Mevalonate kinase deficiencies: from mevalonic aciduria to hyperimmunoglobulinemia D syndrome

TNF inhibitors target a mevalonate metabolite/TRPM2/calcium signaling axis in neutrophils to dampen vasculitis in Behçet's disease

TNF inhibitors have been used to treat autoimmune and autoinflammatory diseases. Here we report an unexpected mechanism underlying the therapeutic effects of TNF inhibitors in Behçet's disease (BD), an autoimmune inflammatory disorder. Using serum metabolomics and peripheral immunocyte transcriptomics, we find that polymorphonuclear neutrophil (PMN) from patients with BD (BD-PMN) has dysregulated mevalonate pathway and subsequently increased farnesyl pyrophosphate (FPP) levels. Mechanistically, FPP induces TRPM2-calcium signaling for neutrophil extracellular trap (NET) and proinflammatory cytokine productions, leading to vascular endothelial inflammation and damage. TNF, but not IL-1β, IL-6, IL-18, or IFN-γ, upregulates TRPM2 expression on BD-PMN, while TNF inhibitors have opposite effects. Results from mice with PMN-specific FPP synthetase or TRPM2 deficiency show reduced experimental vasculitis. Meanwhile, analyses of public datasets correlate increased TRPM2 expressions with the clinical benefits of TNF inhibitors. Our results thus implicate FPP-TRPM2-TNF/NETs feedback loops for inflammation aggravation, and novel insights for TNF inhibitor therapies on BD.

Identification of novel targets associated with cholesterol metabolism in nonalcoholic fatty liver disease: a comprehensive study using Mendelian randomization combined with transcriptome analysis

Background

There is limited research on cholesterol metabolism-related genes (CM-RGs) in non-alcoholic fatty liver disease (NAFLD), despite hypercholesterolemia being a recognized risk factor. The role of CM-RGs in NAFLD remains unclear.

Methods

The differentially expressed genes (DEGs) between NAFLD and control were acquired by differential expression analysis. The differentially expressed genes associated with cholesterol metabolism (DE-CM-RGs) were identified and functional enrichment analyses were performed. Protein-protein interaction network analysis and a two-sample Mendelian randomization study were utilized for identifying hub genes. Nomogram model, competing endogenous RNA and messenger RNA-drug networks were established. In addition, immunoinfiltration analysis was performed.

Results

We identified four hub genes (MVK, HMGCS1, TM7SF2, and FDPS) linked to NAFLD risk. MVK and TM7SF2 were protective factors, HMGCS1 and FDPS were risk factors for NAFLD. The area under the curve values of nomograms in GSE135251 and GSE126848 were 0.79 and 0.848, respectively. The gene set enrichment analysis indicated that hub genes participated in calcium signaling pathways and biosynthesis of unsaturated fatty acids. NAFLD patients showed increased CD56dim NK cells and Th17. Tretinoin, alendronate, zoledronic acid, and quercetin are potential target agents in NAFLD.

Conclusion

Our study has linked cholesterol metabolism genes (MVK, HMGCS1, TM7SF2, and FDPS) to NAFLD, providing a promising diagnostic framework, identifying treatment targets, and offering novel perspectives into its mechanisms.

Tocilizumab effectively reduces flares of hyperimmunoglobulin D syndrome in children: Three cases in China

Hyperimmunoglobulin D syndrome (HIDS) is a rare but severe autoinflammatory disease with a poor prognosis if not diagnosed and treated early. Here, we report three cases of HIDS in children with typical clinical manifestations and a clear genetic diagnosis. Patient 1 experienced recurrent fever flares with a maculo-papular skin rash. Patient 2 presented with periodic fever, cholestasis, lymphadenopathy, aphthous stomatitis, arthralgia, and abdominal pain and underwent surgery for intestinal obstruction. Patient 3, a sibling of patient 2, presented with periodic fever and underwent a surgical procedure for intussusception. All three patients were administered interleukin (IL)-6 receptor antagonist (tocilizumab). The results showed that tocilizumab effectively reduced inflammatory flares. Early diagnosis and tocilizumab treatment are effective at improving the prognosis of HIDS patients.

Phosphomevalonate kinase deficiency expands the genetic spectrum of systemic autoinflammatory diseases

BACKGROUND

In the isoprenoid biosynthesis pathway, mevalonate is phosphorylated in 2 subsequent enzyme steps by MVK and PMVK to generate mevalonate pyrophosphate that is further metabolized to produce sterol and nonsterol isoprenoids. Biallelic pathogenic variants in MVK result in the autoinflammatory metabolic disorder MVK deficiency. So far, however, no patients with proven PMVK deficiency due to biallelic pathogenic variants in PMVK have been reported.

OBJECTIVES

This study reports the first patient with functionally confirmed PMVK deficiency, including the clinical, biochemical, and immunological consequences of a homozygous missense variant in PMVK.

METHODS

The investigators performed whole-exome sequencing and functional studies in cells from a patient who, on clinical and immunological evaluation, was suspected of an autoinflammatory disease.

RESULTS

The investigators identified a homozygous PMVK p.Val131Ala (NM_006556.4: c.392T>C) missense variant in the index patient. Pathogenicity was supported by genetic algorithms and modeling analysis and confirmed in patient cells that revealed markedly reduced PMVK enzyme activity due to a virtually complete absence of PMVK protein. Clinically, the patient showed various similarities as well as distinct features compared to patients with MVK deficiency and responded well to therapeutic IL-1 inhibition.

CONCLUSIONS

This study reported the first patient with proven PMVK deficiency due to a homozygous missense variant in PMVK, leading to an autoinflammatory disease. PMVK deficiency expands the genetic spectrum of systemic autoinflammatory diseases, characterized by recurrent fevers, arthritis, and cytopenia and thus should be included in the differential diagnosis and genetic testing for systemic autoinflammatory diseases.

What General Neurologists Should Know about Autoinflammatory Syndromes?

Autoinflammatory disorders encompass a wide range of conditions with systemic and neurological symptoms, which can be acquired or inherited. These diseases are characterized by an abnormal response of the innate immune system, leading to an excessive inflammatory reaction. On the other hand, autoimmune diseases result from dysregulation of the adaptive immune response. Disease flares are characterized by systemic inflammation affecting the skin, muscles, joints, serosa, and eyes, accompanied by unexplained fever and elevated acute phase reactants. Autoinflammatory syndromes can present with various neurological manifestations, such as aseptic meningitis, meningoencephalitis, sensorineural hearing loss, and others. Early recognition of these manifestations by general neurologists can have a significant impact on the prognosis of patients. Timely and targeted therapy can prevent long-term disability by reducing chronic inflammation. This review provides an overview of recently reported neuroinflammatory phenotypes, with a specific focus on genetic factors, clinical manifestations, and treatment options. General neurologists should have a good understanding of these important diseases.

A case of neonatal sweet syndrome associated with mevalonate kinase deficiency

BACKGROUND

Sweet syndrome (SS), also known as acute febrile neutrophilic dermatosis, is an immunologic syndrome characterized by widespread neutrophilic infiltration. Histiocytoid Sweet syndrome (H-SS) is a histopathologic variant of SS. While SS most commonly occurs in adults, this case report discusses an infant patient who presented with H-SS.

