Mutations in MVK, encoding mevalonate kinase, cause hyperimmunoglobulinaemia D and periodic fever syndrome

Autoinflammatory diseases

Autoinflammatory diseases (AIDs) are illnesses caused by primary dysfunction of the innate immune system. Proteins that are mutated in AIDs mediate the regulation of NFkappaB activation, cell apoptosis, and IL-1beta secretion through cross-regulated and sometimes common signaling pathways. AIDs include a broad number of monogenic [e.g., familial Mediterranean fever (FMF), cryopyrin-associated periodic syndrome (CAPS), mevalonate kinase deficiency (MKD), tumor necrosis factor (TNF)-receptor-associated periodic syndrome (TRAPS)] and multifactorial (e.g., Behçet's syndrome) disorders. These conditions are characterized by recurrent attacks of fever, abdominal pain, arthritis, and cutaneous signs; these symptoms sometimes overlap, obscuring diagnosis. Distinguishing signs and the use of specific functional tests where available (e.g., in MKD) are helpful. However, some patients remain hard to manage despite the advent of new genetic tests and/or due to lack of effective treatment.

Horror autoinflammaticus: the molecular pathophysiology of autoinflammatory disease (*)

The autoinflammatory diseases are characterized by seemingly unprovoked episodes of inflammation, without high-titer autoantibodies or antigen-specific T cells. The concept was proposed ten years ago with the identification of the genes underlying hereditary periodic fever syndromes. This nosology has taken root because of the dramatic advances in our knowledge of the genetic basis of both mendelian and complex autoinflammatory diseases, and with the recognition that these illnesses derive from genetic variants of the innate immune system. Herein we propose an updated classification scheme based on the molecular insights garnered over the past decade, supplanting a clinical classification that has served well but is opaque to the genetic, immunologic, and therapeutic interrelationships now before us. We define six categories of autoinflammatory disease: IL-1beta activation disorders (inflammasomopathies), NF-kappaB activation syndromes, protein misfolding disorders, complement regulatory diseases, disturbances in cytokine signaling, and macrophage activation syndromes. A system based on molecular pathophysiology will bring greater clarity to our discourse while catalyzing new hypotheses both at the bench and at the bedside.

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.

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.

HMG-CoA reductase inhibition induces IL-1beta release through Rac1/PI3K/PKB-dependent caspase-1 activation

Mevalonate kinase deficiency (MKD) is an autoinflammatory disorder characterized by recurring fever episodes and results from disturbed isoprenoid biosynthesis. Lipopolysaccharide-stimulated peripheral blood mononuclear cells from MKD patients secrete high levels of interleukin-1beta (IL-1beta) because of the presence of hyperactive caspase-1, and this has been proposed to be the primary cause of recurring inflammation. Here we show that inhibition of HMG-CoA reductase by simvastatin treatment, mimicking MKD, results in increased IL-1beta secretion in a Rac1/PI3K-dependent manner. Simvastatin treatment was found to activate protein kinase B (PKB)/c-akt, a primary effector of PI3K, and ectopic expression of constitutively active PKB was sufficient to induce IL-1beta release. The small GTPase Rac1 was activated by simvastatin, and this was required for both PKB activation and IL-1beta secretion. IL-1beta release is mediated by caspase-1, and simvastatin treatment resulted in increased caspase-1 activity in a Rac1/PI3K-dependent manner. These data suggest that, in MKD, dysregulated isoprenoid biosynthesis activates Rac1/PI3K/PKB, resulting in caspase-1 activation with increased IL-1beta release. Importantly, inhibition of Rac1 in peripheral blood mononuclear cells isolated from MKD patients resulted in a dramatic reduction in IL-1beta release. These data suggest that pharmacologic inhibition of Rac1 could provide a novel therapeutic strategy for treatment of MKD.

The spectrum of monogenic autoinflammatory syndromes: understanding disease mechanisms and use of targeted therapies

Monogenic autoinflammatory diseases encompass a distinct and growing clinical entity of multisystem inflammatory diseases with known genetic defects in the innate immune system. The diseases present clinically with episodes of seemingly unprovoked inflammation (fever, rashes, and elevation of acute phase reactants). Understanding the genetics has led to discovery of new molecules involved in recognizing exogenous and endogenous danger signals, and the inflammatory response to these stimuli. These advances have furthered understanding of innate inflammatory pathways and spurred collaborative research in rheumatology and infectious diseases. The pivotal roles of interleukin (IL)-1beta in cryopyrin-associated periodic syndromes, tumor necrosis factor (TNF) in TNF receptor-associated periodic syndrome, and links to inflammatory cytokine dysregulation in other monogenic autoinflammatory diseases have resulted in effective therapies targeting proinflammatory cytokines IL-1beta and TNF and uncovered other new potential targets for anti-inflammatory therapies.

Diagnosis and management of autoinflammatory diseases in childhood

INTRODUCTION

Autoinflammatory diseases are a group monogenic inflammatory conditions characterized by an early onset during childhood.

