Autosplenectomy
Template:Short description An autosplenectomy (from 'auto-' self, '-splen-' spleen, '-ectomy' removal) is a negative outcome of disease and occurs when a disease damages the spleen to such an extent that it becomes shrunken and non-functional.<ref>"Autosplenectomy" with sickle cell anemia, gross at WebPath, The Internet Pathology Laboratory for Medical Education at Mercer University School of Medicine. Retrieved September 10, 2011</ref> The spleen is an important immunological organ that acts as a filter for red blood cells, triggers phagocytosis of invaders, and mounts an immunological response when necessary.<ref name="Brousse 165–176">Template:Cite journal</ref> Lack of a spleen, called asplenia, can occur by autosplenectomy or the surgical counterpart, splenectomy. Asplenia can increase susceptibility to infection.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Autosplenectomy can occur in cases of sickle-cell disease where the misshapen cells block blood flow to the spleen, causing scarring and eventual atrophy of the organ.<ref name="Brousse 165–176"/> Autosplenectomy is a rare condition that is linked to certain diseases but is not a common occurrence. It is also seen in systemic lupus erythematosus (SLE).
ConsequencesEdit
Template:Main article Absence of effective splenic function or absence of the whole spleen (asplenia) is associated with increased risks of overwhelming post-splenectomy infection, especially from polysaccharide encapsulated bacteria and organisms that invade erythrocytes.<ref>Template:Cite journal</ref> People without a spleen have a weakened immune system, although other immune organs compensate for the missing spleen.<ref name="Splenectomy Results - Mayo Clinic">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Vaccination against encapsulated bacteria and prophylactic antibiotics can be used to counteract lowered immunity in asplenic patients. Specifically, people without a spleen are recommended to be vaccinated against pneumonia, influenza, Haemophilus influenzae type b and meningococci.<ref name="Splenectomy Results - Mayo Clinic"/>
Testing for autosplenectomyEdit
One of the spleen's main tasks is to filter the blood and remove and recycle damaged or old red blood cells.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Splenic function can be measured by filtering capabilities, as indicated by number of Howell-Jolly bodies or pitted erythrocytes in the blood.<ref name="Brousse 165–176"/> Both of these tests examine whether or not the spleen is functioning normally by testing splenic outputs.
Howell-Jolly bodiesEdit
Howell–Jolly bodies are found on red blood cells and contain chromatin remnants from basophilic cells.<ref>Template:Cite journal</ref> Under normal conditions, these nuclear remnants are removed from the blood by the spleen's filtering capabilities. Howell-Jolly bodies can be identified and quantified using a blood smear or by flow cytometry.<ref name="Brousse 165–176"/> A high number of Howell-Jolly bodies is indicative of splenic hypofunction and potentially autosplenectomy.
Pitted erythrocytesEdit
Erythrocytes with membrane pits can be indicative of splenic dysfunction as a healthy spleen clears blood of pitted erythrocytes. Pitted erythrocytes can be counted using Normarsky optics.<ref>Template:Cite journal</ref> Humans with healthy spleens have less than two percent of their red blood cells contain pits. In comparison, a person with asplenia may have up to 50% of their red blood cells contain pits.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
Diseases that cause autosplenectomyEdit
Sickle cell anemiaEdit
The most frequent cause of autosplenectomy is sickle cell anemia<ref name=radio>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> which causes progressive splenic hypofunction over time. Increased deoxygenation causes sickling of red blood cells, which adhere to the spleen wall and splenic macrophages causing ischemia.<ref name="Brousse 165–176"/> This ischemia can result in splenic sequestration, where large amounts of blood pool in the spleen but do not flow within vasculature.<ref>Template:Cite journal</ref>
Pneumococcal sepsisEdit
Pneumococcal sepsis, or whole-body infection caused by the Streptococcus pneumoniae bacteria, has been reported to cause autosplenectomy but is a very rare and poorly understood complication of the infection.<ref>Template:Cite journal</ref>