A strategy for molecular diagnostics of Fanconi anemia in Brazilian patients

Clinical and cytogenetic profile of Fanconi anemia diagnosed after implementation of mitomycin C cytogenetic test in the state of Pernambuco, Brazil

INTRODUCTION

Fanconi anemia (FA) is a rare autosomal recessive disease characterized by chromosomal instability and increased predisposition to malignancy. The diagnosis of FA requires clinical evaluation, confirmation of chromosomal fragility and/or analysis of genetic mutations. Therefore, this study aims to identify the clinical profile of patients with FA in the state of Pernambuco, Brazil.

METHOD

We analyzed 100 individuals referred from the major hematology and bone marrow (BM) transplant centers in the state of Pernambuco, Brazil, between the years 2018 and 2022. The diagnosis of FA was performed using the mitomycin C chromosomal fragility test, clinical data and classical and molecular cytogenetic analyses.

RESULTS

We enrolled a total of 16 patients with FA to comprise this study. Most of these individuals (87.5%) came from the Agreste and Sertão regions of Pernambuco. We observed a slight female prevalence of FA (1.3:1). The primary clinical and laboratory findings were café au lait spots (62.5%) and bone abnormalities (53%, mainly thumb deformities [40%]). We performed BM cytogenetic analysis for eight patients - seven showed no chromosomal abnormalities and one presented the karyotype 47,XY,+21 [15].

CONCLUSIONS

Our results are important to promote public health measures for the early diagnosis of FA, as well as to foster the engagement of a multidisciplinary group in the treatment of this disease.

Investigation of mutations in Fanconi anemia genes and malignancy predisposition in Brazilian patients

INTRODUCTION

This study proposed to identify Fanconi anemia (FA) mutations in Brazilian patients and to investigate their impact on clinical manifestations and malignancies onset.

METHODS

A total of 116 patients were screened for nine mutations in FANCA, FANCC, FANCG. Those with no mutations were investigated by multiplex ligation-dependent probe amplification (MLPA) and Sanger sequencing for FANCA, FANCC, FANCE, FANCF, FANCG, FANCD1/BRCA2.

RESULTS

Genetic subtype was identified in 107/116 (78 FA-A, 8 FA-C, 13 FA-G, 8 FA-E), with only one mutation in 1/116, and no mutations in 9/116 patients. Before hematopoietic cell transplantation (HCT), malignancies were detected in 16/116 patients (14/78 FA-A, 01/08 FA-C, 01/08 FA-E), and 12 of them were hematological. Observed to expected ratio (O/E) of hematologic malignancy was 303.7 (95% CI = 148.6-458.7).

CONCLUSION

This study allowed the identification of biallelic mutations in 91.4% of patients. FANCG and FANCC mutations had significantly earlier bone marrow failure onset, and FANCG severe cytopenia at diagnosis. Despite the inherent limitations of the small number of malignancy events in each genetic subtype, the hematologic malignancies O/E ratio was very high. Cumulative incidence of malignancy before HCT was higher in the third and fourth decades of life, considering HCT and death as competing risks. The cumulative incidence of HCT increased during the first decade, competing with malignancy development.

Ocular Manifestations in Patients with Fanconi Anemia: A Single-Center Experience Including 106 Patients

OBJECTIVES

To describe the prevalence of acquired ocular manifestations in patients with Fanconi anemia (FA) and to describe and correlate the congenital ocular malformations with the genetic subtypes of the disease.

STUDY DESIGN

This is a cross-sectional observational study of 106 consecutive patients with confirmed diagnosis of FA who were followed at the Hematopoietic Stem Cell Transplantation (HSCT) Service at the Federal University of Paraná, Curitiba, Parana, Brazil. Participants underwent a complete ophthalmologic evaluation and 84 patients underwent ocular ultrasound examination. This study was conducted between November 2014 and August 2017.

