UPD9p is the only UPD investigated in any detail in BCP ALL, where it is often associated with homozygous CDKN2A deletions [4], and, to the best of our knowledge, UPD16p is the only UPD in BCP ALL that has been recurrently shown to result in homozygosity of a mutated gene (CREBBP at 16p13.3) [6]. The gene discussed is CDKN2A; the disease is acute lymphoblastic leukemia.