Functional diversity of NLRP3 gain-of-function mutants associated with CAPS autoinflammation.

NLRP3-associated autoinflammatory disease is a heterogenous group of monogenic conditions caused by NLRP3 gain-of-function mutations. The poor functional characterization of most NLRP3 variants hinders diagnosis despite efficient anti-IL-1 treatments. Additionally, while NLRP3 is controlled by priming and activation signals, gain-of-functions have only been investigated in response to priming. Here, we characterize 34 NLRP3 variants in vitro, evaluating their activity upon induction, priming, and/or activation signals, and their sensitivity to four inhibitors. We highlight the functional diversity of the gain-of-function mutants and describe four groups based on the signals governing their activation, correlating partly with the symptom severity. We identify a new group of NLRP3 mutants responding to the activation signal without priming, associated with frequent misdiagnoses. Our results identify key NLRP3 residues controlling inflammasome activity and sensitivity to inhibitors, and antagonistic mechanisms with broader efficacy for therapeutic strategies. They provide new insights into NLRP3 activation, an explanatory mechanism for NLRP3-AID heterogeneity, and original tools for NLRP3-AID diagnosis and drug development.

Malignant Peritoneal Mesothelioma Complicating Familial Mediterranean Fever on 18 F-FDG PET/CT.

ABSTRACT: A 77-year-old man with a personal history of familial Mediterranean fever presented with a slowly enlarging tumefaction of the left abdominal wall and persistent inflammatory syndrome despite good adherence to colchicine. 18 F-FDG PET/CT showed a hypermetabolic muscular mass of the abdominal wall along with other hypermetabolic lesions including a peritoneal mass and several subcutaneous soft tissue nodules. CT-guided needle biopsy led to the diagnosis of a muscular localization of a malignant peritoneal mesothelioma, which is an extremely rare complication of familial Mediterranean fever. Six courses of chemotherapy with carboplatin and pemetrexed allowed an almost complete response.

Gut microbiota alterations are associated with phenotype and genotype in familial Mediterranean fever.

OBJECTIVE: FMF is the most common monogenic autoinflammatory disease associated with MEFV mutations. Disease phenotype and response to treatment vary from one patient to another, despite similar genotype, suggesting the role of environmental factors. The objective of this study was to analyse the gut microbiota of a large cohort of FMF patients in relation to disease characteristics. METHODS: The gut microbiotas of 119 FMF patients and 61 healthy controls were analysed using 16 s rRNA gene sequencing. Associations between bacterial taxa, clinical characteristics, and genotypes were evaluated using multivariable association with linear models (MaAslin2), adjusting on age, sex, genotype, presence of AA amyloidosis (n = 17), hepatopathy (n = 5), colchicine intake, colchicine resistance (n = 27), use of biotherapy (n = 10), CRP levels, and number of daily faeces. Bacterial network structures were also analysed. RESULTS: The gut microbiotas of FMF patients differ from those of controls in having increased pro-inflammatory bacteria, such as the Enterobacter, Klebsiella and Ruminococcus gnavus group. Disease characteristics and resistance to colchicine correlated with homozygous mutations and were associated with specific microbiota alteration. Colchicine treatment was associated with the expansion of anti-inflammatory taxa such as Faecalibacterium and Roseburia, while FMF severity was associated with expansion of the Ruminococcus gnavus group and Paracoccus. Colchicine-resistant patients exhibited an alteration of the bacterial network structure, with decreased intertaxa connectivity. CONCLUSION: The gut microbiota of FMF patients correlates with disease characteristics and severity, with an increase in pro-inflammatory taxa in the most severe patients. This suggests a specific role for the gut microbiota in shaping FMF outcomes and response to treatment.

Pathogenic variants in the NLRP3 LRR domain at position 861 are responsible for a boost-dependent atypical CAPS phenotype.

BACKGROUND: Cryopyrin-associated periodic syndrome (CAPS) is associated with NLRP3 pathogenic variants, mostly located in the NACHT (neuronal apoptosis inhibitor protein, MHC class 2 transcription activator, incompatibility locus protein from Podospora anserina, telomerase-associated protein) domain. Cold-induced urticarial rash is among the main clinical features. However, this study identified a series of 14 patients with pathogenic variants of the Y861 residue (p.Tyr861) of the LRR domain of NLRP3 and minimal prevalence of cold-induced urticarial rash. OBJECTIVES: This study aimed to address a possible genotype/phenotype correlation for patients with CAPS and to investigate at the cellular levels the impact of the Y861C substitution (p.Tyr861Cys) on NLRP3 activation. METHODS: Clinical features of 14 patients with CAPS and heterozygous substitution at position 861 in the LRR domain of NLRP3 were compared to clinical features of 48 patients with CAPS and pathogenic variants outside the LRR domain of NLRP3. IL-1ß secretion by PBMCs and purified monocytes from patients and healthy donors was evaluated following LPS and monosodium urate crystal stimulation. RESULTS: Patients with substitution at position 861 of NLRP3 demonstrated a higher prevalence of sensorineural hearing loss while being less prone to skin urticarial. In contrast to patients with classical CAPS, cells from patients with a pathogenic variant at position 861 required an activation signal to secrete IL-1ß but produced more IL-1ß during the early and late phase of secretion than cells from healthy donors. CONCLUSIONS: Pathogenic variants of Y861 of NLRP3 drive a boost-dependent oversecretion of IL-1ß associated with an atypical CAPS phenotype.

