Cytogenetics of agnogenic myeloid metaplasia: a study of 61 patients.

Agnogenic myeloid metaplasia (AMM) or idiopathic myelofibrosis is a chronic myeloproliferative disorder characterized by fibrotic bone marrow, extramedullar haematopoiesis, and a leukoerythroblastic picture in circulating blood. The cytogenetic data on AMM are scanty and no recurring chromosome abnormality has been associated with the natural course of this disease. Trisomy 1q, del(13q), del(20q), and trisomy 8, appear in about two thirds of patients with demonstrable chromosome aberrations. We report on the cytogenetic analyses of 61 consecutive patients with AMM studied at diagnosis. The metaphases could not be found in 10/61 (16.4%) patients, and chromosome studies were successful in 51 patients. Twenty-one patients (41%) had an abnormal clone, whereas 30 (59%) patients had a normal karyotype. Most frequent pathological findings included trisomy 8 (either alone or within a complex karyotype) in five patients, aberrations of chromosome 12 (translocation in two, monosomy in two, and trisomy in one patient), and aberrations of chromosome 20 (interstitial deletion in two, monosomy in two, and trisomy in one patient). We also detected aberrations of chromosome 13 (translocation in two and an interstitial deletion and trisomy in one patient each) and chromosome 18 (derivative 18 in two patients and a monosomy and deletion in one patient each). Three patients exhibited complex aberrations involving several chromosomes, sometimes with a mosaicisam. A near-tetraploid karyotype was observed in a single patient. Balanced translocations [t(2;16)(q31;q24), t(5;13)(q13;q32), t(12;13)(p12;q13), and t(12;16)(q24;q24)] were present in four patients. While the series of patients studied displayed chromosomal aberrations that are frequently observed in AMM, we found some new abnormalities (balanced translocations and polyploidy) that are rarely observed in AMM.