+4 or trisomy 4

Clinics and pathology Disease Acute non lymphocytic leukaemia (ANLL) Epidemiology +4 as the sole anomaly is a rare chromosomal abnormality associated with a specific subtype of primary ANLL and secondary (treatment related) ANLL with myelomonocytic morphology; it has been found with the same frequence in the M1-M2 and M4 French-American-British (FAB) phenotypes. Association of +4 with double minute chromosomes has been described in ten cases; five with AML-M2, two with AML-M4, one with refractory anemia with excess of blasts in transformation (RAEB-T), one with chronic myelomonocytic leukemia (CMMoL) and one with unclassified preleukemia. The coincidence of +4 with t(8;21) or its variant t(6;21;8), observed in at least two cases of ANLL (M1 and M2), is therefore recurrent.