Renal amyloidosis: a new time for a complete diagnosis

Amyloidoses are a group of disorders in which soluble proteins aggregate and deposit extracellularly in tissues as insoluble fibrils, causing organ dysfunction. Clinical management depends on the subtype of the protein deposited and the affected organs. Systemic amyloidosis may stem from anomalous proteins, such as immunoglobulin light chains or serum amyloid proteins in chronic inflammation or may arise from hereditary disorders. Hereditary amyloidosis consists of a group of rare conditions that do not respond to chemotherapy, hence the identification of the amyloid subtype is essential for diagnosis, prognosis, and treatment. The kidney is the organ most frequently involved in systemic amyloidosis. Renal amyloidosis is characterized by acellular pathologic Congo red-positive deposition of amyloid fibrils in glomeruli, vessels, and/or interstitium. This disease manifests with heavy proteinuria, nephrotic syndrome, and progression to end-stage kidney failure. In some situations, it is not possible to identify the amyloid subtype using immunodetection methods, so the diagnosis remains indeterminate. In cases where hereditary amyloidosis is suspected or cannot be excluded, genetic testing should be considered. Of note, laser microdissection/mass spectrometry is currently the gold standard for accurate diagnosis of amyloidosis, especially in inconclusive cases. This article reviews the clinical manifestations and the current diagnostic landscape of renal amyloidosis.

Prevalence of autosomal dominant polycystic kidney disease in Persian and Persian-related cats in Brazil / Prevalência da doença renal policística autossômica dominante em gatos Persas e raças relacionadas no Brasil

Autosomal dominant polycystic kidney disease (ADPKD) is the most common genetic disease in cats. However, scarce data on its prevalence are available in Brazil. Persian cats and Persian-related breeds were assessed by molecular genotyping for a C to A transversion in exon 29 of PKD1 gene to determine ADPKD prevalence in a Brazilian population. Genomic DNA extracted from peripheral whole blood or oral swabs samples was used to amplify exon 29 of PKD1 gene employing a PCR-RFLP methodology. From a total of 616 animals, 27/537 Persian and 1/17 Himalayan cats showed the single-nucleotide variant (C to A) at position 3284 in exon 29 of feline PKD1. This pathogenic variation has been identified only in heterozygous state. The prevalence of ADPKD in Persian cats and Persian-related breeds was 5.03% and 1.6%, respectively. There was no significant association between feline breed, gender or age with ADPKD prevalence. Of note, the observed ADPKD prevalence in Persian cats and Persian-related breeds in Brazil was lower than the ones reported in other parts of the world. This finding may be related to genetic counseling and consequent selection of ADPKD-free cats for reproduction.

A doença renal policística autossômica dominante (DRPAD) é a doença genética mais comum em gatos. No entanto, poucos dados sobre sua prevalência estão disponíveis no Brasil. Gatos Persas e de raças relacionadas foram avaliados por genotipagem molecular para a transversão C→A no exon 29 do gene PKD1 felino para determinar a prevalência de DRPAD. DNA genômico extraído de sangue total periférico ou amostras de swabs orais foram utilizados para amplificar o exon 29 do gene PKD1 pela técnica de PCR-RFLP. De um total de 616 gatos, 27/537 Persas e 1/17 Himalaia mostraram a variante de nucleotídeo único (C→A) na posição 3284 no exon 29 do gene PKD1. Esta variante patogênica foi identificada apenas em heterozigose. A prevalência de DRPAD em gatos Persas e raças relacionadas foram de 5,03% e 1,6%, respectivamente. Não houve associações significativas entre raça, gênero ou idade dos felinos e incidência de DRPAD. A prevalência de DRPAD em gatos Persas e raças relacionadas no Brasil foi menor do que em outras partes do mundo, o que pode estar relacionado ao aconselhamento genético e consequente seleção de gatos sem ADPKD para reprodução.