CASE PRESENTATION

Through a multidisciplinary approach, this patient was also found to have very early onset inflammatory bowel disease (VEO-IBD) and Mevalonate kinase-associated disease (MKAD). While prior case studies have characterized an association between VEO-IBD and MKAD, there is no literature describing the association of all three diagnoses this case: H-SS, VEO-IBD and MKAD. Initiation of canakinumab in this patient resulted in successful control of the disease.

CONCLUSIONS

This case highlights the importance of a multidisciplinary approach to rare diagnoses, and collaboration during cases with significant diagnostic uncertainty.

Clinical and biochemical footprints of inherited metabolic diseases. XII. Immunological defects

Immunological problems are increasingly acknowledged manifestations in many inherited metabolic diseases (IMDs), ranging from exaggerated inflammation, autoimmunity and abnormal cell counts to recurrent microbial infections. A subgroup of IMDs, the congenital disorders of glycosylation (CDG), includes CDG types that are even classified as primary immunodeficiencies. Here, we reviewed the list of metabolic disorders reported to be associated with various immunological defects and identified 171 IMDs accompanied by immunological manifestations. Most IMDs are accompanied by immune dysfunctions of which immunodeficiency and infections, innate immune defects, and autoimmunity are the most common abnormalities reported in 144/171 (84%), 44/171 (26%) and 33/171 (19%) of IMDs with immune system involvement, respectively, followed by autoinflammation 17/171 (10%). This article belongs to a series aiming at creating and maintaining a comprehensive list of clinical and metabolic differential diagnoses according to organ system involvement.

Current Evidence on Vaccinations in Pediatric and Adult Patients with Systemic Autoinflammatory Diseases

Systemic autoinflammatory diseases (SAIDs) are defined by recurrent febrile attacks associated with protean manifestations involving joints, the gastrointestinal tract, skin, and the central nervous system, combined with elevated inflammatory markers, and are caused by a dysregulation of the innate immune system. From a clinical standpoint, the most known SAIDs are familial Mediterranean fever (FMF); cryopyrin-associated periodic syndrome (CAPS); mevalonate kinase deficiency (MKD); and periodic fever, aphthosis, pharyngitis, and adenitis (PFAPA) syndrome. Current guidelines recommend the regular sequential administration of vaccines for all individuals with SAIDs. However, these patients have a much lower vaccination coverage rates in 'real-world' epidemiological studies than the general population. The main purpose of this review was to evaluate the scientific evidence available on both the efficacy and safety of vaccines in patients with SAIDs. From this analysis, neither serious adverse effects nor poorer antibody responses have been observed after vaccination in patients with SAIDs on treatment with biologic agents. More specifically, no new-onset immune-mediated complications have been observed following immunizations. Post-vaccination acute flares were significantly less frequent in FMF patients treated with colchicine alone than in those treated with both colchicine and canakinumab. Conversely, a decreased risk of SARS-CoV-2 infection has been proved for patients with FMF after vaccination with the mRNA-based BNT162b2 vaccine. Canakinumab did not appear to affect the ability to produce antibodies against non-live vaccines in patients with CAPS, especially if administered with a time lag from the vaccination. On the other hand, our analysis has shown that immunization against Streptococcus pneumoniae, specifically with the pneumococcal polysaccharide vaccine, was associated with a higher incidence of adverse reactions in CAPS patients. In addition, disease flares might be elicited by vaccinations in children with MKD, though no adverse events have been noted despite concurrent treatment with either anakinra or canakinumab. PFAPA patients seem to be less responsive to measles, mumps, and rubella-vaccine, but have shown higher antibody response than healthy controls following vaccination against hepatitis A. In consideration of the clinical frailty of both children and adults with SAIDs, all vaccinations remain 'highly' recommended in this category of patients despite the paucity of data available.

Trained immunity as a possible newcomer in autoinflammatory and autoimmune diseases pathophysiology

Autoimmune disorders have been well characterized over the years and many pathways-but not all of them-have been found to explain their pathophysiology. Autoinflammatory disorders, on the other hand, are still hiding most of their molecular and cellular mechanisms. During the past few years, a newcomer has challenged the idea that only adaptive immunity could display memory response. Trained immunity is defined by innate immune responses that are faster and stronger to a second stimulus than to the first one, being the same or not. In response to the trained immunity inducer, and through metabolic and epigenetic changes of hematopoietic stem and progenitor cells in the bone marrow that are transmitted to their cellular progeny (peripheral trained immunity), or directly of tissue-resident cells (local innate immunity), innate cells responsiveness and functions upon stimulation are improved in the long-term. Innate immunity can be beneficial, but it could also be detrimental when maladaptive. Here, we discuss how trained immunity could contribute to the physiopathology of autoimmune and autoinflammatory diseases.

Autoinflammatory manifestations in adult patients

Autoinflammatory diseases represent a family of immune-mediated conditions characterized by the unchecked activation of innate immunity. These conditions share common clinical features such as recurrent fever, inflammatory arthritis, and elevation of acute phase reactants, in the absence of an identified infectious etiology, generally without detectable serum autoantibodies, with variable response to glucocorticoids and in some cases colchicine, which represented the mainstay of treatment until cytokine blockade therapies became available. The first autoinflammatory diseases to be described were monogenic disorders caused by missense mutations in inflammasome components and were recognized predominantly during childhood or early adulthood. However, the progress of genetic analyses and a more detailed immunological phenotyping capacity led to the discovery a wide spectrum of diseases, often becoming manifest or being diagnosed in the adult population. The beneficial role of targeting hyperinflammation via interleukin 1 in complex non-immune-mediated diseases is a field of growing clinical interest. We provide an overview of the autoinflammatory diseases of interest to physicians treating adult patients and to analyze the contribution of hyperinflammation in non-immune-mediated diseases; the result is intended to provide a roadmap to orient scientists and clinicians in this broad area.

Increased core body temperature exacerbates defective protein prenylation in mouse models of mevalonate kinase deficiency

Mevalonate kinase deficiency (MKD) is characterized by recurrent fevers and flares of systemic inflammation, caused by biallelic loss-of-function mutations in MVK. The underlying disease mechanisms and triggers of inflammatory flares are poorly understood because of the lack of in vivo models. We describe genetically modified mice bearing the hypomorphic mutation p.Val377Ile (the commonest variant in patients with MKD) and amorphic, frameshift mutations in Mvk. Compound heterozygous mice recapitulated the characteristic biochemical phenotype of MKD, with increased plasma mevalonic acid and clear buildup of unprenylated GTPases in PBMCs, splenocytes, and bone marrow. The inflammatory response to LPS was enhanced in compound heterozygous mice and treatment with the NLRP3 inflammasome inhibitor MCC950 prevented the elevation of circulating IL-1β, thus identifying a potential inflammasome target for future therapeutic approaches. Furthermore, lines of mice with a range of deficiencies in mevalonate kinase and abnormal prenylation mirrored the genotype-phenotype relationship in human MKD. Importantly, these mice allowed the determination of a threshold level of residual enzyme activity, below which protein prenylation is impaired. Elevated temperature dramatically but reversibly exacerbated the deficit in the mevalonate pathway and the defective prenylation in vitro and in vivo, highlighting increased body temperature as a likely trigger of inflammatory flares.

