Patterns and frequency of renal abnormalities in Fanconi anaemia: implications for long-term management

Late Effects Following Hematopoietic Stem Cell Transplantation Among Childhood Transplant Survivors with Fanconi Anemia

Objective

This study was planned to evaluate long-term post-transplant complications in patients who underwent transplantation with the diagnosis of Fanconi anemia (FA) in childhood in our bone marrow transplantation unit and who were still being followed. It was predicted that the results would show the critical importance of determining disease-specific post-transplant long-term follow-up plans and putting them into practice in terms of early detection of complications and improving the survival rates and quality of life of FA patients.

Materials and Methods

In this single-center, cross-sectional study, according to current recommendations, we analyzed the long-term outcomes of 36 patients with FA with a median age of 18.1 years (range: 6.1-36 years, male/female ratio: 24/12) who underwent HSCT in the Pediatric Bone Marrow Transplantation Unit between 1995 and 2019 and survived at least 1 year following the transplantation.

Results

The median long-term follow-up time was 8 years (range: 1-25 years). Gonadal dysfunction was detected in approximately 35% of our patients; more specifically, 31% of the patients had hypergonadotropic hypogonadism and 4% had hypogonadotropic hypogonadism. When the patients were evaluated for growth impairment, 7 of 12 patients who had reached their final adult heights and 12 of 21 patients who had not yet completed their growth had height standard deviation (SD) scores below -2 SDs. Three patients (9%) developed subclinical hypothyroidism, 2 (6%) had overt hypothyroidism, and 1 (3%) had central hypothyroidism. Although none of our patients fully met the criteria for metabolic syndrome, 23% had insulin resistance and 39% had dyslipidemia. Evaluation of organ dysfunctions revealed that nearly 50% of the patients had obstructive and 21% had restrictive changes in their pulmonary function tests. Hepatosteatosis was detected in 15% of the patients and mild valve dysfunction was detected in 50% of evaluable patients. Three patients developed secondary malignancies. Squamous cell cancer developed in 2 patients and basal cell cancer in 1 patient.

Conclusion

A risk-defined multidisciplinary approach for the long-term follow-up of children with FA undergoing HSCT is essential for early detection and management of late effects.

DNA phenotyping and mapping intragenic deletion mutations in Fanconi anemia: Patterns and diagnostic inferences

BACKGROUND

Fanconi anemia is a genetically heterogeneous recessive disorder distinguished by cytogenetic instability, hypersensitivity to DNA crosslinking agents, increased chromosomal breakage, and disturbed DNA repair. To date, Fanconi anemia complementation group (FANC) includes 23 FANC genes identified of which, FANCA gene is the most commonly mutated. The mutation spectrum of the FANCA gene is highly heterogeneous with large intragenic deletions due to Alu elements-mediated recombination. The study aimed to identify different deletion mutations on FANCA gene in Egyptian Fanconi anemia patients by multiplex ligation-dependent probe amplification (MLPA) technique to define the spectrum of FA molecular pathology as a step for disease control. The study included 80 FA patients (36 females and 44 males) whose ages ranged from 4 months to 17 years descending from unrelated consanguineous families referred to the Hereditary Blood Disorders Clinic, National Research Centre (NRC), Egypt. Patients were diagnosed with classical clinical presentation of FA and were confirmed by chromosomal breakage using Diepoxybutane (DEB).

RESULTS

The common clinical presentation in our FA patients were the presence of café au lait spots with hyperpigmentation in 65/80 (81%) followed by skeletal defects in 40/80 (50%). MLPA revealed a total of five different intragenic homozygous deletions of FANCA gene in 16 /80 (20%) patients, among them two deletion patterns were novel.

CONCLUSION

Molecular analysis using MLPA could detect pathogenic mutations in 20% of FA patients, our study generated considerable data on causative mutations that was used for genetic counseling and prenatal diagnosis.

Longitudinal clinical manifestations of Fanconi anemia: A systematized review

Fanconi anemia (FA) is a rare and complex inherited genetic disorder characterized by impaired DNA repair mechanisms leading to genomic instability. Individuals with FA have increased susceptibility to congenital anomalies, progressive bone marrow failure, leukemia and malignant tumors, endocrinopathies and other medical issues. In recent decades, steadily improved approaches to hematopoietic cell transplantation (HCT), the only proven curative therapy for the hematologic manifestations of FA, have significantly increased the life expectancy of affected individuals, illuminating the need to understand the long-term consequences and multi-organ ramifications. Utilizing a systematized review approach with narrative synthesis of each primary issue and organ system, we shed light on the challenges and opportunities for optimizing the care and quality of life for individuals with FA and identify knowledge gaps informing future research directions.

