Karyomegalic Interstitial Nephritis: A Case Report and Review of the Literature

Karyomegalic Interstitial Nephritis in the Allograft Kidney - A Case Report

Karyomegalic interstitial nephritis is a rare progressive renal disease. We report a 36-year-old male patient who developed kidney failure due to this condition, underwent kidney transplantation from his sister, and developed the same condition in the graft. Genetic testing of the donor revealed autosomal recessive compound heterozygous mutation of Fanconi anemia-associated nuclease1 (FAN1) gene. Karyomegalic interstitial nephritis is most probably donor derived in our patient. It should not be mislabeled as viral nephropathy.

Fanconi syndrome with hepatorenal karyomegaly in a young Sphynx cat

Case summary

A 3-year-old male neutered Sphynx cat was referred for history of chronically increased liver enzymes and lower urinary tract signs that were first reported when the cat was 5 months old. Urine metabolic profile revealed increased amino aciduria and glucosuria despite normoglycemia, suggesting Fanconi syndrome. Urine sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed a banding pattern suggestive of primary tubular damage. Serial blood work showed non-regenerative normocytic normochromic anemia, persistently elevated liver enzymes, worsening azotemia and progressive hyperchloremic metabolic acidosis. Ultrasound revealed irregular kidneys and bilaterally hyperechoic cortices and medullae with a loss of normal corticomedullary distinction. Laparoscopic kidney biopsy revealed a moderate-to-severe chronic interstitial fibrosis with chronic lymphoplasmacytic inflammation, tubular degeneration and atrophy, mild glomerulosclerosis and mild large vascular amyloidosis. Tubular epithelial cell karyomegaly was multifocally evident throughout the kidney. The liver had moderate diffuse zone 1 hepatocellular atrophy, periportal fibrosis, biliary hyperplasia, mild perisinusoidal amyloidosis and hepatocyte karyomegaly in zones 2 and 3. The patient continued to decline and developed polyuria, polydipsia, lethargy and hyporexia irrespective of rigorous management, which failed to curtail the progressive anemia and azotemia. The patient was euthanized 8 months from the onset of clinical signs.

Relevance and novel information

Fanconi syndrome in cats is a rare condition, with most reports occurring secondary to chlorambucil treatment. This is the first known case of Fanconi syndrome occurring with concurrent hepatorenal epithelial karyomegaly in a young Sphynx cat.

Karyomegalic interstitial nephritis as a rare cause of kidney graft dysfunction: case report and review of literature

Karyomegalic interstitial nephritis (KIN) is a rare cause of chronic interstitial nephritis characterized by enlarged renal tubular epithelial nuclei. The first case of KIN reported in a kidney graft was in 2019. Here, we report the first case of KIN in 2 brothers receiving kidneys from 2 different unrelated living donors. A male kidney transplant recipient with focal segmental glomerulosclerosis as the original kidney disease presented with graft impairment and proteinuria, and graft biopsy revealed KIN. This patient had a brother who was also a kidney transplant recipient and had one episode of graft impairment and was diagnosed with KIN as well.

The importance of nuclear RAGE-Mcm2 axis in diabetes or cancer-associated replication stress

An elevated frequency of DNA replication defects is associated with diabetes and cancer. However, data linking these nuclear perturbations to the onset or progression of organ complications remained unexplored. Here, we report that RAGE (Receptor for Advanced Glycated Endproducts), previously believed to be an extracellular receptor, upon metabolic stress localizes to the damaged forks. There it interacts and stabilizes the minichromosome-maintenance (Mcm2-7) complex. Accordingly, RAGE deficiency leads to slowed fork progression, premature fork collapse, hypersensitivity to replication stress agents and reduction of viability, which was reversed by the reconstitution of RAGE. This was marked by the 53BP1/OPT-domain expression and the presence of micronuclei, premature loss-of-ciliated zones, increased incidences of tubular-karyomegaly, and finally, interstitial fibrosis. More importantly, the RAGE-Mcm2 axis was selectively compromised in cells expressing micronuclei in human biopsies and mouse models of diabetic nephropathy and cancer. Thus, the functional RAGE-Mcm2/7 axis is critical in handling replication stress in vitro and human disease.

