Asplenia syndrome, also known as right atrial isomerism is a subcategory of heterotaxy. It involves multiple malformations and abnormal location of organs, characteristically including congenital cardiac lesions and the absence of a spleen.
Asplenia syndrome (AS) is a condition that results from failure of normal rotation of thoracic and abdominal structures during embryogenesis. It is often detected soon after birth and constitutes 1% of newborns diagnosed with congenital heart disease. AS is a subtype of heterotaxy, also referred to as right atrial isomerism, and falls within a wide range of lateralization disorders that have variable abnormalities and presentations . In AS, the left side of the body is essentially a copy of the right-hand side, hence the characteristic absence of the spleen, which is normally located on the left. Although hereditary occurrences have been reported, some following an X-linked pattern, most cases of AS are isolated, and the etiology is unknown.
The common signs associated with AS are congenital cardiac malformations, which are often cyanotic and are the most frequent cause of symptoms and death. They usually consist of transposition of great vessels, pulmonary stenosis (and other valvular diseases), and total anomalous pulmonary venous connection (TAPVC).
Furthermore, AS is associated with numerous defects in the chest and abdominal cavities, the most prominent and clinically relevant of these being the lack of development of a spleen. Individuals with asplenia have a weakened immune system and are more susceptible to severe life-threatening infections, particularly those mediated by encapsulated organisms  . This risk exists throughout their entire lives. Other abnormalities reported include a midline or transverse liver, gall bladder and pancreas malformations, three lobes in both lungs, as well as an inferior vena cava that is located anterior to the aorta. AS carries a high mortality rate as over 85% of children born with AS die before the age of one year  . It is thought that those who survive beyond childhood may have milder manifestations and complications.
Entire Body System
- Atrial Septal Defect
septal defect, patent ductus arteriosus, bilateral superior venae cavae, and inferior vena cava draining into the left-sided atrium. [ncbi.nlm.nih.gov]
The most common associated cardiovascular anomalies in polysplenia are noncyanotic congenital heart defects, including atrial septal defect, endocardial cushion defects, partial anomalous pulmonary venous return, and up to 50% of cases are associated [metealpaslan.com]
- Pulmonary Valve Stenosis
Classically, Heterotaxy comprises of: Cardiac looping malformations – commonly Fallot’s Tetralogy, Transposition of the Great Vessels, Pulmonary Valve Stenosis, and ventricular and atrial septal defects. [chdbabies.com]
[…] unable to avoid public transport (for example, if you need to get to hospital for treatment or an appointment), wash your hands after every trip, use the antiseptic hand gel dispensers in the hospital regularly, cover your nose and mouth if you sneeze or cough [dontforgetaboutflu.co.uk]
Those with asplenia 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. [en.wikipedia.org]
The diagnosis of AS depends on a combination of history, physical examination and imaging findings. Features known to be typical in AS are used to guide the choice of investigations, which focus on specific systems or organs. These may include:
- Testing for nucleic acids known as Howell-Jolly bodies, which may be present in the red blood cells as a sign of splenic pathology.
- Electrocardiogram (ECG): This is useful in the detection of arrhythmias and other abnormalities in cardiac function
- Echocardiogram: This is a non-invasive imaging technique used to visualize and confirm structural defects of the heart .
- Prenatal ultrasound: It is possible to diagnose AS before birth, as ultrasound can be used to identify cardiac abnormalities and asplenia .
- Computerized tomography (CT) scan and CT angiography: These accurately detail the nature of malformations, as this information is needed for patient care and treatment .
- Magnetic resonance imaging (MRI) scan: MRI is also useful in defining the relationship between soft tissue structures.
- Howell-Jolly Bodies
Abstract Asplenia was suspected in one patient with combined immunodeficiency syndrome and 5 with congenital cardiac anomalies who had Howell-Jolly bodies on peripheral blood smears. 99mTc-sulfur colloid scans were equivocal for absence of the spleen. [ncbi.nlm.nih.gov]
Relevant laboratory investigations including peripheral blood smear revealed Howell-Jolly bodies. Parathormone and electrolytes were normal. Quantitative measurements of major immunoglobulin classes and T lymphocyte subpopulations were normal. [endocrine-abstracts.org]
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