Exome sequencing identifies MVK mutations in disseminated superficial actinic porokeratosis

Gene-specific somatic epigenetic mosaicism of FDFT1 underlies a non-hereditary localized form of porokeratosis

Porokeratosis is a clonal keratinization disorder characterized by solitary, linearly arranged, or generally distributed multiple skin lesions. Previous studies showed that genetic alterations in MVK, PMVK, MVD, or FDPS-genes in the mevalonate pathway-cause hereditary porokeratosis, with skin lesions harboring germline and lesion-specific somatic variants on opposite alleles. Here, we identified non-hereditary porokeratosis associated with epigenetic silencing of FDFT1, another gene in the mevalonate pathway. Skin lesions of the generalized form had germline and lesion-specific somatic variants on opposite alleles in FDFT1, representing FDFT1-associated hereditary porokeratosis identified in this study. Conversely, lesions of the solitary or linearly arranged localized form had somatic bi-allelic promoter hypermethylation or mono-allelic promoter hypermethylation with somatic genetic alterations on opposite alleles in FDFT1, indicating non-hereditary porokeratosis. FDFT1 localization was uniformly diminished within the lesions, and lesion-derived keratinocytes showed cholesterol dependence for cell growth and altered expression of genes related to cell-cycle and epidermal development, confirming that lesions form by clonal expansion of FDFT1-deficient keratinocytes. In some individuals with the localized form, gene-specific promoter hypermethylation of FDFT1 was detected in morphologically normal epidermis adjacent to methylation-related lesions but not distal to these lesions, suggesting that asymptomatic somatic epigenetic mosaicism of FDFT1 predisposes certain skin areas to the disease. Finally, consistent with its genetic etiology, topical statin treatment ameliorated lesions in FDFT1-deficient porokeratosis. In conclusion, we identified bi-allelic genetic and/or epigenetic alterations of FDFT1 as a cause of porokeratosis and shed light on the pathogenesis of skin mosaicism involving clonal expansion of epigenetically altered cells.

A novel homozygous variant in PMVK is associated with enhanced IL1β secretion and a hyper-IgD syndrome-like phenotype

The evolutionarily conserved mevalonate pathway plays an important role in the synthesis of cholesterol and isoprenoid compounds. Mevalonate kinase (MVK) and phosphomevalonate kinase (PMVK) enzymes regulate key rate-limiting steps in this pathway by sequentially phosphorylating mevalonic acid to yield downstream metabolites that regulate protein prenylation and cell signaling. Biallelic pathogenic variants in MVK cause a spectrum of rare autoinflammatory disorders that encompass milder forms of hyper-IgD syndrome (HIDS) at one end and the more severe mevalonic aciduria on the other. In contrast, pathogenic variants reported in PMVK are heterozygous and associated with porokeratosis, a skin disorder with no systemic manifestations. Recently, biallelic variants in PMVK were reported as a cause for an autoinflammatory disorder for the first time in two unrelated patients. In this study, we describe a child with recurrent arthritis and a HIDS-like phenotype harboring a novel homozygous variant c.398 C>T (p.Ala133Val) in PMVK. Mononuclear cells isolated from the patient showed significantly elevated production of interleukin 1β, a key cytokine that shapes the inflammatory response in HIDS. Protein modeling studies suggested potential defects in PMVK enzyme activity. These results posit a further expanding of the genotypic spectrum of autoinflammatory disease to include biallelic PMVK variants.

Two Novel and Three Recurrent Mutations in the Mevalonate Pathway Genes in Chinese Patients with Porokeratosis

Purpose

Porokeratosis (PK) is a chronic autosomal-dominant cutaneous keratinization disorder exhibiting clinical and genetic heterogeneity. Mevalonate decarboxylase (MVD), farnesyl diphosphate synthase (FDPS), phosphomevalonate kinase(PMVK), and mevalonate kinase genes(MVK), which encode the mevalonate pathway, are disease-causing genes in PK.

