Genetic analysis of NLRP3 in recurrent pericarditis

Background

The mechanisms underlying recurrent pericarditis are poorly understood, although the efficacy of colchicine and targeted inhibitors of the interleukin-1 pathway implicate auto-inflammation in its pathogenesis. NLRP3 (NACHT, leucine-rich repeat, and pyrin domain containing protein 3) forms part of the NLRP3 inflammasome that mediates post-translational processing of interleukin-1, and colchicine has also been demonstrated to inhibit this pathway. Pathogenic mutations in exon 3 of NLRP3 cause the auto-inflammatory disease cryopyrin associated periodic syndrome, and the management of this disease and other auto-inflammatory diseases has been transformed over the last two decades by the use of targeted anti-interleukin-1 agents. More recently, NLRP3 inflammasome activity has been demonstrated to be upregulated in the pericardia of patients with recurrent pericarditis.

Purpose

Given that mutations in exon 3 of NLRP3 are known to cause auto-inflammatory disease and NLRP3 activity is implicated in recurrent pericarditis, we undertook a genetic analysis of exon 3 of NLRP3 in 99 patients with recurrent pericarditis to determine whether pathogenic mutations in this gene are associated with the disease.

Methods

Exon 3 of NLRP3 was analysed either by Sanger (n=30) or amplicon-based next generation (n=69) sequencing. Variants identified by next generation sequencing were validated by Sanger sequencing. Minor allele frequencies were compared to those in the healthy reference population in the Genome Aggregation database (gnomAD) using Fisher's exact test. p values <0.05 were considered statistically significant.

Results

No known pathogenic mutations in exon 3 of NLRP3 were identified in 99 patients with recurrent pericarditis. Three patients harboured variants of unknown significance (V198M, T543M, Q703K) in NLRP3. A burden association test comparing the combined frequency of all variants in exon 3 of NLRP3 in this cohort against that observed in healthy controls in gnomAD found no significant difference in allele frequency.

Conclusions

This is the first reported genetic analysis of NLRP3 in a cohort of patients with recurrent pericarditis and found no evidence to implicate mutations in this gene in the disease. Whilst access to effective therapies for pericarditis is widening, decisions on treatment duration and identification of patients at risk of recurrent or treatment refractory disease remain significant clinical challenges. Further work exploring the mechanisms by which NLRP3 activity is upregulated in recurrent pericarditis is therefore indicated to identify biomarkers of disease activity and to stratify patients at risk of recurrence. Given the recent successes of agents targeting this pathway in coronary artery disease in clinical trials, such studies may also provide important insights that are of wider interest to the field of cardiovascular medicine.

Funding Acknowledgement

Type of funding sources: Foundation. Main funding source(s): British Heart Foundation Clinical Research Training Fellowship

Atrial strain in cardiacATTR amyloidosis from pathophysiology to prognosis: is it time to rethink our approach to disease?

Background

Left atrial (LA) involvement in cardiac ATTR amyloidosis (ATTR-CM) has never being explored. The aim of the study is to characterize the spectrum of changes in LA structure in ATTR-CM, the functional consequences on LA mechanics and the association with mortality.

Methods

We studied 936 patients with ATTR-CM who underwent prospective protocolized evaluations comprising ECG, full echocardiographic assessment, 6MWT, blood biomarkers sampling and survival assessment between 2000 and 2019. Reservoir (LAr), conduit (LAcd) and booster (LAcont) function were assessed according to current guidelines. LA stiffness (LAstiff) was estimated as the ratio between E/e' and LAr. The presence and extent of amyloid infiltration was assessed in two autopsied hearts from patients ATTR-CM with congo red staining and TTR antibodies.