Cyclic Fevers in Adult Diagnosed As Hyperimmunoglobulin D Syndrome

Hyper immunoglobulin D Syndrome (HIDS) is a rare autosomal recessive disease often presents during infancy. The disease is caused by an abnormal gene that codes for mevalonate kinase (MVK). This results in recurrent fever episodes and gastrointestinal discomfort (including diarrhea, joint pain, and oral sores). High fever is the most common symptom, occurring every few weeks to months. Patients may also have other findings, including lymphadenopathy and arthralgia. In this report, we discuss a rare diagnosis of HIDS is an adult and discuss our case in the context of existing literature. Given the nonspecific symptoms and the fact that it is often diagnosed in childhood, HIDS can be a challenging but essential diagnosis in adults with persistent, cyclical fevers.

The genetics behind inflammasome regulation

The inflammasome is a cytosolic multiproteic complex that promotes proinflammatory events through the release of the cytokines IL-1β and IL-18, and in some context by the induction of a lytic cell death called pyroptosis, in response to damage, infections, or changes in the homeostasis. Due to the powerful inflammatory effect, there are several regulatory mechanisms that are essential to modulate or limit the activation of the inflammasome. When these mechanisms fail, the deregulation of the complex leads or contributes to the development of a plethora of diseases characterized by constitutive and/or chronic inflammation, such as autoinflammatory, autoimmune, cardiovascular, neurodegenerative, and metabolic diseases, cancer, or even severe complications of infectious diseases. Either environmental or genetic factors may affect the threshold and/or the level of inflammasome activation, such as hyperglycemia, hyperuricemia, auto-antibodies, unfolded proteins and fibrils, or individual genetic variants in genes coding for inflammasome receptors or effector molecules, and also in regulators. While the genetics of inflammasome itself has been elsewhere characterized and also recently reviewed by our group, less is known about how genetic variants in regulatory molecules could affect inflammatory diseases. Therefore in this work, we selected a group of known or possible regulators of the inflammasome, and through the review of genetic association studies we tried to depict the contribution of these regulators in the development of multifactorial diseases.

Activation of the plant mevalonate pathway by extracellular ATP

The mevalonate pathway plays a critical role in multiple cellular processes in both animals and plants. In plants, the products of this pathway impact growth and development, as well as the response to environmental stress. A forward genetic screen of Arabidopsis thaliana using Ca²⁺-imaging identified mevalonate kinase (MVK) as a critical component of plant purinergic signaling. MVK interacts directly with the plant extracellular ATP (eATP) receptor P2K1 and is phosphorylated by P2K1 in response to eATP. Mutation of P2K1-mediated phosphorylation sites in MVK eliminates the ATP-induced cytoplasmic calcium response, MVK enzymatic activity, and suppresses pathogen defense. The data demonstrate that the plasma membrane associated P2K1 directly impacts plant cellular metabolism by phosphorylation of MVK, a key enzyme in the mevalonate pathway. The results underline the importance of purinergic signaling in plants and the ability of eATP to influence the activity of a key metabolite pathway with global effects on plant metabolism.

Products of the mevalonate pathway support plant development. Here the authors show that the extracellular ATP receptor P2K1 phosphorylates mevalonate kinase and this affects the mevalonate pathway.

Cutaneous signs and mechanisms of inflammasomopathies

The emerging group of autoinflammatory diseases (AIDs) is caused by a dysregulation of the innate immune system while lacking the typical footprint of adaptive immunity. A prominent subgroup of AIDs are inflammasomopathies, which are characterised by periodic flares of cutaneous signs as well as systemic organ involvement and fever. The range of possible skin lesions is vast, ranging from urticarial, erysipelas-like and pustular rashes to erythematous patches, violaceous plaques and eventual necrosis and ulceration. This review provides a structured overview of the pathogenesis and the clinical picture with a focus on dermatological aspects of inflammasomopathies. Current treatment options for these conditions are also discussed.

Case Report: Mevalonic Aciduria Complicated by Acute Myeloid Leukemia After Hematopoietic Stem Cell Transplantation

Mevalonic aciduria (MA) is the most severe clinical subtype of mevalonate kinase deficiency (MKD) caused by an inherited defect in the mevalonate pathway. The treatment of MKD focuses on the suppression of recurrent hyperinflammatory attacks using anti-inflammatory drugs. Recently, allogeneic hematopoietic stem cell transplantation (HCT) was shown to successfully ameliorate autoinflammatory attacks in patients with MKD. Here, we report a case of an infant who showed severe recurrent systemic inflammation and was diagnosed with MA. Although she responded to steroids, her symptoms relapsed after the dose was tapered, and organ deterioration occurred. Therefore, at the age of 11 months, HCT from a matched, unrelated donor was performed for curative treatment. However, at 50 days after transplantation, acute myeloid leukemia was diagnosed, which was chemo-refractory. A second HCT from her haploidentical father was performed to treat the acute myeloid leukemia, but the patient died of sepsis on day 4 after transplantation. This is the first report of malignancy following HCT for MA. Our findings suggest that normalizing the mevalonate pathway after HCT in patients with MKD impacts patients differently depending on the clinical spectrum and severity of disease.

Vasculitis in a patient with mevalonate kinase deficiency (MKD): a case report

BACKGROUND

Mevalonate kinase deficiency (MKD) is a rare autoinflammatory condition caused by biallelic loss-of-function (LOF) mutations in mevalonate kinase (MVK) gene encoding the enzyme mevalonate kinase. Patients with MKD display a variety of non-specific clinical manifestations, which can lead to diagnostic delay. We report the case of a child presenting with vasculitis that was found by genetic testing to be caused by MKD, and now add this autoinflammatory disease to the ever-expanding list of causes of monogenic vasculitides.

CASE PRESENTATION

A 2-year-old male presented with an acute 7-day history of high-grade fever, abdominal pain, diarrhoea, rectal bleeding and extensive purpuric and necrotic lesions, predominantly affecting the lower limbs. He had been suffering from recurrent episodes of fever from early in infancy, associated with maculopapular/petechial rashes triggered by intercurrent infection, and after vaccines. Extensive infection screen was negative. Skin biopsy revealed small vessel vasculitis. Visceral digital subtraction arteriography was normal. With a diagnosis of severe idiopathic cutaneous vasculitis, he was treated with corticosteroids and mycophenolate mofetil. Despite that his acute phase reactants remained elevated, fever persisted and the vasculitic lesions progressed. Next-generation sequencing revealed compound heterozygous mutation in MVK c.928G > A (p.V310M) and c.1129G > A (p.V377I) while reduced mevalonate enzyme activity was confirmed suggesting a diagnosis of MKD as a cause of the severe vasculitis. Prompt targeted treatment with IL-1 blockade was initiated preventing escalation to more toxic vasculitis therapies and reducing unnecessary exposure to cytotoxic treatment.

CONCLUSIONS

Our report highlights the broad clinical phenotype of MKD that includes severe cutaneous vasculitis and emphasizes the need to consider early genetic screening for young children presenting with vasculitis to exclude a monogenic vasculitis which may be amenable to targeted treatment.