DISCUSSION

Under the term "periodic fevers" are gathered some monogenic diseases (familial Mediterranean fever, mevalonate kinase deficiency, and tumor necrosis factor receptor-associated syndrome) characterized by periodic or recurrent episodes of systemic inflammation causing fever often associated with rash, serositis (peritonitis, pleuritis), lymphadenopathy, arthritis, and other clinical manifestations. Systemic reactive (AA) amyloidosis may be a severe long-term complication. Cryopyrinopathies are a group of conditions associated to mutations of the gene Cryopyrin that are responsible for a spectrum of diseases (familial cold autoinflammatory syndrome, Muckle-Wells syndrome, and chronic infantile neurological cutaneous and articular syndrome) characterized by a chronic or recurrent systemic inflammation variably associated with a number of clinical features, such as urticarial-like rash, arthritis, sensorineural deafness, and central nervous system and bone involvement. Other disorders are dominated by the presence of sterile pyogen abscesses prevalently affecting the skin, joints, and bones (pyogenic disorders). These include pyogenic sterile arthritis, pyoderma gangrenosum, and acne syndrome, and Majeed syndrome. Finally, some diseases, such as Blau's syndrome, are characterized by the appearance of typical noncaseating granulomatous inflammation affecting the joints, skin, and uveal tract (granulomatous disorders). In the present review, we will focus on the clinical presentation of these disorders in childhood and report on the available therapeutic strategies.

Biochemical and structural basis for feedback inhibition of mevalonate kinase and isoprenoid metabolism

Mevalonate kinase (MK), which catalyzes a key reaction in polyisoprenoid and sterol metabolism in many organisms, is subject to feedback regulation by farnesyl diphosphate and related compounds. The structures of human mevalonate kinase and a binary complex of the rat enzyme incubated with farnesyl thiodiphosphate (FSPP) are reported. Significant FSPP hydrolysis occurs under crystallization conditions; this results in detection of farnesyl thiophosphate (FSP) in the structure of the binary complex. Farnesyl thiodiphosphate competes with substrate ATP to produce feedback inhibition of mevalonate kinase. The binding sites for these metabolites overlap, with the phosphate of FSP nearly superimposed on ATP's beta-phosphate and FSP's polyisoprenoid chain overlapping ATP's adenosine moiety. Several hydrophobic amino acid side chains are positioned near the polyisoprenoid chain of FSP and their functional significance has been evaluated in mutagenesis experiments with human MK, which exhibits the highest reported sensitivity to feedback inhibition. Results suggest that single and double mutations at T104 and I196 produce a significant inflation of the K(i) for FSPP (approximately 40-fold for T104A/I196A). Such an effect persists when K(i) values are normalized for effects on the K(m) for ATP, suggesting that it may be possible to engineer MK proteins with altered sensitivity to feedback inhibition. Comparison of animal MK protein alignments and structures with those of a MK protein from Streptococcus pneumoniae indicates that sequence differences between N- and C-terminal domains correlate with differences in interdomain angles. Bacterial MK proteins exhibit more solvent exposure of feedback inhibitor binding sites and, consequently, weaker binding of these inhibitors.

Mutations in NALP12 cause hereditary periodic fever syndromes

NALP proteins, also known as NLRPs, belong to the CATERPILLER protein family involved, like Toll-like receptors, in the recognition of microbial molecules and the subsequent activation of inflammatory and immune responses. Current advances in the function of NALPs support the recently proposed model of a disease continuum bridging autoimmune and autoinflammatory disorders. Among these diseases, hereditary periodic fevers (HPFs) are Mendelian disorders associated with sequence variations in very few genes; these variations are mostly missense mutations whose deleterious effect, which is particularly difficult to assess, is often questionable. The growing number of identified sporadic cases of periodic fever syndrome, together with the lack of discriminatory clinical criteria, has greatly hampered the identification of new disease-causing genes, a step that is, however, essential for appropriate management of these disorders. Using a candidate gene approach, we identified nonambiguous mutations in NALP12 (i.e., nonsense and splice site) in two families with periodic fever syndromes. As shown by means of functional studies, these two NALP12 mutations have a deleterious effect on NF-kappaB signaling. Overall, these data identify a group of HPFs defined by molecular defects in NALP12, opening up new ways to manage these disorders. The identification of these first NALP12 mutations in patients with autoinflammatory disorder also clearly demonstrates the crucial role of NALP12 in inflammatory signaling pathways, thereby assigning a precise function to this particular member of an emerging family of proteins whose putative biological properties are currently inferred essentially through in vitro means.

