Differential diagnosis of Fanconi anemia by nitrogen mustard and diepoxybutane

Management of oral leukoplakia in patients with Fanconi anemia

Fanconi anemia (FA) is a rare genetic disease involving an increased risk of developing acute myeloid leukemia and solid tumors, especially head-and-neck squamous cell carcinomas, for which the oral cavity is the most frequent site of occurrence. The patient presented in this study underwent allogeneic hematopoietic stem cell transplantation (HSCT) and developed nonhomogeneous oral leukoplakia after 7 years, which was promptly removed and diagnosed with high-grade epithelial dysplasia. Many risk conditions for oral squamous cell carcinoma were featured in the present case including FA, allogeneic HSCT, graft-versus-host disease, immunosuppressive therapy, female gender, nonsmoker, tongue location and nonhomogeneous type of leukoplakia. Close follow-up of the entire upper aerodigestive tract mucosa and early removal of all suspected lesions are highly recommended in the management of such patients.

Squamous cell carcinoma development in Fanconi anemia patients who underwent hematopoietic stem cell transplantation

We examined SCC development of 24 FA patients, who received HSCT from HLA-matched relatives. In our BMT center, we applied low-dose CY + LFI + ATG (n:13) as conditioning regimen for FA patients between 1992 and 1999, and CY + BU + ATG (n:11) between 1999 and 2002. The aim of this study was to investigate SCC development after HSCT and examine features of the follow-up patients. The 10-year overall survival (OS) of the group with LFI + regimen was 43%, whereas the group without LFI regimen was 60%. There was a statistically significant relationship between infections (viral/bacterial) and overall survival (Fisher's Exact test P < .001). Five out of 13 long-term (>1 year) surviving patients developed SCC in the HNSCC (n:4) and esophagus (n:2) region (a patient with oral SCC developed a second primary esophageal SCC). The SCC rate in our FA patients was 38%, four of the SCC patients were transplanted with irradiation used conditioning regimens, three of them had acuteGvHD (Grade II-III), only one developed chronic GvHD. The interval between HSCT and SCC diagnosis was median 13 (range 6-18) years, the age for the development of cancer was median 21 (range 15-32) years. Survival after SCC was low, median 6 months (range 6-12), due to delayed SCC diagnosis, tumor progression under therapy and treatment-related toxicities of the usually reduced RT and/or CT.

Diagnosis of Fanconi Anaemia by ionising radiation- or mitomycin C-induced micronuclei

Fanconi Anaemia (FA) is an autosomal recessive disorder characterised by defects in DNA repair, associated with chromosomal instability and cellular hypersensitivity to DNA cross-linking agents such as mitomycin C (MMC). The FA repair pathway involves complex DNA repair mechanisms crucial for genomic stability. Deficiencies in DNA repair genes give rise to chromosomal radiosensitivity. FA patients have shown increased clinical radiosensitivity by exhibiting adverse normal tissue side-effects. The study aimed to investigate chromosomal radiosensitivity of homozygous and heterozygous carriers of FA mutations using three micronucleus (MN) assays. The G0 and S/G2MN assays are cytogenetic assays to evaluate DNA damage induced by ionising radiation in different phases of the cell cycle. The MMC MN assay detects DNA damage induced by a crosslinking agent in the G0 phase. Patients with a clinical diagnosis of FA and their parents were screened for the complete coding region of 20 FA genes. Blood samples of all FA patients and parents were exposed to ionising radiation of 2 and 4Gy. Chromosomal radiosensitivity was evaluated in the G0 and S/G2 phase. Most of our patients were homozygous for the founder mutation FANCG c.637_643delTACCGCC; p.(Tyr213Lysfs*6) while one patient was compound heterozygous for FANCG c.637_643delTACCGCC and FANCG c.1379G > A, p.(Gly460Asp), a novel missense mutation. Another patient was compound heterozygous for two deleterious FANCA mutations. In FA patients, the G0- and S/G2-MN assays show significantly increased chromosomal radiosensitivity and genomic instability. Moreover, chromosomal damage was significantly elevated in MMC treated FA cells. We also observed an increase in chromosomal radiosensitivity and genomic instability in the parents using 3 assays. The effect was significant using the MMC MN assay. The MMC MN assay is advantageous as it is less labour intense, time effective and has potential as a reliable alternative method for detecting FA patients from parents and controls.

Comparison of chromosome breakage in non-mosaic and mosaic patients with Fanconi anemia, relatives, and patients with other inherited bone marrow failure syndromes

Fanconi anemia (FA) is a rare inherited bone marrow failure syndrome (IBMFS). Affected individuals must be distinguished from relatives, patients with mosaicism must be identified, and patients with other IBMFS classified as non-FA. The diagnostic feature of FA is increased chromosomal breakage in blood lymphocytes cultured with diepoxybutane or mitomycin C. Here, we sought a method to uniquely identify patients with FA with mosaicism, using cells from participants in the National Cancer Institute IBMFS cohort. Lymphocytes were treated with diepoxybutane or mitomycin C, and metaphases scored for breaks and radials. Analyses included the percentage of cells with any aberration, breaks per cell, and breaks per aberrant cell. There were 26 patients with FA (4 mosaics), 46 FA relatives, and 62 patients with a non-FA IBMFS. By all analytic methods, patients with FA were abnormal compared with other groups. Those with FA mosaicism had more breakage than relatives or patients with non-FA IBMFS, but there was some individual overlap. The choices of clastogen are laboratory-dependent, but there was no method or analysis of lymphocytes that clearly distinguished all individuals mosaic for FA from relatives or patients with other IBMFS. Thus, genotyping remains the best method for providing absolute clarity.

Partial MCM4 deficiency in patients with growth retardation, adrenal insufficiency, and natural killer cell deficiency

Natural killer (NK) cells are circulating cytotoxic lymphocytes that exert potent and nonredundant antiviral activity and antitumoral activity in the mouse; however, their function in host defense in humans remains unclear. Here, we investigated 6 related patients with autosomal recessive growth retardation, adrenal insufficiency, and a selective NK cell deficiency characterized by a lack of the CD56(dim) NK subset. Using linkage analysis and fine mapping, we identified the disease-causing gene, MCM4, which encodes a component of the MCM2-7 helicase complex required for DNA replication. A splice-site mutation in the patients produced a frameshift, but the mutation was hypomorphic due to the creation of two new translation initiation methionine codons downstream of the premature termination codon. The patients' fibroblasts exhibited genomic instability, which was rescued by expression of WT MCM4. These data indicate that the patients' growth retardation and adrenal insufficiency likely reflect the ubiquitous but heterogeneous impact of the MCM4 mutation in various tissues. In addition, the specific loss of the NK CD56(dim) subset in patients was associated with a lower rate of NK CD56(bright) cell proliferation, and the maturation of NK CD56(bright) cells toward an NK CD56(dim) phenotype was tightly dependent on MCM4-dependent cell division. Thus, partial MCM4 deficiency results in a genetic syndrome of growth retardation with adrenal insufficiency and selective NK deficiency.