Abnormal disulfide-linked oligomerization results in ER retention and altered signaling by TNFR1 mutants in TNFR1-associated periodic fever syndrome (TRAPS)

Tumor necrosis factor (TNF) receptor-associated periodic syndrome (TRAPS) is an autosomal dominant systemic autoinflammatory disease associated with heterozygous mutations in TNF receptor 1 (TNFR1). Here we examined the structural and functional alterations caused by 9 distinct TRAPS-associated TNFR1 mutations in transfected cells and a mouse "knock-in" model of TRAPS. We found that these TNFR1 mutants did not generate soluble versions of the receptor, either through membrane cleavage or in exosomes. Mutant receptors did not bind TNF and failed to function as dominant-negative inhibitors of TNFR1-induced apoptosis. Instead, TRAPS mutant TNFR1 formed abnormal disulfide-linked oligomers that failed to interact with wild-type TNFR1 molecules through the preligand assembly domain (PLAD) that normally governs receptor self-association. TRAPS mutant TNFR1 molecules were retained intracellularly and colocalized with endoplasmic reticulum (ER) markers. The capacity of mutant receptors to spontaneously induce both apoptosis and nuclear factor kappaB (NF-kappaB) activity was reduced. In contrast, the R92Q variant of TNFR1 behaved like the wild-type receptor in all of these assays. The inflammatory phenotype of TRAPS may be due to consequences of mutant TNFR1 protein misfolding and ER retention.     

TNF-receptor-associated periodic syndrome (TRAPS): an autosomal dominant multisystem disorder

The TNF-receptor-associated periodic sydrome (TRAPS) is an autosomal dominant auto-inflammatory disorder, characterized by recurrent febrile attacks and localized inflammation. TRAPS is caused by mutations in the gene encoding the TNF Receptor Super Family 1A (TNFRSF1A) on chromosome 12p13. However, the incomplete penetrance and genetic heterogeneity have been reported in this syndrome. Although the ethnic diversity and clinical heterogeneity may propose the role of other genes in the pathogenesis of TRAPS, some low-penetrance TNFRSF1A variants contribute to atypical inflammatory responses in other autoimmune diseases. Furthermore, molecular studies on TRAPS and other auto-inflammatory disorders could be suggested to identify additional genes coding the molecules in the TNF signalling process.     

Typical and severe tumor necrosis factor receptor–associated periodic syndrome in the absence of mutations in the TNFRSF1A gene: a case series

Tumor necrosis factor receptor-1?Cassociated periodic syndrome (TRAPS) is the most common autosomal dominant autoinflammatory disorder and is caused by mutations in the TNFRSF1A gene encoding the 55-kDa receptor for tumor necrosis factor (TNF)-??. TRAPS is characterized by recurrent attacks of fever, typically lasting from 1 to 3?weeks. In addition to fever, common clinical features include periorbital edema, a migratory erythematous plaque simulating erysipela with underlying myalgia, and arthralgia or arthritis. Serosal membrane inflammation is also a common feature, usually in the form of polyserositis. To date, at least 40 different TNFRSF1A mutations have been identified, but few patients with symptoms highly suggestive of TRAPS with no mutations in the TNFRSF1A gene have recently been described, thus suggesting that not all mutations are yet known or that alternative mechanisms might be involved in the pathogenesis of the disease. We report on three such patients here.     

Mutant tumor necrosis factor receptor associated with tumor necrosis factor receptor–associated periodic syndrome is altered antigenically and is retained within patients' leukocytes

Objective

To investigate the effect of mutations in tumor necrosis factor receptor superfamily member 1A (TNFRSF1A) in TNFR‐associated periodic syndrome (TRAPS) on the binding of anti‐TNFRSF1A monoclonal antibodies (mAb), and to investigate the subcellular distribution of mutant versus wild‐type (WT) TNFRSF1A in patients with TRAPS.

Methods

HEK 293 cells transfected with WT and/or mutant TNFRSF1A were used to investigate the interaction of anti‐TNFRSF1A mAb with the WT and mutant proteins. Monoclonal antibodies that differentially bound to C33Y TNFRSF1A were used to investigate the distribution of WT and mutant TNFRSF1A in TRAPS patients with the C33Y mutation.

