Fanconi anemia is an autosomal recessive disease that's characterized by congenital anomalies, defective hematopoiesis and a high risk of developing acute myeloid leukemia and certain solid tumors. The clinical phenotype is extremely variable; therefore, the diagnosis is frequently delayed until the pancytopenia appears. Chromosomal instability, especially on exposure to an alkylating agent, may be seen in affected patients and it is the basis for a diagnostic test. This cellular phenotype can be demonstrated in cultured T cells, B cells, fibroblasts and fetal cells cultured from both amniotic fluid and chorionic villi. But somatic mosaicism may make the diagnosis of Fanconi anemia difficult because of inconclusive chromosome breakage studies. If the test is negative in lymphocytes and yet the clinical setting is highly suspicious, then the skin fibroblasts must be assessed. Because skin fibroblasts are somatic cells, a definitive test can be performed on primary skin fibroblasts. In this report we describe a case of Fanconi anemia that was diagnosed with the use of cultured skin fibroblasts, and this was despite the normal breakage studies in the peripheral blood.