Autoinflammatory syndromes with a dermatological perspective

The term autoinflammatory syndromes describes a distinct group of systemic inflammatory diseases apparently different from infectious, autoimmune, allergic and immunodeficient ones. Originally, it was almost synonymous with clinically defined hereditary periodic fever syndromes, including familial Mediterranean fever, hyper immunoglobulin D syndrome with periodic fever and tumor necrosis factor receptor-associated periodic syndrome. Similar but distinct periodic fever syndromes accompanied by urticarial rash, familial cold autoinflammatory syndrome, Muckle-Wells syndrome and chronic infantile neurological cutaneous articular syndrome, have all been reportedly associated with CIAS1 mutations and are collectively called cryopyrin-associated periodic syndromes. Consequently, the concept of autoinflammatory syndromes has been spread to contain other systemic inflammatory diseases: rare hereditary diseases with or without periodic fevers, such as pyogenic sterile arthritis, pyoderma gangrenosum and acne syndrome, Blau syndrome and chronic recurrent multifocal osteomyelitis, and the more common collagen disease-like diseases, such as Behcet's disease, Crohn's disease, sarcoidosis and psoriatic arthritis. These diseases are all caused by or associated with mutations of genes regulating innate immunity and have common clinical features accompanied with activation of neutrophils and/or monocytes/macrophages. In this review, major autoinflammatory syndromes are summarized and the pathophysiology of related skin disorders is discussed in association with dysregulated innate immune signaling.

Effect of a disulfide bond on mevalonate kinase

Mevalonate kinase is one of ATP-dependent enzymes in the mevalonate pathway and catalyzes the phosphorylation of mevalonate to form mevalonate 5-phosphate. In animal cells, it plays a key role in regulating biosynthesis of cholesterol, while in microorganisms and plants, it is involved in the biosynthesis of isoprenoid derivatives that are one of the largest groups of natural products. Crystal structure and sequence alignment show that a unique disulfide bond exists in mevalonate kinase of thermostable species Methanococcus jannaschii, but not in rat mevalonate kinase. In the present study, we investigated the effect of the disulfide bond in M. jannaschii mevalonate kinase and an engineered disulfide bond in rat mevalonate kinase mutant A141C on the properties of enzymes through characterization of their wild-type and variant enzymes. Our result suggests that the Cys107-Cys281 disulfide bond is important for maintaining the conformation and the thermal activity of M. jannaschii mevalonate kinase. Other interactions could also have contributions. The thiol-titration and fluorescence experiment further indicate that rat mevalonate kinase A141C variant enzyme has a new disulfide bond, which makes the variant protein enhance its thermal activity and resist to urea denaturation.

Enfermedades autoinflamatorias sistémicas hereditarias. Síndromes hereditarios de fiebre periódica

Systemic autoinflammatory diseases are an heterogeneous group of systemic disorders clinically characterized by recurrent or persistent inflammatory episodes, which occur in the absence of infectious, neoplastic or autoimmune etiology. During the past years, genetic defects affecting different proteins involved in the regulation of inflammatory processes have been identified in these diseases. These advances offer new genetic tools to clinicians, in order to achieve an accurate and definitive diagnostic, and to establish a tailored treatment. Present review is an updated and comprehensive overview on hereditary systemic autoinflammatory diseases, and it has been organized in 2 separate and independent parts. The first of them will introduce the group of hereditary periodic fever syndromes, which includes familial Mediterranean fever, hyperimmunoglobulinemia D with periodic fever syndrome (HIDS), and tumour necrosis factor receptor-associated periodic syndrome (TRAPS).

Allogeneic bone marrow transplantation in mevalonic aciduria

Mevalonic aciduria is a rare, inborn error of isoprene biosynthesis characterized by severe, periodic attacks of fever and inflammation, developmental delay, ataxia, and dysmorphic features. This autosomal recessive disease is caused by a mutation in the mevalonate kinase gene that severely reduces mevalonate kinase activity. A 3-year-old boy with mevalonic aciduria whose condition had failed to improve with antiinflammatory treatment underwent allogeneic bone marrow transplantation from an HLA-identical sister who was a heterozygous carrier of the mutant gene. We observed sustained remission of febrile attacks and inflammation during a 15-month follow-up period.

Autoinflammatory gene mutations in Behçet's disease

BACKGROUND

Behçet's disease (BD) shares clinical features with well-recognised autoinflammatory disorders. In addition, mutations in genes for familial Mediterranean fever and tumour necrosis factor receptor-associated periodic syndrome have been reported to have increased in patients with BD.

PATIENTS AND METHODS

DNA samples from 97 patients with BD and 51 matched healthy controls were analysed for the mevalonate kinase (MVK), cold-induced autoinflammatory syndrome 1 (CIAS1) and proline/serine/threonine phosphatase-interacting protein 1 (PSTPIP1) genes, responsible for mevalonate kinase deficiency (MKD), cryopyrin associated periodic syndromes (CAPS) and pyogenic sterile arthritis, pyoderma gangrenosum and acne (PAPA) syndrome, respectively. Over 90% of known mutations were screened using restriction fragment length polymorphism analysis and/or sequencing.

RESULTS

Two patients had paired mutations in the MVK gene (genotypes V377I/V377I and V377I/S135L) and displayed typical features of BD and MKD. Another was heterozygotic for the V377I genotype. The V198M mutation in the CIAS1 gene was identified in one patient with typical BD but no symptoms of CAPS. No mutations were identified in the control group. PSTPIP1 analysis revealed a new exon 10 insertion variant (c.741+33_741+34insGT) in 2 of 97 patients and in 1 of 51 controls (p>0.05), indicating that it is a polymorphism rather than a true mutation.

DISCUSSION

This study could not demonstrate any significant increases in MVK, CIAS1 or PSTPIP1 mutations in patients with BD as compared with controls.