Patients and Methods

Data and blood samples were collected from two Chinese families and five sporadic patients with porokeratosis. Whole-exome and Sanger sequencing were performed to detect pathogenic gene mutation in the patients.

Results

Five heterozygous mutations were identified, including a novel FDPS stop-gain mutation c.438T>G (p.Tyr146Ter), a novel MVD missense mutation c.683G>C (p.R228P), and three previously reported MVD mutations: c.746T>C (p.F249S), c.875A>G (p.N292S), and c.1111_1113del (p.371_371del). The novel FDPS c.438T>G mutation was predicted as "disease-causing" (p = 1) by Mutation Taster. The other novel MVD c.683G>C was also predicted as "deleterious" (score = 0.00) by Sorting Intolerant From Tolerant (SIFT), "probably damaging" (score = 1) by PolyPhen2, and "disease-causing" (p = 0.999) by Mutation Taster.

Conclusion

Our results extended the mutation spectrum of mevalonate pathway genes in porokeratosis and provided useful strategies for a more accurate diagnosis and genetic counseling.

The pyrin inflammasome, a leading actor in pediatric autoinflammatory diseases

The activation of the pyrin inflammasome represents a highly intriguing mechanism employed by the innate immune system to effectively counteract pathogenic agents. Despite its key role in innate immunity, pyrin has also garnered significant attention due to its association with a range of autoinflammatory diseases (AIDs) including familial Mediterranean fever caused by disruption of the MEFV gene, or in other genes involved in its complex regulation mechanisms. Pyrin activation is strictly dependent on homeostasis-altering molecular processes, mostly consisting of the disruption of the small Ras Homolog Family Member A (RhoA) GTPases by pathogen toxins. The downstream pathways are regulated by the phosphorylation of specific pyrin residues by the kinases PKN1/2 and the binding of the chaperone 14-3-3. Furthermore, a key role in pyrin activation is played by the cytoskeleton and gasdermin D, which is responsible for membrane pores in the context of pyroptosis. In addition, recent evidence has highlighted the role of steroid hormone catabolites and alarmins S100A8/A9 and S100A12 in pyrin-dependent inflammation. The aim of this article is to offer a comprehensive overview of the most recent evidence on the pyrin inflammasome and its molecular pathways to better understand the pathogenesis behind the significant group of pyrin-related AIDs.

Porokeratoses-A Comprehensive Review on the Genetics and Metabolomics, Imaging Methods and Management of Common Clinical Variants

Porokeratosis is a heterogeneous group of keratinising disorders characterised by the presence of particular microscopic structural changes, namely the presence of the cornoid lamella. This structure develops as a consequence of a defective isoprenoid pathway, critical for cholesterol synthesis. Commonly recognised variants include disseminated superficial actinic porokeratosis, disseminated superficial porokeratosis, porokeratosis of Mibelli, palmoplantar porokeratosis (including porokeratosis palmaris et plantaris disseminata and punctate porokeratosis), linear porokeratosis, verrucous porokeratosis (also known as genitogluteal porokeratosis), follicular porokeratosis and porokeratoma. Apart from the clinical presentation and epidemiology of each variant listed, this review aims at providing up-to-date information on the precise genetic background, introduces imaging methods facilitating the diagnosis (conventional and ultraviolet-induced fluorescence dermatoscopy, reflectance confocal microscopy and pathology), discusses their oncogenic potential and reviews the literature data on the efficacy of the treatment used, including the drugs directly targeting the isoprenoid-mevalonate pathway.

Successful treatment with anakinra in generalized spiculated porokeratosis and severe hidradenitis suppurativa in a patient with MVK and MEFV mutations

The synergistic effect of two mutations of the innate immune system may facilitate hyperactivation and dysregulation of the inflammasome in skin macrophages. This case connects two diseases, hidradenitis suppurativa and porokeratosis, by the central role of autoinflammation.