Prevalence of autosomal dominant polycystic kidney disease in Persian and Persian-related cats in Brazil

Abstract Autosomal dominant polycystic kidney disease (ADPKD) is the most common genetic disease in cats. However, scarce data on its prevalence are available in Brazil. Persian cats and Persian-related breeds were assessed by molecular genotyping for a C to A transversion in exon 29 of PKD1 gene to determine ADPKD prevalence in a Brazilian population. Genomic DNA extracted from peripheral whole blood or oral swabs samples was used to amplify exon 29 of PKD1 gene employing a PCR-RFLP methodology. From a total of 616 animals, 27/537 Persian and 1/17 Himalayan cats showed the single-nucleotide variant (C to A) at position 3284 in exon 29 of feline PKD1. This pathogenic variation has been identified only in heterozygous state. The prevalence of ADPKD in Persian cats and Persian-related breeds was 5.03% and 1.6%, respectively. There was no significant association between feline breed, gender or age with ADPKD prevalence. Of note, the observed ADPKD prevalence in Persian cats and Persian-related breeds in Brazil was lower than the ones reported in other parts of the world. This finding may be related to genetic counseling and consequent selection of ADPKD-free cats for reproduction.

Resumo A doença renal policística autossômica dominante (DRPAD) é a doença genética mais comum em gatos. No entanto, poucos dados sobre sua prevalência estão disponíveis no Brasil. Gatos Persas e de raças relacionadas foram avaliados por genotipagem molecular para a transversão CA no exon 29 do gene PKD1 felino para determinar a prevalência de DRPAD. DNA genômico extraído de sangue total periférico ou amostras de swabs orais foram utilizados para amplificar o exon 29 do gene PKD1 pela técnica de PCR-RFLP. De um total de 616 gatos, 27/537 Persas e 1/17 Himalaia mostraram a variante de nucleotídeo único (CA) na posição 3284 no exon 29 do gene PKD1. Esta variante patogênica foi identificada apenas em heterozigose. A prevalência de DRPAD em gatos Persas e raças relacionadas foram de 5,03% e 1,6%, respectivamente. Não houve associações significativas entre raça, gênero ou idade dos felinos e incidência de DRPAD. A prevalência de DRPAD em gatos Persas e raças relacionadas no Brasil foi menor do que em outras partes do mundo, o que pode estar relacionado ao aconselhamento genético e consequente seleção de gatos sem ADPKD para reprodução.

Cyst infection in hospital-admitted autosomal dominant polycystic kidney disease patients is predominantly multifocal and associated with kidney and liver volume

Positron-emission tomography/computed tomography (PET/CT) has improved cyst infection (CI) management in autosomal dominant polycystic kidney disease (ADPKD). The determinants of kidney and/or liver involvement, however, remain uncertain. In this study, we evaluated clinical and imaging factors associated with CI in kidney (KCI) and liver (LCI) in ADPKD. A retrospective cohort study was performed in hospital-admitted ADPKD patients with suspected CI. Clinical, imaging and surgical data were analyzed. Features of infected cysts were evaluated by PET/CT. Total kidney (TKV) and liver (TLV) volumes were measured by CT-derived multiplanar reconstruction. CI was detected in 18 patients who experienced 24 episodes during an interval of 30 months (LCI in 12, KCI in 10 and concomitant infection in 2). Sensitivities of CT, magnetic resonance imaging and PET/CT were 25.0, 71.4, and 95.0%. Dysuria (P<0.05), positive urine culture (P<0.01), and previous hematuria (P<0.05) were associated with KCI. Weight loss (P<0.01) and increased C-reactive protein levels (P<0.05) were associated with LCI. PET/CT revealed that three or more infected cysts were present in 70% of the episodes. TKV was higher in kidney-affected than in LCI patients (AUC=0.91, P<0.05), with a cut-off of 2502 mL (72.7% sensitivity, 100.0% specificity). TLV was higher in liver-affected than in KCI patients (AUC=0.89, P<0.01) with a cut-off of 2815 mL (80.0% sensitivity, 87.5% specificity). A greater need for invasive procedures was observed in LCI (P<0.01), and the overall mortality was 20.8%. This study supports PET/CT as the most sensitive imaging method for diagnosis of cyst infection, confirms the multifocal nature of most hospital-admitted episodes, and reveals an association of kidney and liver volumes with this complication.