Diagnosing Fanconi Anemia: A Rare Case Report From Rural India

Fanconi anemia is a rare but most prevalent form of inherited aplastic anemia, predominantly transmitted in an autosomal recessive manner, except for one X-linked variant. It arises from mutations in the genes across 16 different complementation groups that are crucial for DNA stability. It is marked by a wide range of congenital malformations, progressive pancytopenia, and an increased risk of both hematological malignancies and solid tumors. The congenital abnormalities associated with it can affect various organ systems, including the skeletal system, with significant variability among patients. One similar case has been reported here, which had the typical clinical features of FA. Due to varied phenotypic presentation, diagnosing FA can be challenging. A Chromosomal Breakage Study using mitomycin C (MMC) or diepoxybutane (DEB) is a distinctive cellular marker that aids in the diagnosis.

Pathological consequences of DNA damage in the kidney

DNA lesions that evade repair can lead to mutations that drive the development of cancer, and cellular responses to DNA damage can trigger senescence and cell death, which are associated with ageing. In the kidney, DNA damage has been implicated in both acute and chronic kidney injury, and in renal cell carcinoma. The susceptibility of the kidney to chemotherapeutic agents that damage DNA is well established, but an unexpected link between kidney ciliopathies and the DNA damage response has also been reported. In addition, human genetic deficiencies in DNA repair have highlighted DNA crosslinks, DNA breaks and transcription-blocking damage as lesions that are particularly toxic to the kidney. Genetic tools in mice, as well as advances in kidney organoid and single-cell RNA sequencing technologies, have provided important insights into how specific kidney cell types respond to DNA damage. The emerging view is that in the kidney, DNA damage affects the local microenvironment by triggering a damage response and cell proliferation to replenish injured cells, as well as inducing systemic responses aimed at reducing exposure to genotoxic stress. The pathological consequences of DNA damage are therefore key to the nephrotoxicity of DNA-damaging agents and the kidney phenotypes observed in human DNA repair-deficiency disorders.

Modeling Podocyte Ontogeny and Podocytopathies with the Zebrafish

Podocytes are exquisitely fashioned kidney cells that serve an essential role in the process of blood filtration. Congenital malformation or damage to podocytes has dire consequences and initiates a cascade of pathological changes leading to renal disease states known as podocytopathies. In addition, animal models have been integral to discovering the molecular pathways that direct the development of podocytes. In this review, we explore how researchers have used the zebrafish to illuminate new insights about the processes of podocyte ontogeny, model podocytopathies, and create opportunities to discover future therapies.

Fanconi anemia and dyskeratosis congenita/telomere biology disorders: Two inherited bone marrow failure syndromes with genomic instability

Inherited bone marrow failure syndromes (IBMFS) are a complex and heterogeneous group of genetic diseases. To date, at least 13 IBMFS have been characterized. Their pathophysiology is associated with germline pathogenic variants in genes that affect hematopoiesis. A couple of these diseases also have genomic instability, Fanconi anemia due to DNA damage repair deficiency and dyskeratosis congenita/telomere biology disorders as a result of an alteration in telomere maintenance. Patients can have extramedullary manifestations, including cancer and functional or structural physical abnormalities. Furthermore, the phenotypic spectrum varies from cryptic features to patients with significantly evident manifestations. These diseases require a high index of suspicion and should be considered in any patient with abnormal hematopoiesis, even if extramedullary manifestations are not evident. This review describes the disrupted cellular processes that lead to the affected maintenance of the genome structure, contrasting the dysmorphological and oncological phenotypes of Fanconi anemia and dyskeratosis congenita/telomere biology disorders. Through a dysmorphological analysis, we describe the phenotypic features that allow to make the differential diagnosis and the early identification of patients, even before the onset of hematological or oncological manifestations. From the oncological perspective, we analyzed the spectrum and risks of cancers in patients and carriers.

Acute kidney injury in pediatric hematopoietic cell transplantation: critical appraisal and consensus

Hematopoietic cell transplantation (HCT) is a common therapy for the treatment of neoplastic and metabolic disorders, hematological diseases, and fatal immunological deficiencies. HCT can be subcategorized as autologous or allogeneic, with each modality being associated with their own benefits, risks, and post-transplant complications. One of the most common complications includes acute kidney injury (AKI). However, diagnosing HCT patients with AKI early on remains quite difficult. Therefore, this evidence-based guideline, compiled by the Pediatric Continuous Renal Replacement Therapy (PCRRT) working group, presents the various factors that contribute to AKI and recommendations regarding optimization of therapy with minimal complications in HCT patients.

Bilaterally ectopic pelvic kidneys masquerading as horseshoe kidney in Fanconi anemia

Fanconi anemia (FA) is a genetic disease associated with the risk of different congenital malformations, bone marrow failure, and predisposition to cancer. Congenital abnormalities of the kidney and urinary tract are not infrequent in FA with renal ectopia being one of them. The incidence of the bilateral pelvic ectopic kidney is restricted to only a few reported cases; however, its association with FA has never been reported in the literature. We present a case of Fanconi anemia in a young girl with apparently fused kidneys on a 99mTc-DMSA planar scan which was confirmed to be bilateral pelvic kidneys on hybrid cross-sectional imaging.