An Atypical Presentation of Mevalonate Kinase Deficiency in Response to Colchicine Treatment

Mevalonate kinase deficiency (MKD) is a periodic fever syndrome. Nonsteroidal anti-inflammatory drugs, corticosteroids, and anakinra are the most common treatments. However, colchicine is considered insufficient in disease control. In this case report, we present an 8-month-old infant with an atypical presentation of MKD. She had recurrent fever episodes, diarrhea, and lethargy. Elevated mevalonic acid was not detected in the urine. However, the genetic investigation showed a novel pathogenic heterozygous c.925G&#x3e;C (p.Gly309Arg) variant and a heterozygous c.1129G&#x3e;A (p.Val377Ile) mutation in the <i>MVK</i> gene. The patient was treated with colchicine for 8 months. During treatment, no further fever episode had been observed. It should be kept in mind that mevalonic acid excretion may not be present in the urine with mild MKD. Colchicine may be a reasonable option in mild MKD patients for a longer duration of treatment due to favorable adverse event profiles.

Mevalonate Kinase Deficiency: A Cause of Severe Very-Early-Onset Inflammatory Bowel Disease

Mevalonate kinase deficiency should be considered in patients with severe very-early-onset inflammatory bowel disease (IBD), especially in patients with a history of recurrent or chronic fever, peritoneal adhesions, and atypical IBD pathology. Anti-interleukin-1 therapy may be efficacious in these patients with monogenic very-early-onset IBD.

Phenotypic diversity, disease progression, and pathogenicity of MVK missense variants in mevalonic aciduria

Mevalonic aciduria (MVA) and hyperimmunoglobulinemia D syndrome (MKD/HIDS) are disorders of cholesterol biosynthesis caused by variants in the MVK gene and characterized by increased urinary excretion of mevalonic acid. So far, 30 MVA patients have been reported, suffering from recurrent febrile crises and neurologic impairment. Here, we present an in-depth analysis of the phenotypic spectrum of MVA and provide an in-silico pathogenicity model analysis of MVK missense variants. The phenotypic spectrum of 11 MVA patients (age range 0-51 years) registered in the Unified European Registry for Inherited Metabolic Disorders database was systematically analyzed using terms of the Human Phenotype Ontology. Biochemical, radiological as well as genetic characteristics were investigated. Six of eleven patients have reached adulthood and four have reached adolescence. One of the adolescent patients died at the age of 16 years and one patient died shortly after birth. Symptoms started within the first year of life, including episodic fever, developmental delay, ataxia, and ocular involvement. We also describe a case with absence of symptoms despite massive excretion of mevalonic acid. Pathogenic variants causing MVA cluster within highly conserved regions, which are involved in mevalonate and ATP binding. The phenotype of adult and adolescent MVA patients is more heterogeneous than previously assumed. Outcome varies from an asymptomatic course to early death. MVK variants cluster in functionally important and highly conserved protein domains and show high concordance regarding their expected pathogenicity.

The combined prevalence of classified rare rheumatic diseases is almost double that of ankylosing spondylitis

BACKGROUND

Rare diseases (RDs) affect less than 5/10,000 people in Europe and fewer than 200,000 individuals in the United States. In rheumatology, RDs are heterogeneous and lack systemic classification. Clinical courses involve a variety of diverse symptoms, and patients may be misdiagnosed and not receive appropriate treatment. The objective of this study was to identify and classify some of the most important RDs in rheumatology. We also attempted to determine their combined prevalence to more precisely define this area of rheumatology and increase awareness of RDs in healthcare systems. We conducted a comprehensive literature search and analyzed each disease for the specified criteria, such as clinical symptoms, treatment regimens, prognoses, and point prevalences. If no epidemiological data were available, we estimated the prevalence as 1/1,000,000. The total point prevalence for all RDs in rheumatology was estimated as the sum of the individually determined prevalences.

RESULTS

A total of 76 syndromes and diseases were identified, including vasculitis/vasculopathy (n = 15), arthritis/arthropathy (n = 11), autoinflammatory syndromes (n = 11), myositis (n = 9), bone disorders (n = 11), connective tissue diseases (n = 8), overgrowth syndromes (n = 3), and others (n = 8). Out of the 76 diseases, 61 (80%) are classified as chronic, with a remitting-relapsing course in 27 cases (35%) upon adequate treatment. Another 34 (45%) diseases were predominantly progressive and difficult to control. Corticosteroids are a therapeutic option in 49 (64%) syndromes. Mortality is variable and could not be determined precisely. Epidemiological studies and prevalence data were available for 33 syndromes and diseases. For an additional eight diseases, only incidence data were accessible. The summed prevalence of all RDs was 28.8/10,000.

CONCLUSIONS

RDs in rheumatology are frequently chronic, progressive, and present variable symptoms. Treatment options are often restricted to corticosteroids, presumably because of the scarcity of randomized controlled trials. The estimated combined prevalence is significant and almost double that of ankylosing spondylitis (18/10,000). Thus, healthcare systems should assign RDs similar importance as any other common disease in rheumatology.

Gene Expression Analysis of Mevalonate Kinase Deficiency Affected Children Identifies Molecular Signatures Related to Hematopoiesis

Mevalonate kinase deficiency (MKD) is a rare autoinflammatory genetic disorder characterized by recurrent fever attacks and systemic inflammation with potentially severe complications. Although it is recognized that the lack of protein prenylation consequent to mevalonate pathway blockade drives IL1β hypersecretion, and hence autoinflammation, MKD pathogenesis and the molecular mechanisms underlaying most of its clinical manifestations are still largely unknown. In this study, we performed a comprehensive bioinformatic analysis of a microarray dataset of MKD patients, using gene ontology and Ingenuity Pathway Analysis (IPA) tools, in order to identify the most significant differentially expressed genes and infer their predicted relationships into biological processes, pathways, and networks. We found that hematopoiesis linked biological functions and pathways are predominant in the gene ontology of differentially expressed genes in MKD, in line with the observed clinical feature of anemia. We also provided novel information about the molecular mechanisms at the basis of the hematological abnormalities observed, that are linked to the chronic inflammation and to defective prenylation. Considering the broad and unspecific spectrum of MKD clinical manifestations and the difficulty in its diagnosis, a better understanding of MKD molecular bases could be translated to the clinical level to facilitate diagnosis, and improve management and therapy.

Cardiac Complications of Propionic and Other Inherited Organic Acidemias

Clinical observations and experimental studies have determined that systemic acid-base disturbances can profoundly affect the heart. A wealth of information is available on the effects of altered pH on cardiac function but, by comparison, much less is known about the actions of the organic anions that accumulate alongside H⁺ ions in acidosis. In the blood and other body fluids, these organic chemical species can collectively reach concentrations of several millimolar in severe metabolic acidoses, as in the case of inherited organic acidemias, and exert powerful biological actions on the heart that are not intuitive to predict. Indeed, cardiac pathologies, such as cardiomyopathy and arrhythmia, are frequently reported in organic acidemia patients, but the underlying pathophysiological mechanisms are not well established. Research efforts in the area of organic anion physiology have increased dramatically in recent years, particularly for propionate, which accumulates in propionic acidemia, one of the commonest organic acidemias characterized by a high incidence of cardiac disease. This Review provides a comprehensive historical overview of all known organic acidemias that feature cardiac complications and a state-of-the-art overview of the cardiac sequelae observed in propionic acidemia. The article identifies the most promising candidates for molecular mechanisms that become aberrantly engaged by propionate anions (and its metabolites), and discusses how these may result in cardiac derangements in propionic acidemia. Key clinical and experimental findings are considered in the context of potential therapies in the near future.

