Hyper IgD syndrome (HIDS) associated with in vitro evidence of defective monocyte TNFRSF1A shedding and partial response to TNF receptor blockade with etanercept

The Relationship between NALP3 and Autoinflammatory Syndromes

The nucleotide-binding domain, leucine-rich repeat/pyrin domain-containing-3 (NALP3) inflammasome, which is required for synthesis of interleukin-1β, has been implicated in the pathogenesis of several autoinflammatory syndromes. This review of the literature summarizes the interconnectedness of NALP3 inflammasome with some of these disorders. Familial Mediterranean fever results from a mutation in the Mediterranean fever (MEFV) gene, which encodes the pyrin protein. Previous study results suggest that pyrin suppresses caspase-1 activation, perhaps by competing for the adaptor protein, termed, pyrin domain of apoptosis/speck-like protein containing a caspase-recruitment domain (ACS) which therefore interferes with NALP3 inflammasome activation. The nucleotide-binding domain, leucine-rich repeat/pyrin domain-containing-3 (NALP3) inflammasome is constitutively activated in cryopyrin-associated periodic syndromes due to gain-of-function mutations resulting from point mutations within the neuronal apoptosis inhibitor protein/class 2 transcription factor/heterokaryon incompatibility/telomerase-associated protein-1 (NACHT) domain of the NALP3 protein. Pyogenic arthritis, pyoderma gangrenosum and acne (PAPA) syndrome is caused by mutations in the genes encoding proline-serine-threonine phosphatase interacting protein 1 (PSTPIP1). These PSTPIP1 mutants are thought to bind to pyrin causing an increase in the pyrin domain of apoptosis/speck-like protein containing a caspase-recruitment domain (ASC) pyroptosome assembly leading to procaspase-1 recruitment and therefore its activation. Hyperimmunoglublinemia D syndrome is caused by mevalonate kinase (MVK) deficiency, which may be affected by protein accumulation that leads to NALP3 inflammasome activation. Tumor necrosis factor receptor-associated periodic syndrome is associated with mutations in the tumor necrosis factor receptor superfamily, member 1A (TNFRSF1A) gene which decreases the level of soluble tumor necrosis factor receptor-1 (TNFR1) leading to neutralization of tumor necrosis factor (TNF)-α. In general, these autoinflammatory disorders have shown a clinical response to interleukin-1 (IL-1) antagonists, suggesting that the NALP3 inflammasome serves a critical role in their pathogenesis.

Treatment of hyperimmunoglobulinemia D syndrome with biologics in children: review of the literature and Finnish experience

Hyperimmunoglobulinemia D syndrome (HIDS) is an autoinflammatory disorder that is caused by mevalonate kinase deficiency (MKD). Recent advances in the pathogenesis of MKD, including the proposed mechanisms of inflammasome activation, provide the basis for the development of new treatment modalities. So far, feedback on the treatment of HIDS with biological medicines has come from case reports with limited numbers of patients. In this review, we summarize the data that is currently available on the treatment of HIDS in children, with the emphasis on new therapies, and present three Finnish pediatric cases treated with anakinra. Case reports have been published on 33 pediatric HIDS patients who have been treated with biological medicines, and in some cases, they were treated with more than one drug. Of these patients, 21 were treated with anakinra and 16 with etanercept, resulting in complete or partial responses in 90 and 50% of cases, respectively. A further five patients were treated with canakinumab, with complete or partial responses.

CONCLUSION

The accumulating evidence on the efficacy and safety of biological drugs in pediatric HIDS suggests that the anti-interleukin-1 agent anakinra is the drug of choice for HIDS in children.

WHAT IS KNOWN

• Various biologic drugs have been tried for the treatment of HIDS. What is New: • Based on the 90% response rate, anakinra seems to be the drug of choice for HIDS in children.

Overlap of familial Mediterranean fever and hyper-IgD syndrome in an Arabic kindred

Hyperimmunoglobulinemia D Syndrome (HIDS) has rarely been reported in Arabs. Moreover, the simultaneous presence of mutations in MEFV and MVK segregating in the same family is exceptional. We report an Arabic girl presenting since the age of 8-years with two patterns of recurrent episodes of fever, and associated with a spectrum of clinical features suggestive of overlap between familial Mediterranean fever (FMF) and HIDS. Her 19-year old brother presented since the age of 1 year with prolonged episodes of fever and was diagnosed with HIDS at the age of 7 years based on clinical features and homozygosity for p.V377I mutation in MVK. Shorter episodes of fever and abdominal pain more consistent with FMF ensued since the age of 17 years. Genetic testing done for both patients and all other family members revealed simultaneous presence of mutations in MEFV and MVK but with a variable clinical spectrum ranging from asymptomatic to severe manifestations. Both of our patients are homozygous for p.V377I MVK mutation; the girl is a compound heterozygote for p.E148Q/p.P369S/p.R408G and p.E167D/p.F479L MEFV mutations whereas the brother is a compound heterozygote for p.E148Q/p.P369S/p.R408G and p.M680I MEFV mutations. The clinical implications of having more than one mutation in different genes of monogenic autoinflammatory diseases in the same individual are not clear but may explain atypical clinical manifestations such as the overlap features of both FMF and HIDS in this family.

Clinical and genetic profile of children with periodic fever syndromes from a single medical center in South East Michigan

OBJECTIVE

To report a cohort of children with periodic fever syndromes (PFS) from Southeast Michigan.

METHODS

A retrospective review of medical records for patients referred for periodic fever over 5 years.

RESULTS

Sixty-six patients including 21 FMF, 15 PFAPA, four TRAPS and one patient with combined HIDS and FMF were included. In addition, 25 patients were categorized as clinical PFS (cPFS) based on their clinical features however their genetic workup was either negative or inconclusive. Majority of the patients with FMF were from Middle Eastern background (88 %), but positive family history was noted in only 55 % of cases. Mean age at diagnosis was 40.8 months with a mean delay in diagnosis of 24 months. Most common MEFV mutations were p.M694V and p.M694I. Four patients with TRAPS were from mixed European descent and age at onset of symptoms was 6, 12, 12, and 84 months respectively. TNFRSF1A sequence variants in the TRAPS patients included p.R121Q (R92Q) and p.C99G (C70G); one patient had a rare occurrence of a concurrent p.V726A/-MEFV mutation. One patient with HIDS and FMF presented with atypical overlapping PFS clinical manifestations and genetic evaluation showed a unique combination of p.I268T/p.V377I MVK mutations and p.E230K/-MEFV variant. All patients with PFAPA group were from mixed European descent, symptoms started at a mean age of 34.6 months with a mean delay in diagnosis of 23.3 months. Symptoms started during infancy in six patients. All patients fulfilled the diagnostic criteria for PFAPA. The mean age of onset of symptoms in cPFS group was 17.2 months. Empiric colchicine and glucocorticosteroids controlled flares in majority of patients with cPFS. No evidence of amyloidosis was found in this entire cohort of 66 patients after a mean of 29.2 months of follow-up.