Results

We identified a mAb whose binding to TNFRSF1A was completely abolished by the C33Y or C52F TRAPS‐associated mutations, whereas other mutations (T50M, C88Y, R92Q) had lesser effects on the binding of this mAb. A different mAb was found to bind efficiently to all of the mutant forms of TNFRSF1A examined as well as to the WT receptor. Exploitation of the differential binding properties of these mAb indicated that mutant (as distinct from WT) TNFRSF1A showed abnormal intracellular retention in the neutrophils of TRAPS patients with the C33Y mutation, with little if any expression of mutant TNFRSF1A on the cell surface or as soluble receptor in plasma.

Conclusion

TRAPS‐associated mutant TNFRSF1A has an antigenically altered structure and shows abnormal retention in the leukocytes of patients with TRAPS, which is consistent with previous findings from in vitro and transgenic model systems. This is consistent with a misfolded protein response contributing to the pathophysiology of TRAPS.

     

Gender differences in injury induced mesenchymal stem cell apoptosis and VEGF, TNF, IL-6 expression: role of the 55 kDa TNF receptor (TNFR1)

Concomitant pro- and anti-inflammatory properties of bone marrow stem cells (BMSC) may be an important aspect of their ability to heal injured tissue. However, very few studies have examined whether gender differences exist in BMSC function. Indeed, it remains unknown whether gender differences exist in BMSC function and ability to resist apoptosis, and if so, whether TNF receptor 1 (TNFR1) plays a role in these differences. We hypothesized that TNFR1 ablation equalizes gender differences in bone marrow mesenchymal stem cell (MSC) apoptosis, as well as expression of vascular endothelial growth factor (VEGF), TNF and interleukin (IL)-6. Mouse MSCs from male wild type (WT), female WT, male TNFR1 knockouts (TNFR1KO) and female TNFR1KO were stressed by endotoxin 200 ng/ml or 1 h hypoxia. MSC activation was determined by measuring VEGF, TNF and IL-6 production (ELISA). Differences considered significant if p<0.05. LPS and hypoxia resulted in significant activation in all experimental groups compared to controls. Male WT demonstrated significantly greater TNF and IL-6 and significantly less VEGF release than female WT MSCs. However, release of TNF, IL-6 and VEGF in male TNFR1 knockouts differed from male WT, but was not different from female WT MSCs. Similarly apoptosis in hypoxic male TNFRIKO differed from male WT, but it was not different from apoptosis from WT female. Female WT did not differ in TNF, IL-6 and VEGF release compared to female TNFR1KO. Gender differences exist in injury induced BMSC VEGF, TNF and IL-6 expression. TNFR1 may autoregulate VEGF, TNF and IL-6 expression in males more than females. MSCs are novel therapeutic agents for organ protection, but further study of the disparate expression of VEGF, TNF and IL-6 in males and females as well as the role of TNFR1 in these gender differences is necessary to maximize this protection.     

Exclusive tumor necrosis factor (TNF) signaling by the p75TNF receptor triggers inflammatory ischemia in the CNS of transgenic mice

Tumor necrosis factor (TNF) is up-regulated in a variety of central nervous system (CNS) diseases with diverse etiology and pathologic manifestation. TNF mediates multiple biological activities through two membrane receptors, the p55 and p75 TNF receptors (TNFRs). We have shown previously that human transmembrane TNF (tmTNF)p55TNFR signaling in transgenic mice triggers oligodendrocyte apoptosis, endothelial cell activation, parenchymal inflammation, and primary demyelinating lesions similar to those of acute multiple sclerosis. To address the role of the p75TNFR in the CNS, we have generated "humanized" mice that express human tmTNF in astrocytes and a physiologically regulated human p75TNFR transgene, in the absence of the endogenous (murine) p55TNFR. Human tmTNFp75TNFR transgenic mice develop CNS vascular pathology, characterized by endothelial cell activation, meningeal inflammation, and vessel fibrosis. There is no evidence of oligodendrocyte apoptosis or primary demyelination in these mice. Late in disease, vasculitis can result in vessel occlusion and secondary, multifocal CNS ischemic injury. These results identify a proinflammatory role for the p75TNFR at the level of the CNS vascular endothelium, which correlates with the expression pattern of this receptor in the CNS, and indicate that the differential expression patterns of the two TNFRs within the CNS play a significant role in shaping the outcome of TNF signaling during neuroimmune interactions.     

Modeling of tumor necrosis factor receptor superfamily 1A mutants associated with tumor necrosis factor receptor–associated periodic syndrome indicates misfolding consistent with abnormal function

Objective

To investigate the effect of mutations in the tumor necrosis factor receptor superfamily 1A (TNFRSF1A) gene on the conformation and behavior of the TNFRSF1A protein. Mutations in TNFRSF1A cause the autosomal‐dominant, autoinflammatory TNFR‐associated periodic syndrome (TRAPS).

