Fanconi anemia laboratory findings

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Shyam Patel [2]

Overview

The laboratory findings in Fanconi anemia include decreased hemoglobin on CBC and increased chromosomal breakage with mitomycin C or diepoxybutane. There may also be single-lineage or multi-lineage cytopenias. Flow cytometry of hematopoietic cells may show cell cycle arrest in G2/M phase.

Laboratory Findings

Complete blood count (CBC)

In Fanconi anemia, the complete blood count (CBC) may reveal trilineage pancytopenia or may only show RBCs that are macrocytic for age. Macrocytosis, thrombocytopenia, and/or leukopenia may precede full-blown aplasia.

Chromosomal breakage test

• Chromosome breakage is usually examined in short-term cultures of peripheral blood mitogen–stimulated T lymphocytes in the presence of DNA cross-linkers, such as diepoxybutane (DEB) or mitomycin C (MMC). These agents lead to increased numbers of breaks, gaps, rearrangements, and quadraradii in Fanconi anemia homozygote cells. It is considered as screening test for Fanconi anemia.
• Some patients may have hematopoietic somatic mosaicism, with correction of the Fanconi anemia defect in the blood. In these cases, skin fibroblasts may be needed for the chromosome breakage test.
• FA gene sequencing is generally suggested for all patients with a positive result from chromosomal breakage testing. The reason is that identification of the genetic defect definitively confirms the diagnosis and eliminates other chromosomal breakage disorders as the cause of the abnormal screening test. Furthermore, sequencing allows screening of family members for the purposes of identifying HCT donors, performing prenatal testing, and genetic counseling, given that heterozygous carriers will not have abnormal chromosomal breakage analysis.

Flow cytometry

Flow cytometry of Fanconi anemia cells cultured with nitrogen mustard and other clastogens demonstrates an arrest in G2/M. Flow cytometry for cell cycle analysis can be performed through propidium iodide staining, Hoechst staining, or pyronin Y staining.