CONCLUSION

PFS can present with atypical manifestations and should not be excluded based on a negative family history. Concomitant mutations in different autoinflammatory disorders genes can be present and possibly explain atypical manifestations. Various therapies may be considered even if genetic testing is inconclusive or negative.

Inborn errors of metabolism underlying primary immunodeficiencies

A number of inborn errors of metabolism (IEM) have been shown to result in predominantly immunologic phenotypes, manifesting in part as inborn errors of immunity. These phenotypes are mostly caused by defects that affect the (i) quality or quantity of essential structural building blocks (e.g., nucleic acids, and amino acids), (ii) cellular energy economy (e.g., glucose metabolism), (iii) post-translational protein modification (e.g., glycosylation) or (iv) mitochondrial function. Presenting as multisystemic defects, they also affect innate or adaptive immunity, or both, and display various types of immune dysregulation. Specific and potentially curative therapies are available for some of these diseases, whereas targeted treatments capable of inducing clinical remission are available for others. We will herein review the pathogenesis, diagnosis, and treatment of primary immunodeficiencies (PIDs) due to underlying metabolic disorders.

Overlap syndrome between Familial Mediterranean fever and tumor necrosis factor receptor-associated periodic syndrome in a lupus patient

Autoinflammatory diseases represent an expanding spectrum of genetic and non-genetic inflammatory diseases characterized by recurrent episodes of fever and systemic inflammation, affecting joints, skin and serosal surfaces. Familial Mediterranean fever (FMF) is the most common autosomal recessive hereditary autoinflammatory disease. Tumor necrosis factor receptor-associated periodic syndrome (TRAPS) is an autosomal dominant hereditary autoinflammatory disease. They share some clinical manifestations such as a periodic fever and skin rash. We present here the association of FMF with TRAPS in a systemic lupus erythematosus (SLE) patient. A 54-year-old SLE patient with recurrent attacks of fever, arthritis, and skin rashes was referred to our hospital. She had been diagnosed with lupus nephritis at 19 years old. Her lupus nephritis was controlled by steroid treatments; however, since childhood she has suffered from recurrent episodes of periodic fever, abdominal pain, arthritis, and erythematous skin rashes. An initial diagnosis of FMF was suspected based on the genetic analysis, showing the compound heterozygous L110P/E148Q mutations in the MEFV gene that is responsible for FMF. Her symptoms responded to colchicine, but the febrile attacks were not completely resolved. Therefore, genetic testing for TRAPS was performed. The results revealed a heterozygous T61I mutation in the TNFRSF1A gene that encodes tumor necrosis factor-α receptor and is responsible for TRAPS. The patient was diagnosed with overlapping FMF and TRAPS, in addition to SLE. This is the first report of SLE associated with both FMF and TRAPS.

Monogenic autoinflammatory diseases

During the past 15 years, a growing number of monogenic inflammatory diseases have been described and their respective responsible genes identified. The proteins encoded by these genes are involved in the regulatory pathways of inflammation and are mostly expressed in cells of the innate immune system. Diagnosis remains clinical, with genetic confirmation where feasible. Although a group of patients exhibit episodic systemic inflammation (periodic fevers), these disorders are mediated by continuous overproduction and release of pro-inflammatory mediators, such as IL-1 and IL-6, and TNF and are best considered as autoinflammatory diseases rather than periodic fevers. Treatment with biologic agents that block these cytokines, particularly IL-1, has proved to be dramatically effective in some patients. Still, in many cases of autoinflammation no genetic abnormalities are detected and treatment remains suboptimal, raising the question of novel pathogenic mutations in unexplored genes and pathways.

Systemic AA amyloidosis as a unique manifestation of a combined mutation of TNFRSF1A and MEFV genes

We report the case of a 22-year-old Caucasian woman presenting with a new-onset nephrotic syndrome with normal renal function during the 35th week of pregnancy. AA (secondary) amyloidosis was further diagnosed at the renal biopsy. Extensive genetic testing revealed that the patient was heterozygous for both TNFRSF1A p.R92Q and MEFV p.M694I mutations leading to an autoinflammatory syndrome characterized by amyloid deposition as the sole manifestation.

Autoinflammatory syndromes

There has been an expansion of the autoinflammatory syndromes due to the discovery of new diseases related to mutations in genes regulating the innate immune system and the knowledge gained from these diseases as applied to more common nongenetic inflammatory conditions. Autoinflammatory syndromes are characterized by unprovoked (or triggered by minor events) recurrent episodes of systemic inflammation involving various body systems, which are often accompanied by fever. Inflammation is mediated by polymorphonuclear and macrophage cells through cytokines, particularly interleukin-1. This article reviews the clinical approach to patients with suspected autoinflammatory syndromes, several of the main and new (mostly genetics) syndromes, advances in treatment, and prognosis.

Periodic Fever syndromes

The periodic syndromes represent a heterogeneous group of disorders that can be very difficult for practicing physicians to diagnosis and treat. This article presents an orderly approach to hyperimmunoglobulin D syndrome; tumor necrosis factor receptor-1 periodic syndrome; familial Mediterranean fever; periodic fever with aphthous stomatitis, pharyngitis, and adenitis syndrome; and cryopyrin-associated periodic syndromes by highlighting the disease presentation, diagnosis, pathogenesis, and treatment. Recent advances are also discussed.

Hyperimmunoglobulinemia D and periodic fever syndrome in children. Review on therapy with biological drugs and case report

Hyperimmunoglobulinemia D syndrome (HIDS) is a rare, autosomal recessively inherited autoinflammatory disease caused by mutations in the mevalonate kinase gene. HIDS usually starts in infancy with recurrent fever episodes lasting 3-7 days and recurring every 4-6 weeks, with only partial symptom decrease in adulthood. Fever is typically accompanied by abdominal pain, vomiting, diarrhoea and cervical lymphadenopathy, and sometimes by skin and joint symptoms. Blood leukocytes and serum C-reactive protein are elevated during the episode, and in addition, high levels of interleukine-1 (IL-1), IL-6 and tumour necrosis factor (TNF) and respective soluble receptors have been measured. Instead, serum immunoglobulin D (IgD) is usually normal until 3 years of age. Currently, there is no established treatment for HIDS. Thus far, four children have been successfully treated with etanercep, TNF-alpha inhibitor, and three children with anakinra, IL-1 receptor antagonist.