Cholesterol partially rescues the inhibition effect of pravastatin on keratinocytes proliferation by regulating cell cycle relative proteins through AKT and ERK pathway

Mevalonate pathway plays a key role in skin physiological process in human. Recently, it has been reported that mutation of some genes in the mevalonate pathway cause disseminated superficial actinic porokeratosis (DSAP). But the pathogenesis is still unknown. Pravastatin (PRA), one of HMG-CoA reductase (HMGCR) inhibitors, has been found to inhibit cells proliferation, including keratinocytes (KCs). In this study, we use PRA to block the mevalonate pathway in KCs with or without the down-stream intermediate products replenishment. The results demonstrated that PRA strongly inhibited proliferation of KCs and caused the G₀ /G₁ arrest. When some down-stream intermediate products were added, only cholesterol (CH) could partially rescue the inhibition effect of PRA on KCs proliferation, but not other products, such as mevalonic acid, farnesyl pyrophosphate or geranylgeranyl pyrophosphate. Mechanistic analysis revealed that PRA down-regulated expression of cyclin B1, but up-regulated cyclin E and p21 expression. And PRA increased the phosphorylation level of Protein Kinase B (AKT) but decreased the phosphorylation level of Extracellular Signal Regulated Kinase (ERK1/2). CH could attenuate the elevated cyclin E and activated AKT induced by PRA. These results indicated that CH could rescue the proliferation inhibition of KCs caused by PRA, which laid a foundation for elucidating the pathogenesis of DSAP clearly.

Spectrum of clinical features and genetic variants in mevalonate kinase (MVK) gene of South Indian families suffering from Hyperimmunoglobulin D Syndrome

Hyper-IgD syndrome (HIDS, OMIM #260920) is a rare autosomal recessive autoinflammatory disorder caused by pathogenic variants in the mevalonate kinase (MVK) gene. HIDS has an incidence of 1:50,000 to 1:5,000, and is thought to be prevalent mainly in northern Europe. Here, we report a case series of HIDS from India, which includes ten patients from six families who presented with a wide spectrum of clinical features such as recurrent fever, oral ulcers, rash, arthritis, recurrent diarrhea, hepatosplenomegaly, and high immunoglobulin levels. Using whole exome sequencing (WES) and/or Sanger capillary sequencing, we identified five distinct genetic variants in the MVK gene from nine patients belonging to six families. The variants were classified as pathogenic or likely pathogenic as per the American College of Medical Genetics and Genomics and the Association for Molecular Pathology (ACMG-AMP) guidelines for annotation of sequence variants. Over 70% of patients in the present study had two recurrent mutations in MVK gene i.e. a nonsynonymous variant p.V377I, popularly known as the ‘Dutch mutation’, along with a splicing variant c.226+2delT in a compound heterozygous form. Identity by descent analysis in two patients with the recurrent variants identified a 6.7 MB long haplotype suggesting a founder effect in the South Indian population. Our analysis suggests that a limited number of variants account for the majority of the patients with HIDS in South India. This has implications in clinical diagnosis, as well as in the development of cost-effective approaches for genetic diagnosis and screening. To our best knowledge, this is the first and most comprehensive case series of clinically and genetically characterized patients with HIDS from India.

Autoinflammatory diseases in childhood, part 1: monogenic syndromes

Autoinflammatory diseases constitute a family of disorders defined by aberrant stimulation of inflammatory pathways without involving antigen-directed autoimmunity. They may be divided into monogenic and polygenic types. Monogenic autoinflammatory syndromes are those with identified genetic mutations, such as familial Mediterranean fever, tumor necrosis factor receptor-associated periodic fever syndrome (TRAPS), mevalonate kinase deficiency or hyperimmunoglobulin D syndrome, cryopyrin-associated periodic fever syndromes (CAPS), pyogenic arthritis pyoderma gangrenosum and acne (PAPA) syndrome, interleukin-10 and interleukin-10 receptor deficiencies, adenosine deaminase 2 deficiency and pediatric sarcoidosis. Those without an identified genetic mutation are known as polygenic and include systemic-onset juvenile idiopathic arthritis, idiopathic recurrent acute pericarditis, Behçet syndrome, chronic recurrent multifocal osteomyelitis and inflammatory bowel disease among others. Autoinflammatory disorders are defined by repeating episodes or persistent fever, rash, serositis, lymphadenopathy, arthritis and increased acute phase reactants, and thus may mimic infections clinically. Most monogenic autoinflammatory syndromes present in childhood. However, because of their infrequency, diverse and nonspecific presentation, and the relatively new genetic recognition, diagnosis is usually delayed. In this article, which is Part 1 of a two-part series, the authors update monogenic autoinflammatory diseases in children with special emphasis on imaging features that may help establish the correct diagnosis.

Mevalonic aciduria: Does stem cell transplant fully cure disease?

MA is a rare, autosomal recessive disorder characterized by episodes of inflammation and periodic fevers. In its most severe form, it can result in facial dysmorphism, growth inhibition, ataxia, liver dysfunction, intellectual disability, and at times can be fatal. A number of case reports exist stating that SCT is curative in these patients. We present the case of a patient diagnosed with MA at birth, who underwent SCT at the age of 14 months with intent to cure. She achieved complete engraftment and urine mevalonate became undetectable. However, 18 months following transplant, she developed frequent episodes of fevers, rashes, arthritis, and a rising urinary mevalonate. She was subsequently diagnosed with relapse. She now requires treatment with steroids and canakinumab to manage her disease. This case is the first report of disease relapse following transplant for MA. It runs contrary to prior reports that SCT is fully curative of MA and suggests that transplant may instead provide a means of decreasing disease severity without entirely eradicating the condition.

Omnipresence of inflammasome activities in inflammatory bone diseases

The inflammasomes are intracellular protein complexes that are assembled in response to a variety of perturbations including infections and injuries. Failure of the inflammasomes to rapidly clear the insults or restore tissue homeostasis can result in chronic inflammation. Recurring inflammation is also provoked by mutations that cause the constitutive assembly of the components of these protein platforms. Evidence suggests that chronic inflammation is a shared mechanism in bone loss associated with aging, dysregulated metabolism, autoinflammatory, and autoimmune diseases. Mechanistically, inflammatory mediators promote bone resorption while suppressing bone formation, an imbalance which over time leads to bone loss and increased fracture risk. Thus, while acute inflammation is important for the maintenance of bone integrity, its chronic state damages this tissue. In this review, we discuss the role of the inflammasomes in inflammation-induced osteolysis.

Mevalonate kinase deficiency masked by cytomegalovirus infection and obscure liver disease

BACKGROUND

Chronic liver disease with conjugated hyperbilirubinaemia and failure to thrive can have multifactorial aetiologies. Investigations can be complex and difficult especially when obscured by a viral infection affecting liver function.

METHODS

A 5 month old male infant was referred for investigation of chronic liver disease and a history of jaundice with multiple febrile episodes. Liver function tests were performed followed by a liver biopsy and microbiological workup for infectious disease. In addition, urine analysis of organic acids was also performed.

RESULTS

There was marked conjugated hyperbilirubinaemia with markedly elevated hepatocellular enzymes and normal ductal enzymes. Proteinuria and near normal renal function suggested early renal impairment. There was also leukocytosis and bicytopenia. An extensive bacteriological investigation including TB workup was negative. CMV infection was confirmed by viral load and antibody reactivity. There was prolonged PT and PTT and high INR. The liver biopsy showed giant cell transformation of hepatocytes with mild cholestasis, portal and peri-cellular fibrosis with alpha-1-antitrypsin positive granules in the hepatocyte cytoplasm suggesting alpha-1-antitrypsin deficiency. Urine organic acids revealed significantly elevated mevalonolactone.

