Ann Lab Med.  2012 Sep;32(5):380-384. 10.3343/alm.2012.32.5.380.

A Case Report of Fanconi Anemia Diagnosed by Genetic Testing Followed by Prenatal Diagnosis

• Lee HJ
• Park S
• Kang HJ
• Jun JK
• Lee JA
• Lee DS
• Park SS
• Seong MW

• KMID: 1387356
• DOI: http://doi.org/10.3343/alm.2012.32.5.380

Abstract

Fanconi anemia (FA) is a rare genetic disorder affecting multiple body systems. Genetic testing, including prenatal testing, is a prerequisite for the diagnosis of many clinical conditions. However, genetic testing is complicated for FA because there are often many genes that are associated with its development, and large deletions, duplications, or sequence variations are frequently found in some of these genes. This study describes successful genetic testing for molecular diagnosis, and subsequent prenatal diagnosis, of FA in a patient and his family in Korea. We analyzed all exons and flanking regions of the FANCA, FANCC, and FANCG genes for mutation identification and subsequent prenatal diagnosis. Multiplex ligation-dependent probe amplification analysis was performed to detect large deletions or duplications in the FANCA gene. Molecular analysis revealed two mutations in the FANCA gene: a frameshift mutation c.2546delC and a novel splice-site mutation c.3627-1G>A. The FANCA mutations were separately inherited from each parent, c.2546delC was derived from the father, whereas c.3627-1G>A originated from the mother. The amniotic fluid cells were c.3627-1G>A heterozygotes, suggesting that the fetus was unaffected. This is the first report of genetic testing that was successfully applied to molecular diagnosis of a patient and subsequent prenatal diagnosis of FA in a family in Korea.

Keyword

Fanconi anemia; FANCA; Molecular diagnosis; Prenatal diagnosis

MeSH Terms

Base Sequence
Child, Preschool
Exons
Fanconi Anemia/*diagnosis/genetics
Fanconi Anemia Complementation Group A Protein/genetics
Fanconi Anemia Complementation Group C Protein/genetics
Fanconi Anemia Complementation Group G Protein/genetics
Female
Frameshift Mutation
Genetic Testing
Heterozygote
Humans
Karyotyping
Male
Pregnancy
Prenatal Diagnosis
RNA Splice Sites
Reverse Transcriptase Polymerase Chain Reaction
Sequence Analysis, DNA

Figure

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  Fig. 1 Clinodactyly with brachymesophalangia on bilateral 5th fingers.

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  Fig. 2 Cytogenetic findings of a chromosome breakage test with (A) DEB (diepoxybutane) and (B) MMC (mitomycin C) in a peripheral blood lymphocyte culture. Increased mean number of breaks per metaphase (DEB: 5.5, MMC: 11.2, FA cutoff >2.0), ratio of mean number of breaks per metaphase in patient/control (DEB: 275, MMC: 112, FA cutoff >10), and number of chromosome breaks per aberrant mitosis (DEB: 6.05, MMC: 11.2, FA cutoff >5.5) are recorded.

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  Fig. 3 Sequencing results of the FANCA gene show compound heterozygous mutations of c.2546delC (denoted by an asterisk; A) and c.3627-1G>A (denoted by an asterisk; B) in the proband. The c.2546delC mutation was inherited paternally, whereas the c.3627-1G>A mutation was transmitted maternally. The fetus was a heterozygous carrier of the c.3627-1G>A mutation.

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  Fig. 4 Results of agarose gel electrophoresis of RT-PCR products (A), capillary electrophoresis of RT-PCR products (B), and sequence analysis (C) for the novel potential splice-site mutation c.3627-1G>A. RT-PCR was conducted using following primers: F-5'-TTGACCTCTGCTCTGGTGTG-3', R-5'-AACCAATAGCTCCTCTCTCTCG-3'. In addition to the normal transcript (276-bp-sized band), an abnormal transcript (260-bp-sized band) was discernible on capillary electrophoresis. Sequence analysis demonstrated that this abnormal transcript resulted from skipping of the first 16 bp (yellow) of exon 37 rather than all of exon 37 (blue). Abbreviation: RT-PCR, reverse transcription PCR.

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  Fig. 5 Results of STR marker analysis that was performed to determine maternal cell contamination into amniotic fluid. For the FGA marker, maternal blood has allele 20.3 and allele 24.3, while the amniotic fluid has only allele 20.3 (A). For the D3S1358 marker, amniotic fluid has allele 15.1, which is not shared with maternal blood, as well as allele 16.2 (B). Abbreviation: STR, short tandem repeat.

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