Disseminated superficial actinic porokeratosis following hydroxyurea treatment: A case report

Porokeratosis encompass a group of acquired and familial, preneoplastic, keratinization disorders, clinically characterized by atrophic macules or patches with a peripheral keratotic rim, the cornoid lamella. Genetic background is recognized as crucial in its pathophysiology, while immunosuppression and ultraviolet radiation represent triggering factors. We report the case of a woman who developed disseminate superficial actinic porokeratosis following the intake of hydroxyurea for a polycythaemia vera. Clinical, dermoscopic and histopathology data are showed, and the role of drug as a second-hit mutation trigger is discussed.

Porokeratosis is one of the most common genodermatoses and is associated with an increased risk of keratinocyte cancer and melanoma

BACKGROUND

Porokeratosis is a clinically heterogeneous group of keratinization disorders with a genetic background mainly affecting the mevalonate pathway, which is involved in the synthesis of cholesterol, an essential component for the formation of the extracellular lipid lamellae in the stratum corneum. Porokeratosis is reportedly associated with an increased risk of keratinocyte cancer, but to date, no large epidemiological studies have been conducted to further address this association.

OBJECTIVES

The first objective was to characterize a cohort of patients diagnosed with porokeratosis at the Department of Dermatology and Venereology, Sahlgrenska University Hospital (SU), Gothenburg, Sweden. The second objective was to conduct a nationwide registry-based cohort study to investigate the association, if any, between porokeratosis and the cutaneous malignancies squamous cell carcinoma (SCC), basal cell carcinoma (BCC) and melanoma.

METHODS

For the SU cohort, the hospital registry was searched for patients with a diagnosis of porokeratosis recorded between 2016 and 2020. Clinical data were extracted from the records of the identified patients. For the nationwide cohort, national registries were searched to identify patients with a diagnosis of porokeratosis between 2001 and 2020. A tenfold control cohort was formed by Statistics Sweden. The data was cross-referenced with the Swedish Cancer Register to study the associations between porokeratosis and SCC, BCC and melanoma.

RESULTS

Disseminated superficial actinic porokeratosis was the most common clinical type among the 108 patients in the SU cohort. In the nationwide search, 2277 patients with porokeratosis were identified (prevalence 1/4132). Porokeratosis was associated with an increased risk for SCC, BCC and melanoma with hazard ratios (95% CI) of 4.3 (3.4-5.4), 2.42 (1.97-2.98) and 1.83 (1.18-2.82), respectively, in the patient cohort, compared to the matched control group.

CONCLUSION

Porokeratosis is a common genodermatosis, and it is associated with an enhanced risk of skin cancer.

A possibly new autoinflammatory disease due to compound heterozygous phosphomevalonate kinase gene mutation

BACKGROUND

Mevalonate kinase (MVK) plays a role in cholesterol and non-sterol isoprenoid biosynthesis and its deficiency-related diseases are caused by bi-allelic pathogenic mutations in the MVK gene, (MVK), which leads to rare hereditary autoinflammatory diseases. The disease may manifest different clinical phenotypes depending on the degree of the deficiency in the enzyme activity. The complete deficiency of the enzyme activity results in the severe metabolic disease called mevalonic aciduria, while a partial deficiency results in a broad spectrum of clinical presentations called hyper-immunoglobulin D syndrome (HIDS). Serum immunoglobulin (Ig) D and urine mevalonic acid levels may be increased during inflammatory attacks of HIDS.

CASE PRESENTATION

Herein, for the first time in the literature, we present a 6-year-old male patient who suffered from recurrent episodes of fever, polyarthritis, skin rash, diarrhea, abdominal pain, and inflammatory bowel disease-like manifestations with elevated levels of serum IgD, and urine mevalonic acid. Eventually we detected compound heterozygous mutations in the phosphomevalonate kinase (PMVK) gene coding the second enzyme after mevalonate kinase in the mevalonate pathway.

CONCLUSION

For patients presenting with HIDS-like findings, disease exacerbations and persistent chronic inflammation, and having high urinary mevalonic acid and serum IgD levels, raising suspicion in terms of MVK deficiency (MVKD), it is recommended to study all mevalonate pathway enzymes, even if there is no mutation in the MVK gene. It should be kept in mind that novel mutations might be seen such as PMVK gene.

