Aberrant expression of costimulatory molecules in splenocytes of the mevalonate kinase-deficient mouse model of human hyper-IgD syndrome (HIDS)

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.

Hyper-IgD syndrome/mevalonate kinase deficiency: what is new?

Mevalonate kinase deficiency or hyper-IgD syndrome is a hereditary autoinflammatory syndrome caused by mutations in the mevalonate kinase gene. In this review, we will discuss new findings in this disorder that have been published in the last 2 years. This includes new insights into pathophysiology, treatment, and the clinical phenotype linked to the genetic defect.

Current advances in the understanding and treatment of mevalonate kinase deficiency

Mevalonate kinase deficiency (MKD) is a rare autosomal recessive autoinflammatory metabolic disease that is caused by mutations in the MVK gene. Patients with MKD typically have an early onset in infancy. MKD is characterized by recurrent episodes of high fever, abdominal distress, diffuse joint pain, and skin rashes. In a subset of patients, MKD is also associated with elevated serum immunoglobulin D (IgD) levels (hyperimmunoglobulinemia D syndrome, HIDS). The clinical phenotype of MKD varies widely and depends on the severity of the impaired mevalonate kinase activity. Complete impairment results in the severe metabolic disease, mevalonic aciduria, while a partial deficiency results in a broad spectrum of clinical presentation, including HIDS. The precise molecular mechanisms behind the elevated serum IgD levels and inflammation that occurs in MKD remain unknown. Children who exhibit symptoms of MKD should be tested for mutations in the MKD gene. However, the complexity of MKD often results in delays in its definitive diagnosis and the outcome in adult age is not completely known. Therapeutic options for MKD are based on limited data and include non-steroidal anti-inflammatory drugs, corticosteroids, and biological agents that target specific cytokine pathways. In recent years, some studies have reported promising results for new biological drugs; however, these cases have failed to achieve satisfactory remission. Therefore, further studies are needed to understand the pathogenesis of MKD and identify innovative therapeutic tools for its management.

30 years hids-Travels between bedside and bench

In this paper I describe more than 30 years of investigations of the autoinflammatory syndrome hyper-IgD syndrome (HIDS). In the first paper after the recognition of the syndrome published in 1984, we described the characteristics of this periodic fever syndrome. The hypotheses regarding the pathogenesis of the fever and the acute phase response in these patients prompted us to study interleukin-1 (IL-1), the cytokine formerly described as endogenous pyrogen and lymphocyte activating factor. Although we were unable to find elevated concentrations of IL-1 in the circulation, we discovered that white blood cells spontaneously produced elevated amounts of IL-1b. A major next discovery was the identification of the gene defect by us and others in 1999: quite unexpectedly the mevalonate kinase, an enzyme in the cholesterol synthesis pathway was found to be mutated. We were able to describe a founder effect and a phenotypic continuum with the classical mevalonate aciduria in the years to follow. A major step forward was the finding that recombinant interleukin-1 receptor antagonist (anakinra) was an effective treatment for the majority of patients. Thus, research over a period of three decades after the first recognition of the syndrome, has yielded much insight into the pathogenesis as well as an effective therapy for HIDS.

Splicing mutation in MVK is a cause of porokeratosis of Mibelli

Porokeratosis is a chronic skin disorder characterized by the presence of patches with elevated, thick, keratotic borders, with histological cornoid lamella. Classic porokeratosis of Mibelli (PM) frequently appears in childhood with a risk of malignant transformation. Disseminated superficial actinic porokeratosis (DSAP) is the most common subtype of porokeratosis with genetic heterogeneities, and mevalonate kinase gene (MVK) mutations have been identified in minor portion of DSAP families of Chinese origin. To confirm the previous findings about MVK mutations in DSAP patients and test MVK's role(s) in PM development, we performed genomic sequence analysis for 3 DSAP families and 1 PM family of Chinese origin. We identified a splicing mutation of MVK gene, designated as c.1039+1G>A, in the PM family. No MVK mutations were found in three DSAP families. Sequence analysis for complementary DNA templates from PM lesions of all patients revealed a mutation at splice donor site of intron 10, designated as c.1039+1G>A, leading to the splicing defect and termination codon 52 amino acids after exon 10. Although no MVK mutations in DSAP patients were found as reported previously, we identified MVK simultaneously responsible for PM development.

Long chain fatty acid (Lcfa) abnormalities in hyper Igd syndrome (Hids) and Familial Mediterranean Fever (Fmf): new insight into heritable periodic fevers

OBJECTIVE

To examine essential fatty acids (EFAs) in hyper-IgD syndrome (HIDS) and Familial Mediterranean Fever (FMF).

METHODS

EFAs were determined in sera derived from an archival, cross-sectional group of HIDS/FMF patients, stratified for presence and absence of fever. Control populations included healthy afebrile adults, and individuals with non-periodic fever (septic shock). EFAs were quantified using isotope dilution gas chromatography-mass spectrometry and data analyzed employing a Kruskal-Wallis non-parametric ANOVA with Dunn's post-hoc test.

RESULTS

Sera samples derived from HIDS patients showed significantly decreased C20, C26, phytanic and pristanic acids during febrile crises that normalized in the afebrile state, and a significantly increased afebrile C22_4ω6 level that normalized with fever. Samples derived from FMF patients revealed increased ω-oxidized LCFAs as compared to controls, and the trend was for these same species to be increased in comparison to febrile, but not afebrile, HIDS patients. Individuals with non-periodic fever demonstrated global decreases in C10-C24 fatty acids, both saturated and unsaturated, accompanied by an elevated triene/tetraene ratio.

CONCLUSIONS

Our results suggest that different mechanisms are active in hereditary periodic fever syndromes that appear unrelated to fever, including depletion of very long chain fatty acids (VLCFAs) in febrile HIDS patients and increased ω-oxidized LCFAs in patients with FMF. These findings underscore new roles for EFAs in the potential production of inflammatory species in patients with hereditary periodic fever.

[Hyperimmunoglobulinemia D and periodic fever syndrome]

Hyperimmunogloblinemia D and periodic fever syndrome (HIDS) is inherited autoinflammatory syndrome caused by deficiency of the mevalonate kinase (MK), which is involved in metabolism of cholesterol. The disease is characterized as periodic fever from early infancy accompanied by elevated serum C-reactive protein. Since clinical symptoms such as abdominal symptom, skin rash, and arthritis are common to other autoinflammatory disease, the diagnosis of HIDS during clinical work is difficult for the physicians without suspicion of HIDS for infants suffering from fever of unknown origin. Moreover, serum IgD levels are not high during infancy conflicting to the name of the disease, which is often misunderstood in the clinicians. Thus, the diagnosis of HIDS in Japan is bothering, depending on the lack of correct recognition of the disease and on the lack of commercially available examination for the disease. It is important for clinicians, especially pediatricians to update current knowledge about HIDS and to learn the appropriate way to the definitive diagnosis of HIDS, because HIDS patients exist also in Japan and the specific therapies for HIDS would be developed in the near future.