Homozygosity for the V377I mutation in mevalonate kinase causes distinct clinical phenotypes in two sibs with hyperimmunoglobulinaemia D and periodic fever syndrome (HIDS)

Mevalonate kinase-deficient THP-1 cells show a disease-characteristic pro-inflammatory phenotype

Objective

Bi-allelic pathogenic variants in the MVK gene, which encodes mevalonate kinase (MK), an essential enzyme in isoprenoid biosynthesis, cause the autoinflammatory metabolic disorder mevalonate kinase deficiency (MKD). We generated and characterized MK-deficient monocytic THP-1 cells to identify molecular and cellular mechanisms that contribute to the pro-inflammatory phenotype of MKD.

Methods

Using CRISPR/Cas9 genome editing, we generated THP-1 cells with different MK deficiencies mimicking the severe (MKD-MA) and mild end (MKD-HIDS) of the MKD disease spectrum. Following confirmation of previously established disease-specific biochemical hallmarks, we studied the consequences of the different MK deficiencies on LPS-stimulated cytokine release, glycolysis versus oxidative phosphorylation rates, cellular chemotaxis and protein kinase activity.

Results

Similar to MKD patients' cells, MK deficiency in the THP-1 cells caused a pro-inflammatory phenotype with a severity correlating with the residual MK protein levels. In the MKD-MA THP-1 cells, MK protein levels were barely detectable, which affected protein prenylation and was accompanied by a profound pro-inflammatory phenotype. This included a markedly increased LPS-stimulated release of pro-inflammatory cytokines and a metabolic switch from oxidative phosphorylation towards glycolysis. We also observed increased activity of protein kinases that are involved in cell migration and proliferation, and in innate and adaptive immune responses. The MKD-HIDS THP-1 cells had approximately 20% residual MK activity and showed a milder phenotype, which manifested mainly upon LPS stimulation or exposure to elevated temperatures.

Conclusion

MK-deficient THP-1 cells show the biochemical and pro-inflammatory phenotype of MKD and are a good model to study underlying disease mechanisms and therapeutic options of this autoinflammatory disorder.

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.

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.

Central nervous system manifestations of monogenic autoinflammatory disorders and the neurotropic features of SARS-CoV-2: Drawing the parallels

Central nervous system (CNS) involvement in monogenic autoinflammatory disorders (AID) is increasingly recognized and can be life threatening. Therefore, a low threshold to consider CNS disease should be maintained in patients with systemic inflammation. Hyperinflammation is also a key feature of severe acute COVID-19 and post COVID-19 entities such as multisystem inflammatory syndrome in children. Like AID, COVID-19 patients can present with severe CNS involvement. The impact of COVID-19 on AID and CNS involvement in particular is still obscure, nevertheless dreaded. In the current review, we synthesize the spectrum of CNS manifestations in monogenic AID. We explore common pathophysiological and clinical features of AID and COVID-19. Moreover, we assess the impact of immune dysregulation associated with SARS-CoV-2 infections and post COVID-19 hyperinflammation in AID. The striking commonalities found between both disease entities warrant caution in the management of AID patients during the current pandemic.

Twists and turns of the genetic story of mevalonate kinase-associated diseases: A review

Mevalonate kinase (MK)-associated diseases encompass a broad spectrum of rare auto-inflammatory conditions, all resulting from pathogenic variants in the mevalonate kinase gene (MVK). Their clinical manifestations are highly variable, ranging from more or less serious systemic disorders, such as hereditary recurrent fevers, to purely localized pathologies such as porokeratosis. The oldest condition identified as linked to this gene is a metabolic disease called mevalonic aciduria, and the most recent is disseminated superficial actinic porokeratosis, a disease limited to the skin. The modes of inheritance of MK-associated diseases also diverge among the different subtypes: recessive for the systemic subtypes and dominant with a post-zygotic somatic genetic alteration for MVK-associated porokeratosis. This review quickly retraces the historical steps that led to the description of the various MK-associated disease phenotypes and to a better understanding of their pathophysiology, then summarizes and compares the different genetic mechanisms involved in this group of disorders, and finally discusses the diverse causes that could underlie this phenotypic heterogeneity.