Kidney complications in 107 Fanconi anemia patients submitted to hematopoietic cell transplantation

Fanconi anemia (FA) is a rare disease characterized by progressive bone marrow failure, cancer predisposition, and multiple systemic malformations, including congenital abnormalities of the kidney and urinary tract (CAKUT). Hematopoietic cell transplantation (HCT), the only potentially curative treatment for the hematological complications of FA, may precipitate acute kidney injury (AKI) and hypertension. We retrospectively investigated 107 FA patients who underwent HCT between 2009 and 2017. We investigated the incidence and risk factors of AKI within 100 days after HCT in a cohort of FA patients, and kidney function and hypertension over 2-year follow-up.The incidence of AKI (mainly stage I) was 18.7%. Patients aged ≥ 11 years at transplantation showed a higher risk of AKI (OR 3.53). The eGFR was 60-90 mL/min/1.73 m² in 53 (49.5%), 55 (51.4%), 50 (50.5%), 50 (51%), and 46 (59.7%) patients before HCT, at 100 days, 6 months, 1 year, and 2 years. Within the first 100 days after HCT, hypertension was observed in 72% of the patients and was associated with cyclosporine therapy. Most (62.3%) patients had stage 2 hypertension. CAKUT was observed in 33.7% of the patients and was associated with both hypertension (86%) and diminished kidney function but not with AKI.Conlusion: Although AKI, a commonly known HCT complication, was mild in this study, the prevalence of chronic kidney disease (CKD), as well as the high incidence of hypertension, specially associated with CAKUT point out the importance of kidney care in short and long-term follow up of FA patients. What is Known: • Fanconi anemia (FA) is the most frequent inherited bone marrow failure in children, and 30% of cases have congenital anomalies of kidney (CAKUT). • Acute kidney injury and hypertension after hematopoietic cell transplantation (HCT) may impact the outcomes.. What is New: • Despite the presence of CAKUT and stage 2 CKD in 33.7% and 50% of the patients, respectively, AKI was mild and transitory after HCT in FA patients. • CAKUT in FA patients was associated with lower kidney function and hypertension after HCT.

Distinguishing constitutional from acquired bone marrow failure in the hematology clinic

Distinguishing constitutional from immune bone marrow failure (BMF) has important clinical implications. However, the diagnosis is not always straightforward, and immune aplastic anemia, the commonest BMF, is a diagnosis of exclusion. In this review, we discuss a general approach to the evaluation of BMF, focusing on clinical presentations particular to immune and various constitutional disorders as well as the interpretation of bone marrow histology, flow cytometry, and karyotyping. Additionally, we examine the role of specialized testing in both immune and inherited BMF, and discuss genetic testing, both its role in patient evaluation and interpretation of results.

A Genome-Wide Association Study for Hypertensive Kidney Disease in Korean Men

Hypertension is one of the major risk factors for chronic kidney disease (CKD), and the coexistence of hypertension and CKD increases morbidity and mortality. Although many genetic factors have been identified separately for hypertension and kidney disease, studies specifically focused on hypertensive kidney disease (HKD) have been rare. Therefore, this study aimed to identify loci or genes associated with HKD. A genome-wide association study (GWAS) was conducted using two Korean cohorts, the Health Examinee (HEXA) and Korean Association REsource (KARE). Consequently, 19 single nucleotide polymorphisms (SNPs) were found to be significantly associated with HKD in the discovery and replication phases (p < 5 × 10⁻⁸, p < 0.05, respectively). We further analyzed HKD-related traits such as the estimated glomerular filtration rate (eGFR), creatinine, blood urea nitrogen (BUN), systolic blood pressure (SBP) and diastolic blood pressure (DBP) at the 14q21.2 locus, which showed a strong linkage disequilibrium (LD). Expression quantitative trait loci (eQTL) analysis was also performed to determine whether HKD-related SNPs affect gene expression changes in glomerular and arterial tissues. The results suggested that the FANCM gene may affect the development of HKD through an integrated analysis of eQTL and GWAS and was the most significantly associated candidate gene. Taken together, this study indicated that the FANCM gene is involved in the pathogenesis of HKD. Additionally, our results will be useful in prioritizing other genes for further experiments.

