Autosplenectomy
{{Short description|Loss of function of the spleen}}
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.[http://library.med.utah.edu/WebPath/HEMEHTML/HEME116.html "Autosplenectomy" with sickle cell anemia, gross] at [http://library.med.utah.edu/WebPath/ WebPath], The Internet Pathology Laboratory for Medical Education at Mercer University School of Medicine. Retrieved September 10, 2011 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.{{Cite journal|title = The spleen and sickle cell disease: the sick(led) spleen|journal = British Journal of Haematology|date = 2014-07-01|issn = 1365-2141|pages = 165–176|volume = 166|issue = 2|doi = 10.1111/bjh.12950|language = en|first1 = Valentine|last1 = Brousse|first2 = Pierre|last2 = Buffet|first3 = David|last3 = Rees|pmid=24862308|s2cid = 40448991|doi-access = free}} Lack of a spleen, called asplenia, can occur by autosplenectomy or the surgical counterpart, splenectomy. Asplenia can increase susceptibility to infection.{{Cite web|url = http://www.mayoclinic.org/tests-procedures/splenectomy/basics/risks/prc-20014837|title = Splenectomy Risks - Mayo Clinic|website = www.mayoclinic.org|access-date = 2016-03-02}} 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. 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).
Consequences
{{Main article|Asplenia}}
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.{{Cite journal|title = Detection, Education and Management of the Asplenic or Hyposplenic Patient - American Family Physician|url = http://www.aafp.org/afp/2001/0201/p499.html|journal = American Family Physician|access-date = 2016-02-16|first = Malcolm L.|last = Brigden|date = February 2001|volume = 63|issue = 3|page = 499}} People without a spleen have a weakened immune system, although other immune organs compensate for the missing spleen.{{Cite web|url=http://www.mayoclinic.org/tests-procedures/splenectomy/basics/results/prc-20014837|title=Splenectomy Results - Mayo Clinic|website=www.mayoclinic.org|access-date=2016-03-03}} 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.
= Testing for autosplenectomy =
One of the spleen's main tasks is to filter the blood and remove and recycle damaged or old red blood cells.{{Cite web|url=http://www.chp.edu/our-services/transplant/liver/education/organs/spleen-information|title=What Is the Spleen? Functions & Info {{!}} Children's Hospital Pittsburgh|website=www.chp.edu|access-date=2016-03-03}} Splenic function can be measured by filtering capabilities, as indicated by number of Howell-Jolly bodies or pitted erythrocytes in the blood. Both of these tests examine whether or not the spleen is functioning normally by testing splenic outputs.
== Howell-Jolly bodies ==
Howell–Jolly bodies are found on red blood cells and contain chromatin remnants from basophilic cells.{{Cite journal|pmc = 4103047|title = Functional hyposplenism|last = Kirkineska|first = L|date = 2014|journal = Hippokratia|pmid = 25125944|volume=18|issue = 1|pages=7–11}} 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. A high number of Howell-Jolly bodies is indicative of splenic hypofunction and potentially autosplenectomy.
== Pitted erythrocytes ==
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.{{Cite journal|title = Post-splenectomy and hyposplenic states|last = Di Sabatino|first = Antonio|date = April 6, 2011|journal = Lancet|volume = 378|issue = 9785|pages = 86–97|doi = 10.1016/s0140-6736(10)61493-6 |pmid = 21474172|s2cid = 30554953}} 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.{{Cite web|url=http://www.rbclab.com/Pages/200/210/120%20Pit/210%20120.html|title=Red Blood Cell Pit Count|date=2010|website=Red Blood Cell Lab|publisher=Children's Hospital Oakland Research Institute|access-date=March 2, 2016}}
Diseases that cause autosplenectomy
=Sickle cell anemia=
The most frequent cause of autosplenectomy is sickle cell anemia{{cite web |url=http://radiopaedia.org/articles/autosplenectomy |title=Autosplenectomy |publisher=radiopaedia.org |access-date=30 December 2015 |author1=Henry Knipe |author2=Frank Gaillard }} 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. This ischemia can result in splenic sequestration, where large amounts of blood pool in the spleen but do not flow within vasculature.{{Cite journal|url = http://aje.oxfordjournals.org/content/151/9/839.full.pdf|archive-url = https://web.archive.org/web/20150906103431/http://aje.oxfordjournals.org/content/151/9/839.full.pdf|url-status = dead|archive-date = 2015-09-06|title = Sickle Hemoglobin (Hb S) Allele and Sickle Cell Disease: A HuGE Review|last = Ashley-Koch|first = A|date = 2000|journal = American Journal of Epidemiology|volume = 151|issue = 9|pages = 839–845|doi = 10.1093/oxfordjournals.aje.a010288|pmid = 10791557}}
= Pneumococcal sepsis =
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.{{Cite journal|title = Autosplenectomy and Antiphospholipid Antibodies in Systemic Lupus Erythematosus: A Pathogenic Relationship?|last = Santilli|first = Daniele|date = 2003|journal = Seminars in Arthritis and Rheumatism|volume = 33|issue = 2|pages = 125–133|doi = 10.1016/S0049-0172(03)00004-0|pmid = 14625820}}