Trisomies 9 and 8 detected by fluorescence in situ hybridization in patients with systemic mastocytosis

Background: Systemic mastocytosis is a rare disease characterized by proliferation of mast cells in one or more organs. The origin of the mast cells is still debated, although it has been recently shown that they derive from CD34⁺ hematopoietic progenitors. Some clinical and in vitro studies have suggested a possible link between myeloproliferative disorders and systemic mast cell disease. Objective: This study was designed to further evaluate the association between systemic mast cell disease and other hematologic disorders by means of conventional cytogenetic analysis and fluorescent in situ hybridization. Methods: We used cytogenetic analysis and fluorescent in situ hybridization with probes to chromosomes 8 and 9 in six patients with systemic mast cell disease. Results: Fluorescent in situ hybridization helped to identify five patients with trisomy 9 and one with trisomy 8. In contrast, chromosomal analysis demonstrated an abnormal karyotype (45,XO/46,XY) in only one patient. Conclusion: The association between myeloproliferative disorders and systemic mast cell disease may be explained by the finding that trisomy 9 and trisomy 8 are common in both disorders. A trisomy was detected in all of the patients in our small group compared with nearly 40% of previously reported patients with myeloproliferative disorders. FISH is more sensitive than conventional cytogenetics in detecting these aberrations.