Methods

The expression of recombinant TNFRSF1A was compared in SK–HEp‐1 endothelial cells and HEK 293 epithelial cells stably transfected with full‐length R347A or Δsig constructs of wild‐type or TRAPS‐associated mutant TNFRSF1A. TNF binding was assessed in HEK 293 cell lines expressing R347A wild‐type or mutant TNFRSF1A. Homology modeling of the 3‐dimensional structure of the ectodomains of wild‐type and mutant TNFRSF1A was performed.

Results

TRAPS‐associated mutant and wild‐type TNFRSF1A behaved differently and had different localization properties within the cell, as a direct result of mutations in the ectodomains of TNFRSF1A. From a structural perspective, mutants with a predicted structure similar to that of the wild‐type protein (e.g., R92Q) behaved similarly to wild‐type TNFRSF1A, whereas forms of TNFRSF1A with mutations predicted to drastically destabilize the protein structure (e.g., cysteine mutations) showed defects in cell surface expression and TNF binding.

Conclusion

The results obtained from the in vitro experiments, in combination with the modeled structures, indicate that the phenotype and clinical differences between different TRAPS‐associated mutants of TNFRSF1A result from different conformations of the TNFRSF1A ectodomains.

     

Mutant tumor necrosis factor receptor associated with tumor necrosis factor receptor-associated periodic syndrome is altered antigenically and is retained within patients' leukocytes

OBJECTIVE: To investigate the effect of mutations in tumor necrosis factor receptor superfamily member 1A (TNFRSF1A) in TNFR-associated periodic syndrome (TRAPS) on the binding of anti-TNFRSF1A monoclonal antibodies (mAb), and to investigate the subcellular distribution of mutant versus wild-type (WT) TNFRSF1A in patients with TRAPS. METHODS: HEK 293 cells transfected with WT and/or mutant TNFRSF1A were used to investigate the interaction of anti-TNFRSF1A mAb with the WT and mutant proteins. Monoclonal antibodies that differentially bound to C33Y TNFRSF1A were used to investigate the distribution of WT and mutant TNFRSF1A in TRAPS patients with the C33Y mutation. RESULTS: We identified a mAb whose binding to TNFRSF1A was completely abolished by the C33Y or C52F TRAPS-associated mutations, whereas other mutations (T50M, C88Y, R92Q) had lesser effects on the binding of this mAb. A different mAb was found to bind efficiently to all of the mutant forms of TNFRSF1A examined as well as to the WT receptor. Exploitation of the differential binding properties of these mAb indicated that mutant (as distinct from WT) TNFRSF1A showed abnormal intracellular retention in the neutrophils of TRAPS patients with the C33Y mutation, with little if any expression of mutant TNFRSF1A on the cell surface or as soluble receptor in plasma. CONCLUSION: TRAPS-associated mutant TNFRSF1A has an antigenically altered structure and shows abnormal retention in the leukocytes of patients with TRAPS, which is consistent with previous findings from in vitro and transgenic model systems. This is consistent with a misfolded protein response contributing to the pathophysiology of TRAPS.     

Requirement of TNF and TNF receptor type 2 for LPS-induced protection from lethal septic peritonitis

Pretreatment of mice with low quantities of LPS induces endotoxin tolerance characterized by enhanced resistance to lethal doses of LPS and to a number of infectious challenges. Mice subjected to cecal ligation and puncture (CLP) survived the ensuing septic peritonitis significantly better when they had been pretreated with LPS. This LPS-induced protection was dependent on endogenous TNF production capacity since LPS pretreatment did not protect TNF-deficient mice from death after CLP. While mice deficient in the TNF receptor type 2 (p75TNFR) were as sensitive to CLP-induced mortality as control mice, LPS pretreatment could not reduce mortality in p75TNFR-deficient mice after CLP. Therefore, activation of the TNF receptor type 2 by endogenous TNF constitutes an important interaction for the development of LPS-induced resistance to bacterial infection.     

