asplenia

Asplenia refers to the absence of the spleen or to nonfunctional splenic tissue. It can be congenital or acquired, most commonly resulting from splenectomy or infarction. Congenital asplenia may occur in isolation or as part of heterotaxy syndromes, particularly the asplenia syndrome, which is associated with right-sided isomerism and often complex congenital heart disease.

The spleen has important roles in immune defense and in filtering blood cells. Loss of splenic function increases susceptibility to infections, especially by encapsulated bacteria such as Streptococcus pneumoniae, Haemophilus influenzae, and Neisseria meningitidis. Infants and young children with asplenia are at high risk for overwhelming post-splenectomy infection (OPSI), which can be rapidly fatal, though vaccination and prophylactic antibiotics reduce risk.

Diagnosis can be made by imaging showing absent spleen, or functional asplenia assessed by peripheral blood findings such as Howell-Jolly bodies, target cells, or pitted erythrocytes. Splenic radionuclide scans can confirm absence of splenic tissue.

Management centers on reducing infection risk. Vaccination against pneumococcus, meningococcus, and Haemophilus influenzae type b is recommended, especially for those with congenital asplenia or planned splenectomy. Lifelong antibiotic prophylaxis may be advised in children and other high-risk individuals, along with prompt antibiotic therapy at the onset of fever. Regular medical follow-up and education, including medical alert identification, are important.

Prognosis varies with the underlying cause and associated anomalies, particularly in heterotaxy syndromes. With appropriate vaccination and prophylaxis, the risk of severe infection can be reduced, but the absence of splenic function generally requires ongoing infection vigilance.