Homozygous V377I mutation causing mevalonate kinase

Hyperimmunoglobulinaemia D syndrome (HIDS) is a rare autosomal recessive disorder caused by mutations in the mevalonate kinase (MVK) gene, located on chromosome 12. The most common mutation identified in MVK gene so far is V377I. Compound heterozygotes that include this variant may exhibit a more severe phenotype of the disease and homozygotes are rarely found in clinical practice probably they express a milder phenotype. HIDS is a chronic autoinflammatory disease characterised by recurrent febrile episodes, associated with lymphadenopathies, abdominal pain, rash and arthritis. These flares can be triggered by vaccination, minor trauma, surgery and stress.We report a case of a 2-year-old girl who had recurrent attacks of fever associated with cervical lymphadenopathy, macular erythematous skin rash, abdominal pain and aphthous ulcers in the mouth. The patient was found to excrete elevated amounts of urinary mevalonic acid and a homozygous V337I mutation in the MVK gene was identified.

Mevalonate Kinase-Associated Diseases: Hunting for Phenotype-Genotype Correlation

Mevalonate kinase-associated diseases (MKAD) are caused by pathogenic mutations in the mevalonate kinase gene (MVK) and encompass several phenotypically different rare and hereditary autoinflammatory conditions. The most serious is a recessive systemic metabolic disease called mevalonic aciduria, and the most recently recognized is disseminated superficial actinic porokeratosis, a dominant disease limited to the skin. To evaluate a possible correlation between genotypes and (1) the different MKAD clinical subtypes or (2) the occurrence of severe manifestations, data were reviewed for all patients with MVK variants described in the literature (N = 346), as well as those referred to our center (N = 51). The genotypes including p.(Val377Ile) (homozygous or compound heterozygous) were more frequent in mild systemic forms but were also sometimes encountered with severe disease. We confirmed that amyloidosis was more prevalent in patients compound heterozygous for p.(Ile268Thr) and p.(Val377Ile) than in others and revealed new associations. Patients homozygous for p.(Leu264Phe), p.(Ala334Thr) or compound heterozygous for p.(His20Pro) and p.(Ala334Thr) had increased risk of severe neurological or ocular symptoms. All patients homozygous for p.(Leu264Phe) had a cataract. The variants associated with porokeratosis were relatively specific and more frequently caused a frameshift than in patients with other clinical forms (26% vs. 6%). We provide practical recommendations focusing on phenotype-genotype correlation in MKAD that could be helpful for prophylactic management.

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.

Positive Impact of Expert Reference Center Validation on Performance of Next-Generation Sequencing for Genetic Diagnosis of Autoinflammatory Diseases

Monogenic autoinflammatory diseases (AIDs) are caused by variants in genes that regulate innate immunity. The current diagnostic performance of targeted next-generation sequencing (NGS) for AIDs is low. We assessed whether pre-analytic advice from expert clinicians could help improve NGS performance from our 4 years of experience with the sequencing of a panel of 55 AIDs genes. The study included all patients who underwent routine NGS testing between September 2014 and January 2019 at the laboratory of autoinflammatory diseases (Montpellier, France). Before March 2018, all medical requests for testing were accepted. After this time, we required validation by a reference center before NGS: the positive advice could be obtained after a face-to-face consultation with the patient or presentation of the patient's case at a multidisciplinary staff meeting. Targeted NGS resulted in an overall 7% genetic confirmation, which is consistent with recent reports. The diagnostic performance before and after implementation of the new pre-requisite increased from 6% to 10% (p = 0.021). Our study demonstrated, for the first time, the beneficial effect of a two-step strategy (clinical expert advice, then genetic testing) for AIDs diagnosis and stressed the possible usefulness of the strategy in anticipation of the development of pan-genomic analyses in routine settings.