MicroRNA-874 targets phosphomevalonate kinase and inhibits cancer cell growth via the mevalonate pathway

The microRNA (miR) miR-874, a potential tumour suppressor, causes cell death via target gene suppression in various cancer types. Mevalonate pathway inhibition also causes cell death in breast cancer. However, the relationship between the mevalonate pathway and miR-874-induced apoptosis or its association with the tumour suppressor p53 has not been elucidated. We identified phosphomevalonate kinase (PMVK), a key mevalonate pathway enzyme, and sterol regulatory element-binding factor 2 (SREBF2), the master cholesterol biosynthesis regulator, as direct miR‑874 targets. Next-generation sequencing analysis revealed a significant miR-874-mediated downregulation of PMVK and SREBF2 gene expression and p53 pathway enrichment. Luciferase reporter assays showed that miR-874 directly regulated PMVK and SREBF2. miR-874-induced apoptosis was p53 dependent, and single-cell RNA sequencing analysis demonstrated that miR-874 transfection resulted in apoptosis and p53 pathway activation. Downregulation of PMVK expression also caused cell cycle arrest and p53 pathway activation, which was rescued by geranylgeranyl pyrophosphate (GGPP) supplementation. Analysis of The Cancer Genome Atlas (TCGA) database indicated a negative correlation between miR-874 and PMVK expression and between miR-874 and SREBF2 expression. These findings suggest that miR-874 suppresses the mevalonate pathway by targeting SREBF2 and PMVK, resulting in GGPP depletion, which activates the p53 pathway and promotes cycle arrest or apoptosis.

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.

A Novel Gene CDC27 Causes SLE and Is Associated With the Disease Activity

Background

As genetic genetic factors are important in SLE, so screening causative genes is of great significance for the prediction and early prevention in people who may develop SLE. At present, it is very difficult to screen causative genes through pedigrees. The analytical method described herein can be used to screen causative genes for SLE and other complex diseases through pedigrees.

Methods

For the first time, 24 lupus pedigrees were analyzed by combining whole exon sequencing and a variety of biological information tools including common-specific analysis, pVAAST (pedigree variant annotation, analysis and search tool), Exomiser (Combining phenotype and PPI associated analysis), and FARVAT (family based gene burden), and the causative genes of these families with lupus identified. Selected causative genes in peripheral-blood mononuclear cells (PBMCs) were evaluated by quantitative polymerase chain reaction (qPCR).

Results

Cell division cycle 27 (CDC27) was screened out by common-specific analysis and Exomiser causative gene screening. FARVAT analysis on these families detected only CDC27 at the extremely significant level (false discovery rate <0.05) by three family-based burden analyses (BURDEN, CALPHA, and SKATO). QPCR was performed to detect for CDC27 in the PBMCs of the SLE family patients, sporadic lupus patients, and healthy people. Compared with the healthy control group, CDC27 expression was low in lupus patients (familial and sporadic patients) (P<0.05) and correlated with lupus activity indicators: negatively with C-reactive protein (CRP) (P<0.05) and erythrocyte sedimentation rate (P<0.05) and positively with complement C3 and C4 (P<0.05). The CDC27 expression was upregulated in PBMCs from SLE patients with reduced lupus activity after immunotherapy (P<0.05). Based on Receiver operating characteristic (ROC) curve analysis, the sensitivity and specificity of CDC27 in diagnosing SLE were 82.30% and 94.40%.

Conclusion

The CDC27 gene, as found through WES combined with multiple analytical method may be a causative gene of lupus. CDC27 may serve as a marker for the diagnosis of SLE and is closely related to the lupus activity. We hope that the analytical method in this study will be used to screen causative genes for other diseases through small pedigrees, especially among non-close relatives.

