An autosplenectomy (from'' 'auto-' ''self,'' '-splen-' ''spleen,'' ' -ectomy' ''removal) is a negative outcome of disease and occurs when a

disease A disease is a particular abnormal condition that negatively affects the structure or function of all or part of an organism, and that is not immediately due to any external injury. Diseases are often known to be medical conditions that a ...

damages the

spleen The spleen is an organ found in almost all vertebrates. Similar in structure to a large lymph node, it acts primarily as a blood filter. The word spleen comes .

to such an extent that it becomes shrunken and non-functional. The spleen is an important immunological organ that acts as a filter for

red blood cell Red blood cells (RBCs), also referred to as red cells, red blood corpuscles (in humans or other animals not having nucleus in red blood cells), haematids, erythroid cells or erythrocytes (from Greek ''erythros'' for "red" and ''kytos'' for "hol ...

s, triggers

phagocytosis Phagocytosis () is the process by which a cell uses its plasma membrane to engulf a large particle (≥ 0.5 μm), giving rise to an internal compartment called the phagosome. It is one type of endocytosis. A cell that performs phagocytosis is ...

of invaders, and mounts an immunological response when necessary. Lack of a spleen, called

asplenia Asplenia refers to the absence of normal spleen function and is associated with some serious infection risks. Hyposplenism is used to describe reduced ('hypo-') splenic functioning, but not as severely affected as with asplenism. ''Functional'' ...

, can occur by autosplenectomy or the surgical counterpart,

splenectomy A splenectomy is the surgical procedure that partially or completely removes the spleen. The spleen is an important organ in regard to immunological function due to its ability to efficiently destroy encapsulated bacteria. Therefore, removal of ...

. Asplenia can increase susceptibility to infection. Autosplenectomy can occur in cases of

sickle-cell disease Sickle cell disease (SCD) is a group of blood disorders typically inherited from a person's parents. The most common type is known as sickle cell anaemia. It results in an abnormality in the oxygen-carrying protein haemoglobin found in red ...

where the misshapen cells block blood flow to the spleen, causing

scarring A scar (or scar tissue) is an area of fibrous tissue that replaces normal skin after an injury. Scars result from the biological process of wound repair in the skin, as well as in other organs, and tissues of the body. Thus, scarring is a na ...

and eventual

atrophy Atrophy is the partial or complete wasting away of a part of the body. Causes of atrophy include mutations (which can destroy the gene to build up the organ), poor nourishment, poor circulation, loss of hormonal support, loss of nerve supply ...

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 Lupus, technically known as systemic lupus erythematosus (SLE), is an autoimmune disease in which the body's immune system mistakenly attacks healthy tissue in many parts of the body. Symptoms vary among people and may be mild to severe. Commo ...

(SLE).

Consequences

Absence of effective splenic function or absence of the whole spleen (

) is associated with increased risks of overwhelming post splenectomy infection, especially from

polysaccharide encapsulated bacteria The bacteria capsule is a large structure common to many bacteria. It is a polysaccharide layer that lies outside the cell envelope, and is thus deemed part of the outer envelope of a bacterial cell. It is a well-organized layer, not easily washe ...

and organisms that invade erythrocytes. People without a spleen have a weakened immune system, although other immune organs compensate for the missing spleen.

Vaccination Vaccination is the administration of a vaccine to help the immune system develop immunity from a disease. Vaccines contain a microorganism or virus in a weakened, live or killed state, or proteins or toxins from the organism. In stimulat ...

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 Pneumonia is an inflammatory condition of the lung primarily affecting the small air sacs known as alveoli. Symptoms typically include some combination of productive or dry cough, chest pain, fever, and difficulty breathing. The severit ...

influenza Influenza, commonly known as "the flu", is an infectious disease caused by influenza viruses. Symptoms range from mild to severe and often include fever, runny nose, sore throat, muscle pain, headache, coughing, and fatigue. These symptom ...

, ''

Haemophilus influenzae ''Haemophilus influenzae'' (formerly called Pfeiffer's bacillus or ''Bacillus influenzae'') is a Gram-negative, non-motile, coccobacillary, facultatively anaerobic, capnophilic pathogenic bacterium of the family Pasteurellaceae. The bact ...

'' 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. 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

s and contain chromatin remnants from basophilic cells. 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. 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.

Diseases that cause autosplenectomy

Sickle cell anemia

The most frequent cause of autosplenectomy is

sickle cell anemia Sickle cell disease (SCD) is a group of blood disorders typically inherited from a person's parents. The most common type is known as sickle cell anaemia. It results in an abnormality in the oxygen-carrying protein haemoglobin found in red bl ...

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 Ischemia or ischaemia is a restriction in blood supply to any tissue, muscle group, or organ of the body, causing a shortage of oxygen that is needed for cellular metabolism (to keep tissue alive). Ischemia is generally caused by problems w ...

. This ischemia can result in splenic sequestration, where large amounts of blood pool in the spleen but do not flow within vasculature. This lack of blood flow can cause atrophy in the spleen and can lead to autosplenectomy.

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.

References

{{reflist Immune system disorders Diseases of spleen