Failure of anti-TNF therapy in TNF Receptor 1-Associated Periodic Syndrome (TRAPS)

SIR, Hereditary fevers are a group of multisystem disorderscharacterized by recurrent attacks of fever and organ-localizedinflammation that mainly affect musculoskeletal system, skinand serosal cavities [1]. The acronym TRAPS (Tumour necrosisfactor Receptor Associated Periodic Syndrome) designates a dominantlyinherited disease, with mutations affecting the 55 KDa tumournecrosis factor (TNF) receptor gene. We report on two Frenchpatients suffering from TRAPS, treated with anti-TNF drugs (etanercept,infliximab). Case 1: A 23-yr-old-woman was referred for recurrent fever withrepeated sub-cutaneous inflammation of the trunk or limbs. Theonset     

Proinflammatory action of the antiinflammatory drug infliximab in tumor necrosis factor receptor–associated periodic syndrome

Objective

Tumor necrosis factor receptor (TNFR)–associated periodic syndrome (TRAPS) is an autosomal‐dominant autoinflammatory condition caused by mutations in the TNFRSF1A gene. Unlike other autoinflammatory diseases in which anti‐TNF therapy is largely a successful treatment option, therapy with the anti‐TNF drug infliximab is often ineffective in patients with TRAPS. Moreover, in certain cases, infliximab actually triggers severe episodes of inflammation. The aim of this study was to elucidate the mechanisms underlying such a reaction.

Methods

Peripheral blood mononuclear cells (PBMCs) were obtained from patients with TRAPS. Both caspase 3 activity and NF‐κB subunit activity were determined by enzyme‐linked immunosorbent assay. Cytokine secretion was assessed using a specific customized human multiplex bead immunoassay kit.

Results

Unlike findings in controls, cells from a family of 9 patients, all of whom carried the T50M mutation in TNFRSF1A, failed to respond to infliximab through proapoptotic induction of caspase 3 activity. Instead, we observed enhanced antiapoptotic c‐Rel subunit activity, accompanied by a significant increase in secretion of the proinflammatory cytokines interleukin‐ 1β (IL‐1β), IL‐1 receptor, IL‐6, IL‐8, and IL‐12.

Conclusion

Altered extracellular conformation of TNFRI, resulting from the T50M mutation in TNFRSF1A, results in failure of PBMCs to induce an apoptotic response to infliximab. We hypothesize that failure to shed infliximab‐bound TNF/TNFRI from the cell surface of cells from patients with the T50M mutation triggers c‐Rel activation, and that this leads to a marked increase in cytokine secretion and an increased proinflammatory response. In light of these findings, we strongly advise caution when prescribing infliximab as anti‐TNF therapy to patients with TRAPS.

     

Intra-abdominal abscess in a patient with tumour necrosis factor receptor-associated periodic syndrome

Tumour necrosis factor (TNF) receptor-associated periodic syndrome (TRAPS) is an autoinflammatory disorder characterized by periodic attacks of fever and inflammation, due to mutations in the gene coding for the TNF type I receptor (TNFRSF1A). A 16-year-old patient with the diagnosis of TRAPS was admitted to hospital because of fever and abdominal pain. Initially, the symptoms were interpreted as manifestations of another TRAPS attack, but the patient's condition worsened, despite treatment with corticosteroids and antibiotics. A repeated computer tomography revealed an intra-abdominal abscess, which necessitated urgent surgical intervention. This case stresses the importance of differential diagnostic vigilance when dealing with patients with rare genetic diseases.     

Le syndrome de fièvre prolongée associée aux mutations du gène du récepteur au TNF de type 1 : un diagnostic différentiel de la fièvre méditerranéenne familiale à ne pas méconnaître chez les patients d’origine méditerranéenne

IntroductionTumor Necrosis Factor Type 1 Receptor Associated Periodic Syndrome (TRAPS) is a rare autosomal dominant autosomal autoinflammatory disease associated with mutations in the TNF type 1 receptor gene (TNFRSF1A). It is characterized by relatively long recurrent febrile seizures with an average duration of 7 days accompanied by arthralgia, myalgia, and usually a rash. In a patient of Mediterranean origin with recurrent fever, familial Mediterranean fever is the first diagnosis to be suspected by argument of frequency.MethodsA retrospective observational study was conducted on patients from Mediterranean origin followed for TRAPS and included in the “Juvenile Inflammatory Rheumatism” (JIR) observational cohort in the national French autoinflammatory center. The age of onset of symptoms, age of diagnosis, number of years of wandering and treatments received were collected for each index case.ResultsNine patients from 6 families of Mediterranean origin were included. A molecular diagnosis confirmed TRAPS in all patients. The median age at diagnosis was 26 years, the mean number of years of wandering was 17 years. The diagnosis of FMF was made first in all patients. AA amyloidosis revealed TRAPS in 2 patients. Colchicine was started without any efficacy in all cases. Five patients were treated with interleukin-1 inhibitory biotherapy with 100% efficacy.ConclusionIn a patient of Mediterranean origin presenting with recurrent febrile abdominal pain of AA amyloidosis, the first diagnosis to be suspected is FMF. Long relapses, dominant transmission, a non-Mediterranean relative, and the ineffectiveness of colchicine should evoke TRAPS.     