Defective Protein Prenylation in a Spectrum of Patients With Mevalonate Kinase Deficiency

The rare autoinflammatory disease mevalonate kinase deficiency (MKD, which includes HIDS and mevalonic aciduria) is caused by recessive, pathogenic variants in the MVK gene encoding mevalonate kinase. Deficiency of this enzyme decreases the synthesis of isoprenoid lipids and thus prevents the normal post-translational prenylation of small GTPase proteins, which then accumulate in their unprenylated form. We recently optimized a sensitive assay capable of detecting unprenylated Rab GTPase proteins in peripheral blood mononuclear cells (PBMCs) and showed that this assay distinguished MKD from other autoinflammatory diseases. We have now analyzed PBMCs from an additional six patients with genetically-confirmed MKD (with different compound heterozygous MVK genotypes), and compared these with PBMCs from three healthy volunteers and four unaffected control individuals heterozygous for the commonest pathogenic variant, MVK^V377I. We detected a clear accumulation of unprenylated Rab proteins, as well as unprenylated Rap1A by western blotting, in all six genetically-confirmed MKD patients compared to heterozygous controls and healthy volunteers. Furthermore, in the three subjects for whom measurements of residual mevalonate kinase activity was available, enzymatic activity inversely correlated with the extent of the defect in protein prenylation. Finally, a heterozygous MVK^V377I patient presenting with autoinflammatory symptoms did not have defective prenylation, indicating a different cause of disease. These findings support the notion that the extent of loss of enzyme function caused by biallelic MVK variants determines the severity of defective protein prenylation, and the accumulation of unprenylated proteins in PBMCs may be a sensitive and consistent biomarker that could be used to aid, or help rule out, diagnosis of MKD.

Hyperimmunoglobulinemia D syndrome with recurrent perianal abscess successfully treated with canakinumab

Hyperimmunoglobulinaemia D syndrome is an autoinflammatory disease usually representing recurrent episodes of fever, arthralgia/arthritis, cervical lymphadenopathy, vomiting, diarrhoea, abdominal pain and skin rashes lasting 3-7 days every 4-8 weeks since their infancy. Recent reports suggested a link between perianal fistulae/abscess and severe colitis with hyperimmunoglobulinaemia D syndrome resembling an inflammatory bowel disease phenotype. Herein, we report an 18-month-old patient with recurrent attacks of fever and pharyngitis lasting 2-3 days every 10-15 days since the first two weeks of life. Inflammatory attacks were accompanied by diarrhoea, oral aphthous ulcers, cervical lymphadenopathy, maculopapular rash, severe leukocytosis and perianal fistulae/abscess. After the initiation of canakinumab, the patient was clinically improved with complete healing of perianal fistulas/abscesses. In conclusion, hyperimmunoglobulinaemia D syndrome should be considered in differential diagnosis of inflammatory bowel disease and recurrent perianal abscess/fistula in a patient with inflammatory attacks.

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.

Effects of Anakinra on Health-Related Quality of Life in a Patient with 1129G>A/928G>A Mutations in MVK Gene and Heterozygosity for the Mutation 2107C>A in CIAS1 Gene

Mevalonate kinase deficiency impairs several aspects of the patient's quality of life, thus early diagnosis and treatment are required to improve health-related quality of life (HRQOL). A 15-year-old patient with double heterozygosity for the mutations 1129G>A and 928G>A in MVK gene, heterozygosity for the mutation 2107C>A in CIAS1 gene and hyper-IgD syndrome phenotype, has been treated with anakinra with a reduction of 50% in the number of fever episodes per month, a reduction of 33% in the days of fever for each attack and normal blood tests in the intercritical phase. The RAND 36-Item Health Survey has been used for the assessment of HRQOL before and after the treatment with anakinra. The patient's quality of life showed an overall improvement of 27%; results showed a better improvement in role limitations due to physical health (50%).