Patterns of renal toxicity from the combination of pemetrexed and pembrolizumab for advanced nonsquamous non-small-cell lung cancer (NSCLC): A single-center experience

OBJECTIVES

The combination of immune-checkpoint inhibitors (ICI) and platinum-pemetrexed chemotherapy (CT) in first-line setting improved survival outcomes of advanced non-small cell lung cancer (NSCLC) patients. Among the various adverse events, renal toxicity can be a relevant safety issue.

MATERIALS AND METHODS

We conducted a single-center, observational retrospective study including consecutive patients treated with upfront CT-ICI for advanced nonsquamous NSCLC to investigate incidence and clinical characteristics of acute kidney injury (AKI) using 'Acute Kidney Injury Working Group of Kidney Disease: Improving Global Outcomes' (KDIGO) definition.

RESULTS

A total of 89 patients received a first-line CT/ICI. The median age was 69 years. 60.7 % were male, and 87.6 % had an ECOG PS of 0-1. 92.1 % had a baseline glomerular filtration rate of at least 60 ml/min. According to KDIGO criteria, 25 (28 %) patients developed AKI. Considering risk factors for AKI onset, patients receiving >10 cycles of CT/ICI were more likely to experience AKI (p < 0.001). No other associations were found with other variables, including concomitant medications. Any component of the treatment was discontinued (pemetrexed pembrolizumab or both) in 10 (40 %) patients, and 9 patients (36 %) were addressed to nephrological consultation. These patients had higher mean creatinine variation from baseline (1 vs 0.6 mg/dl, p = 0.025) and creatine level (1.8 vs 1.4 mg/dl, p = 0.015), but lower eGFR (35.7 vs 54.2 ml/min, p = 0.011) in comparison to patients not addressed. No patients had microscopic hematuria or pyuria, but mild proteinuria (<0.8 g/24 h) was found in 4 patients. A renal biopsy was performed on 3 patients, revealing acute tubule interstitial nephritis (ATIN), karyomegalic interstitial nephritis, and acute tubular necrosis (ATN).

CONCLUSION

Renal toxicity represents a challenging adverse event that could negatively impact outcomes of metastatic nonsquamous NSCLC patients receiving CT/ICI demanding a multidisciplinary approach.

Proceedings of the 2022 National Toxicology Program Satellite Symposium

The 2022 annual National Toxicology Program Satellite Symposium, entitled "Pathology Potpourri," was held in Austin, Texas at the Society of Toxicologic Pathology's 40th annual meeting during a half-day session on Sunday, June 19. The goal of this symposium was to present and discuss challenging diagnostic pathology and/or nomenclature issues. This article presents summaries of the speakers' talks along with select images that were used by the audience for voting and discussion. Various lesions and topics covered during the symposium included induced and spontaneous neoplastic and nonneoplastic lesions in the mouse lung, spontaneous lesions in the reproductive tract of a female cynomolgus macaque, induced vascular lesions in a mouse asthma model and interesting case studies in a rhesus macaque, dog and genetically engineered mouse model.

Heterozygous Variants in a Patient with Karyomegalic Interstitial Nephritis

Karyomegalic interstitial nephritis (KIN) is a rare kidney disease marked by large tubular nuclei, interstitial inflammation, tubular atrophy, and interstitial fibrosis. The current study presented the case of a 39-year-old man with deteriorating kidney function and a serum creatinine level of 2.08 mg/dL. The renal biopsy revealed that the main pathological features of renal tubular epithelial cells were obvious enlargement, irregular shape, and hyperchromatic nuclei. The genetic analysis of the patient revealed two heterozygous variants in the FAN1 gene, c.2485c>T, and c.2928dupT, located in exons 10 and 13, respectively. A diagnosis of KIN was rendered. The two variations of the proband are identified in separate alleles from the father and mother, respectively, according to his family's sequencing. This phenotype is consistent with an autosomal recessive pattern of inheritance. The patient was treated with the Chinese patent medicine Niaoduqing Particles. After 38 months of follow-up, renal function was barely changed with a serum creatinine of 1.73 mg/dL.

