Sickle cell anemia affects about 72,000 people in the United States. Most Americans who have sickle cell anemia are of African descent. The disease also affects Americans from the Caribbean, Central America, and parts of South America, Turkey, Greece, Italy, the Middle East and East India. Sickle-cell disease and the associated trait are most prevalent in Africa and Central America, which is attributed to natural selection:  the sickle-cell trait confers a survival advantage in areas with a high occurrence of malaria, which has a high death rate among individuals without the trait.There also have been studies that show changes in the globin genes. There have been noted changes in the beta-globin sequence, to what is known as the sickle hemoglobin. The significance of the sickle-cell trait is that it does not show any symptoms, nor does it cause any major difference in blood cell count. The trait confers about 30% protection against malaria and its occurrence appears to have risen tremendously in Africa, India and the Middle East. Some findings also show the reduction of the sickle-cell trait in those who retain much more fetal hemoglobin than usual in adulthood. Fetal hemoglobin likely plays a role in the prevention of sickling. Elevated fetal hemoglobin levels have been observed in populations where sickle-cell disease is prevalent. Whole genome sequence analysis has identified a single origin of the sickle trait, with one haplotype ancestral to all sickle-cell variants. This haplotype is thought to have originated in the Sahara during the Holocene Wet Phase around 7,300 years ago.
Acromicric dysplasia is an extremely rare inherited disorder characterized by abnormally short hands and feet, growth retardation and delayed bone maturation leading to short stature. Most cases have occurred randomly for no apparent reason (sporadically). However, autosomal dominant inheritance has not been ruled out. The disorder is different (but similar to) from other syndromic entities such as geleophysic dysplasia, Weill-Marchesani syndrome, and Myhre syndrome. Genetics
This condition has been associated with mutations in the Fibrillin 1 (FBN1) gene.Mutations in this gene have also been associated with stiff skin syndrome, Marfan syndrome and its variant Marfanoid–progeroid–lipodystrophy syndrome, autosomal dominant Weill-Marchesani syndrome, isolated ectopia lentis, MASS phenotype, and Shprintzen-Goldberg syndrome. References
External links
GeneReview/NIH/UW entry on Geleophysic Dysplasia