ERCC1 mutations impede DNA damage repair and cause liver and kidney dysfunction in patients

ERCC1-XPF is a multifunctional endonuclease involved in nucleotide excision repair (NER), interstrand cross-link (ICL) repair, and DNA double-strand break (DSB) repair. Only two patients with bi-allelic ERCC1 mutations have been reported, both of whom had features of Cockayne syndrome and died in infancy. Here, we describe two siblings with bi-allelic ERCC1 mutations in their teenage years. Genomic sequencing identified a deletion and a missense variant (R156W) within ERCC1 that disrupts a salt bridge below the XPA-binding pocket. Patient-derived fibroblasts and knock-in epithelial cells carrying the R156W substitution show dramatically reduced protein levels of ERCC1 and XPF. Moreover, mutant ERCC1 weakly interacts with NER and ICL repair proteins, resulting in diminished recruitment to DNA damage. Consequently, patient cells show strongly reduced NER activity and increased chromosome breakage induced by DNA cross-linkers, while DSB repair was relatively normal. We report a new case of ERCC1 deficiency that severely affects NER and considerably impacts ICL repair, which together result in a unique phenotype combining short stature, photosensitivity, and progressive liver and kidney dysfunction.

Chromosome Instability in Fanconi Anemia: From Breaks to Phenotypic Consequences

Fanconi anemia (FA), a chromosomal instability syndrome, is caused by inherited pathogenic variants in any of 22 FANC genes, which cooperate in the FA/BRCA pathway. This pathway regulates the repair of DNA interstrand crosslinks (ICLs) through homologous recombination. In FA proper repair of ICLs is impaired and accumulation of toxic DNA double strand breaks occurs. To repair this type of DNA damage, FA cells activate alternative error-prone DNA repair pathways, which may lead to the formation of gross structural chromosome aberrations of which radial figures are the hallmark of FA, and their segregation during cell division are the origin of subsequent aberrations such as translocations, dicentrics and acentric fragments. The deficiency in DNA repair has pleiotropic consequences in the phenotype of patients with FA, including developmental alterations, bone marrow failure and an extreme risk to develop cancer. The mechanisms leading to the physical abnormalities during embryonic development have not been clearly elucidated, however FA has features of premature aging with chronic inflammation mediated by pro-inflammatory cytokines, which results in tissue attrition, selection of malignant clones and cancer onset. Moreover, chromosomal instability and cell death are not exclusive of the somatic compartment, they also affect germinal cells, as evidenced by the infertility observed in patients with FA.

Ligase IV syndrome can present with microcephaly and radial ray anomalies similar to Fanconi anaemia plus fatal kidney malformations

Ligase IV (LIG4) syndrome is a rare disorder of DNA damage repair caused by biallelic, pathogenic variants in LIG4. This is a phenotypically heterogeneous condition with clinical presentation varying from lymphoreticular malignancies in developmentally normal individuals to significant microcephaly, primordial dwarfism, radiation hypersensitivity, severe combined immunodeficiency and early mortality. Renal defects have only rarely been described as part of the ligase IV disease spectrum.

We identified a consanguineous family where three siblings presenting with antenatal growth retardation, microcephaly, severe renal anomalies and skeletal abnormalities, including radial ray defects. Autozygosity mapping and exome sequencing identified a novel homozygous frameshift variant in LIG4, c.597_600delTCAG, p.(Gln200LysfsTer33), which segregated in the family. LIG4 is encoded by a single exon and so this frameshift variant is predicted to result in a protein truncated by 678 amino acids. This is the shortest predicted LIG4 protein product reported and correlates with the most severe clinical phenotype described to date. We note the clinical overlap with Fanconi anemia and suggest that LIG4 syndrome is considered in the differential diagnosis of this severe developmental disorder.

Urothelial carcinoma within the prostatic utricle of an adult with hypospadias and Fanconi anemia

Prostatic utricles are rare in the general population and are often otherwise unremarkable anatomic variants. These structures are contiguous with the prostatic urethra and are nevertheless susceptible to urothelial carcinoma. This case report discusses the first reported patient with Fanconi anemia with urothelial carcinoma within an enlarged prostatic utricle.

Chromosome instability syndromes

Fanconi anaemia (FA), ataxia telangiectasia (A-T), Nijmegen breakage syndrome (NBS) and Bloom syndrome (BS) are clinically distinct, chromosome instability (or breakage) disorders. Each disorder has its own pattern of chromosomal damage, with cells from these patients being hypersensitive to particular genotoxic drugs, indicating that the underlying defect in each case is likely to be different. In addition, each syndrome shows a predisposition to cancer. Study of the molecular and genetic basis of these disorders has revealed mechanisms of recognition and repair of DNA double-strand breaks, DNA interstrand crosslinks and DNA damage during DNA replication. Specialist clinics for each disorder have provided the concentration of expertise needed to tackle their characteristic clinical problems and improve outcomes. Although some treatments of the consequences of a disorder may be possible, for example, haematopoietic stem cell transplantation in FA and NBS, future early intervention to prevent complications of disease will depend on a greater understanding of the roles of the affected DNA repair pathways in development. An important realization has been the predisposition to cancer in carriers of some of these gene mutations.