Histamine elevation in familial Mediterranean fever: A study from the Juvenile Inflammatory Rheumatism cohort.

BACKGROUND: Familial Mediterranean Fever (FMF) is the most frequent monogenic autoinflammatory disease (AID). Some patients have persistent symptoms despite colchicine intake. Mast cells (MC) are innate immune cells involved in inflammatory conditions including AID. Their activation is responsible for various symptoms such as abdominal pain, bloating and pruritus. OBJECTIVE: Our objective was to evaluate features of a systemic MC activation in FMF adult patients. METHODS: FMF adult patients prospectively filled a MC activation survey and usual MC mediators (tryptase and histamine in whole blood, plasma and urine) were measured. They were compared with a healthy control group (HC) and a systemic mastocytosis (SM) group. When digestive biopsies were realized during follow-up, MC infiltration in digestive mucosa was analyzed in FMF, in comparison with SM, Crohn disease (CD) and normal biopsies. RESULTS: Forty-four FMF patients, 44 HC and 44 SM patients were included. Thirty-one (70%) FMF patients had symptoms of mast cell activation, versus 14 (32%) in the HC group (p = 0.0006). Thirty (68%) FMF patients had at least one elevated MC mediator: mainly whole blood histamine, in 19 (43%) and urinary histamine, in 14 (32%), which were significantly higher than in HC subjects. MC infiltration was comparable in FMF digestive biopsies, biopsies of CD and normal biopsies but was lower than in SM biopsies. CONCLUSION: FMF patients show frequent symptoms of MC activation and an increase of blood or urinary histamine never described before in this disease. This suggests an implication of MC and possibly basophils in FMF pathophysiology.

Diagnostic and therapeutic algorithms for monogenic autoinflammatory diseases presenting with recurrent fevers among adults.

Autoinflammatory diseases (AIDs) are defined as disorders of innate immunity. They were initially defined in contrast to autoimmune diseases because of the lack of involvement of the adaptive immune system and circulating autoantibodies. The four monogenic AIDs first described are called the 'historical' AIDs and include FMF (associated with MEFV mutations), cryopyrinopathies (associated with NLRP3 mutations), TNF receptor-associated periodic syndrome (associated with TNFRSF1A mutations) and mevalonate kinase deficiency (MKD; associated with MVK mutations). In the last 10 years, >50 new monogenic AIDs have been discovered due to genetic advances. The most important discovery for adult patients is VEXAS syndrome associated with somatic UBA1 mutations leading to an AID affecting mostly elderly men. Diagnosis of monogenic AIDs is based on personal and family history and detailed analysis of symptoms associated with febrile attacks in the context of elevated peripheral inflammatory markers. This review proposes a practical approach for the diagnosis of the main monogenic AIDs among adult patients.

Vasculitis and familial Mediterranean fever: Description of 22 French adults from the juvenile inflammatory rheumatism cohort.

Objective: The frequency of vasculitis may be increased in patients with Familial Mediterranean Fever (FMF), according to several studies. Our aim was to assess the characteristics of French adult patients with both diseases. Methods: Patients with vasculitis were selected from patients followed for FMF in the French JIR-cohort. Results: Twenty-two patients were included [polyarteritis nodosa (PAN) n = 10, IgA vasculitis n = 8, unclassified vasculitis n = 2, granulomatosis with polyangiitis n = 1, and microscopic polyangiitis n = 1]. Pathogenic mutations in exon 10 were found in all 21 patients (96%) for which MEFV testing results were available, and 18 (82%) had two pathogenic mutations. Histology showed vasculitis in 59% of patients. Most patients with FMF-associated PAN were HBV-negative and had an inactive FMF before PAN onset, and 40% had a peri-renal or central nervous system bleeding. Most patients with FMF-associated IgA vasculitis had an active FMF before vasculitis onset, and 25% had digestive bleeding. Both patients with unclassified vasculitis had ischemic and/or hemorrhagic complications. Conclusion: This study confirms the predominance of PAN and IgA vasculitis in patients with FMF and the high frequency of bleeding in FMF-associated PAN. FMF should be considered in case of persistent symptoms and/or inflammatory syndrome despite vasculitis treatment in Mediterranean patients.