Association of karyomegalic interstitial nephritis with focal segmental glomerulosclerosis

Karyomegalic interstitial nephritis (KIN), first described in 1974, is a rare form of chronic tubulointerstitial nephritis. It is defined by the presence of markedly enlarged, hyperchromatic nuclei with prominent nucleoli, mainly involving tubular epithelial cells of the kidney, accompanied by marked interstitial fibrosis. The disease presents as asymptomatic proteinuria, gradually progresses to chronic kidney disease and eventually leads to end-stage renal disease by 30-40 years. The etiology of the disease remains unclear; however, genetic risk factors and possible association with HLA (B27/35) is proposed by some. It has also been linked to FAN1 (FANCD2/FANC1- associated nuclease 1) mutation.

New familial cases of karyomegalic interstitial nephritis with mutations in the FAN1 gene

Background

Karyomegalic interstitial nephritis (KIN) is a rare disease entity first described by Burry in 1974. The term KIN was introduced by Mihatsch et al. in 1979. KIN is characterized by chronic tubulointerstitial nephritis associated with enlarged tubular epithelial cell nuclei, which leads to a progressive decline of renal function. The prevalence of this disease is less than 1% of all biopsies, and its pathogenesis is unclear. KIN results from mutations in FAN1 (FANCD2/FANCI-Associated Nuclease 1), a gene involved in the DNA damage response pathway, particularly in the kidney. In this study, we report two Tunisian consanguineous families with KIN caused by mutations in the FAN1 gene.

Methods

Direct sequencing of the coding regions and flanking intronic sequences of the FAN1 gene was performed in three affected members. Three prediction programs (Polyphen-2 software, SIFT, and MutationTaster) were used to predict the functional effect of the detected variations.

Results

Two causative frameshift variants in the FAN1 gene were identified in each family: The previously described frameshift mutation c.2616delA (p.Asp873ThrfsTer17) and a novel mutation c.2603delT (p.Leu868ArgfsTer22) classified as "pathogenic" according to the American College of Medical Genetics and Genomics (ACMG) guidelines.

Conclusion

To our best knowledge, this is the first Tunisian study involving familial cases of KIN with mutations in the FAN1 gene. We hypothesize that these findings can expand the mutational spectrum of KIN and provide valuable information on the genetic cause of KIN.

Karyomegalic interstitial nephritis: diagnosed only when suspected

Background

Karyomegalic interstitial nephritis (KIN) is an uncommon cause of chronic interstitial nephritis that eventually progresses to end-stage renal disease. Overall less than 50 cases have been reported in the literature.

Case presentation

We describe an asymptomatic 25-year-old gentleman with a family history of chronic interstitial nephritis who came to check the status of his kidney functions. On evaluation, he was found to have chronic interstitial nephritis which could not be attributed to a specific etiology. Renal biopsy confirmed the diagnosis of KIN.

Conclusion

KIN remains underdiagnosed. It is important to recognize this entity because of the familial nature, a wide range of differential diagnoses, and prognostic implications. A high index of clinical suspicion is necessary to perform renal biopsy which remains the gold standard for the diagnosis of KIN.

