Sickle cell disease (SCD)
or drepanocytosis, is an autosomal recessive genetic blood disorder with over
dominance characterized by red blood cells that assume an abnormal, rigid,
sickle shape. Sickling decreases the cells flexibility and results in a risk of
various complications. This sickling occurs because of a mutation in the
haemoglobin gene. Life expectancy is shortened, with studies reporting an
average life expectancy of 42 in males and 48 in females. Sickle disease
usually presenting in childhood, occurs more commonly in people (or their
descendants) from parts of tropical and sub-tropical regions. The prevalence of
the disease in the United States is approximately 1 in 5,000 mostly affecting
American of sub-Saharan African descent, according to the National Institutes
of Health. In the United
or drepanocytosis, is an autosomal recessive genetic blood disorder with over
dominance characterized by red blood cells that assume an abnormal, rigid,
sickle shape. Sickling decreases the cells flexibility and results in a risk of
various complications. This sickling occurs because of a mutation in the
haemoglobin gene. Life expectancy is shortened, with studies reporting an
average life expectancy of 42 in males and 48 in females. Sickle disease
usually presenting in childhood, occurs more commonly in people (or their
descendants) from parts of tropical and sub-tropical regions. The prevalence of
the disease in the United States is approximately 1 in 5,000 mostly affecting
American of sub-Saharan African descent, according to the National Institutes
of Health. In the United
States, about 1 in 500 African American children born
will have sickle cell anaemia.
Sickle cell anaemia is
caused by a point mutation in the B-globin chain of haemoglobin causing the
hydrophilic amino acid glutamic acid to be replaced with the hydrophobic
amino-acid valine at the sixth position. The B-globin gene is found on the
short arm of chromosome 11. The association of two wild type a-globin sub-units
with two mutant B-globin subunits forms haemoglobin S (Hbs). Under low oxygen
condition (being at high attitude for example) the absence of a polar amino
acid at position six of the B-globin Chain promotes the non-covalent
polymerization (aggregation) of haemoglobin, which distorts red blood cells,
into a sickle shape and decreases their elasticity.
caused by a point mutation in the B-globin chain of haemoglobin causing the
hydrophilic amino acid glutamic acid to be replaced with the hydrophobic
amino-acid valine at the sixth position. The B-globin gene is found on the
short arm of chromosome 11. The association of two wild type a-globin sub-units
with two mutant B-globin subunits forms haemoglobin S (Hbs). Under low oxygen
condition (being at high attitude for example) the absence of a polar amino
acid at position six of the B-globin Chain promotes the non-covalent
polymerization (aggregation) of haemoglobin, which distorts red blood cells,
into a sickle shape and decreases their elasticity.