CONCLUSION

This review summarizes currently available data on the use biological medicines for HIDS in children. A Finnish 1.5-year-old patient with disease onset at 6 months of age, treated successfully with anakinra, is presented.

Autoinflammatory syndromes: diagnosis and management

During the last decades the description of autoinflammatory syndromes induced great interest among the scientific community. Mainly rheumatologists, immunologists and pediatricians are involved in the discovery of etiopathogenesis of these syndromes and in the recognition of affected patients. In this paper we will discuss the most important clues of monogenic and non-genetic inflammatory syndromes to help pediatricians in the diagnosis and treatment of these diseases.

Familial mediterranean Fever: a retrospective clinical and molecular study in the East of anatolia region of Turkey

Familial Mediterranean Fever (FMF) is an autoinflammatory periodic disorder. We aim to identify the distribution and the frequency of the Mediterranean Fever (MEFV) gene mutations in the east of Anatolia in Turkey and perform a genotype/phenotype correlation in the patients’ cohort. The study was carried out on 415 clinically diagnosed Turkish FMF patients and 103 healthy controls. The tested individuals were screened for the most common twelve MEFV mutations. The most important features were the predominance of the M694V and E148Q mutations in patient group and the earlier of onset of the disease in M694V mutation carriers compared with the carriers of other mutations (P=0.00). We discuss the high frequency of E148Q mutations in patient group compared with controls, genetic counseling in intermarriage families and the variations in mutation frequency according to regions of Turkey.

A novel Y331X nonsense mutation in TNFRSF1A gene in two unrelated Turkish families with periodic fever syndrome

The autoinflammatory disorders differ in severity, as well as age of onset, duration, and manifestations, but they all share some common features: recurring fever peaks, inflammation of serosal membranes, musculoskeletal involvement, varying types of skin rash, amyloidosis as a sequel of the disease. TRAPS is very rare in Turkish population and we present two unrelated Turkish children with similar clinical phenotypes and laboratory findings related with autoinflammatory disorders and with novel p. Y331X mutation in TNFRSF1A gene. Both of the patients were male and they had recurrent fever without abdominal pain and arthralgia. Full cDNA and exon-intron binding regions of TNFRSF1A, MEFV, MVK, CIAS1 genes were analysed by direct DNA sequencing methods in order to differentiate TRAPS, FMF, HIDS, CINCA/MWS/FCAS respectively. We screened ten exons of TNFRSF1A gene, and detected a heterozygous c.1080C>G nucleotide substitution in exon 10 in both of the unrelated patients, resulting p.Y360X nonsense (protein truncated) mutation. According to classical TNFRSF1A gene nomenclature and the agreement of 30th amino acid as the first one, it is accepted as p.Y331X. It was interesting to determine same mutations in fathers of two patients. In one of the cases, E148Q heterozygous mutation, which is one of the disease-causing mutations of MEFV gene, was detected. No nucleotide substitution was identified in exon and exon-intron splicing regions encoding 396 amino acid of MVK gene in both of the patients. In CIAS1 gene, two different nucleotide substitutions resulting synonymous amino acid mutation were detected in exon 3: c.[732G>A] and c.[786A>G] nucleotide substitutions and compatible p.A242A (according to c.DNA p.A244A) and p.R260R (according to c.DNA p.R262R) synonymous amino acid mutations. These nucleotide substitutions were also detected in parents and were reported to be normal variations in Turkish population. In conclusion, in Turkish patients, with dominantly inherited recurrent fever, TRAPS is a diagnosis worthy of attention and novel mutations have to be reported with phenotype associations.

Familial Mediterranean fever with a single MEFV mutation: where is the second hit?

OBJECTIVE

Familial Mediterranean fever (FMF) has traditionally been considered an autosomal-recessive disease; however, it has been observed that a substantial number of patients with clinical FMF possess only 1 demonstrable MEFV mutation. The purpose of this study was to perform an extensive search for a second MEFV mutation in 46 patients diagnosed clinically as having FMF and carrying only 1 high-penetrance FMF mutation.

METHODS

MEFV and other candidate genes were sequenced by standard capillary electrophoresis. In 10 patients, the entire 15-kb MEFV genomic region was resequenced using hybridization-based chip technology. MEFV gene expression levels were determined by quantitative reverse transcription-polymerase chain reaction. Pyrin protein levels were examined by Western blotting.

RESULTS

A second MEFV mutation was not identified in any of the patients who were screened. Haplotype analysis did not identify a common haplotype that might be associated with the transmission of a second FMF allele. Western blots did not demonstrate a significant difference in pyrin levels between patients with a single mutation and those with a double mutation; however, FMF patients of both types showed higher protein expression as compared with controls and with non-FMF patients with active inflammation. Screening of genes encoding pyrin-interacting proteins identified rare mutations in a small number of patients, suggesting the possibility of digenic inheritance.

CONCLUSION

Our data underscore the existence of a significant subset of FMF patients who are carriers of only 1 MEFV mutation and demonstrate that complete MEFV sequencing is not likely to yield a second mutation. Screening for the set of the most common mutations and detection of a single mutation appears to be sufficient in the presence of clinical symptoms for the diagnosis of FMF and the initiation of a trial of colchicine.

Web resources for rare auto-inflammatory diseases: towards a common patient registry

OBJECTIVES

To review information resources on rare auto-inflammatory disorders (AIDs) for use by health care professionals, focusing particularly on patient registries.

METHODS

Using relevant key words, we surveyed the websites of several scientific societies of immunology, paediatrics and rheumatology, as well as Pubmed and specialized databases for AIDs.

RESULTS

The Internet provides a wide variety of information related to AIDs. Moreover, several other initiatives have been undertaken to create new resources for professionals. We reviewed six patient registries for rare AIDs, taking a special interest in the submission questionnaire. We revealed a wide overlap between the items used in the questionnaires, whereas the currently available registries appeared inappropriate for AIDs patients with complex or undefined diagnosis.