RESULTS

The patients ranged in age from 6 months to 43 years of age. Microphthalmia was the most common congenital ocular abnormality (95.2%). A decrease in anthropometric measurements was observed, including palpebral fissure length (78/103 patients [76.5%]), microcornea (48/103 patients [46.6%]), and ptosis (31/103 patients [30.1%]). We identified a new ophthalmic condition in 15 patients with FA, that is, epiretinal tissue on the optic disc. The genetic subtype was identified in 78 patients (79.6%), the FA-A subtype was most prevalent (50%). The most common acquired ocular manifestation (non-graft-versus-host disease [GVHD] related) in patients who did not undergo HSCT (n = 44) was limbal neovascularization (13.6%), whereas in patients who underwent HSCT (n = 62), the GVHD-related manifestation was ocular GVHD (51.6%). The most frequent symptom of ocular GVHD was keratoconjunctivitis sicca (29%).

CONCLUSIONS

Several ocular manifestations were identified in patients with FA.

A comprehensive molecular study identified 12 complementation groups with 56 novel FANC gene variants in Indian Fanconi anemia subjects

Fanconi anemia (FA) is a rare autosomal or X-linked genetic disorder characterized by chromosomal breakages, congenital abnormalities, bone marrow failure (BMF), and cancer. There has been a discovery of 22 FANC genes known to be involved in the FA pathway. This wide number of pathway components makes molecular diagnosis challenging for FA. We present here the most comprehensive molecular diagnosis of FA subjects from India. We observed a high frequency (4.42 ± 1.5 breaks/metaphase) of chromosomal breakages in 181 FA subjects. The major clinical abnormalities observed were skin pigmentation (70.2%), short stature (46.4%), and skeletal abnormalities (43.1%), along with a few minor clinical abnormalities. The combination of Sanger sequencing and Next Generation Sequencing could molecularly characterize 164 (90.6%) FA patients and identified 12 different complementation groups [FANCA (56.10%), FANCG (16.46%), FANCL (12.80%), FANCD2 (4.88%), FANCJ (2.44%), FANCE (1.22%), FANCF (1.22%), FANCI (1.22%), FANCN (1.22%), FANCC (1.22%), FANCD1 (0.61%) and FANCB (0.61%)]. A total of 56 novel variants were identified in our cohort, including a hotspot variant: a deletion of exon 27 in the FANCA gene and a nonsense variant at c.787 C>T in the FANCG gene. Our comprehensive molecular findings can aid in the stratification of molecular investigation in the diagnosis and management of FA patients.

FANCA Gene Mutations in North African Fanconi Anemia Patients

Populations in North Africa (NA) are characterized by a high rate of consanguinity. Consequently, the proportion of founder mutations might be higher than expected and could be a major cause for the high prevalence of recessive genetic disorders like Fanconi anemia (FA). We report clinical, cytogenetic, and molecular characterization of FANCA in 29 North African FA patients from Tunisia, Libya, and Algeria. Cytogenetic tests revealed high rates of spontaneous chromosome breakages for all patients except two of them. FANCA molecular analysis was performed using three different molecular approaches which allowed us to identify causal mutations as homozygous or compound heterozygous forms. It included a nonsense mutation (c.2749C > T; p.Arg917Ter), one reported missense mutation (c.1304G > A; p.Arg435His), a novel missense variant (c.1258G > A; p.Asp409Glu), and the FANCA most common reported mutation (c.3788_3790delTCT; p.Phe1263del). Furthermore, three founder mutations were identified in 86.7% of the 22 Tunisian patients: (1) a deletion of exon 15, in 36.4% patients (8/22); (2), a deletion of exons 4 and 5 in 23% (5/22) and (3) an intronic mutation c.2222 + 166G > A, in 27.3% (6/22). Despite the relatively small number of patients studied, our results depict the mutational landscape of FA among NA populations and it should be taken into consideration for appropriate genetic counseling.

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.