FAN1, a DNA Repair Nuclease, as a Modifier of Repeat Expansion Disorders

FAN1 encodes a DNA repair nuclease. Genetic deficiencies, copy number variants, and single nucleotide variants of FAN1 have been linked to karyomegalic interstitial nephritis, 15q13.3 microdeletion/microduplication syndrome (autism, schizophrenia, and epilepsy), cancer, and most recently repeat expansion diseases. For seven CAG repeat expansion diseases (Huntington's disease (HD) and certain spinocerebellar ataxias), modification of age of onset is linked to variants of specific DNA repair proteins. FAN1 variants are the strongest modifiers. Non-coding disease-delaying FAN1 variants and coding disease-hastening variants (p.R507H and p.R377W) are known, where the former may lead to increased FAN1 levels and the latter have unknown effects upon FAN1 functions. Current thoughts are that ongoing repeat expansions in disease-vulnerable tissues, as individuals age, promote disease onset. Fan1 is required to suppress against high levels of ongoing somatic CAG and CGG repeat expansions in tissues of HD and FMR1 transgenic mice respectively, in addition to participating in DNA interstrand crosslink repair. FAN1 is also a modifier of autism, schizophrenia, and epilepsy. Coupled with the association of these diseases with repeat expansions, this suggests a common mechanism, by which FAN1 modifies repeat diseases. Yet how any of the FAN1 variants modify disease is unknown. Here, we review FAN1 variants, associated clinical effects, protein structure, and the enzyme's attributed functional roles. We highlight how variants may alter its activities in DNA damage response and/or repeat instability. A thorough awareness of the FAN1 gene and FAN1 protein functions will reveal if and how it may be targeted for clinical benefit.

Integration of genetic and histopathology data in interpretation of kidney disease

For many years renal biopsy has been the gold standard for diagnosis in many forms of kidney disease. It provides rapid, accurate and clinically useful information in most individuals with kidney disease. However, in recent years, other diagnostic modalities have become available that may provide more detailed and specific diagnostic information in addition to, or instead of, renal biopsy. Genomics is one of these modalities. Previously prohibitively expensive and time consuming, it is now increasingly available and practical in a clinical setting for the diagnosis of inherited kidney disease. Inherited kidney disease is a significant cause of kidney disease, in both the adult and paediatric populations. While individual inherited kidney diseases are rare, together they represent a significant burden of disease. Because of the heterogenicity of inherited kidney disease, diagnosis and management can be a challenge and often multiple diagnostic modalities are needed to arrive at a diagnosis. We present updates in genomic medicine for renal disease, how genetic testing integrates with our knowledge of renal histopathology and how the two modalities may interact to enhance patient care.

Generation of a human induced pluripotent stem cell line (CMCi001-A) from a patient with karyomegalic interstitial nephritis with homozygous frameshift deletion mutation c.1985_1994del10 of the FANCD2/FANCI-Associated Nuclease 1 gene

The human-induced pluripotent stem cell (KIN-hiPSCs) line (CMCi001-A), derived from peripheral blood mononuclear cells (PBMCs) of a 42-year-old woman with karyomegalic interstitial nephritis (KIN) caused by the mutation of FANCD2/FANCI-Associated Nuclease 1 (FAN1) gene, was generated using Sendai virus. KIN-hiPSCs showed a typical human embryonic stem cell like morphology and expressed all pluripotency-associated markers, and directly differentiated into all three germ layers. Karyotyping of PBMCs of the patient and KIN-hiPSCs showed 47, XXX. In summary, we generated a novel patient-specific hiPSC line containing the mutation of FAN1 gene and it can be used to provide additional insights for KIN pathophysiology.

IgA Nephropathy Concomitant With Karyomegalic Interstitial Nephritis

Immunoglobulin A (IgA) nephropathy is one of the most common glomerulonephritis characterized by the deposition of IgA in glomerular mesangium. Karyomegalic interstitial nephritis (KIN) is a rare interstitial nephritis with potential hereditary factors. IgA nephropathy concomitant with KIN has not yet been reported. Herein, we describe the clinical course, ultrasonic images and gastrointestinal endoscopy findings of a 28-year-old-male patient with IgA nephropathy with KIN. The pathologic examination of the renal biopsy specimen demonstrated mild mesangial proliferative IgA nephropathy with KIN. Molecular genetic testing detected an abnormality in FAN1 gene. The heterozygous mutation was present on chromosome 15q13.3. However, IgA nephropathy with KIN is a rare disorder, and its pathogenesis is yet to be clarified.