CONCLUSIONS

AIDs share common clinical features, pathophysiological pathways and therapeutic approaches. Although several resources are now available for rare AIDs, a unique and dedicated site gathering all aspects of these diseases as a whole is still lacking, i.e. covering research as well as the needs of AIDs patients and health care professionals. Our study thus advocates a merging of existing patient registries or the creation of a common database.

Dysregulation of innate immunity: hereditary periodic fever syndromes

The hereditary periodic fever syndromes encompass a rare group of diseases that have lifelong recurrent episodes of inflammatory symptoms and an acute phase response in common. Clinical presentation can mimic that of lymphoproliferative disorders and patients often go undiagnosed for many years. These syndromes follow an autosomal inheritance pattern, and the major syndromes are linked to specific genes, most of which are involved in regulation of the innate immune response through pathways of apoptosis, nuclear factor kappaBeta activation and cytokine production. In others, the link between the protein involved and inflammation is less clear. The recurrent inflammation can lead to complications, such as renal impairment due to amyloidosis and vasculitis, visual impairment, hearing loss, and joint destruction, depending on the specific syndrome. In recent years, treatment options for these diseases have improved significantly. Early establishment of an accurate diagnosis and start of appropriate therapy improves prognosis in these patients.

A novel TNFRSF1A splice mutation associated with increased nuclear factor kappaB (NF-kappaB) transcription factor activation in patients with tumour necrosis factor receptor associated periodic syndrome (TRAPS)

OBJECTIVE

To characterise and investigate the functional consequences of a novel TNFRSF1A splice site mutation causing tumour necrosis factor receptor associated periodic syndrome (TRAPS) in a 16-year-old male patient and his mother.

METHODS

Mutational DNA screening was performed in the patient and his mother. Western blotting was used to analyse protein expression levels of TNFR1. A multiplex bead immunoassay was used to quantify serum levels of range of cytokines, and an ELISA-based transcription factor assay to measure nuclear factor (NF)-kappaB transactivation. Serum levels of soluble TNFR1 (sTNFR1) were measured by ELISA and fluorescence-activated cell sorting (FACS) analysis used to measure monocyte TNFR1 cell surface expression.

RESULTS

A novel mutation, c.472+1G>A (C158delinsYERSSPEAKPSPHPRG), involving a splice site in intron 4 of TNFRSF1A, was found in the proband and affected mother leading to a 45 nucleotide insertion of intronic DNA into the mRNA, resulting in an in-frame insertion of 15 amino acids in the mature TNFR1 protein and a deletion of a cysteine residue C129 (158) in cysteine rich domain (CRD)3. The patients had reduced serum sTNFR1 and surface expression levels of TNFR1, with marked increases in pro- and anti-inflammatory cytokine. Their peripheral blood mononuclear cells (PBMC) had increased basal NF-kappaB activation compared with healthy controls and also had increased p50 nuclear expression following tumour necrosis factor (TNF) stimulation compared with PBMC from healthy controls, as well as T50M (T79M) and C88R (C117R) patients with TRAPS and patients with rheumatoid arthritis (RA).

CONCLUSION

A novel, TRAPS causing, TNFRSF1A splice site mutation is associated with decreased sTNFR1 levels, cell surface and whole cell extract expression and increased NF-kappaB transcription factor activation.

Long-term follow-up, clinical features, and quality of life in a series of 103 patients with hyperimmunoglobulinemia D syndrome

The hyperimmunoglobulinemia D and periodic fever syndrome (HIDS), one of the autoinflammatory syndromes, is caused by mutations in the gene coding for mevalonate kinase (MVK). We conducted the current study to assess the genetic, laboratory, and clinical features as well as the complications and course of disease in patients with genetically confirmed HIDS. In addition, we studied the quality of life and course of life in a selection of patients. Follow-up data were obtained by a questionnaire sent to all physicians of patients in the International HIDS Database. In addition, we assessed the course of life and quality of life in Dutch patients aged >16 years using validated quality of life instruments. Data were obtained from 103 patients from 18 different countries. The median age of first attack was 6 months (range, 0-120 mo), with a median period of 9.9 years from onset of disease to diagnosis. The most frequent symptoms that accompanied attacks of fever were lymphadenopathy, abdominal pain, arthralgia, diarrhea, vomiting, skin lesions, and aphthous ulcers. Amyloidosis was a severe but infrequent complication (2.9%). The median serum IgD level was 400 U/mL. IgD levels were normal in 22% of patients. The 4 most prevalent mutations (V377I, I268T, H20P/N, P167L) accounted for 71.5% of mutations found. The frequency of attacks decreased with the patient's increasing age, although 50% of patients over the age of 20 years still had 6 or more attacks per year. Many drugs have been tried in HIDS. Some patients responded to high-dose prednisone (24.4% response). Anakinra and etanercept can also be effective (33.3% response). Quality of life was determined in a subgroup of patients (n = 28). Social functioning, general health perception, and vitality were significantly lower in patients with HIDS than in controls, as were autonomy and social development. In addition, HIDS had an adverse impact on educational achievements and employment status. In conclusion, HIDS is an early-onset disease that is accompanied by an array of inflammatory symptoms. Although the frequency of attacks decreases during the patient's life, many patients continue to have frequent attacks. HIDS impairs several aspects of quality of life.

Hyperimmunoglobulinemia D and periodic fever syndrome; treatment with etanercept and follow-up

The hyperimmunoglobulinemia D and periodic fever syndrome (HIDS) is an autoinflammatory syndrome. It is caused by the mutations of the mevalonate kinase gene. There is no consensus for specific therapy of HIDS, but there are some case reports and studies in regards to its treatment with drugs like colchicine, steroids, nonsteroid anti-inflammatory drugs, simvastatin, anakinra, thalidomide, and etanercept. We are reporting a case evaluated for the complaints of abdominal pain and febrile episodes with massive hepatomegaly, not common finding on physical examination, its treatment with etanercept, and long-term follow-up.

Abnormal tumor necrosis factor receptor I cell surface expression and NF-kappaB activation in tumor necrosis factor receptor-associated periodic syndrome

OBJECTIVE

Tumor necrosis factor receptor-associated periodic syndrome (TRAPS) is an autosomal-dominant autoinflammatory condition caused by mutations in the TNFRSF1A gene. The cellular mechanisms by which mutations in this gene trigger inflammation are currently unclear. Because NF-kappaB is the major intracellular signaling component inducing secretion of proinflammatory cytokines, we sought to determine whether differences in the clinical phenotype of patients with TRAPS may be attributable to variable effects of TNFRSF1A mutations on TNFRI expression, localization, or NF-kappaB activity.

