Novel Variations of FANCA Gene Provokes Fanconi Anemia: Molecular Diagnosis in a Special Chinese Family

Novel FANCA mutation in the first fully-diagnosed patient with Fanconi anemia in Polish population - case report

BACKGROUND

Fanconi anemia is a rare genetic disorder caused by mutations in genes which protein products are involved in replication, cell cycle control and DNA repair. It is characterized by congenital malformations, bone marrow failure, and high risk of cancer. The diagnosis is based on morphological and hematological abnormalities such as pancytopenia, macrocytic anaemia and progressive bone marrow failure. Genetic examination, often very complex, includes chromosomal breakage testing and mutational analysis.

CASE PRESENTATION

We present a child with clinical diagnosis of Fanconi anemia. Although morphological abnormalities of skin and bones were present from birth, diagnosis was only suspected at the age of 8. Chromosome breakage test in patient's lymphocytes showed increased level of aberrations (gaps, chromatid breaks, chromosome breaks, radial figures and rearrangements) compared to control. Next generation sequencing revealed presence of two pathogenic variants in FANCA gene, one of which was not previously reported.

CONCLUSIONS

The article provides additional supportive evidence that compound biallelic mutations of FANCA are associated with Fanconi anemia. It also illustrates the utility of combination of cytogenetic and molecular tests, together with detailed clinical evaluation in providing accurate diagnosis of Fanconi anemia. This report, to the best of our knowledge, describes the first fully diagnosed FA patient in Polish population.

Functional analysis of Fanconi anemia mutations in China

Fanconi anemia (FA) is a rare recessive disease characterized by progressive bone marrow failure, congenital abnormalities, and increased incidence of cancers. To date, mutations in 22 genes can cause FA or an FA-like phenotype. In China, in addition to clinical information, FA diagnosis primarily relies on genetic sequencing because the chromosome breakage test is rarely performed. Here, we employed multiple genetic diagnostic tools (DNA sequencing, multiplex ligation-dependent probe amplification, and chromosome microarray) and a variant-based functional assay platform to investigate the genetic cause in 25 Chinese suspected FA patients. A total of 45 distinct candidate variants were detected in six FA genes (FA-A, FA-B, FA-C, FA-D2, FA-G, and FA-J), of which 36 were novel. Eight missense variants and one indel variant were unable to restore FANCD2 mono-ubiquitination and mitomycin C resistance in a panel of FA indicator cell lines, indicating that these mutations are deleterious. Three missense variants (FANCA-L424V, FANCC-E273K, and FANCG-A153G) were harmless. Finally, 23 patients were molecularly diagnosed with FA, consistent with their clinical phenotype. In the FA-A subgroup, large deletions accounted for 14% of the disease-causing variants. We have established a comprehensive molecular diagnostic workflow for Chinese FA patients that can substitute for standard FA cytogenetic analysis.