CONCLUSIONS

We confirmed the genetic diagnosis of mevalonic aciduria caused by MVK deficiency which had been masked by liver disease and the possible misdiagnosis of alpha-1-antitrypsin deficiency.

A case report of mevalonate kinase deficiency in a 14-month-old female with fevers and lower extremity weakness

Background

This case follows a 14-month-old female, who despite multiple presentations to several physicians, continued to have recurrent febrile episodes with gross motor delay. Her case revealed an often missed diagnosis of Mevalonate Kinase Deficiency, that now has an FDA approved treatment that both reduces recurrence and produces remission.

Case presentation

A 14-month-old female with a history of gross motor delay, frequent Upper Respiratory Tract infections, and otitis media presented to an urgent care for inconsolability and refusal to bear weight on her right leg. She had recently been treated with amoxicillin for acute otitis media and had developed a diffuse maculopapular rash, without any associated respiratory or gastrointestinal distress that persisted beyond cessation of the antibiotics. The patient presented multiple times to an urgent care over the subsequent week for fussiness, fever, anorexia, lymphadenopathy, with labs concerning for worsening anemia and elevated inflammatory markers. Subsequently, the patient was admitted to the hospital for suspected osteomyelitis versus oncologic process. X-Ray imaging of the patient’s lower extremities showed osseous abnormalities inconsistent with infection. A metabolic work-up showed elevated urine mevalonic acid, and follow-up genetic testing was positive for mutations in both copies of her mevalonate kinase gene. This led to the diagnosis of MKD.

Conclusions

Often, episodic presentations require multiple perspectives to reveal the underlying cause. This case illustrates how apparent simple febrile episodes has the potential for more complexity upon further evaluation.

Multi-OMICS analyses unveil STAT1 as a potential modifier gene in mevalonate kinase deficiency

OBJECTIVES

The objective of the present study was to explain why two siblings carrying both the same homozygous pathogenic mutation for the autoinflammatory disease hyper IgD syndrome, show opposite phenotypes, that is, the first being asymptomatic, the second presenting all classical characteristics of the disease.

METHODS

Where single omics (mainly exome) analysis fails to identify culprit genes/mutations in human complex diseases, multiomics analyses may provide solutions, although this has been seldom used in a clinical setting. Here we combine exome, transcriptome and proteome analyses to decipher at a molecular level, the phenotypic differences between the two siblings.

RESULTS

This multiomics approach led to the identification of a single gene-STAT1-which harboured a rare missense variant and showed a significant overexpression of both mRNA and protein in the symptomatic versus the asymptomatic sister. This variant was shown to be of gain of function nature, involved in an increased activation of the Janus kinase/signal transducer and activator of transcription signalling (JAK/STAT) pathway, known to play a critical role in inflammatory diseases and for which specific biotherapies presently exist. Pathway analyses based on information from differentially expressed transcripts and proteins confirmed the central role of STAT1 in the proposed regulatory network leading to an increased inflammatory phenotype in the symptomatic sibling.

CONCLUSIONS

This study demonstrates the power of a multiomics approach to uncover potential clinically actionable targets for a personalised therapy. In more general terms, we provide a proteogenomics analysis pipeline that takes advantage of subject-specific genomic and transcriptomic information to improve protein identification and hence advance individualised medicine.

Tocilizumab for the Treatment of Mevalonate Kinase Deficiency

Mevalonate kinase deficiency (MKD) is a severe autoinflammatory disease caused by recessive mutations in MVK resulting in reduced function of the enzyme mevalonate kinase, involved in the cholesterol/isoprenoid pathway. MKD presents with periodic episodes of severe systemic inflammation, poor quality of life, and life-threatening sequelae if inadequately treated. We report the case of a 12-year-old girl with MKD and severe autoinflammation that was resistant to IL-1 and TNF-α blockade. In view of this, she commenced intravenous tocilizumab (8 mg/kg every 2 weeks), a humanised monoclonal antibody targeting the IL-6 receptor (IL-6R) that binds to membrane and soluble IL-6R, inhibiting IL-6-mediated signaling. She reported immediate cessation of fever and marked improvement in her energy levels following the first infusion; after the fifth dose, she was in complete clinical and serological remission, now sustained for 24 months. This is one of the first reported cases of a child with MKD treated successfully with tocilizumab and adds to the very limited experience of this treatment for MKD. IL-6 blockade could therefore be an important addition to the armamentarium for the treatment of this rare monogenic autoinflammatory disease.

Neuronal Dysfunction Associated with Cholesterol Deregulation

Cholesterol metabolism is crucial for cells and, in particular, its biosynthesis in the central nervous system occurs in situ, and its deregulation involves morphological changes that cause functional variations and trigger programmed cell death. The pathogenesis of rare diseases, such as Mevalonate Kinase Deficiency or Smith–Lemli–Opitz Syndrome, arises due to enzymatic defects in the cholesterol metabolic pathways, resulting in a shortage of downstream products. The most severe clinical manifestations of these diseases appear as neurological defects. Expanding the knowledge of this biological mechanism will be useful for identifying potential targets and preventing neuronal damage. Several studies have demonstrated that deregulation of the cholesterol pathway induces mitochondrial dysfunction as the result of respiratory chain damage. We set out to determine whether mitochondrial damage may be prevented by using protective mitochondria-targeted compounds, such as MitoQ, in a neuronal cell line treated with a statin to induce a biochemical block of the cholesterol pathway. Evidence from the literature suggests that mitochondria play a crucial role in the apoptotic mechanism secondary to blocking the cholesterol pathway. Our study shows that MitoQ, administered as a preventive agent, could counteract the cell damage induced by statins in the early stages, but its protective role fades over time.

Prolonged treatment with mevalonolactone induces oxidative stress response with reactive oxygen species production, mitochondrial depolarization and inflammation in human glioblastoma U-87 MG cells

Mevalonate pathway impairment has been observed in diverse diseases, including Mevalonate Kinase Deficiency (MKD). MKD is a hereditary auto-inflammatory disorder, due to mutations at mevalonate kinase gene (MVK), encoding mevalonate kinase (MK) enzyme. To date, the most accredited MKD pathogenic hypothesis suggests that the typical MKD phenotypes might be due to a decreased isoprenoid production rather than to the excess and accumulation of mevalonic acid, as initially supported. Nevertheless, recent studies provide clear evidences that accumulating metabolites might be involved in MKD pathophysiology by exerting a toxic effect. Our work aims at describing the effects of accumulating mevalonolactone, mostly produced by a dehydration reaction due to mevalonic acid accumulation, using an in vitro cellular model mimicking the glial component of the central nervous system (human glioblastoma U-87 MG cells). In order to mimic its progressive increase, occurring during the disease, U-87 MG cells have been treated repeatedly with growing doses of mevalonolactone, followed by the assessment of oxidative stress response (evaluated by measuring SOD2 and HemeOX expression levels), ROS production, mitochondrial damage and inflammatory response (evaluated by measuring IL1B expression levels). Our results suggest that protracted treatments with mevalonolactone induce oxidative stress with augmented ROS production and mitochondrial damage accompanied by membrane depolarization. Furthermore, an increment in IL1B expression has been observed, thus correlating the accumulation of the metabolite with the development of a neuroinflammatory response. Our experimental work suggests to reconsider the presence of a possible synergy between the two major MKD pathogenic hypotheses in attempt of unravelling the different pathogenic pathways responsible for the disease.

