.5%, p<0.05) were all higher, and autosplenectomy (50.4% vs 53.3%, p<0.05) and mean age of mortality were lower in males, significantly (30.2 vs 33.3 years, p<0.05). Conclusion: The hardened RBCs-induced capillary endothelial damage initiates at birth, and terminates with multiorgan failures even at childhood. Parallel to digital clubbing, all of the atherosclerotic risk factors or consequences including smoking, alcohol, disseminated teeth losses, COPD, ileus, cirrhosis, leg ulcers, CHD, CRD, and stroke were higher, and autosplenectomy and mean age of mortality were lower in males which can not be explained by effects of smoking and alcohol alone at the relatively younger mean age. So autosplenectomy may be a good whereas male gender alone may be a bad prognostic factor, and digital clubbing may have an atherosclerotic background in SCDs. Key words: Sickle cell diseases, hardened red blood cells, capillary endothelial damage, capillary endothelial edema, sudden deaths, atherosclerosis, digital clubbing