The SPRY domain of Pyrin, mutated in familial Mediterranean fever patients, interacts with inflammasome components and inhibits proIL-1beta processing

The autoinflammatory disorders Muckle-Wells syndrome, familial cold urtecaria and chronic infantile neurological cutaneous and articular syndrome are associated with mutations in the NALP3 (Cryopyrin) gene, which is the central platform of the proinflammatory caspase-1 activating complex, named the inflammasome. In patients with another autoinflammatory disorder, familial Mediterranean fever (FMF), mutations in the SPRY domain of the Pyrin protein are frequently found. Recent evidence suggests that Pyrin associates with ASC, an inflammasome component, via its Pyrin domain, thereby halting the inflammatory response. This interaction, however, does not explain the effects of mutations of the SPRY domain found in FMF patients. Here we show that the Pyrin SPRY domain not only interacts with NALP3, but also with caspase-1 and its substrate pro-interleukin(IL)-1beta. Whereas a Pyrin knockdown results in increased caspase-1 activation and IL-1beta secretion, overexpression of the SPRY domain alone blocks these processes. Thus Pyrin binds to several inflammasome components thereby modulating their activity.

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.

Crystal structure of the Streptococcus pneumoniae mevalonate kinase in complex with diphosphomevalonate

Streptococcus pneumoniae, a ubiquitous gram-positive pathogen with an alarming, steadily evolving resistance to frontline antimicrobials, poses a severe global health threat both in the community and in the clinic. The recent discovery that diphosphomevalonate (DPM), an essential intermediate in the isoprenoid biosynthetic pathway, potently and allosterically inhibits S. pneumoniae mevalonate kinase (SpMK) without affecting the human isozyme established a new target and lead compound for antimicrobial design. Here we present the crystal structure of the first S. pneumoniae mevalonate kinase, at a resolution of 2.5 A and in complex with DPM.Mg(2+) in the active-site cleft. Structural comparison of SpMK with other members of the GHMP kinase family reveals that DPM functions as a partial bisubstrate analog (mevalonate linked to the pyrophosphoryl moiety of ATP) in that it elicits a ternary-complexlike form of the enzyme, except for localized disordering in a region that would otherwise interact with the missing portion of the nucleotide. Features of the SpMK-binding pockets are discussed in the context of established mechanistic findings and inherited human diseases linked to MK deficiency.

Biological and clinical aspects of Muckle-Wells syndrome

Muckle-Wells syndrome (MWS), as well as familial cold autoinflammatory syndrome (FCAS) and chronic infantile neurological cutaneous and articular syndrome (CINCA), arises from a missense mutation in the CIAS1 gene. Current progress of biology revealed that NALP3, a protein coded by the CIAS1 and expressed in monocytes, recognizes some bacterial products or harmful metabolites invaded in the cytoplasm, and forms inflammasome with other molecules. As a result, caspase-1 is activated leading to cleavage of pro-IL-1beta and extracellular release of IL-1beta. NALP3 of patients with MWS can be spontaneously activated without obvious stimulation, which causes recurrent attacks of inflammatory symptoms characterized by fever, urticarial rash, conjunctivitis and arthritis, and some patients develop amyloidosis. In addition, sensorineural hearing disturbance progresses gradually. Recently, significant efficacy of anakinra, a recombinant IL-1 receptor antagonist, has been demonstrated in treatment of MWS. So far, only a few cases have been reported from Japan, however an accurate diagnosis has to be established for the latent cases who have not received optimum treatment before occurrence of irreversible deafness or renal failure.

MVK gene abnormality and new approach to treatment of hyper IgD syndrome and periodic fever syndrome

Hyper IgD and periodic fever syndrome (HIDS; OMIM 260920) is one of the hereditary autoinflammatory syndromes characterized by recurrent episodes of fever and inflammation.. HIDS is an autosomal recessive disorder characterized by recurrent fever attacks in early childhood. HIDS caused by mevalonate kinase (MK) mutations, also that is the gene of mevalonic aciduria (OMIM 251170). During febrile episodes, urinary mevalonate concentrations were found to be significantly elevated in patients. Diagnosis of HIDS was retrieving gene or measurement of the enzyme activity in peripheral blood lymphocyte in general. This of HIDS is an activity decline of MK, and a complete deficiency of MK becomes a mevalonic aciduria with a nervous symptom. The relation between the fever and inflammation of mevalonate or isoprenoid products are uncertain. The therapy attempt with statins, which is inhibited the next enzyme after HMG-CoA reductase, or inhibit the proinflammatory cytokines.

Falling into TRAPS--receptor misfolding in the TNF receptor 1-associated periodic fever syndrome

TNF receptor-associated periodic syndrome (TRAPS) is a dominantly inherited disease caused by missense mutations in the TNF receptor 1 (TNFR1) gene. Patients suffer from periodic bouts of severe abdominal pain, localised inflammation, migratory rashes, and fever. More than 40 individual mutations have been identified, all of which occur in the extracellular domain of TNFR1. In the present review we discuss new findings describing aberrant trafficking and function of TNFR1 harbouring TRAPS mutations, challenging the hypothesis that TRAPS pathology is driven by defective receptor shedding, and we suggest that TNFR1 might acquire novel functions in the endoplasmic reticulum, distinct from its role as a cell surface receptor. We also describe the clinical manifestations of TRAPS, current treatment regimens, and the widening array of patient mutations.