METHODS

Peripheral blood mononuclear cells were obtained from patients (following informed consent), and cellular nuclear and cytosolic fractions were generated by subcellular fractionation. Localization of IkappaBalpha and NF-kappaB was determined by Western blotting of the resultant fractions. NF-kappaB subunit activity was determined by enzyme-linked immunosorbent assay analysis and confirmed by electrophoretic mobility shift assay. Subcellular localization of TNFRI was determined by immunofluorescence confocal microscopy or by immunoblotting following affinity isolation of plasma membrane by subcellular fractionation.

RESULTS

Cells from patients with the fully penetrant C73R mutation had marked activation of the proinflammatory p65 subunit of NF-kappaB. In contrast, cells from patients with the low-penetrant R92Q mutation displayed high levels of DNA binding by the p50 subunit, an interaction previously linked to repression of inflammation. Interestingly, although cells from patients with the C73R mutation have no TNFRI shedding defect, there was nonetheless an unusually high concentration of functional TNFRI at the plasma membrane.

CONCLUSION

High levels of TNFRI at the cell surface in patients with the C73R mutation hypersensitizes cells to stimulation by TNF, leading to increased NF-kappaB p65 subunit activation and an exaggerated proinflammatory response.

Mevalonate pathway: a review of clinical and therapeutical implications

Mevalonate pathway is an important metabolic pathway which plays a key role in multiple cellular processes by synthesizing sterol isoprenoids, such as cholesterol, and non-sterol isoprenoids, such as dolichol, heme-A, isopentenyl tRNA and ubiquinone. While extensively studied in regard with cholesterol synthesis and its implications in cardiovascular diseases, in recent years the mevalonate pathway has become a challenging and, in the meantime, fascinating topic, when a large number of experimental and clinical studies suggested that inhibition of non-sterol isoprenoids might have valuable interest in human pathology. These molecules that are essential for cell growth and differentiation appear to be potential interesting therapeutic targets for many areas of ongoing research: oncology, autoimmune disorders, atherosclerosis, and Alzheimer disease. Also, considerable progress has been made in the past decade in understanding the pathophysiology of two auto-inflammatory disorders resulting from an inherited deficiency of mevalonate kinase, the first committed enzyme of the mevalonate pathway. Here we present a brief description of the biochemistry of the mevalonate pathway, together with a review of the current knowledge of the clinical and therapeutical implications of this fascinating and complex metabolic pathway.

A patient with hyper-IgD syndrome responding to anti-TNF treatment

The hyperimmunoglobulinemia D periodic fever syndrome (HIDS) is caused by recessive mutations in the mevalonate kinase gene, which encodes an enzyme involved in cholesterol and nonsterol isoprenoid biosynthesis. The pathogenesis and treatment remains unclear. We describe a 6-year-old Turkish girl with severe disease. Her clinical features were accompanied with very high acute-phase reactants including a very high serum amyloid A level. The patient responded well to anti-tumor necrosis factor treatment. Our findings support the use of this anti-cytokine treatment in HIDS.

Is IL-1 a good therapeutic target in the treatment of arthritis?

Inflammation is an important homeostatic mechanism that limits the effects of infectious agents. However, inflammation might be self-damaging and therefore has to be tightly controlled or even abolished by the organism. Interleukin 1 (IL-1) is a crucial mediator of the inflammatory response, playing an important part in the body's natural responses and the development of pathological conditions leading to chronic inflammation. While IL-1 production may be decreased or its effects limited by so-called anti-inflammatory cytokines, in vitro IL-1 inflammatory effects are inhibited and can be abolished by one particularly powerful inhibitor, IL-1 receptor antagonist (IL-1Ra). Recent research has shown that in the processes of rheumatoid arthritis (RA) IL-1 is one of the pivotal cytokines in initiating disease, and IL-1Ra has been shown conclusively to block its effects. In laboratory and animal studies the inhibition of IL-1 by either antibodies to IL-1 or IL-1Ra proved beneficial to the outcome. Because of its beneficial effects in many animal disease models, IL-1Ra has been used as a therapeutic agent in human patients. The recombinant form of IL-1Ra, anakinra (Kineret, Amgen) failed to show beneficial effects in septic shock and displays weak effects in RA patients. However, IL-1 blockade by anakinra is dramatically effective in systemic-onset juvenile idiopathic arthritis, in adult Still's disease and in several autoinflammatory disorders, most of the latter being caused by mutations of proteins controlling IL-1beta secretion. Importantly, to be efficacious, anakinra required daily injections, suggesting that administered IL-1Ra displays very short-term effects. Better IL-1 antagonists are in the process of being developed.

Hereditary auto-inflammatory disorders and biologics

The term auto-inflammatory disorders has been coined to describe a group of conditions characterized by spontaneously relapsing and remitting bouts of systemic inflammation without apparent involvement of antigen-specific T cells or significant production of auto-antibodies. The hereditary periodic fever syndromes are considered as the prototypic auto-inflammatory diseases, and genetic studies have yielded important new insights into innate immunity. DNA analysis has greatly enhanced the clinical characterization of these conditions, and elucidation of their molecular aetiopathogenesis has suggested that therapies may be aimed at specific targets within the immune cascade. The availability of biologic response modifiers such as inhibitors of tumour necrosis factor (TNF) and interleukin-1beta has greatly improved the outlook for some of these disorders, although effective therapies remain elusive in patients with certain conditions, including hyperimmunoglobulinaemia-D with periodic fever syndrome (HIDS) and a proportion of those with TNF-receptor associated periodic syndrome (TRAPS). Indeed, outstanding challenges and the unique potential to further elucidate molecular mechanisms in innate immunity are illustrated by the dashed early hope that TNF blockade would be a panacea for TRAPS: not only is etanercept (Enbrel) ineffective in some cases, but there are anecdotal reports of this condition being greatly exacerbated by infliximab (Remicade).

Manipulation of isoprenoid biosynthesis as a possible therapeutic option in mevalonate kinase deficiency

OBJECTIVE

In cells from patients with the autoinflammatory disorder mevalonate kinase (MK) deficiency, which includes the hyperimmunoglobulin D with periodic fever syndrome, MK becomes the rate-limiting enzyme in the isoprenoid biosynthesis pathway. This suggests that up-regulation of residual MK activity in these patients could be a way in which to prevent or alleviate the associated symptoms. We studied the effect of 2 specific inhibitors of isoprenoid biosynthetic enzymes on the residual activity of MK in cells from patients with MK deficiency.

