Sickle cell disease or anaemia

Sickle cell disease or anaemia 

Definition
sickle cell disease is a genetic mutation commonly inherited causing changes in haemoglobin structure and altered oxygen binding it may be homozygous or heterozygous (sickle cell trait) the disease has predominance in Africa and is found in India and Middle east clinical problem include 1- haemolytic anaemia 2- vaso-occlusive crises

• genetics of sickle cell at birth the majority of the haemoglobin in the body is fetal haemoglobin -HbF by the age of 6 months 80-90 % of this is replaced by adult haemoglobin -HbA haemoglobin is made up two alpha and two beta chains an inherited genetic mutation of the beta chain leads to the formation of sickle cell haemoglobin ,HbS this is a single amino acid substitution . glutamine at position six on the beta chain is replaced by valine this changes the oxygen binding capacity of the molecule 
• sickle cell haemoglobin can be present as a trait in the hetrozygous state -HbAS 
• or as sickle cell disease in the homozygous state -HbSS the disease usually manifests itself at the age of six months when HbF  level fall 
• what are the clinical aspect of sickle cell disease
• deoxygenated HbS  is insoluble and polymerises causing the red blood cells to form rigid inflexible shapes repeated exposure to low oxygen tensions whilst travelling through capillaries causes red blood cells to adopt a rigid sickle shape . this is primarily reversible with reoxygenation and as such responds to oxygen therapy this is results in 
• 1-haemolytic anaemia and sequelae  such as pigment gall stone formation due to the hyperbilirubinaemia 
• 2- vaso- occlussive crises cause infarction and severe ischaemic pain and commonly seen in the bone especially fingers (dactylitis) and in chest kidney liver and penis causing(priapism) in the long term there is an increased susceptibility to infections especially streptococcus pneumoniae and salmonella meningitis chronic renal failure and blindness 
• sickle cell disease and surgery diagnosis by full blood count(FBC)  peripheral blood film and sickle solubility test this is confirmed by Hb electrophoresis it is important in surgery to try to avoid precipitating factors these include hypothermia hypoxia infection hypotension dehydration and acidosis all common problems in surgical patients 
• sickle cell traits usually asymptomatic , cells do not sickle unless oxygen saturations are below 40% which is very rare anaesthetists should be made aware of patients with the trait preoperatively in order to avoid any degree of hypoxia

 tags:sickle,anaemia,diseases,cell