Molecular and cellular pathogenesis of autosomal dominant polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) is one of the most common human life-threatening monogenic disorders. The disease is characterized by bilateral, progressive renal cystogenesis and cyst and kidney enlargement, often leading to end-stage renal disease, and may include extrarenal manifestations. ADPKD is caused by mutation in one of two genes, PKD1 and PKD2, which encode polycystin-1 (PC1) and polycystin-2 (PC2), respectively. PC2 is a non-selective cation channel permeable to Ca2+, while PC1 is thought to function as a membrane receptor. The cyst cell phenotype includes increased proliferation and apoptosis, dedifferentiation, defective planar polarity, and a secretory pattern associated with extracellular matrix remodeling. The two-hit model for cyst formation has been recently extended by the demonstration that early gene inactivation leads to rapid and diffuse development of renal cysts, while inactivation in adult life is followed by focal and late cyst formation. Renal ischemia/reperfusion, however, can function as a third hit, triggering rapid cyst development in kidneys with Pkd1 inactivation induced in adult life. The PC1-PC2 complex behaves as a sensor in the primary cilium, mediating signal transduction via Ca2+ signaling. The intracellular Ca2+ homeostasis is impaired in ADPKD, being apparently responsible for the cAMP accumulation and abnormal cell proliferative response to cAMP. Activated mammalian target for rapamycin (mTOR) and cell cycle dysregulation are also significant features of PKD. Based on the identification of pathways altered in PKD, a large number of preclinical studies have been performed and are underway, providing a basis for clinical trials in ADPKD and helping the design of future trials.

Molecular and cellular pathogenesis of autosomal recessive polycystic kidney disease

Autosomal recessive polycystic kidney disease (ARPKD) is an inherited disease characterized by a malformation complex which includes cystically dilated tubules in the kidneys and ductal plate malformation in the liver. The disorder is observed primarily in infancy and childhood, being responsible for significant pediatric morbidity and mortality. All typical forms of ARPKD are caused by mutations in a single gene, PKHD1 (polycystic kidney and hepatic disease 1). This gene has a minimum of 86 exons, assembled into multiple differentially spliced transcripts and has its highest level of expression in kidney, pancreas and liver. Mutational analyses revealed that all patients with both mutations associated with truncation of the longest open reading frame-encoded protein displayed the severe phenotype. This product, polyductin, is a 4,074-amino acid protein expressed in the cytoplasm, plasma membrane and primary apical cilia, a structure that has been implicated in the pathogenesis of different polycystic kidney diseases. In fact, cholangiocytes isolated from an ARPKD rat model develop shorter and dysmorphic cilia, suggesting polyductin to be important for normal ciliary morphology. Polyductin seems also to participate in tubule morphogenesis and cell mitotic orientation along the tubular axis. The recent advances in the understanding of in vitro and animal models of polycystic kidney diseases have shed light on the molecular and cellular mechanisms of cyst formation and progression, allowing the initiation of therapeutic strategy designing and promising perspectives for ARPKD patients. It is notable that vasopressin V2 receptor antagonists can inhibit/halt the renal cystic disease progression in an orthologous rat model of human ARPKD.

Ionic dependence of cell volume regulation by the thin ascending limb of henle's loop

Thin ascending limb cells from Henle's loop were optical and video techniques to evaluate cell volume regulation in response to anisoosmotic media and its ionic dependence. Cell volume regulation was observed when these cells were exposed to, hypoosmotic solutions. Under hyperosmotic conditions only an osmometric reponse was found, with no volume regulatory increase (VRI). The removal of Cl- or HCO3- abolished the volume regulatory decrease (VRD) normally observed during exposure to hypoosmotic soloutions. Re-addition of these ions did not elicit the VRD response. The removal of K+ from hypoosmotic solutions abolished VRD but is re-introduction restored the volume regulatory reponse. In the absence of Na+, a partial inhibition of VRD was found; re-addition of Na+ completely restored the regulatory response. These indicate that cells from the thin ascending limb of Henle's loop regulate their volume under hypoosmotic conditions, and that this process is dependent upon Cl-, HCO3-, Na+ and K+, with different patterns of response being observed upon addition or deltion of these ions