Sibling Test - A Distinct Diagnostic Approach for Fanconi Anemia in a Patient with Negative Chromosomal Breakage Analysis

Fanconi anemia (FA) is a rare form of an inherited disorder that mainly results in aplastic anemia. In our case, a three-year-old female child presented with recurrent episodes of fever and persistent pancytopenia refractory to any treatment. The chromosomal breakage analysis (CBA) with mitomycin C and solid staining was done, which showed no chromosomal breakage. Considering negative results due to mosaicism, her younger brother's CBA was performed, which showed a positive result. Therefore, based on clinical features, persistent cytopenia, and the younger siblings' CBA, both children were diagnosed with FA.