Role of non-invasive methods in detecting liver impairment in familial Mediterranean fever adult patients with persistent hepatic cytolysis.

Familial Mediterranean fever (FMF) patients may have hepatic cytolysis, although its origin is not formally elucidated. We aimed to evaluate liver involvement in familial Mediterranean fever (FMF) using non-invasive methods. All adult FMF patients harboring two non-ambiguous mutations of the MEFV gene with hepatic cytolysis were identified in a French tertiary adult center for FMF. Liver impairment was explored with FibroMax (a non-invasive method to estimate hepatic steatosis, necrosis, inflammation and fibrosis) and liver ultrasound. Among 520 FMF adult patients, 43 had persistent hepatic cytolysis and 20 patients were included (11 women, median age at inclusion: 49.5 years). According to the FibroMax results, patients were classified as having steatosis, fibrosis, and possible or definite nonalcoholic steato-hepatitis in 10 (50%), 9 (45%) and 7 (35%) of cases, respectively. The score of steatosis did not seem associated with the usual metabolic risk factors. No significant association was found between the cumulated dose of colchicine and any of the scores included in FibroMax. In adult FMF patients with persistent hepatic cytolysis, steatosis is the first cause to consider even in the absence of usual metabolic risk factors, suggesting other mechanisms. Colchicine did not seem to be involved in this toxicity.

Neurological manifestations in mevalonate kinase deficiency: A systematic review.

INTRODUCTION: Mevalonate kinase deficiency (MKD) is a monogenic auto-inflammatory disease. Its manifestations range from partial MKD to mevalonic aciduria (MVA). All patients display a periodic fever, and MVA patients additionally exhibit severe neurological involvement. The objective of this work was to describe neurological manifestations of MKD. METHODS: A systematic literature review was performed from January 1990 to January 2022. Forty-five patients from 18 case reports and five cohort studies were included in the analysis. RESULTS: In cohort studies, the most-reported manifestations were headaches (41%) and fatigue (31%). Serious involvements including ataxia and developmental delay were described less than 1% of patients but 22-31% of case reports. They consistently appeared in the first years of life. Retinal dystrophy was frequently reported (31%) in case reports. Other manifestations, including uveitis, aseptic meningitis, and stroke remained rare. DISCUSSION: Severe neurological manifestations are rare in MKD but are responsible for major functional disabilities. They are present at onset and never appear at follow-up of patients with mild MKD. Conversely, headaches and fatigue are frequent symptoms that should be investigated. Visual examinations should be performed on the appearance of visual symptoms. The efficacy of anti-IL-1ß therapy on neurological manifestations should be further investigated.

COVID-19 infection among patients with autoinflammatory diseases: a study on 117 French patients compared with 1545 from the French RMD COVID-19 cohort: COVIMAI - the French cohort study of SARS-CoV-2 infection in patient with systemic autoinflammatory diseases.

OBJECTIVE: There is little known about SARS-CoV-2 infection in patients with systemic autoinflammatory disease (SAID). This study aimed to describe epidemiological features associated with severe disease form and death. Mortality between patients with and without SAID hospitalised for SARS-CoV-2 infection was compared. METHODS: A national multicentric prospective cohort study was conducted from the French Rheumatic and Musculoskeletal Diseases (RMD) COVID-19 cohort. Patients with SAID were matched with patients with non-SAID on age±7 years, gender and number of comorbidities to consider important confounding factors. Impact of SAID on severity of SARS-CoV-2 infection was analysed using multinomial logistic regression for severity in three classes (mild, moderate and severe with mild status as reference). Fine-Gray regression model for length of hospital stay and binomial logistic regression model for risk of death at 30 days. RESULTS: We identified 117 patients with SAID (sex ratio 0.84, 17 children) and compared them with 1545 patients with non-autoinflammatory immune-mediated inflammatory disorders (non-SAID). 67 patients had a monogenic SAID (64 with familial Mediterranean fever). Other SAIDs were Behçet' disease (n=21), undifferentiated SAID (n=16), adult-onset Still disease (n=9) and systemic-onset juvenile idiopathic arthritis (n=5). Ten adults developed severe form (8.6%). Six patients died. All children had a benign disease. After matching on age±7 years, sex and number of comorbidities, no significant difference between the two groups in length of stay and the severity of infection was noted. CONCLUSION: As identified in the whole French RMD COVID-19 cohort, patients with SAID on corticosteroids and with multiple comorbidities are prone to develop more severe COVID-19 forms.

Mosaic variants in TNFRSF1A: an emerging cause of tumour necrosis factor receptor-associated periodic syndrome.