Recent advances in the molecular pathogenesis of hereditary recurrent fevers

PURPOSE OF REVIEW

To discuss recent developments in the molecular basis of several hereditary recurrent fever syndromes, specifically the cryopyrin-associated periodic syndromes, familial Mediterranean fever and the tumor necrosis factor receptor associated periodic syndrome.

RECENT FINDINGS

Mutations of CIAS1, the gene encoding cryopyrin/NALP3, lead to a spectrum of disease states termed the cryopyrinopathies. Recently, cryopyrin-deficient mice have been used to show that the protein is a key regulator of interleukin-1beta production that functions by recognizing stimuli such as bacterial RNA and infectious agents. Tumor necrosis factor receptor-associated periodic syndrome was initially thought to be caused by deficient metalloprotease-induced tumor necrosis factor receptor shedding, however new findings suggest that mutations in this receptor may result in inappropriate protein folding, leading to a host of other functional abnormalities that may cause inflammatory disease. Finally, data are emerging that address the possible function of the C-terminal B30.2 domain of pyrin, the familial Mediterranean fever protein. This motif has recently been shown to interact with and inhibit caspase-1, and the modeled structure of this complex highlights how mutations may affect the binding interface.

SUMMARY

Recent reports have advanced our understanding of the structural and functional biology underlying the hereditary recurrent fevers, and are beginning to suggest possible mechanisms by which specific mutations cause disease.

A decision tree for genetic diagnosis of hereditary periodic fever in unselected patients

BACKGROUND

The diagnostic value of molecular analysis of the familial Mediterranean fever (FMF) gene (Mediterranean fever (MEFV)) has been well established only in patients selected on the basis of ethnic background or clinical criteria. Genetic diagnosis for other hereditary periodic fever syndromes has been poorly evaluated.

OBJECTIVE

To determine the diagnostic contribution of genetic tests for hereditary periodic syndromes in a large, unselected series of patients.

METHODS

A retrospective study was conducted on 1941 patients referred to us for FMF genetic tests between 1997 and 2005. MEFV genotypes were compared with clinical data to appraise criteria for FMF diagnosis. Genetic tests for tumour necrosis factor receptor-associated periodic syndrome (TRAPS), hyperimmunoglobulinaemia D syndrome (HIDS) and cryopyrin-associated periodic syndromes (CAPS) were also reviewed.

RESULTS

71% of the 1574 patients with enough data had a clinical diagnosis of FMF according to the widely used Israeli criteria. Two MEFV mutations were found in only 409 patients of this subgroup (sensitivity = 37%) and in 15 (3.3%) of the patients with an improbable clinical diagnosis of FMF (specificity = 97%). Molecular diagnosis for alternate hereditary periodic syndromes was carried out in 456 of the patients having a non-conclusive FMF genetic test. A positive diagnosis was obtained in 31 of these patients (TRAPS (n = 19), HIDS (n = 4) and CAPS (n = 8)).

CONCLUSIONS

First-line MEFV mutation screening in patients with clinically typical FMF may be appropriate only in particular areas. To optimise genetic diagnosis, we propose a decision tree, which, with the advice of an expert practitioner, could help redirect test indications towards non-FMF hereditary periodic syndromes.

Purification of IgD from human serum--a novel application of recombinant M. catarrhalis IgD-binding protein (MID)

Moraxella catarrhalis IgD-binding protein (MID) is a multimeric outer membrane protein belonging to the family of autotransporters. The IgD-binding domain of MID is located between amino acids MID 962-1200 and binds to amino acids 198-224 of the IgD C(H)1 region. In the present study, we describe a method to purify IgD from serum with high levels of IgD using a two-step affinity chromatography process. The first step involves depletion of MID-specific antibodies of all classes from serum using the non-IgD-binding fragment MID(1000-1200). This step is followed by selective capture of IgD with MID(962-1200). Furthermore, we demonstrate that the eluted IgD is pure, intact and functional for use in downstream applications. Our approach reduces the non-specificity commonly associated with lectin-based IgD purification regimes that rely on glycosylation of the IgD molecule.

The systemic autoinflammatory diseases: inborn errors of the innate immune system