A preliminary study of peripheral T-cell subsets in porokeratosis patients with MVK or MVD variants

Background

Porokeratosis (PK) is considered a skin‐specific autoinflammatory keratinization disease. Intriguingly, four causative genes of PK are in turn arranged in mevalonate pathway, with MVD variants being the commonest followed by MVK variants in a cohort of Chinese patients. Evidence indicates that mevalonate metabolites induce trained immunity in human monocytes and regulate T cells at multiple levels. Of note, γδT cells are dually regulated by intracellular and extracellular mevalonate metabolism.

Aims

To identify the possible differences in T‐cell between MVK or MVD variants from PK patients.

Materials & Methods

Targeted exome sequencing and exonic CNV screening were performed in 26 patients with PK. Sanger sequencing was used to validate all identified variants. Among them, 22 patients were identified with MVK or MVD variants. PBMCs from 22 PK patients and 27 normal controls (NCs) were analysed by flow cytometry for the frequencies of T cells subsets, including IFN‐γ‐, and TNF‐α‐producing T cells.

Results

There were 14 mutations identified in the 26 PK patients, including 6 novel mutations (MVK: c.118_226+1337dup, c.388_392delGATATinsC, c.613A>T, c.768G>C, and MVD: c.250C>T, c.988T>G). In contrast to NCs, significantly decreased frequencies of CD8⁺ and Vγ9Vδ2 T cells were observed in the PK patients with MVD variants. Moreover, it was found that dysregulated secretion of pro‐inflammatory cytokines by T cells in both PK patients with MVK and MVD variants.

Conclusions

Our findings enriched the Human Gene Mutation Databases and showed probable differences in peripheral T cells subsets between PK patients and controls.

Autoinflammation: Interferonopathies and Other Autoinflammatory Diseases

The family of autoinflammatory diseases (AIDs) continues to expand and now includes over 40 genetically defined disorders. Their defining feature is a dysregulated inflammatory innate immune response. Many AIDs have overlapping clinical characteristics, and dermatological manifestations are common. Autoinflammatory features have also been recognized in more common dermatological conditions such as psoriasis. Furthermore, there is an increasing understanding that immunodeficiencies, autoimmune disorders, and even some allergic disorders share overlapping autoinflammatory features. The discovery that certain somatic mutations, arising within the bone marrow and restricted to the myeloid cell lineage can cause acquired AID heralds a new era of discoveries in this field.

Compromised Protein Prenylation as Pathogenic Mechanism in Mevalonate Kinase Deficiency

Mevalonate kinase deficiency (MKD) is an autoinflammatory metabolic disorder characterized by life-long recurring episodes of fever and inflammation, often without clear cause. MKD is caused by bi-allelic pathogenic variants in the MVK gene, resulting in a decreased activity of the encoded enzyme mevalonate kinase (MK). MK is an essential enzyme in the isoprenoid biosynthesis pathway, which generates both non-sterol and sterol isoprenoids. The inflammatory symptoms of patients with MKD point to a major role for isoprenoids in the regulation of the innate immune system. In particular a temporary shortage of the non-sterol isoprenoid geranylgeranyl pyrophosphate (GGPP) is increasingly linked with inflammation in MKD. The shortage of GGPP compromises protein prenylation, which is thought to be one of the main causes leading to the inflammatory episodes in MKD. In this review, we discuss current views and the state of knowledge of the pathogenetic mechanisms in MKD, with particular focus on the role of compromised protein prenylation.

Molecular mechanisms of phenotypic variability in monogenic autoinflammatory diseases

