Asplenia

Overview
Asplenia refers to the absence ('a-') 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.

Causes
Asplenia may rarely be a congenital due to genetic disorders or exposure to environmental factors during gestation. More commonly it is acquired through surgery (splenectomy) or through processes that destroy the spleen, generally through its function to filter the blood and therefore referred to as autosplenectomy (eg spherocytosis and sickle-cell disease).

Risks
Asplenia increases the risk of septicaemia from encapsulated bacteria, and can result in a syndrome known as overwhelming post splenectomy infection (OPSI) which can kill within a few hours. In particular patients are at risk from Pneumococcus, but also Haemophilus influenzae & Meningococcus.

The risk to asplenic patients has been expressed as equivalent for a child to die in home accident, and for adults dying in a road traffic accident (reference UK Splenectomy Trust Advice) - so sensible precautions are needed, but no panic.

Management
To minimise the risks, antibiotic & vaccination protocols have been established, but are often poorly adhered to by doctors and patients.

Antibiotic prophylaxis
Because of the increased risk of infection, physicians administer oral antibiotics as a prophylaxis after a surgical splenectomy. The duration suggested varies: one suggestion is that antibiotics be taken for two years or until the age of sixteen years old is reached, whichever is longer.

Patients are also cautioned to start a full-dose course of antibiotics at the first onset of an upper or lower respiratory tract infection (for example, sore throat or cough), or at the onset of any fever.

Vaccinations
It is suggested that splenectomized persons receive the following vaccinations, and ideally prior to planned splenectomy surgery:
 * pneumococcus every 6 years (a conjugated form is used for children under 2 years)
 * Haemophilus influenzae - whilst in many countries now routinely given to all children, a single booster is advised following the development of asplenia, but for those adults who have not been previously vaccinated, two doses given two months apart were advised in the new 2006 UK vaccination guidelines (in the UK may be given as a combined Hib/MenC vaccine).
 * meningococcus-'C' conjugate vaccine - again routinely given to children in many countries, previously vaccinated adults require a single booster and non-immunised adults advised, in UK since 2006, to have two doses given two months apart.
 * annual flu vaccinations - to help prevent getting secondary bacterial infection.

Travel measures
In addition to the normal immunisations advised for the countries to be visited, Group A meningococcus should be included if visiting counties of particular risk (e.g. sub-saharan Africa). The non-conjugated Meningitis A&C vaccines usually used for this purpose give only 3 years coverage and provide less-effective long-term cover for Meningitis C than the conjugated form already mentioned.

Those lacking a functional spleen are at higher risk of catching malaria and dying from this. Travel to malarial areas will carry greater risks and may be best avoided. Travellers should take the most appropriate anti-malarial prophylaxis medication and be extra vigilant over measures to prevent mosquito bites.

The pneumococcal vaccinations may not cover some of the other strains of pneumococcal bacteria present in other countries. Likewise their antibiotic resistance may also vary, requiring a different choice of stand-by antibiotic.

Additional measures

 * Surgical and Dental procedures - Antibiotic prophylaxis may be required before certain surgical or dental procedures.
 * Animal bites - adequate antibiotic cover is required after even minor dog or other animal bites. Asplenic patients are particularly susceptible to infection by C. canimorsus and should receive a five day course of co-amoxiclav (erythromycin in patients allergic to penicillin).
 * Tick bites - Babesiosis is a rare tickborne infection. Patients should check themselves or have themselves inspected for tick bites if they are in an at-risk situation. Presentation with fever, fatigue, and haemolytic anaemia requires diagnostic confirmation by identifying the parasites within red blood cells on blood film and by specific serology. Quinine (with or without clindamycin) is usually an effective treatment.
 * Alert warning - Consider carrying a card, or wearing a special bracelet or necklet which says that you do not have a working spleen. This would alert a doctor to take rapid action if you are seriously ill and cannot tell them yourself.