Results

936 patients with ATTR-CM were included, 567 with wtATTR-CM and 346 with hATTR-CM, of whom 246 had the V122I variant and 100 the T60A variant. LA indexed area was similar across the 3 genotypes, whilst LAr, LAcd and LAcont were significantly reduced in V122I patients compared to Wt and T60A patients (LAr: 10.4±6.4 vs 12.8±8.5 vs 8.59±5.7%, p<0.0001; LAcd: 5.6±5.0 vs 6.9±5.7 vs 4.0±3.6%, p<0.0001; LAcont 7.5±4.1 vs 8.2±4.9 vs 6.7±4.2%, p=0.023; in Wt, T60 and V122I respectively). Similarly, LAstiff was significantly worse in V122I compared to Wt and T60A (LAstiff: 2.39±2.62 vs 2.59±4.83 vs 2.96±2.88, p<0.0001, in Wt, T60 and V122I respectively). In the overall population, LAstiff remained independently associated with mortality, after adjusting for rhythm, systolic and diastolic functional parameters, ventricular longitudinal strain, genotypes, clinical variables and NAC staging system (lnLA stiff: HR=1.26, CI: 1.07–1.57; p=0.009). In the overall population, 584 patients were in sinus rhythm and 344 in atrial fibrillation, atrial flutter or atrial tachycardia (non-sinus rhythm group – NSR). Among patients in SR, 21.6% did not show a measurable LA mechanical contraction on strain analysis (LAcont). Patients in SR without LAcont on strain analysis showed similar structural and functional LA changes, NTproBNP, NYHA class, and 6MWT to NSR patients. Mortality of patients in SR with no LAcont was significantly reduced compared to patients in SR with LAcont and similar to patients in AF (Figure 1). On the two autopsies hearts there was extensive amyloid infiltration of TTR type in the atrial wall as confirmed with CR and TTR antibodies (Figure 1).

Conclusions

ATTR-CM is characterized by primary infiltration of the atrial walls with progressive loss of atrial function and increased stiffness. LA stiffness is a strong independent predictor of mortality after adjusting for known predictors. Atrial electro-mechanical dissociation emerged as a distinctive functional phenotype identifying patients in SR with worse prognosis.

Figure 1

Funding Acknowledgement

Type of funding source: None

Oculoleptomeningeal Amyloidosis associated with transthyretin Leu12Pro in an African patient

Oculoleptomeningeal amyloidosis is a rare manifestation of hereditary transthyretin (TTR) amyloidosis. Here, we present the first case of leptomeningeal amyloidosis associated with the TTR variant Leu12Pro mutation in an African patient. A 43-year-old right-handed Nigerian man was referred to our centre with rapidly progressive neurological decline. He presented initially with weight loss, confusion, fatigue, and urinary and erectile dysfunction. He then suffered recurrent episodes of slurred speech with right-sided weakness. He went on to develop hearing difficulties and painless paraesthesia. Neurological examination revealed horizontal gaze-evoked nystagmus, brisk jaw jerk, increased tone, brisk reflexes throughout and bilateral heel-shin ataxia. Magnetic resonance imaging showed extensive leptomeningeal enhancement. Cerebrospinal fluid analysis showed a raised protein of 6.4 g/dl. Nerve conduction studies showed an axonal neuropathy. Echocardiography was characteristic of cardiac amyloid. TTR gene sequencing showed that he was heterozygous for the leucine 12 proline mutation. Meningeal and brain biopsy confirmed widespread amyloid angiopathy. TTR amyloidosis is a rare cause of leptomeningeal enhancement, but should be considered if there is evidence of peripheral or autonomic neuropathy with cardiac or ocular involvement. The relationship between different TTR mutations and clinical phenotype, disease course, and response to treatment remains unclear.

Renal transplantation in systemic amyloidosis-importance of amyloid fibril type and precursor protein abundance

Renal transplantation remains contentious in patients with systemic amyloidosis due to the risk of graft loss from recurrent amyloid and progressive disease. Outcomes were sought among all patients attending the UK National Amyloidosis Centre who received a renal transplant (RTx) between January 1978 and May 2011. A total of 111 RTx were performed in 104 patients. Eighty-nine percent of patients with end-stage renal disease (ESRD) due to hereditary lysozyme and apolipoprotein A-I amyloidosis received a RTx. Outcomes following RTx were generally excellent in these diseases, reflecting their slow natural history; median graft survival was 13.1 years. Only 20% of patients with ESRD due to AA, AL and fibrinogen amyloidosis received a RTx. Median graft survival was 10.3, 5.8 and 7.3 years in these diseases respectively, and outcomes were influenced by fibril precursor protein supply. Patient survival in AL amyloidosis was 8.9 years among those who had achieved at least a partial clonal response compared to 5.2 years among those who had no response (p = 0.02). Post-RTx chemotherapy was administered successfully to four AL patients. RTx outcome is influenced by amyloid type. Suppression of the fibril precursor protein is desirable in the amyloidoses that have a rapid natural history.