The autoinflammatory syndromes are a newly recognized group of immune disorders that lack the high titers of self-reactive antibodies and T cells characteristic of classic autoimmune disease. Nevertheless, patients with these illnesses experience unprovoked inflammatory disease in the absence of underlying infection. Here we discuss recent advances in eight Mendelian autoinflammatory diseases. The causative genes and the proteins they encode play a critical role in the regulation of innate immunity. Both pyrin and cryopyrin, the proteins mutated in familial Mediterranean fever and the cryopyrinopathies, respectively, are involved in regulation of the proinflammatory cytokine, IL-1beta, and may influence the activity of the transcription factor, NFkappaB. NOD2, the Blau syndrome protein, shares certain domains with cryopyrin and appears to be a sensor of intracellular bacteria. PSTPIP1, mutated in the syndrome of pyogenic arthritis with pyoderma gangrenosum and acne, interacts both with pyrin and a protein tyrosine phosphatase to regulate innate and adaptive immune responses. Somewhat unexpectedly, mutations in the p55 TNF receptor lead not to immunodeficiency but to dramatic inflammatory disease, the mechanisms of which are still under investigation. Finally, the discovery of the genetic basis of the hyperimmunoglobulinemia D with periodic fever syndrome has provided a fascinating but incompletely understood link between cholesterol biosynthesis and autoinflammation. In this manuscript, we summarize the current state of the art with regard to the diagnosis, pathogenesis, and treatment of these inborn errors of the innate immune system.

Pathogenesis of familial periodic fever syndromes or hereditary autoinflammatory syndromes

Familial periodic fever syndromes, otherwise known as hereditary autoinflammatory syndromes, are inherited disorders characterized by recurrent episodes of fever and inflammation. The general hypothesis is that the innate immune response in these patients is wrongly tuned, being either too sensitive to very minor stimuli or turned off too late. The genetic background of the major familial periodic fever syndromes has been unraveled, and through research into the pathophysiology, a clearer picture of the innate immune system is emerging. After an introduction on fever, interleukin-1beta and inflammasomes, which are involved in the majority of these diseases, this manuscript offers a detailed review of the pathophysiology of the cryopyrin-associated periodic syndromes, familial Mediterranean fever, the syndrome of pyogenic arthritis, pyoderma gangrenosum and acne, Blau syndrome, TNF-receptor-associated periodic syndrome and hyper-IgD and periodic fever syndrome. Despite recent major advances, there are still many questions to be answered regarding the pathogenesis of these disorders.

A child with a systemic febrile illness – differential diagnosis and management

Fever is a common symptom in children and may sometimes be prolonged or recurrent. There are many differential diagnoses, which may lead to significant diagnostic delay. Diagnosis is based on the clinical presentation as well as a widespread panel of investigations that are necessary in order to exclude the many potential causes of fever before reaching a definite diagnosis. In particular, the physician will look for infections and malignancies before considering the disease as inflammatory. This chapter reviews the differential diagnosis of prolonged or recurrent fever, and discusses most of the inflammatory syndromes presenting with fever.

Statin-induced proinflammatory response in mitogen-activated peripheral blood mononuclear cells through the activation of caspase-1 and IL-18 secretion in monocytes

Statins, which inhibit 3-hydroxy-3-methylglutaryl CoA reductase, have been shown recently to promote proinflammatory responses. We show in this study that both atorvastatin and simvastatin induced proinflammatory responses in mitogen-activated PBMCs by increasing the number of T cells secreting IFN-gamma. This is abolished by the presence of mevalonate, suggesting that statins act specifically by blocking the mevalonate pathway for cholesterol synthesis to promote the proinflammatory response. Both statins at low concentrations induced a dose-dependent increase in the number of IFN-gamma-secreting T cells in mitogen-activated PBMCs, whereas at higher concentrations the effect was abolished. The proinflammatory effect of statins was not seen in purified T cells per se activated with mitogen. However, conditioned medium derived from statin-treated PBMCs enhanced the number of IFN-gamma-secreting cells in activated purified T cells. This effect was not blocked by mevalonate, but was abolished by neutralizing Abs to IL-18 and IL-12. Similarly, the up-regulation of IFN-gamma-secreting T cells in PBMCs costimulated with statins and mitogens was blocked by the neutralizing anti-IL-18 and anti-IL-12. We showed that simvastatin stimulates the secretion of IL-18 and IL-1beta in monocytes. Active caspase-1, which is required for the processing and secretion of IL-18 and IL-1beta, was activated in simvastatin-treated monocytes. This was blocked by mevalonate and the caspase inhibitor benzyloxycarbonyl-Val-Ala-Asp (OMe) fluoromethylketone. Taken together, the proinflammatory response mediated by statins in activated PBMCs is mediated mainly via the activation of caspase-1 and IL-18 secretion in the monocytes and to a lesser extent by IL-12.

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).

[Auto-inflammatory disease with hyperimmunoglobulinemia D of late onset]

BACKGROUND

The term "auto-inflammatory diseases" encompasses a group of disorders characterised by febrile episodes of sudden onset associated with joint, abdominal, lymph node and cutaneous signs, each presenting a genetic and/or laboratory specificity allowing their identification. Polyclonal elevation of serum IgD is highly suggestive of hyper-IgD syndrome, a disease with autosomal recessive transmission that usually begins before the age of one year.

CASE REPORT

We report the case of a 46-year-old woman presenting a disease since the age of 30 years clinically very similar to hyper-IgD syndrome except for ocular and pulmonary involvement. However, tests revealed neither mevalonate kinase gene mutation nor elevation of urinary mevalonic acid. The near-monthly attacks were controlled with mycophenolate mofetil.

