What does aplasia mean?
Aplasia is a medical term describing the complete failure of an organ or tissue to develop, leaving it absent from the body. It may be present from birth — as in certain forms of thymic aplasia — or acquired later, as when bone-marrow aplasia halts the production of blood cells. Clinicians distinguish aplasia carefully from hypoplasia, in which a tissue develops but remains underdeveloped, and from atrophy, in which a normally formed structure wastes away over time. The word appears chiefly in pathology reports, haematology literature, and specialist discussions of congenital anomalies, and it has no figurative or colloquial use outside medicine. Because it names a total rather than a partial absence, aplasia typically signals a more serious clinical picture than related terms such as hypoplasia. Its precision makes it indispensable in diagnosis, where identifying exactly what failed to form guides treatment decisions and prognosis.
nounThe congenital or acquired failure of an organ or tissue to develop, resulting in its complete absence from the body.
- {'sense': 'Complete failure of an organ or tissue to develop, so that it is absent (medical/pathology).'}
"The infant was diagnosed with thymic aplasia shortly after birth."
"The biopsy revealed aplasia of the bone marrow, explaining the patient's severe anaemia."
"Pure red cell aplasia is a rare condition in which the marrow fails to produce red blood cells."
Rarely used; clinicians usually refer to specific instances rather than counting them.
"Several distinct plasias were noted across the patient's imaging."
Aplasia means an organ simply never showed up — the body's blueprint was read, but one part went entirely unprinted.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of aplasia
Aplasia derives from Greek: the prefix a- meaning 'without' combined with plasis, meaning 'formation' or 'moulding', itself rooted in plassein, 'to form or mould'. It entered English through New Latin medical usage, becoming established in anatomical and pathological vocabulary alongside related terms like hyperplasia, hypoplasia, and dysplasia, all built on the same Greek root for formation. Cognates sharing this root include plasma, plastic, and protoplasm, reflecting the ancient Greek idea of shaping or moulding matter.
How aplasia is actually used
Strictly a medical and pathological term, used almost exclusively by clinicians, pathologists, and researchers. It carries no figurative or everyday usage. The plural 'plasias' is rare; clinicians more often name the specific affected tissue.
Easily confused with aplasia
Aplasia is the complete absence of an organ or tissue, while hypoplasia refers to underdevelopment of a tissue that is present but smaller than normal.
Agenesis is the failure of an organ to develop during embryonic growth; aplasia is the broader term for absence of tissue, whether developmental or acquired.