METHODS

Skin fibroblasts from MK-deficient patients and from controls were cultured for 7 days with either simvastatin, an inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A reductase, or zaragozic acid A, an inhibitor of squalene synthase. Following culture, MK activity, MK protein levels, MVK messenger RNA levels, and the effect on the pathway flux toward non-sterol isoprenoid biosynthesis were determined.

RESULTS

Treatment of the fibroblasts with either of the inhibitors led to a marked increase in residual MK enzyme activity, which was largely attributable to increased MVK gene transcription. This effect was even more pronounced when the cells were cultured in lipoprotein-depleted medium. The flux toward nonsterol isoprenoid end-product synthesis was reduced when cells were treated with simvastatin but was partly restored by concomitant treatment with zaragozic acid A.

CONCLUSION

Our results indicate that manipulations of the isoprenoid biosynthesis pathway that promote the synthesis of nonsterol isoprenoids may provide an interesting therapeutic option for the treatment of MK deficiency.

Mutational spectrum and genotype–phenotype correlations in mevalonate kinase deficiency

Mevalonate kinase deficiency (MKD) is an autosomal recessive autoinflammatory disorder caused by mutations in the MVK gene resulting in deficient activity of mevalonate kinase (MK). Depending on the clinical severity, MKD may present as hyper-IgD and periodic fever syndrome (HIDS) or the more severe mevalonic aciduria (MA). We analyzed the MVK gene in 57 patients with MKD and found 39 different mutations including 15 novel mutations, expanding the total mutational spectrum of MKD to 63 mutations. To get more insight into the genotype-phenotype correlation in MKD, we studied the effect of selected missense mutations on MK protein stability and activity in various patient fibroblast cell lines. All MKD cell lines showed markedly decreased MK activities that correlated well with the clinical severity and, for most of the cell lines, with the amount of MK protein. When fibroblasts of MKD patients were cultured under conditions known to promote a more controlled protein folding, all cell lines of patients with the HIDS phenotype and few cell lines of patients with the MA phenotype showed an increase in the residual MK activity. This increase in enzyme activity correlates well with an increase in the MK protein levels in these cell lines, indicating that most of the mutations in MKD affect stability and/or folding of the MK protein rather than affecting the catalytic properties of the enzyme. The finding that the residual activity in MKD can be manipulated by environmental conditions may offer therapeutic options to alleviate or prevent the clinical symptoms associated with MKD.

Neutrophils from patients withTNFRSF1A mutations display resistance to tumor necrosis factor–induced apoptosis: Pathogenetic and clinical implications

OBJECTIVE

To explore tumor necrosis factor (TNF)-induced apoptosis in neutrophils from patients with TNF receptor-associated periodic syndrome (TRAPS) and to correlate the results with the different kinds of TNFRSF1A mutations.

METHODS

Two hundred sixty-five patients with clinically suspected inherited autoinflammatory syndrome were screened for mutations of the TNFRSF1A gene. Neutrophils were isolated from heparinized blood by dextran sedimentation and incubated with and without cycloheximide (CHX) and TNFalpha. Cell apoptosis was assessed by human annexin V binding, and caspase 8 activation was assessed by flow cytometry.

RESULTS

Twenty-one patients were found to carry a variant of the TNFRSF1A gene: 13 patients had an R92Q substitution, and 8 patients presented other missense substitutions, 1 splicing mutation, and 1 in-frame interstitial deletion. Neutrophil stimulation with TNF and CHX was associated with induction of apoptosis in 12 normal controls and in 10 subjects with the R92Q mutation. Conversely, neutrophils from 8 TRAPS patients with mutations of cysteine or threonine residues or interstitial deletion did not show any induction of apoptosis after stimulation. The incidence of the R92Q mutation among patients with recurrent autoinflammatory syndromes was similar to that observed in the normal population.

CONCLUSION

Resistance to TNF-mediated apoptosis is a feature in TRAPS patients who have mutations of cysteine residues or interstitial deletion, and may play a pathogenic role. The R92Q mutation does not appear to be significantly associated with TRAPS.

Approach to genetic analysis in the diagnosis of hereditary autoinflammatory syndromes

OBJECTIVE

Hereditary autoinflammatory syndromes are characterized by recurrent episodes of fever and inflammation. Seven subtypes have been described, caused by mutations in four different genes. Apart from a common phenotype of lifelong recurrent inflammatory attacks, all subtypes have distinct features and specific therapeutic options, which emphasizes the need for a specific diagnosis in each case. Our aim was to examine whether genetic screening would allow classification of previously unclassified patients, and whether individual patients suffering from an autoinflammatory syndrome carry additional mutations in one of the other autoinflammatory genes.

METHODS

We included 60 patients with an unclassified autoinflammatory syndrome, 87 patients diagnosed with either hyper-IgD syndrome, familial Mediterranean fever (FMF) or tumour necrosis factor (TNF)-receptor-associated periodic syndrome and 50 healthy controls. Deoxyribonucleic acid samples were screened for the most prevalent mutations in the MEFV, TNFRSF1A, MVK and CIAS1 genes.

RESULTS

We found only one possible diagnosis of FMF in the 60 previously unclassified patients. Two low-penetrance mutations were found in equal numbers in the groups of patients and controls.

CONCLUSIONS

Screening of highly prevalent mutations in known genes involved in these disorders does not yield additional relevant information. Differential diagnosis of hereditary autoinflammatory syndromes can be made by thorough clinical examination followed by targeted genetic analysis of the one or two most likely syndromes. High-prevalence low-penetrant mutations from autoinflammatory genes do not occur more frequently in patients with hereditary autoinflammatory syndromes compared with the general population.

Familial autoinflammatory diseases: genetics, pathogenesis and treatment

PURPOSE OF REVIEW

The systemic autoinflammatory diseases are characterized by seemingly unprovoked inflammation, without major involvement of the adaptive immune system. This review focuses mainly on a subset of these illnesses, the hereditary recurrent fevers, which include familial Mediterranean fever, the tumor necrosis factor receptor-associated periodic syndrome, the hyperimmunoglobulinemia D with periodic fever syndrome, and cryopyrin-associated periodic syndromes. This review elucidates how recent advances have impacted diagnosis, pathogenesis, and treatment.