Monogenic autoinflammatory diseases are a group of rheumatologic disorders caused by dysregulation in the innate immune system. The molecular mechanisms of these disorders are linked to defects in inflammasome-mediated, NF-κB-mediated or interferon-mediated inflammatory signalling pathways, cytokine receptors, the actin cytoskeleton, proteasome complexes and various enzymes. As with other human disorders, disease-causing variants in a single gene can present with variable expressivity and incomplete penetrance. In some cases, pathogenic variants in the same gene can be inherited either in a recessive or dominant manner and can cause distinct and seemingly unrelated phenotypes, although they have a unifying biochemical mechanism. With an enhanced understanding of protein structure and functionality of protein domains, genotype-phenotype correlations are beginning to be unravelled. Many of the mutated proteins are primarily expressed in haematopoietic cells, and their malfunction leads to systemic inflammation. Disease presentation is also defined by a specific effect of the mutant protein in a particular cell type and, therefore, the resulting phenotype might be more deleterious in one tissue than in another. Many patients present with the expanded immunological disease continuum that includes autoinflammation, immunodeficiency, autoimmunity and atopy, which necessitate genetic testing.

Topical simvastatin-cholesterol for disseminated superficial actinic porokeratosis: An open-label, split-body clinical trial

BACKGROUND/OBJECTIVES

Disseminated superficial actinic porokeratosis (DSAP) is a porokeratosis variant that is cosmetically disfiguring and may be associated with squamous cell carcinoma. It is an autosomal dominant condition caused by germline mutations in mevalonate pathway genes involved in cholesterol synthesis. Lesions are precipitated by ultraviolet radiation-induced second-hit mutations. Modulation of this pathway by topical simvastatin-cholesterol may lead to improvement.

METHODS

This open-label, split-body clinical trial was carried out in 2020 at a metropolitan dermatology clinic. Eight patients contributing 13 limb pairs were recruited. Limbs within each pair were randomly allocated to 2% simvastatin/2% cholesterol cream applied twice daily or bland emollients. Lesion number, erythema, scale and patient-reported disease activity were measured at baseline and 6 weeks. Data were analysed using Bayesian ordinal logistic regression. Odds ratios compare the odds of a higher score at 6 weeks in treated limbs with the odds in controls. Values less than one indicate improvement.

RESULTS

Patients had a median age of 65 years (interquartile range [IQR] 58 to 69 years). The median baseline DLQI was 5 (range 2-21). Odds ratios were 0.12 (95% credible interval [CI] 0.01 to 0.72) for lesion number, 0.25 (95% CI 0.05 to 0.79) for erythema score, 0.18 (95% CI 0.03 to 0.64) for scale score and 0.33 (95% CI 0.09 to 0.89) for patient-reported disease activity.

CONCLUSIONS

Topical simvastatin-cholesterol cream improved lesion number, erythema and scale on treated limbs compared with controls. Patient-reported disease activity also improved. These findings warrant confirmation in blinded, vehicle-controlled trials.

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.

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.

Physiopathological roles of vesicular nucleotide transporter (VNUT), an essential component for vesicular ATP release

Vesicular nucleotide transporter (VNUT) is the last identified member of the SLC17 organic anion transporter family, which plays a central role in vesicular storage in ATP-secreting cells. The discovery of VNUT demonstrated that, despite having been neglected for a long time, vesicular ATP release represents a major pathway for purinergic chemical transmission, which had been mainly attributed to ATP permeation channels. This article summarizes recent advances in our understanding of the mechanism of VNUT and its physiopathological roles as well as the development of inhibitors. Regulating the activity and/or the expression of VNUT represents a new and promising therapeutic strategy for the treatment of multiple diseases.

Second-Hit Somatic Mutations in Mevalonate Pathway Genes Underlie Porokeratosis

Familial and sporadic porokeratosis are associated with germline heterozygous mutations in mevalonate pathway genes. Kubo et al. show that each skin lesion of disseminated superficial actinic porokeratosis originates from a postnatal keratinocyte clone with a different second-hit genetic event in the wild-type allele of the corresponding gene. They also confirm that linear porokeratosis derives from a single prenatal clone of keratinocytes with a second-hit genetic event.

