Chromosomal breakage analysis in a patient with presumptive diagnosis of Fanconi anemia

摘要

Fanconi anemia (FA) is a chromosomal instability syndrome characterized by various dysmorphic features, progressive pancytopenia and predisposition to hematological malignancies. The assay sensitivity to mitomycin C (MMC) provides a unique cell marker for the diagnosis of the disease. In order to introduce this chromosomal breakage test the technique was applied in two samples from a patient with clinical suspicion of AF and a control subject. Peripheral blood samples were cultured by protocols established for cytogenetic studies. Four flasks were prepared for each sample culture. Only sodium chloride was added to one of the flasks (control) and to the remaining flasks increasing concentrations of MMC (50, 150 and 300 nM) were added. Fifty metaphases were analyzed for each bottle. Exposure of lymphocytes from the patient at all concentrations of MMC caused significant differences in the number of cells with chromosome breaks with respect to the same exposure in the control (p 0.005). Assay success was proved considering that in 300 nM in healthy control only 32 % shows cell breakage. It is interesting to remark that in the patient sample with highest concentration, the presence of two cell lines were observed, one with little or no breakage (38 %) similar to those found in no-F cells and other with multiple breaks (62 %), typical of AF cells. These results indicated the presence of somatic mosaicism in patient´s T lymphocytes. The results obtained confirmed the clinical suspicion that this is an AF patient, due to the hypersensitivity to the action of MMC and the presence of somatic mosaicism in T lymphocytes.