Abnormalities of chromosome 13 in myelofibrosis

19 patients with myelofibrosis, primary or following polycythaemia vera were studied cytogenetically. Bone marrow cells, unstimulated and stimulated cells from peripheral blood were investigated. 7 patients were found to have clonal aberrations, 3 of whom had a structural rearrangement of chromosome 13. In 2 additional cases single mitoses with 13q- were found. Reviewing the files on patients previously studied in our laboratory, 2 more patients with 13q- markers were noted. Both had had haematologic disorders in which fibrosis of the bone marrow can be found, but this feature could not be evaluated retrospectively, because no biopsies had been taken. Our data and those found in the literature suggest that rearrangements of 13q12----q22 are often associated with myelofibrosis, both in its primary form or following polycythaemia vera.