DISCUSSION

Three cases with identical clinical and laboratory profiles have been reported in the literature and diagnosed as late-onset hyper-IgD syndrome. Our case is the only one involving indirect screening for mutation of the mevalonate kinase gene, which proved negative. This finding rules out the diagnosis of classic hyper-IgD syndrome in our case and raises the possibility of auto-inflammatory disease with reactional hyper-IgD of a different cause, either acquired or secondary to an as yet unidentified mutation.

Mevalonate kinase deficiencies: from mevalonic aciduria to hyperimmunoglobulinemia D syndrome

Mevalonic aciduria (MVA) and hyperimmunoglobulinemia D syndrome (HIDS) represent the two ends of a clinical spectrum of disease caused by deficiency of mevalonate kinase (MVK), the first committed enzyme of cholesterol biosynthesis. At least 30 patients with MVA and 180 patients with HIDS have been reported worldwide. MVA is characterized by psychomotor retardation, failure to thrive, progressive cerebellar ataxia, dysmorphic features, progressive visual impairment and recurrent febrile crises. The febrile episodes are commonly accompanied by hepatosplenomegaly, lymphadenopathy, abdominal symptoms, arthralgia and skin rashes. Life expectancy is often compromised. In HIDS, only febrile attacks are present, but a subgroup of patients may also develop neurological abnormalities of varying degree such as mental retardation, ataxia, ocular symptoms and epilepsy. A reduced activity of MVK and pathogenic mutations in the MVK gene have been demonstrated as the common genetic basis in both disorders. In MVA, the diagnosis is established by detection of highly elevated levels of mevalonic acid excreted in urine. Increased levels of immunoglobulin D (IgD) and, in most patients of immunoglobulin A (IgA), in combination with enhanced excretion of mevalonic acid provide strong evidence for HIDS. The diagnosis is confirmed by low activity of mevalonate kinase or by demonstration of disease-causing mutations. Genetic counseling should be offered to families at risk. There is no established successful treatment for MVA. Simvastatin, an inhibitor of HMG-CoA reductase, and anakinra have been shown to have beneficial effect in HIDS.

Diagnostic challenge of hyper-IgD syndrome in four children with inflammatory gastrointestinal complaints

OBJECTIVE

Hyper-IgD syndrome (HIDS) is a rare autosomal recessive disease characterized by recurrent fever, lymphadenopathy, diarrhoea, abdominal pain, headache, arthralgia and skin rash. Abdominal symptomatology may mimic inflammatory bowel disease. We report on four patients with HIDS who had been previously investigated for Crohn's disease (CD). The levels of IgD were measured in a series of patients with CD to evaluate the specificity of this assay in the differential diagnosis between the two conditions.

MATERIAL AND METHODS

Diagnosis of HIDS was based on clinical criteria as well as immunological or genetic data. IgD levels were measured in the four subjects affected by HIDS, in 59 patients with CD and in a group of 160 healthy controls.

RESULT

All patients underwent a variety of gastroenterological investigations because inflammatory bowel disease was suspected. Ultrasonography was pathologic in all the patients, showing enlargement of mesenteric lymph nodes. Abdominal leucocyte scintigraphy displayed diffuse signals of mild to moderate degree. IgD and IgA levels were elevated in three out of four patients. No difference in IgD values was found in CD patients as compared to the control group.

CONCLUSIONS

Gastrointestinal complaints associated with recurrent fever and mesenteric adenopathy warrant genetic investigation for HIDS, in order to avoid unnecessary invasive investigations and treatment.

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.

A role for geranylgeranylation in interleukin-1β secretion

OBJECTIVE

Mevalonate kinase deficiency (MKD) is an autosomal-recessive disorder characterized by recurring episodes of inflammation. MK catalyzes the phosphorylation of mevalonic acid, which is an early step in isoprenoid biosynthesis. The goal of our study was to determine whether a temporary shortage of certain isoprenoid end products and/or the accumulation of mevalonic acid is the cause of interleukin-1beta (IL-1beta) secretion in MKD.

METHODS

We studied the effect of the addition of intermediate metabolites and inhibitors of the isoprenoid biosynthesis pathway on IL-1beta secretion by peripheral blood mononuclear cells (PBMCs) of patients with MKD and healthy controls.

RESULTS

Inhibition of enzymes involved in geranylgeranyl pyrophosphate (GGPP) synthesis or geranylgeranylation of proteins led to a marked increase of lipopolysaccharide-stimulated IL-1beta secretion in PBMCs of control subjects. Furthermore, the increased IL-1beta secretion by PBMCs of patients with MKD was reversed by supplementation with GGPP as well as with mevalonic acid. IL-1beta secretion was increased only when control PBMCs were incubated with excessive amounts of mevalonic acid. Finally, a reduction in IL-1beta secretion by MKD PBMCs was also observed when sterol biosynthesis was inhibited, favoring nonsterol isoprenoid biosynthesis.

CONCLUSION

Our results indicate that a shortage of geranylgeranylated proteins, rather than an excess of mevalonate, is likely to cause increased IL-1beta secretion by PBMCs of patients with MKD.

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.