Tumor necrosis factor receptor I from patients with tumor necrosis factor receptor–associated periodic syndrome interacts with wild‐type tumor necrosis factor receptor I and induces ligand‐independent NF‐κB activation

Objective

To investigate the molecular consequences of expressing mutated forms of tumor necrosis factor receptor I (TNFRI) as found in patients with TNFR‐associated periodic syndrome (TRAPS).

Methods

We cloned and expressed full‐length wild‐type (WT) and T50K and P46L variants of TNFRI using a new tightly regulated doxycycline‐dependent expression system. This system enabled the study of molecular interactions between these receptors at both physiologic and pathophysiologic levels of expression.

Results

We used chemical crosslinking on the cell surface to show that WT and mutant forms of TNFRI, derived from TRAPS patients, interact in the absence of TNF ligand. Doxycycline‐controlled up‐regulation of one TNFRI allele, either WT or mutant, caused down‐regulation of the other allele, indicating dynamic control of cell surface assembly. We also demonstrated that increased expression of mutant TNFRI (T50K) was associated with a parallel increase in NF‐κB p65 (RelA) subunit activation, which did not occur with increased expression of WT TNFRI.

Conclusion

The T50K TRAPS‐related variant is capable of sustaining inappropriate NF‐κB activation, resulting in persistent autoinflammation in target organs such as skin, synovial membrane, and the central nervous system. We conclude that some of the inflammatory processes seen in TRAPS do not involve direct interaction of TNF with its receptors, but that other proinflammatory mechanisms capable of up‐regulating TNFRI expression may cause cellular activation through the NF‐κB signaling pathway.

     

The TNF receptor-associated periodic syndrome (TRAPS): emerging concepts of an autoinflammatory disorder

The present report describes and expands the clinical and genetic spectrum of the autoinflammatory disorder, tumor necrosis factor (TNF) receptor-associated periodic syndrome (TRAPS). A total of 20 mutations have been identified since our initial discovery of 6 missense mutations in TNF receptor super family 1A (TNFRSF1A) in 1999. Eighteen of the mutations result in amino acid substitutions within the first 2 cysteine-rich domains (CRDs) of the extracellular portion of the receptor. A single splicing mutation also affects the first CRD by causing the insertion of 4 amino acids. Haplotype analysis of the most commonly occurring and ethnically heterogeneous mutation, R92Q, demonstrates an ancient founder; however, analysis of the T50M mutation, another commonly occurring mutation in Irish and Scottish families, does not, suggesting that T50M is a recurring mutation. Mutations that result in cysteine substitutions demonstrate a higher penetrance of the clinical phenotype (93% versus 82% for noncysteine residue substitutions), and also increase the probability of developing life-threatening amyloidosis (24% versus 2% for noncysteine residue substitutions). Retrospective and prospective evaluation of more than 50 patients, representing 10 of the 20 known mutations, allows us to expand and better define the clinical spectrum of TRAPS. Recurrent episodes of fever, myalgia, rash, abdominal pain, and conjunctivitis that often last longer than 5 days are the most characteristic clinical features of TRAPS. Defective shedding of TNFRSF1A can only partially explain the pathophysiologic mechanism of TRAPS, since some mutations have normal shedding. Consequently, other mechanisms may be mediating the observed phenotype. We are currently investigating other possible mechanisms using stable and transiently transfected cell systems in vitro, as well as developing a knockin mouse model. Preliminary data suggest that etanercept may be effective in decreasing the severity, duration, and frequency of symptoms in TRAPS patients. Additionally, it provides a viable therapeutic alternative to glucocorticoid therapy, which has numerous serious, long-term adverse effects. Two clinical trials are being conducted to evaluate the efficacy of etanercept in decreasing the frequency and severity of symptoms in TRAPS. Lastly, we have summarized data that R92Q and P46L, and probably as yet undiscovered substitutions, represent very low penetrance mutations that may play a much larger role in more broadly defined inflammatory diseases such as rheumatoid arthritis. Our laboratories are currently undertaking both clinical and basic research studies to define the role of these mutations in more common inflammatory diseases.     

