Intrachromosomal Amplification of Chromosome 21

**Semantic type:** Cell or Molecular Dysfunction

**Definition:** A cytogenetic abnormality that refers to the allelic gain of an internal part of chromosome 21. It is a rare high-risk chromosomal abnormality that occurs in approximately 2-5% of pediatric patients with B-cell precursor Acute Lymphoblastic Leukemia. This abnormality has been associated with a poor outcome in patients treated by standard protocols.

**Synonyms:** - iAMP21 - iAMP21 - iAMP21