MMAB, a novel candidate gene to be screened in the molecular diagnosis of Mevalonate Kinase Deficiency

Mevalonate kinase deficiency (MKD) is an autosomal recessive inflammatory disease. Mutations in MVK gene are associated with MKD with modest genotype-phenotype correlation. In spite of recent guidelines indicating specific MVK mutations for the more severe form or the milder one, little is known about MVK variability within and between populations. The aim of this work is to provide supplementary information about MVK variability useful in the molecular diagnosis of MKD, as well as to unravel the presence of novel genes potentially involved as involved in the clinical heterogeneity of MKD phenotype. We used a population-based approach, coupled with Combined Annotation-Dependent Depletion (CADD) score, to analyze the level of genetic variability for common and putatively deleterious MVK variants. We also performed Exome screening with the Illumina Human Exome Bead Chip on 21 MKD patients to double-check our in silico findings. Haplotype block detection in different populations revealed the existence of two blocks in MVK; interestingly, the first haploblock comprises the promoter region shared with MMAB gene. Analyses of MMAB and MVK genetic variants in 21 MKD patients strengthen our observations showing a novel scenario in which the same mutations commonly associated with MKD are found coupled with different combination of MMAB rs7134594 SNP was already described as associated with HDL cholesterol level and present in the haploblock promoter region. The rs7134594 SNP is reported as an eQTL for MVK and MMAB. Hypothesizing the presence of genetic variants modulating the complex phenotypic spectrum of MKD, we suggest that future directions in screening for MKD pathogenic variants should focus both MMAB and MVK genes.

Disorder of the mevalonate pathway inhibits calcium-induced differentiation of keratinocytes

Mutation of genes encoding the enzymes of the mevalonate pathway cause a variety of diseases, including skin disorders. Mutation of four genes in this pathway, including mevalonate kinase, phosphomevalonate kinase, mevalonate diphosphate decarboxylase and farnesyl diphosphate synthase, have demonstrated to be responsible for porokeratosis (PK). However, the pathogenesis of PK remains unclear. In the present study, specific enzyme inhibitors of the mevalonate pathway, including pravastatin (PRA), alendronate (ALD), farnesyl transferase inhibitor (FTI‑277) and geranylgeranyl transferase inhibitor (GGTI‑298), were used to investigate the effect on differentiation of keratinocytes (KCs). Western blotting demonstrated that PRA, ALD, FTI‑277 or GGTI‑298 alone, or in combination, inhibited the expression level of calcium‑induced differentiation maker involucrin (INV) in KCs. ALD and PRA induced greater inhibition of INV compared with FTI‑277 and GGTI‑298 treatment. These inhibitors additionally influenced the expression levels of keratin1. Mechanistic studies revealed that treatment of cells with inhibitors decreased the expression levels of p53 and Notch1, and regulated activation of the mitogen activated protein kinase and phosphoinositide‑3‑kinase/protein kinase B signaling pathways. The results of the present study suggested that regulation of the mevalonate pathway may be necessary for differentiation of KCs, and the pathogenesis of disseminated superficial actinic PK.

Posttranslational Modification as a Critical Determinant of Cytoplasmic Innate Immune Recognition

Cell surface innate immune receptors can directly detect a variety of extracellular pathogens to which cytoplasmic innate immune sensors are rarely exposed. Instead, within the cytoplasm, the environment is rife with cellular machinery and signaling pathways that are indirectly perturbed by pathogenic microbes to activate intracellular sensors, such as pyrin, NLRP1, NLRP3, or NLRC4. Therefore, subtle changes in key intracellular processes such as phosphorylation, ubiquitination, and other pathways leading to posttranslational protein modification are key determinants of innate immune recognition in the cytoplasm. This concept is critical to establish the “guard hypothesis” whereby otherwise homeostatic pathways that keep innate immune sensors at bay are released in response to alterations in their posttranslational modification status. Originally identified in plants, evidence that a similar guardlike mechanism exists in humans has recently been identified, whereby a mutation that prevents phosphorylation of the innate immune sensor pyrin triggers a dominantly inherited autoinflammatory disease. It is also noteworthy that even when a cytoplasmic innate immune sensor has a direct ligand, such as bacterial peptidoglycan (NOD1 or NOD2), RNA (RIG-I or MDA5), or DNA (cGAS or IFI16), it can still be influenced by posttranslational modification to dramatically alter its response. Therefore, due to their existence in the cytoplasmic milieu, posttranslational modification is a key determinant of intracellular innate immune receptor functionality.

Potential of IL-1, IL-18 and Inflammasome Inhibition for the Treatment of Inflammatory Skin Diseases

In 2002, intracellular protein complexes known as the inflammasomes were discovered and were shown to have a crucial role in the sensing of intracellular pathogen- and danger-associated molecular patterns (PAMPs and DAMPs). Activation of the inflammasomes results in the processing and subsequent secretion of the pro-inflammatory cytokines IL-1β and IL-18. Several autoinflammatory disorders such as cryopyrin-associated periodic syndromes and Familial Mediterranean Fever have been associated with mutations of genes encoding inflammasome components. Moreover, the importance of IL-1 has been reported for an increasing number of autoinflammatory skin diseases including but not limited to deficiency of IL-1 receptor antagonist, mevalonate kinase deficiency and PAPA syndrome. Recent findings have revealed that excessive IL-1 release induced by harmful stimuli likely contributes to the pathogenesis of common dermatological diseases such as acne vulgaris or seborrheic dermatitis. A key pathogenic feature of these diseases is IL-1β-induced neutrophil recruitment to the skin. IL-1β blockade may therefore represent a promising therapeutic approach. Several case reports and clinical trials have demonstrated the efficacy of IL-1 inhibition in the treatment of these skin disorders. Next to the recombinant IL-1 receptor antagonist (IL-1Ra) Anakinra and the soluble decoy Rilonacept, the anti-IL-1α monoclonal antibody MABp1 and anti-IL-1β Canakinumab but also Gevokizumab, LY2189102 and P2D7KK, offer valid alternatives to target IL-1. Although less thoroughly investigated, an involvement of IL-18 in the development of cutaneous inflammatory disorders is also suspected. The present review describes the role of IL-1 in diseases with skin involvement and gives an overview of the relevant studies discussing the therapeutic potential of modulating the secretion and activity of IL-1 and IL-18 in such diseases.

