Aplasia (from Greek a- + plasis) is the complete failure of an organ, tissue, or cell line to develop, form, or regenerate — either congenitally (structural aplasia, a developmental arrest) or acquired (functional aplasia, a failure of ongoing cell production). It sits at the most severe end of the -plasia spectrum: where hypoplasia is under-development (some cells form, but not enough) and dysplasia is disordered development, aplasia represents no meaningful formation at all. In clinical medicine, the two most critical and commonly encountered forms are aplastic anemia (D61.x) — bone marrow failure affecting all three cell lines (pancytopenia) — and pure red cell aplasia (PRCA) (D60.x) — selective failure of erythroid precursor production while WBC and platelet lines are preserved. Other organ-level examples include thymic aplasia (DiGeorge syndrome), vaginal aplasia (Mayer-Rokitansky-Küster-Hauser syndrome), and radial aplasia (congenital absence of the radius). Aplasia is distinct from agenesis — a subtle but real distinction: agenesis refers to failure of an organ to develop due to absence of the primordial tissue itself, while aplasia implies the primordial tissue was present but failed to develop into the mature structure.
“Formation,” “molding,” “growth,” “development” — from the verb “to mold or shape”
The term entered medical Latin as aplasia in 1876, coined from Greek elements to describe “defective or arrested development of a body part.” The root plassein (“to mold”) gives the word its developmental sense — literally, “without molding/formation.” The same root yields plasma (something molded), plastic (capable of being molded), rhinoplasty (-plasty = surgical reshaping), and the entire -plasia family: hyperplasia (over-formation), dysplasia (disordered formation), metaplasia (changed formation), anaplasia (backward formation/de-differentiation), and neoplasia (new/abnormal formation). The PIE root behind plassein is *plath- (“to spread flat”), connecting aplasia etymologically to words as wide-ranging as “flat,” “floor,” and “palm” of the hand.
🔀 ALIASES / ALTERNATE TERMS
Aplastic(adjective form — e.g., “aplastic anemia,” “aplastic crisis”)
Aplastic anemia (AA)(bone marrow failure with pancytopenia — the most clinically common aplasia)
Pure red cell aplasia (PRCA)(selective erythroid failure; acquired D60.x or congenital D61.01)
Bone marrow failure syndrome (BMFS)(clinical grouping encompassing aplastic anemia, MDS, PNH, and PRCA)
Hypoplastic anemia(near-synonym for aplastic anemia; partially preserved marrow function)
Diamond-Blackfan anemia (DBA)(congenital PRCA; D61.01 — constitutional pure red blood cell aplasia)
Fanconi anemia(constitutional aplastic anemia with chromosomal fragility; D61.09)
Thymic aplasia(DiGeorge syndrome; absent thymus → severe T-cell immunodeficiency; D82.1)
Aplastic crisis(acute, temporary cessation of RBC production — typically parvovirus B19 in hemolytic anemia patients)
Agenesis(overlapping term; failure of organ primordium to form — aplasia = primordium present, failed to mature)
🔗 RELATED TERMS
Hypoplasia — partial under-development; hypo- (under) + -plasia; less severe than aplasia on the developmental failure spectrum
dysplasia — disordered development; dys- (bad/abnormal) + -plasia; cells form but are structurally abnormal
hyperplasia — over-formation; hyper- (excess) + -plasia; too many cells produced
⚠️ Coding Note:D61.1 (Drug-induced aplastic anemia) requires an additional T-code per ICD-10-CM instructions to identify the drug — e.g., T45.1X5A (adverse effect of antineoplastic drugs) or the appropriate T36-T50 code for the offending agent; this is a high-yield query on oncology/hematology inpatient claims. D61.3 (Idiopathic aplastic anemia) should only be coded when the workup is complete and no cause is identified — early in the admission before results return, D61.9 (unspecified) is more appropriate. For bone marrow procedures, 38222 replaces the old paired billing of 38220 + 38221 when both aspiration and biopsy are done at the same session through the same incision — billing both 38220 and 38221 together will deny; use modifier -59 only when performed at truly separate sites or separate skin incisions. 88305 for pathology interpretation is separately billable and should always be captured. The PNH-aplastic anemia association is clinically critical: flow cytometry for GPI-anchor deficient cells (PNH clone) is part of the standard aplastic anemia workup — confirm the physician is ordering and documenting this, as it affects treatment decisions and coding of a second, highly specific diagnosis (D59.5).
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