Porokeratosis: A Review of Its Pathophysiology, Clinical Manifestations, Diagnosis, and Treatment

Porokeratosis comprises a group of heterogeneous and uncommon acquired or congenital skin diseases of unknown origin characterized by a keratinization disorder resulting from abnormal clonal expansion of keratinocytes. Numerous genetic mutations are thought to be involved. These conditions are characterized histologically by the presence of a cornoid lamella. Clinical manifestations are variable, with localized, disseminated, and even eruptive forms. Porokeratosis has been associated with immunosuppression, ultraviolet radiation, and systemic, infectious, and neoplastic diseases. Many authors consider it to be a premalignant condition because of the potential for malignant transformation to squamous cell or basal cell carcinoma. Therefore, long-term follow-up is a key component of treatment, which is usually complex and often unsatisfactory. We review the latest advances in our understanding of the pathogenesis, diagnosis, and treatment and propose a treatment algorithm.

KLICK Syndrome Linked to a POMP Mutation Has Features Suggestive of an Autoinflammatory Keratinization Disease

Keratosis linearis with ichthyosis congenita and sclerosing keratoderma (KLICK) syndrome is a rare autosomal recessive skin disorder characterized by palmoplantar keratoderma, linear hyperkeratotic plaques, ichthyosiform scaling, circular constrictions around the fingers, and numerous papules distributed linearly in the arm folds and on the wrists. Histologically, the affected skin shows hypertrophy and hyperplasia of the spinous, granular, and horny epidermal layers with mild infiltration of inflammatory cells in the upper dermis. There are 14 patients with KLICK syndrome described in the literature, and they all carry the same nucleotide deletion. Proteasome maturation protein (POMP), encoded by POMP, is an ubiquitously expressed protein that functions as a chaperone for proteasome maturation. KLICK syndrome is caused by a reduction in POMP levels that leads to proteasome insufficiency in differentiating keratinocytes. It is noteworthy that POMP is also known to be the causative gene for proteasome-associated autoinflammatory syndrome-2 (PRAAS2). It is considered that the disrupted proteasome assembly caused by the POMP mutation might lead to both skin inflammation and then hyperkeratosis in KLICK syndrome. Inflammation caused by the hyperactivation of innate immunity occasionally leads to inflammatory diseases of the skin, recently denoted as autoinflammatory keratinization diseases (AiKDs). We propose that KLICK syndrome caused by the specific 1-bp nucleotide deletion mutation in the regulatory region of POMP might be in a spectrum of proteasome-associated phenotypes.

Effects of mevalonate kinase interference on cell differentiation, apoptosis, prenylation and geranylgeranylation of human keratinocytes are attenuated by farnesyl pyrophosphate or geranylgeranyl pyrophosphate

Mevalonate kinase (MVK) mutations were previously identified in disseminated superficial actinic porokeratosis. However, the role of MVK in differentiation, apoptosis and prenylation of keratinocytes requires further investigation. Farnesyl pyrophosphate (FPP) and geranylgeranyl pyrophosphate (GGPP) of the mevalonate pathway attach to small G proteins, and serve as molecular switches in biochemical pathways. Therefore, the aim of the present study was to investigate the role of MVK in the expression of keratin 1 and involucrin, apoptosis, protein prenylation and the processing of small G proteins. HaCat human keratinocytes were transfected with viruses carrying MVK interference and overexpression vectors, respectively. The mRNA expression of MVK, keratin 1 and involucrin was detected by reverse transcription-quantitative PCR. Protein expression of MVK, keratin 1, involucrin, lamin A, HRAS, KRAS, NRAS, Rho E, Rho B, Rho A, RAC1 and cdc42 in HaCat cells was detected by western blotting. The apoptotic rates of HaCat cells and protein prenylation levels were examined by flow cytometry. The expression of MVK in HaCat cells was significantly decreased in the interference groups, and markedly increased in the overexpression group compared with the negative control groups. The mRNA and protein expression levels of keratin 1 and involucrin were significantly decreased following interference of MVK expression, and the decrease was markedly attenuated by FPP. Furthermore, the apoptotic rate was markedly increased following MVK interference, and the increase was significantly attenuated by GGPP. The overexpression of MVK significantly decreased the apoptotic rate of HaCat cells. The prenylation levels after MVK interference was notably decreased, which was markedly attenuated by GGPP. The overexpression of MVK significantly increased the prenylation levels of HaCat cells. FPP or GGPP reversed MVK interference-induced decrease in geranylgeranylation levels of lamin A, HRAS, KRAS, NRAS, Rho E, Rho B, Rho A, RAC1 and cdc42. In conclusion, MVK interference decreases the expression of differentiation markers, increases apoptosis, and decreases protein prenylation and geranylgeranylation levels in keratinocytes. These changes are attenuated by FPP or GGPP.