OBJECTIVE: To identify the molecular basis of a systemic autoinflammatory disorder (SAID) evocative of TNF receptor-associated periodic syndrome (TRAPS). METHODS: (i) Deep next generation sequencing (NGS) through a SAID gene panel; (ii) variant allele distribution in peripheral blood subpopulations; (iii) in silico analyses of mosaic variants using TNF receptor superfamily 1A (TNFRSF1A) crystal structure; (iv) review of the very rare TNFRSF1A mosaic variants reported previously. RESULTS: In a 36-year-old man suffering from recurrent fever for 12 years, high-depth NGS revealed a TNFRSF1A mosaic variant, c.176G>A p.(Cys59Tyr), which Sanger sequencing failed to detect. This mosaic variant displayed a variant allele fraction of 14% in whole blood; it affects both myeloid and lymphoid lineages. p.(Cys59Tyr), a recurrent germline pathogenic variant, affects a crucial cysteine located in the first cysteine-rich domain (CRD1) and involved in a disulphide bridge. Introduction of a tyrosine at this position is expected to disrupt the CRD1 structure. Review of the three previously reported TNFRSF1A mosaic variants revealed that they are all located in a small region of CRD2 and that germinal cells can be affected. CONCLUSION: This study expands the localization of TNFRSF1A mosaic variants to the CRD1 domain. Noticeably, residues involved in germline TNFRSF1A mutational hot spots can also be involved in post-zygotic mutational events. Including our study, only four patients have been thus far reported with TNFRSF1A mosaicism, highlighting the need for a high-depth NGS-based approach to avoid the misdiagnosis of TRAPS. Genetic counselling has to consider the potential occurrence of TNFRSF1A mosaic variants in germinal cells.

AA amyloidosis complicating cryopyrin-associated periodic syndrome: a study of 86 cases including 23 French patients and systematic review.

OBJECTIVE: Cryopyrin-associated periodic syndrome (CAPS) is a rare but treatable inherited autoinflammatory condition including familial cold autoinflammatory syndrome (FCAS), Muckle-Wells syndrome (MWS) and chronic infantile neurologic cutaneous articular syndrome (CINCA). Our objective was to describe the main features of CAPS AA amyloidosis (AA-CAPS) associated and the efficacy of IL-1 inhibitors in this indication. METHODS: Retrospective study in France associated with a systematic literature review. RESULTS: Eighty-six patients were identified: 23 new French cases and 63 from the literature, with a median age at amyloidosis diagnosis of 39 years old. CAPS subtypes were MWS (n = 62), FCAS (n = 9), frontier forms between MWS and FCAS (n = 12) and between CINCA and MWS (n = 3). NLRP3 had been sequenced in 60 patients (70%) and the most frequent mutation was R260W (60%). Three AA-CAPS patients displayed somatic NLRP3 mutations. Death occurred in 35 patients (41%), none of whom having ever received IL-1 inhibitors. Twenty-eight patients (33%) received IL-1 inhibitors, with a >50% decrease in proteinuria in 89% of cases. CONCLUSION: AA amyloidosis can occur in nearly all CAPS subtypes. IL-1 inhibitors are effective, underlining the necessity of an early diagnosis of CAPS in order to start this treatment as soon as possible among AA-CAPS patients.

Amyloidosis from the patient perspective: the French daily impact of amyloidosis study.

BACKGROUND: Amyloidosis is a complex group of rare conditions. For patients, amyloidosis is severely debilitating: physically and psychologically. Currently, data are lacking to evaluate the medical, economic, and social burden of systemic amyloidosis. OBJECTIVE: To analyse the patient burden according to the main types of systemic amyloidosis. METHODS: The French Daily Impact of Amyloidosis study was an observational, cross-sectional and non-interventional study. Adults diagnosed with light chain (AL), transthyretin (ATTR), amyloid A (AA) and other rare forms of amyloidosis were eligible. Data regarding amyloidosis prevalence, diagnosis, management, and impact on everyday life were collected using a study-specific survey built by the Association Française Contre l'Amylose (AFCA) and the four French National Referral Centres for Amyloidosis. RESULTS: A total of 603 patients, predominantly male (65%) with an average age of 66.8 years, including 170 AL, 224 ATTRv, 109 ATTRwt and 25 AA amyloidosis patients, completed the study-specific survey. The median delay from presentation to confirmed diagnosis was 27.4 months but varied according to amyloidosis type. Patients before diagnosis had breathlessness (49%), tingling sensation (33%), pain (28%), difficulty in walking (28%) and weight loss (22%). Amyloidosis was most frequently suspected (49%) and confirmed (57%) in local hospitals but managed in French amyloidosis referral centres (58%). Patients often reported problems with mobility, usual activities, pain/discomfort and anxiety/depression, but not with self-care. CONCLUSIONS: Systemic amyloidosis severely impacts daily life. The delay to confirmed amyloidosis diagnosis needs to be reduced. Early, effective treatment is required to optimise patient benefits.