Case report: a 58 -year -old man with small kidneys and elevated liver enzymes

BACKGROUND

The conjunction of hepatitis and renal disease can be seen in several clinical context, including karyomegalic nephritis (KIN). Karyomegalic nephritis (KIN) is a rare genetic disease, with less than 50 cases reported, which incidence is probably underestimated. We report here an unusual case presentation of KIN with obtention of several organ biopsies and a novel mutation leading to the disease.

CASE PRESENTATION

A 58 year old Caucasian without relevant family history presents with advanced chronic kidney disease, elevated liver enzymes and recurrent pulmonary infection. Familial history was negative. Renal biopsy revealed a chronic tubulo-intertsitial nephritis with enlarged and irregular hyperchromatic nuclei. Karyomegalic nephritis (KIN) was confirmed by genetic testing with a non-sense mutation and a deletion in the Fanconi anemia associated nuclease 1 (FAN1) gene.

CONCLUSIONS

KIN is rare disease to be suspected in the presence of renal disease, biological hepatitis and recurrent pulmonary infections, even without a familial history. Diagnosis of this condition is crucial to perform family screening, avoid progression factors, and adapt post transplantation immunosuppression. Finally, avoiding familial heterozygote donors appears of major importance in this condition.

Karyomegalic interstitial nephritis with a novel FAN1 gene mutation and concurrent ALECT2 amyloidosis

Background

Karyomegalic interstitial nephritis (KIN) is a rare hereditary cause of chronic kidney disease. It typically causes progressive renal impairment with haemoproteinuria requiring renal replacement therapy before 50 years of age. It has been associated with mutations in the Fanconi anaemia-associated nuclease 1 (FAN1) gene and has an autosomal recessive pattern of inheritance. Leukocyte chemotactic factor 2 amyloidosis (ALECT2) is the third most common cause of amyloid nephropathy presenting with chronic kidney disease and variable proteinuria. We report a novel mutation in the FAN1 gene causing KIN and to our knowledge, the first case of concurrent KIN and ALECT.

Case presentation

We describe the case of 44 year old Pakistani woman, presenting with stage four non-proteinuric chronic kidney disease, and a brother on dialysis. Renal biopsy demonstrated KIN and concurrent ALECT2. Genetic sequencing identified a novel FAN1 mutation as the cause of her KIN and she is being managed conservatively for chronic kidney disease. Her brother also had KIN with no evidence of amyloidosis and is being worked up for kidney transplantation.

Conclusion

This case highlights two rare causes of chronic kidney disease considered underdiagnosed in the wider population due to their lack of proteinuria, and may contribute to the cohort of patients reaching end stage renal disease without a renal biopsy. We report a novel mutation of the FAN1 gene causing KIN, and report the first case of concurrent KIN and ALECT2. This case highlights the importance of renal biopsy in chronic kidney disease of unclear aetiology which has resulted in a diagnosis with implications for kidney transplantation and family planning.

Pulmonary manifestations of systemic karyomegaly

Over 40 years ago, abnormal enlargement of the nucleus of tubular epithelial cells was reported in a rare distinct hereditary chronic interstitial nephritis, karyomegalic interstitial nephritis (KIN). Here, we report the second case of systemic karyomegaly with pulmonary manifestations and present a detailed characterization of the karyomegalic cells in lung parenchyma. A 59-year-old woman who was diagnosed with KIN developed renal failure and eventually received a renal transplant later evaluated for chronic and progressive restrictive lung disease. The KIN diagnosis prompted us to carefully examine her lung parenchyma. Karyomegalic cells were identified in the alveolar epithelium, interstitium, as well as, in the vascular wall. Viral serological and biochemical blood analyses were negative. We consider that the pulmonary manifestations of karyomegaly expands the differential diagnosis of interstitial lung disease in patients with KIN.