Hereditary lysozyme amyloidosis -- phenotypic heterogeneity and the role of solid organ transplantation

OBJECTIVES

Lysozyme amyloidosis (ALys) is a form of hereditary systemic non-neuropathic amyloidosis, which is inherited in an autosomal dominant fashion. Lysozyme, which is the amyloidogenic precursor protein in ALys, is a ubiquitous bacteriolytic enzyme synthesized by hepatocytes, polymorphs and macrophages. The aim of this study is to describe the phenotype and outcome of patients with ALys including the role of solid organ transplantation.

DESIGN

Retrospective evaluation of patients with ALys.

SETTING

UK National Amyloidosis Centre.

PATIENTS

All 16 patients with ALys followed at the centre.

RESULTS

A family history of amyloidosis was present in every affected individual. Although the phenotype was broadly similar amongst those from the same kindred, there were marked phenotypic differences between kindreds who possessed the same amyloidogenic mutation. Symptomatic gastrointestinal (GI) amyloid was prevalent, and macroscopically visible amyloidotic lesions were present in nine of 10 patients who underwent GI endoscopy. All symptomatic ALys individuals had hepatic amyloid. Four patients received orthotopic liver transplants (OLT), three for spontaneous hepatic rupture and one case, who had extensive hepatic amyloid and a strong family history of hepatic rupture, pre-emptively. All of the liver grafts were functioning at censor 1.7, 5.8, 9.0 and 11.0 years after OLT. Five patients had progressive amyloidotic renal dysfunction culminating in end-stage renal failure, three of whom underwent renal transplantation (RTx). There was no evidence of renal allograft dysfunction at censor 6.6, 1.8 and 0.8 years after RTx.

CONCLUSIONS

Lysozyme amyloidosis is a disease of the GI tract, liver and kidneys, which has a slow natural history. There was a clear family history in all cases within this cohort, demonstrating a high clinical penetrance in the presence of an amyloidogenic lysozyme mutation. There is currently no amyloid-specific therapy for the condition which is managed symptomatically. OLT and RTx appear to be successful treatments for patients with liver rupture or end-stage renal disease, respectively, with excellent outcomes in terms of medium-term graft function and patient survival.

Guidelines for the genetic diagnosis of hereditary recurrent fevers

Hereditary recurrent fevers (HRFs) are a group of monogenic autoinflammatory diseases characterised by recurrent bouts of fever and serosal inflammation that are caused by pathogenic variants in genes important for the regulation of innate immunity. Discovery of the molecular defects responsible for these diseases has initiated genetic diagnostics in many countries around the world, including the Middle East, Europe, USA, Japan and Australia. However, diverse testing methods and reporting practices are employed and there is a clear need for consensus guidelines for HRF genetic testing.

Draft guidelines were prepared based on current practice deduced from previous HRF external quality assurance schemes and data from the literature. The draft document was disseminated through the European Molecular Genetics Quality Network for broader consultation and amendment. A workshop was held in Bruges (Belgium) on 18 and 19 September 2011 to ratify the draft and obtain a final consensus document. An agreed set of best practice guidelines was proposed for genetic diagnostic testing of HRFs, for reporting the genetic results and for defining their clinical significance.

Organ transplantation in hereditary apolipoprotein AI amyloidosis

Patients with hereditary apolipoprotein AI (apoAI) amyloidosis often have extensive visceral amyloid deposits, and many develop end-stage renal failure as young adults. Solid organ transplantation to replace failing organ function in systemic amyloidosis is controversial due to the multisystem and progressive nature of the disease and the risk of recurrence of amyloid in the graft. We report the outcome of solid organ transplantation, including dual transplants in 4 cases, among 10 patients with apoAI amyloidosis who were followed for a median (range) of 16 (4-28) and 9 (0.2-27) years from diagnosis of amyloidosis and transplantation, respectively. Eight of 10 patients were alive, seven with a functioning graft at censor. Two patients died, one of disseminated cytomegalovirus infection 2 months after renal transplantation and the other of multisystem failure following severe trauma more than 13 years after renal transplantation. The renal transplant of one patient failed due to recurrence of amyloid after 25 years. Amyloid disease progression was very slow and the natural history of the condition was favorably altered in both cases in which the liver was transplanted. Failing organs in hereditary apoAI amyloidosis should be replaced since graft survival is excellent and confers substantial survival benefit.