Periodic fever (TRAPS) caused by mutations in the TNFα receptor 1 (TNFRSF1A) gene of three German patients

TNF-receptor-associated periodic syndrome (TRAPS) is a recently recognized disorder characterized by prolonged attacks of high fever and severe localized inflammation. TRAPS is caused by dominant mutations in the 55 kDa TNF receptor gene (TNFRSF1A). We here describe three German TRAPS patients of two families with Cys30-->Arg and Thr50-->Met mutations, respectively. Both mutations have already been observed before in other nonrelated families. The Thr50-->Met amino acid exchange, caused by an ACG-->ATG transition, has been reported in two other families of different ethnic background. The possibility that the ACG-->ATG sequence alteration is a mutational hot spot causing TRAPS is discussed. Furthermore, we describe and discuss the symptoms of our patients, possible inducers of febrile attacks, and treatments which the patients had received when their diagnoses were still unknown.     

The proinflammatory cytokines interleukin-1 and tumor necrosis factor and treatment of the septic shock syndrome

Treating the septic shock syndrome with antibodies that block only endotoxin has its limitations. Other targets for treating septic shock include neutralizing antibodies to the complement fragment C5a, platelet-activating factor antagonists, and blockade of endothelial cell leukocyte adhesion molecules. Specific blockade of the proinflammatory cytokines interleukin-1 (IL-1) or tumor necrosis factor (TNF) reduces the morbidity and mortality associated with septic shock. Moreover, blocking IL-1 and TNF likely has uses in treating diseases other than septic shock. Use of neutralizing antibodies to TNF or to IL-1 receptors have reduced the consequences of infection and inflammation, including lethal outcomes in animal models. The IL-1 receptor antagonist, a natural-occurring cytokine, blocks shock and death due to Escherichia coli and ameliorates a variety of inflammatory diseases. Soluble TNF and IL-1 surface receptors, which bind their respective cytokines, also ameliorate disease processes. Current clinical trials are evaluating the safety and efficacy of these anticytokine therapies either alone or together.     

TNF and sepsis

Recent experiments have demonstrated that TNF plays an important role in the pathogenesis of septic shock. To confirm the involvement of TNF in human septic shock, serum TNF levels were measured in 10 adult patients admitted to the intensive care unit for sepsis with or without shock. Septic shock was corroborated by hemodynamic data (right catheterization, measurement of cardiac output by thermodilution). For TNF measurement, venous blood samples were withdrawn, as soon as possible after the onset of sepsis, into a pyrogen--free tube. Serum TNF levels were determined using a radioimmunoenzymatic assay (IRE Medgenix). During septic shock (n = 7), TNF levels were significantly higher (m = 354 +/- 131 pg/ml) than during sepsis without shock (n = 8; m = 145 +/- 35 pg/ml) (p less than 0.0005). TNF levels were also significantly higher in non-survivors (m = 392 +/- 111 pg/ml) than in survivors (m = 167 +/- 81 pg/ml) (p less than 0.0005). The value of 250 pg/ml seems to be critical: no patient without shock had TNF levels above 250 and all the patients who died early during the first 24 h) had TNF levels above 250. The TNF level is negatively correlated with the platelet count (r = -0.70; p less than 0.05). These data favor a pathophysiological for TNF in human sepsis and septic shock.     

"Periodic fever" without fever: two cases of non-febrile TRAPS with mutations in the TNFRSF1A gene presenting with episodes of inflammation or monosymptomatic amyloidosis

BACKGROUND: Tumour necrosis factor (TNF) receptor associated periodic syndrome (TRAPS) is caused by dominant mutations in the TNFRSF1A gene. In typical cases TRAPS begins early in childhood and is characterised by high and remittent fever over a period of 1-4 weeks or longer, accompanied by systemic and local inflammation. CASE REPORTS: Patient 1 presented with recurrent episodes of weakness, migrating myalgias, arthralgias, exanthema, and chest pain lasting for 1-4 weeks, but without any fever over an initial period of 4 years at least. Diagnosis of TRAPS was confirmed by the heterozygous mutation Y20H in TNFRSF1A. Patient 2, a 23 year old woman never had any symptoms indicative of TRAPS. Genetic evaluation of all members of her family with a TRAPS index patient disclosed the T50M mutation in TNFRSF1A. A medical check up showed proteinuria, and renal biopsy disclosed AA amyloidosis. CONCLUSIONS: TRAPS associated mutations can induce considerable inflammation that is not necessarily accompanied by fever. Even monosymptomatic severe amyloidosis can occur in these patients. Genetic counselling and appropriate management to prevent or mitigate amyloidosis may be necessary.