Interstitial deletion of the long arm of chromosome 5 (5q-) in leukemia and other hematological disorders: clinical and biological relevance of variable breakpoint patterns.

From January 1983 to January 1985, we have found a deletion of the long arm of chromosome 5 (5q-) in the bone marrow cells of 8 patients; they represent consecutive patients referred to our institution for investigation and treatment of the following hematological disorders in whom the 5q- abnormality was found: acute nonlymphocytic leukemia (ANLL) (3), refractory anemia with excess blasts (RAEB) (2), preleukemia (PL) (1), sideroblastic anemia (SA) (1), refractory anemia (RA) (1). The deletion proved to be interstitial in all patients, with 3 different breakpoint patterns emerging: q13q33, q11.2q21, q11.2q33. Proximal breakpoint q11.2 was found only in patients with an initial diagnosis of ANLL. The common region deleted in all patients was comprised between bands q13q21. The clinical relevance and biological meaning of the heterogeneity of proximal and distal breakpoints found in this study are discussed.