CHARACTERIZATION OF 20Q DELETIONS IN PATIENTS WITH MYELOPROLIFERATIVEDISORDERS OR MYELODYSPLASTIC SYNDROMES

Deletions of the long arm of chromosome 20 are associated with several myeloid malignancies. We have analyzed the structure of the del(20q) in 30 patients and two cell lines. Twenty-one of the patients presente d with a myeloproliferative disorder and nine with a myelodysplastic s yndrome. Two categories of deletions were identified. Eighteen patient s had a large deletion with loss of both G(+) bands from the long arm of chromosome 20. Twelve patients had small deletions with loss of one G(+) band from the long arm of chromosome 20. A chromosome paint was generated from a del 20q marker carrying a small deletion. This probe was hybridized to normal metaphases (reverse chromosome painting) and also to metaphases from patients with a del 20q (comparative reverse c hromosome painting). All six small deletions analyzed were characteriz ed by loss of the proximal G(+) band (q12) and retention of the distal G(+) band (q13.2). These data define a minimal deleted region extendi ng from 20q11.2-20q13.1.