Tendonitis in variant hyperimmunoglobulinaemia D and periodic fever syndrome--a rare disease with a new symptom

Hyperimmunoglobulinaemia D syndrome (HIDS) is defined as recurrent fever, generalised lymphadenitis, abdominal pain, arthritis and raised polyclonal serum IgD >100 IU/ml. The cause is a mutation in the mevalonate kinase gene. Other periodic fever syndromes are known. We report a new patient and describe orbital tendonitis as a hitherto unreported symptom

CONCLUSION

Without any underlying cause, the tendonitis must be seen as new symptom of variant hyperimmunoglobulinaemia D syndrome. We speculate that the inflammation of the Tenon spatium is similar to the process of inflammation of the connective tissue in the joint in hyperimmunoglobulinaemia D syndrome where deposits of C3 and IgM are present. Variant hyperimmunoglobulinaemia D syndrome can be present in one family.

Distinguishing among prolonged, recurrent, and periodic fever syndromes: approach of a pediatric infectious diseases subspecialist

Most children with prolonged, recurrent, or periodic fever are healthy and have self-limited, common illnesses, and the primary care practitioner usually can reassure families and continue to reassess the patient as circumstances dictate. For a child with true fever of unknown origin, a pediatric infectious diseases subspecialist should be consulted. This article discusses three objectives for the clinician: (1) to categorize patterns of fever illnesses and prioritize differential diagnoses; (2) to diagnose and manage the most frequently encountered prolonged fever syndrome, deconditioning; and (3) to expand knowledge and approach to diagnosing periodic fever syndromes. The approach described in this article represents the honed, 30-year experience of a pediatric infectious diseases subspecialist.

Familial Mediterranean fever--a not so unusual cause of abdominal pain

Familial Mediterranean fever is a hereditary syndrome characterised by recurrent episodes of fever and serositis, resulting in pain in the abdomen, chest, joints and muscles. It is primarily diagnosed in people of Jewish, Arabic, Turkish or Armenian ancestry and is caused by mutations in the gene encoding for pyrin. Abdominal FMF attacks resemble the clinical presentation of 'acute abdomen', with severe abdominal pain and rigidity, but in FMF symptoms always resolve spontaneously. It is important to distinguish these regular pain episodes from small bowel obstruction due to adhesions to prevent life-threatening bowel strangulation. In most cases, colchicine will prevent new painful attacks. This seminar also discusses other causes of abdominal pain in FMF patients.

Infevers: an evolving mutation database for auto-inflammatory syndromes

The Infevers database (http://fmf.igh.cnrs.fr/infevers/) was established in 2002 to provide investigators with access to a central source of information about all sequence variants associated with periodic fevers: Familial Mediterranean fever (FMF), TNF Receptor Associated Periodic Syndrome (TRAPS), Hyper IgD Syndrome (HIDS), Familial Cold Autoinflammatory Syndrome/Muckle-Wells Syndrome/Chronic Infantile Neurological Cutaneous and Articular Syndrome (FCAS/MWS/CINCA). The prototype of this group of disorders is FMF, a recessive disease characterized by recurrent bouts of unexplained inflammation. FMF is the pivotal member of an expanding family of autoinflammatory disorders, a new term coined to describe illnesses resulting from a defect of the innate immune response. Therefore, we decided to extend the Infevers database to genes connected with autoinflammatory diseases. We present here the biological content of the Infevers database, including the introduction of two new entries: Crohn/Blau and Pyogenic sterile arthritis, pyoderma gangrenosum and acne (PAPA syndrome). Infevers has a range of query capabilities, allowing for simple or complex interrogation of the database. Currently, the database contains 291 sequence variants in related genes (MEFV, TNFRSF1A, MVK, CARD15, PSTPIP1, and CIAS1), consisting of published data and personal communications, which has revealed or refined the preferential mutational sites for each gene. This database will continue to evolve in its content and to improve in its presentation.

Henoch-Schönlein purpura in a child with hyperimmunoglobulinemia D and periodic fever syndrome

This report describes a 3-year-old girl with a long history of periodic fever who presented with Henoch-Schönlein purpura. She was diagnosed with hyperimmunoglobulinemia D and periodic fever syndrome by means of mutation analysis of the mevalonate kinase gene. The serum IgA concentration was markedly elevated, but the serum IgD concentration was normal. This report emphasizes that Henoch-Schönlein purpura may be an important clinical feature of hyperimmunoglobulinemia D and periodic fever syndrome. In addition, this syndrome should be considered in patients with Henoch-Schonlein purpura in whom there is a history of recurrent fevers, even when the serum IgD concentration is normal.

3beta-hydroxysterol Delta7-reductase and the Smith-Lemli-Opitz syndrome

In the final step of cholesterol synthesis, 7-dehydrocholesterol reductase (DHCR7) reduces the double bond at C7-8 of 7-dehydrocholesterol to yield cholesterol. Mutations of DHCR7 cause Smith-Lemli-Opitz syndrome (SLOS). Over 100 different mutations of DHCR7 have been identified in SLOS patients. SLOS is a classical multiple malformation, mental retardation syndrome, and was the first human malformation syndrome shown to result from an inborn error of cholesterol synthesis. This paper reviews the biochemical, molecular, and mutational aspects of DHCR7.