Each column keeps its native condition scope. Initial features are displayed alphabetically, not ranked by clinical importance. Counts remain separate, and an empty cell does not mean a feature cannot occur.
"},"coverage":{"countRecords":0,"emptyColumnKeys":[],"hpoRelease":"2026-06-23","narrativeSourceChanges":[],"records":3,"sourceGroups":{"omim":2,"orphanet":0,"published":1}},"features":[{"hpoId":"HP:0001746","label":"Asplenia","primary":false},{"hpoId":"HP:0032550","label":"Howell-Jolly bodies","primary":false},{"hpoId":"HP:0001894","label":"Thrombocytosis","primary":false}],"ledeHtml":"Isolated congenital asplenia is a condition in which affected individuals are missing their spleen (asplenia) but have no other developmental abnormalities. While most individuals with this condition have no spleen at all, some people have a very small, nonfunctional spleen (hyposplenism).","mondoId":"MONDO:0010066","records":[{"frequencyKind":"reported","key":"4506a33ae8e843e77fe2459dd3ed6e9e6b591f06fb33198182d57369d85bc675","raw":{"aspect":"P","body_system":"blood","disease_id":"OMIM:271400","disease_name":"Asplenia, isolated congenital","evidence":"PCS","frequency_raw":null,"hpo_id":"HP:0032550","is_excluded":false,"label":"Howell-Jolly bodies","onset_id":null,"reference":"PMID:12111187","source_release":"2026-06-23"},"sourceGroups":["published"]},{"frequencyKind":"reported","key":"a1877d526fe6ef87de15a583115935ad30394512dba02ecb733f62de96f85fcf","raw":{"aspect":"P","body_system":"digestive","disease_id":"OMIM:271400","disease_name":"Asplenia, isolated congenital","evidence":"TAS","frequency_raw":null,"hpo_id":"HP:0001746","is_excluded":false,"label":"Asplenia","onset_id":null,"reference":"OMIM:271400","source_release":"2026-06-23"},"sourceGroups":["omim"]},{"frequencyKind":"range","key":"d7132c60dd631ebd4454d0b96f6fd39407b7f3e296aa98b8a56edb95be8d3f22","raw":{"aspect":"P","body_system":"blood","disease_id":"OMIM:271400","disease_name":"Asplenia, isolated congenital","evidence":"TAS","frequency_raw":"HP:0040283","hpo_id":"HP:0001894","is_excluded":false,"label":"Thrombocytosis","onset_id":null,"reference":"OMIM:271400","source_release":"2026-06-23"},"sourceGroups":["omim"]}],"referenceLabels":{},"references":{"causeHtml":"","identityNote":"MONDO cross-references identify native condition entries. Ancestor membership does not transfer phenotype values between groups.","importantHtml":""},"sections":[{"bodyHtml":"About 40 percent of cases of isolated congenital asplenia are caused by mutations in a gene called RPSA. This gene provides instructions for making a protein called ribosomal protein SA, which is a component of ribosomes. Ribosomes are cellular structures that process the cell's genetic instructions to create proteins.
Each ribosome has two parts (subunits) called the large and small subunits. Ribosomal protein SA is one of several proteins that make up the small subunit. Within the ribosome, the function of the ribosomal protein SA is unclear. Research suggests that it helps the ribosome control the production of certain proteins, many of which are likely important for development before birth.
RPSA gene mutations are thought to reduce the amount of functional ribosomal protein SA. A shortage of the normal protein likely impairs the assembly of ribosomes, but the specific effects of the mutations are not known. It is unclear why RPSA gene mutations appear to solely affect development of the spleen.
When isolated congenital asplenia is not caused by mutations in the RPSA gene, the cause of the condition is unknown.
","key":"forms","title":"What causes Isolated congenital asplenia?"},{"bodyHtml":"The spleen plays an important role in the immune system. This organ is part of the lymphatic system, which produces and transports fluids and immune cells throughout the body. The spleen produces certain immune system cells called phagocytes that help remove bacteria from the blood in order to prevent infections. The spleen also stores particular blood cells that fight foreign invaders until they are needed and filters old blood cells for removal. Because people with isolated congenital asplenia lack these immune functions, they are highly susceptible to bacterial infections.
People with isolated congenital asplenia are prone to developing severe, recurrent infections. Infections most commonly affect the whole body (sepsis), the membrane covering the brain and spinal cord (meningitis), or the ears (otitis media). Infections are most often caused by the Streptococcus pneumoniae bacteria.
Without preventative care and proper treatment, the frequent infections caused by isolated congenital asplenia can be life-threatening.
Source: MedlinePlus Genetics
","key":"overview","title":"Condition overview"}],"sharedSources":[],"slug":"isolated-congenital-asplenia","sourceDocuments":[{"name":"Isolated congenital asplenia","reviewed":"2019-04","sections":{"causes":{"fetchedAt":"2026-10-20T20:22:31.288060+00:00","label":"Causes","pageSha256":"e41d2606b126bafdd999ffa65eca95c3855701e76752745ad566612135cb511f","sourceUrl":"https://medlineplus.gov/genetics/condition/isolated-congenital-asplenia/#causes","status":"available"}},"source_release":"2026-10-01","url":"https://medlineplus.gov/genetics/condition/isolated-congenital-asplenia"}],"sourceNote":"MedlinePlus descriptions and Causes; original HPO annotations.","takeawayHtml":"Cause explanations are from MedlinePlus Genetics. Feature values below retain their original sources and patient groups.","title":"Isolated congenital asplenia"},"schemaVersion":1}