Novel Homozygous FAN1 Mutation in a Familial Case of Karyomegalic Interstitial Nephritis

Karyomegalic interstitial nephritis (KIN) is a rare genetic kidney disease associated with a mutation in FAN1 gene and is often underdiagnosed. The histomorphology demonstrates chronic interstitial nephritis with tubular epithelial cells showing bizarre enlarged nuclei. We present a case report of a 47-year-old multiparous South-Indian woman presenting with bilateral pitting pedal oedema and mild hypertension. At the time of presentation, her serum creatinine was 1.52 mg/dL and urine analysis showed mild proteinuria. Kidney biopsy showed features of tubular injury with bizarre enlarged nuclei and focal mild chronic tubulointerstitial nephritis. Immunohistochemistry was negative for cytomegalovirus (CMV) Ag and SV40 Ag. Real-time polymerase chain reaction (PCR) done for CMV and BK virus genomes was negative. Relevant family history was that her older brother was also diagnosed with kidney failure and is on renal replacement therapy. Genetic analysis for FAN1 gene of the proband and her sibling showed two rare mutations of the FAN1 gene in the exon 4, of which, one is non-synonymous mutation and the other is a stop-gain mutation in the proband. This case illustrates a rare presentation of karyomegalic interstitial nephritis in siblings with previous unknown FAN1 gene mutations.

Karyomegalic interstitial nephritis in a renal allograft

Karyomegalic interstitial nephritis (KIN) is a rare renal interstitial disease entity characterized by large tubular nuclei, accompanied by interstitial inflammation, tubular atrophy, and interstitial fibrosis. Approximately 50 cases of KIN have been described in the native kidney. In this case study, we describe the first case of KIN in a kidney allograft. A 41-year-old man presented with declining kidney function and a serum creatinine of 2.7 mg/dL. The native kidney biopsy showed large pleomorphic nuclei in the proximal and distal tubular epithelial cells, which was associated with interstitial inflammation, and extensive interstitial fibrosis and tubular atrophy. Immunohistochemistry for cytomegalovirus, adenovirus, and simian virus 40 were negative. A diagnosis of KIN was rendered. The patient received a living-related kidney transplant from his sister. At 4-, 12-, and 24-months posttransplant, protocol allograft biopsies showed KIN with large pleomorphic nuclei in the proximal and distal tubules with mild interstitial inflammation, minimal tubular atrophy, and interstitial fibrosis. At 24.7 months of follow-up, the patient has stable renal function with a serum creatinine of 1.6 mg/dL. The KIN may represent recurrent KIN or donor-associated KIN. Recognition of this rare disease entity is important as it can be mistaken for a viral infection.

Genomic medicine for kidney disease

Technologies such as next-generation sequencing and chromosomal microarray have advanced the understanding of the molecular pathogenesis of a variety of renal disorders. Genetic findings are increasingly used to inform the clinical management of many nephropathies, enabling targeted disease surveillance, choice of therapy, and family counselling. Genetic analysis has excellent diagnostic utility in paediatric nephrology, as illustrated by sequencing studies of patients with congenital anomalies of the kidney and urinary tract and steroid-resistant nephrotic syndrome. Although additional investigation is needed, pilot studies suggest that genetic testing can also provide similar diagnostic insight among adult patients. Reaching a genetic diagnosis first involves choosing the appropriate testing modality, as guided by the clinical presentation of the patient and the number of potential genes associated with the suspected nephropathy. Genome-wide sequencing increases diagnostic sensitivity relative to targeted panels, but holds the challenges of identifying causal variants in the vast amount of data generated and interpreting secondary findings. In order to realize the promise of genomic medicine for kidney disease, many technical, logistical, and ethical questions that accompany the implementation of genetic testing in nephrology must be addressed. The creation of evidence-based guidelines for the utilization and implementation of genetic testing in nephrology will help to translate genetic knowledge into improved clinical outcomes for patients with kidney disease.