RECENT FINDINGS

More than 170 mutations have been identified in the four genes underlying the six hereditary recurrent fevers. Genetic testing has broadened the clinical and geographic boundaries of these illnesses, given rise to the concept of the cryopyrin-associated periodic syndromes as a disease spectrum, and permitted diagnosis of compound heterozygotes for mutations in two different hereditary recurrent fever genes. Genetics has also advanced our understanding of amyloidosis, a complication of the hereditary recurrent fevers, and suggested a possible role for common hereditary recurrent fever variants in other inflammatory conditions. Recent advances in molecular pathophysiology include the elucidation of the N-terminal PYRIN domain in protein-protein interactions, the description of the NALP3 (cryopyrin) inflammasome as a macromolecular complex for interleukin-1beta activation, and the identification of signaling defects other than defective receptor shedding in patients with tumor necrosis factor receptor-associated periodic syndrome. These molecular insights form the conceptual basis for targeted biologic therapies.

SUMMARY

Advances in molecular genetics extend our ability to recognize and treat patients with systemic autoinflammatory diseases and inform our understanding of the regulation of innate immunity in humans.

Unexpected high frequency of P46L TNFRSF1A allele in sub-Saharan West African populations

TNF receptor-associated periodic syndrome (TRAPS) is an autosomal dominant disorder characterized by recurrent attacks of fever and serositis. To date, more than 30 mutations have been reported in TNFRSF1A, the responsible gene. In Caucasian populations, the P46L (c.224C>T) TNFRSF1A sequence variation is considered as a low-penetrance mutation because its allele frequency is similar in patients and controls ( approximately 1%). Whereas the spectrum of TNFRSF1A gene mutations has been well established in Caucasian and several Mediterranean populations, it remains unknown in sub-Saharan African populations. In this study, we found an unexpected high P46L allele frequency ( approximately 10%) in two groups from West Africa - a group of 145 patients with sickle cell anaemia and a group of 349 healthy controls. These data suggest that the P46L variant is rather a polymorphism than a TRAPS causative mutation. We propose that the P46L high frequency in West African populations could be explained by some biological advantage conferred to carriers.

Identification of a novel mevalonate kinase gene mutation in combination with the common MVK V377I substitution and the low-penetrance TNFRSF1A R92Q mutation

The hyperimmunoglobulinemia D and periodic fever syndrome (HIDS) is an autosomal recessively inherited autoinflammatory disease caused by mutations in the mevalonate kinase (MVK) gene on chromosome 12q24, which lead to a depressed enzymatic activity of mevalonate kinase (MK). TNF-receptor associated periodic syndrome (TRAPS), on the other hand, is the most frequent autosomal dominantly inherited periodic fever syndrome due to mutations in exons 2-4 and 6 of the TNFRSF1A gene on chromosome 12p13.2. We describe a girl with heterozygosity for the common MVK V377I mutation and for a novel T(1132) --> C transition, leading to the exchange of serine (TCC) by proline (CCC) at amino-acid position 378. Interestingly, our patient presented only with mild clinical features typical of HIDS and slightly increased immunoglobulin D levels, but a distinctly diminished MK activity. The girl was also heterozygous for the TNFRSF1A R92Q low-penetrance mutation, which may have significant proinflammatory effects. However, at the time of presentation, the patient had no TRAPS-associated symptoms.

Tumor necrosis factor receptor-associated periodic syndrome (TRAPS): definition, semiology, prognosis, pathogenesis, treatment, and place relative to other periodic joint diseases

Tumor necrosis factor receptor-associated periodic syndrome (TRAPS) is an autosomal dominant inherited condition of periodic fever and pain. Most patients are of northern European descent. The attacks manifest as fever and pain in the joints, abdomen, muscles, skin, or eyes, with variations across patients. An acute-phase response occurs during the attacks. Patients with TRAPS are at risk for AA amyloidosis, the most common targets being the kidneys and liver. Soluble TNFRSF1A is usually low between the attacks and may be normal during the attacks, when TNF levels are high. TNFRSF1A is found in abnormally high numbers on leukocyte cell membranes. TRAPS is the first condition for which naturally occurring mutations in a TNF receptor were found; the mutations affect the soluble TNFRSF1A gene in the 12p13 region. In some patients, the pathogenesis involves defective TNFRSF1A shedding from cell membranes in response to a given stimulus. Thus, TRAPS is a model for a novel pathogenic concept characterized by failure to shed a cytokine receptor. This review compares TRAPS to other inherited periodic febrile conditions, namely, familial Mediterranean fever, Muckle-Wells syndrome, cold urticaria, and hyper-IgD syndrome. The place of TRAPS relative to other intermittent systemic joint diseases is discussed. Colchicine neither relieves nor prevents the attacks, whereas oral glucocorticoid therapy is effective when used in dosages greater than 20 mg/day. The pathogenic hypothesis involving defective TNFRSF1A shedding suggests that medications targeting TNF may be effective in TRAPS.

The genetic background of tumour necrosis factor receptor-associated periodic syndrome and other systemic autoinflammatory disorders

Systemic autoinflammatory disorders are hereditary diseases with symptoms of acute inflammation and a rise in serum acute phase proteins as a consequence, but with no signs of autoimmunity. By the end of the 1990s, four types of hereditary periodic fever had been described in the medical literature: familial Mediterranean fever, hyperimmunoglobulinemia D with periodic fever syndrome (HIDS), tumour necrosis factor receptor-associated periodic fever syndrome (TRAPS) and Muckle-Wells syndrome. Since then, the number of diseases classified as systemic autoinflammatory disorders has increased to eight. In patients of Nordic descent, cases of HIDS and TRAPS have been reported. We provide an overview of the genetic background and main clinical aspects of the different autoinflammatory disorders, with an emphasis on TRAPS.

Molecular analysis of the MVK and TNFRSF1A genes in patients with a clinical presentation typical of the hyperimmunoglobulinemia D with periodic fever syndrome: A low-penetrance TNFRSF1A variant in a heterozygous MVK carrier possibly influences the phenot

OBJECTIVE

To describe biochemical findings and the spectrum of mevalonate kinase (MVK) gene mutations as well as an associated TNFRSF1A low-penetrance variant in a series of patients with clinical features of the hyperimmunoglobulinemia D with periodic fever syndrome (HIDS).

METHODS

The MVK gene was sequenced in 8 children and 1 adult (including 2 siblings) fulfilling the clinical criteria for HIDS. In addition, sequencing of exons 2, 3, 4, and 6 of the TNFRSF1A gene was performed in patients with only one or no MVK mutation. Mevalonate kinase (MK) enzyme activity in leukocytes and renal excretion of mevalonic acid were also measured.