Mevalonolactone disrupts mitochondrial functions and induces permeability transition pore opening in rat brain mitochondria: Implications for the pathogenesis of mevalonic aciduria

Mevalonic aciduria (MVA) is caused by severe deficiency of mevalonic kinase activity leading to tissue accumulation and high urinary excretion of mevalonic acid (MA) and mevalonolactone (ML). Patients usually present severe neurologic symptoms whose pathophysiology is poorly known. Here, we tested the hypothesis that the major accumulating metabolites are toxic by investigating the in vitro effects of MA and ML on important mitochondrial functions in rat brain and liver mitochondria. ML, but not MA, markedly decreased mitochondrial membrane potential (ΔΨm), NAD(P)H content and the capacity to retain Ca²⁺ in the brain, besides inducing mitochondrial swelling. These biochemical alterations were totally prevented by the classical inhibitors of mitochondrial permeability transition (MPT) cyclosporine A and ADP, as well as by ruthenium red in Ca²⁺-loaded mitochondria, indicating the involvement of MPT and an important role for mitochondrial Ca²⁺ in these effects. ML also induced lipid peroxidation and markedly inhibited aconitase activity, an enzyme that is highly susceptible to free radical attack, in brain mitochondrial fractions, indicating that lipid and protein oxidative damage may underlie some of ML-induced deleterious effects including MTP induction. In contrast, ML and MA did not compromise oxidative phosphorylation in the brain and all mitochondrial functions evaluated in the liver, evidencing a selective toxicity of ML towards the central nervous system. Our present study provides for the first time evidence that ML impairs essential brain mitochondrial functions with the involvement of MPT pore opening. It is therefore presumed that disturbance of brain mitochondrial homeostasis possibly contributes to the neurologic symptoms in MVA.

Association of KCTD10, MVK, and MMAB polymorphisms with dyslipidemia and coronary heart disease in Han Chinese population

Background

Several genome-wide association studies have discovered novel loci at chromosome 12q24, which includes mevalonate kinase (MVK), methylmalonic aciduria (cobalamin deficiency) cbIB type (MMAB), and potassium channel tetramerization domain-containing 10 (KCTD10), all of which influence HDL-cholesterol concentrations. However, there are few reports on the associations between these polymorphisms and HDL-C concentrations in Chinese population. This study aimed to evaluate the associations between functional polymorphisms in three genes (MVK, MMAB and KCTD10) and HDL-C concentrations, as well as coronary heart disease (CHD) susceptibility in Chinese individuals.

Methods

We systematically selected and genotyped 18 potentially functional polymorphisms in MVK, MMAB and KCTD10 by using the TaqMan OpenArray Genotyping System in a Chinese population including 399 dyslipidemia cases, 697 CHD cases and 465 controls. Multivariate logistic regression analyses were performed to estimate the relationship between the genotypes and dyslipidemia, CHD risk with adjustment of relevant confounders.

Results

Among six polymorphisms showing significant associations with dyslipidemia, the minor alleles of rs11066782 in KCTD10, rs11613718 in KCTD10 and rs11067233 in MMAB were significantly associated with a decreased risk of CHD (additive model: OR = 0.71, 95 % CI = 0.53–0.97, P = 0.029 for rs11066782; OR = 0.73, 95 % CI = 0.54–0.99, P = 0.044 for rs11613718 and OR = 0.57, 95 % CI = 0.40–0.80, P = 0.001 for rs11067233). Further combined analysis showed that individuals carrying “3-4” favorable alleles presented a 62 % (OR = 0.38, 95 % CI = 0.21–0.66) decreased risk of CHD compared with those carrying “0–2” favorable alleles.

Conclusions

These findings suggest that rs11066782 in KCTD10, rs11613718 in KCTD10 and rs11067233 in MMAB may contribute to the susceptibility of CHD by altering plasma HDL-C levels in Han Chinese.

Electronic supplementary material

The online version of this article (doi:10.1186/s12944-016-0348-7) contains supplementary material, which is available to authorized users.

Mevalonate kinase deficiency: current perspectives

Mevalonate kinase deficiency (MKD) is a recessively inherited autoinflammatory disorder with a spectrum of manifestations, including the well-defined clinical phenotypes of hyperimmunoglobulinemia D and periodic fever syndrome and mevalonic aciduria. Patients with MKD have recurrent attacks of hyperinflammation associated with fever, abdominal pain, arthralgias, and mucocutaneous lesions, and more severely affected patients also have dysmorphisms and central nervous system anomalies. MKD is caused by mutations in the gene encoding mevalonate kinase, with the degree of residual enzyme activity largely determining disease severity. Mevalonate kinase is essential for the biosynthesis of nonsterol isoprenoids, which mediate protein prenylation. Although the precise pathogenesis of MKD remains unclear, increasing evidence suggests that deficiency in protein prenylation leads to innate immune activation and systemic hyperinflammation. Given the emerging understanding of MKD as an autoinflammatory disorder, recent treatment approaches have largely focused on cytokine-directed biologic therapy. Herein, we review the current genetic and pathologic understanding of MKD, its various clinical phenotypes, and the evolving treatment approach for this multifaceted disorder.

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.

Natural history of mevalonate kinase deficiency: a literature review

Mevalonate kinase deficiency (MKD), a very rare autosomal recessive autoinflammatory disease with multiple organ involvement, presents clinically as hyperimmunoglobulinemia D syndrome (HIDS), a less severe phenotype and more common form, and mevalonic aciduria (MVA), a more severe phenotype and rare form. MKD is characterized by recurrent febrile attacks that are frequently accompanied by lymphadenopathy, gastrointestinal symptoms, arthralgia, myalgia, skin rash, and aphthous ulcers. Patients with MVA also have intrauterine growth retardation, congenital defects (cataracts, shortened limbs, and dysmorphic craniofacial features), neurological disease, and failure to thrive. Mean age at onset of symptoms is within the first year of life. There is a delay by several years between symptom onset and diagnosis, which is in part attributable to the initial misdiagnosis due to the rarity and nonspecific clinical manifestations of disease. The frequency of recurrent febrile attacks is highest in childhood and gradually decreases after adolescence. MKD is associated with rare long-term complications such as type AA amyloidosis, joint contractures, abdominal adhesions, renal angiomyolipoma, and severe pneumococcal infections. Frequent febrile attacks significantly impair several aspects of patients' and caregivers' quality of life, with an adverse impact on patients' daily activities, education, and employment. Lifespan is generally normal for HIDS whereas MVA can be fatal in early childhood.

Perinatal manifestation of mevalonate kinase deficiency and efficacy of anakinra

BACKGROUND

Mevalonate kinase deficiency is a metabolic autoinflammatory syndrome caused by mutations in the MVK gene, mevalonate kinase, the key enzyme in the non-sterol isoprenoid biosynthesis pathway. Two phenotypes of mevalonate kinase deficiency are known based on the level of enzymatic deficiency, mevalonic aciduria and hyperimmunoglobulinemia D syndrome, but a wide spectrum of intermediate phenotypes has been reported. Currently one of the most effective treatments is biological therapy (with interleukin-1 antagonist anakinra or tumour necrosis factor-α inhibitor etanercept).

CASE PRESENTATION

The patient in this case has a phenotype contributing to a severe disease that caused the symptoms to manifest very early, in the prenatal period. Mevalonate kinase deficiency was suspected on the basis of clinical (hydrops fetalis, hepatosplenomegaly, hypotonia) and laboratory signs (anaemia, intense acute phase reaction, increased urinary excretion of mevalonic acid). Mutation analysis of the MVK gene confirmed the biochemical diagnosis. Treatment with the interleukin-1 antagonist anakinra was started (minimal dose of 1 mg/kg/day) and revealed its efficacy after three days.

CONCLUSIONS

Our case highlights the need for a very detailed clinical and laboratory assessment in new-borns with any suggestion of autoinflammatory disorders. It is important that patients are diagnosed as early as possible to provide better multidisciplinary follow-up and therapy when needed.