RESULTS

Mutations in the coding region of the MVK gene were detected in 6 patients, and the most common mutation was V377I. Among these patients were 2 novel mutations, both of which were located in exon 6. These novel mutations resulted in the substitution of tryptophan (TGG) by a stop codon (TGA) at amino acid position 188 (W188X) and in the exchange of valine (GTG) for alanine (GCG) at amino acid position 203 (V203A). In 1 patient, a combination of one MVK (V377I) mutation and one TNFRSF1A (R92Q) mutation was present. The patient's clinical phenotype resembled a mixture of variant-type HIDS and tumor necrosis factor receptor-associated periodic syndrome (TRAPS). Her IgD values varied between normal and slightly increased, and the MK activity was in the low-normal range, while urinary mevalonate concentrations were always normal.

CONCLUSION

The genotype findings indicate that a relatively small number of genes may be involved in the clinical manifestation of HIDS, with low-penetrance TNFRSF1A variants possibly influencing the HIDS phenotype or MVK mutations contributing to TRAPS.

Identifying Mutations in Autoinflammatory Diseases

Autoinflammatory diseases are defined as illnesses caused by primary dysfunction of the innate immune system. This new concept includes a broad number of disorders, but the spotlight has been focused for the past two years on periodic fevers (familial Mediterranean fever [FMF]; mevalonate kinase deficiency [MVK]; tumor necrosis factor [TNF] receptor-associated periodic syndrome [TRAPS]; cryopyrin-associated periodic syndrome [CAPS]), Crohn's disease and Blau syndrome, thanks to the recent understanding of their molecular basis. Indeed, until recently, these conditions were defined only by phenotypical features, the main ones being recurrent attacks of fever, abdominal pain, arthritis, and cutaneous signs, which sometimes overlap, obscuring diagnosis. The search for distinguishing signs such as periorbital edema in TRAPS, and the use of specific functional tests where available, are valuable. Needless to say, molecular screening of the causative genes has dramatically improved patient quality-of-life by providing early and accurate diagnosis, subsequently allowing for the appropriate treatment. Some patients, however, remain hard to manage despite the advent of new genetic tests, and/or due to the lack of effective treatment. The original clinical link between the aforementioned diseases can now be confirmed by a molecular one, following the exciting discovery that most of the altered proteins are related to the death domain fold (DDF) superfamily involved in inflammation and apoptosis. These molecules mediate the regulation of nuclear factor-kappa B (NF-kappa B) activation, cell apoptosis, and interleukin-1 beta secretion through cross-regulated and, sometimes, common signaling pathways. Knowledge of the defective step in autoinflammation has already led to the elucidation of the mechanisms of action of existing drugs and may allow the development of new therapies.

Favorable preliminary experience with etanercept in two patients with the hyperimmunoglobulinemia D and periodic fever syndrome

OBJECTIVE

The hyperimmunoglobulinemia D and periodic fever syndrome (HIDS; MIM 260920) is caused by recessive mutations in the mevalonate kinase gene (MVK), which encodes an enzyme involved in cholesterol and nonsterol isoprenoid biosynthesis. HIDS is characterized by persistently elevated polyclonal IgD and recurrent febrile episodes. Although abnormalities in tumor necrosis factor alpha (TNF alpha) are not the primary cause of HIDS, plasma TNF alpha levels are elevated in HIDS patients during attacks and thus may be a therapeutic target. This study assessed the effects of etanercept, a soluble p75 TNF alpha receptor-Fc fusion protein, in 2 patients with HIDS.

METHODS

We performed biochemical and molecular genetic analyses on 2 girls with periodic episodes of fever, skin rash, abdominal pain, and arthralgia, of whom 1 had elevated levels of serum IgD. After the diagnosis of HIDS was made, treatment with etanercept was initiated in both patients. Clinical response was recorded in a standardized diary, and serum levels of cytokines and their decoy receptors were serially measured in 1 of the 2 patients.

RESULTS

Urinary mevalonate levels were elevated in both girls. Patient 1 was heterozygous for a known MVK missense mutation (V377I) and a novel mutation that led to skipping of exon 3. Patient 2 was found to have V377I and a new missense mutation, S329R. Neither patient had mutations in TNFRSF1A or MEFV, the genes for the TNF receptor-associated periodic syndrome and familial Mediterranean fever, respectively. Etanercept reduced the frequency and severity of symptoms in both patients, whereas the levels of serum IgD and urine mevalonate remained unchanged.

CONCLUSION

Our favorable experience with etanercept for the treatment of HIDS suggests that further investigation of this therapy is warranted.

Heterogeneity among patients with tumor necrosis factor receptor-associated periodic syndrome phenotypes

OBJECTIVE

To investigate the prevalence of tumor necrosis factor receptor-associated periodic syndrome (TRAPS) among outpatients presenting with recurrent fevers and clinical features consistent with TRAPS.

METHODS

Mutational screening was performed in affected members of 18 families in which multiple members had symptoms compatible with TRAPS and in 176 consecutive subjects with sporadic (nonfamilial) "TRAPS-like" symptoms. Plasma concentrations of soluble tumor necrosis factor receptor superfamily 1A (sTNFRSF1A) were measured, and fluorescence-activated cell sorter analysis was used to measure TNFRSF1A shedding from monocytes.

RESULTS

Eight novel and 3 previously reported TNFRSF1A missense mutations were identified, including an amino acid deletion (Delta D42) in a Northern Irish family and a C70S mutation in a Japanese family, both reported for the first time. Only 3 TNFRSF1A variants were found in patients with sporadic TRAPS (4 of 176 patients). Evidence for nonallelic heterogeneity in TRAPS-like conditions was found: 3 members of the "prototype familial Hibernian fever" family did not possess C33Y, present in 9 other affected members. Plasma sTNFRSF1A levels were low in TRAPS patients in whom renal amyloidosis had not developed, but also in mutation-negative symptomatic subjects in 4 families, and in 14 patients (8%) with sporadic TRAPS. Reduced shedding of TNFRSF1A from monocytes was demonstrated in vitro in patients with the T50M and T50K variants, but not in those with other variants.

CONCLUSION

The presence of TNFRSF1A shedding defects and low sTNFRSF1A levels in 3 families without a TNFRSF1A mutation indicates that the genetic basis among patients with "TRAPS-like" features is heterogeneous. TNFRSF1A mutations are not commonly associated with nonfamilial recurrent fevers of unknown etiology.