Second-Hit, Postzygotic PMVK and MVD Mutations in Linear Porokeratosis

Importance

Linear porokeratosis features linear and whorled configurations of keratotic papules and plaques, with coronoid lamellae present on histologic examination. Because linear porokeratosis manifests in the lines of Blaschko representing the dorsoventral migration patterns of keratinocyte precursors, it has been suggested that postzygotic somatic mutation underlies the disease. However, no genetic evidence has supported this hypothesis to date.

Objective

To identify genetic mutations associated with linear porokeratosis.

Design, Setting, and Participants

Paired whole-exome sequencing of affected skin and blood/saliva samples from 3 participants from 3 academic medical centers with clinical and histologic diagnoses of linear porokeratosis.

Interventions or Exposures

Whole-exome sequencing of paired blood/saliva and affected tissue samples isolated from linear porokeratosis lesions.

Main Outcomes and Measures

Germline and somatic genomic characteristics of participants with linear porokeratosis.

Results

Of the 3 participants, 2 were male. Participant ages ranged from 5 to 20 years old. We found a combination of a novel germline mutation and a novel somatic mutation within affected tissue in all cases. One participant had a germline heterozygous PMVK c.329G>A mutation and a somatic copy-neutral loss of heterozygosity confined to the lesional skin, while a second had a germline heterozygous PMVK c.79G>T mutation and an additional PMVK c.379C>T mutation in the lesional skin. In a third participant, there was a germline splice-site mutation in MVD (c.70 + 5G>A) and a somatic deletion in MVD causing frameshift and premature codon termination within the lesional skin (c.811_815del, p.F271Afs*33 frameshift).

Conclusions and Relevance

Our findings suggest that linear porokeratosis is associated with the presence of second-hit postzygotic mutations in the genes that encode enzymes within the mevalonate biosynthesis pathway, and provide further evidence that the mevalonate pathway may be a potential target for therapeutic intervention in porokeratosis.

Topical cholesterol/lovastatin for the treatment of porokeratosis: A pathogenesis-directed therapy

BACKGROUND

Porokeratosis is associated with mevalonate pathway gene mutations. Therapeutic options are few and often limited in efficacy. We hypothesized that topical therapy that aims to replenish cholesterol, an essential mevalonate pathway end-product, and block the accumulation of mevalonate pathway toxic metabolites could alleviate porokeratosis.

OBJECTIVE

To study the efficacy of topical cholesterol/lovastatin in different variants of porokeratosis.

METHODS

We enrolled a series of 5 porokeratosis patients,1 with disseminated superficial actinic porokeratosis, 2 with porokeratosis palmaris et plantaris disseminata, and 2 with linear porokeratosis. Patients were genotyped before initiation of therapy. Patients then applied topical cholesterol/lovastatin twice daily to a unilaterally defined treatment area for up to 3 months. The response was evaluated and patients photographed at every visit.

RESULTS

Three patients had MVD mutations, and 2 patients had PMVK mutations. Treatment with topical cholesterol/lovastatin (but not cholesterol alone) resulted in near complete clearance of disseminated superficial actinic porokeratosis lesions after 4 weeks of therapy and moderate improvement of porokeratosis palmaris et plantaris disseminata lesions and linear porokeratosis lesions. There were no adverse events.

LIMITATIONS

Case series design with a small number of patients.

CONCLUSION

Topical cholesterol/lovastatin is an effective and well-tolerated therapy for porokeratosis that underscores the utility of a pathogenesis-based therapy that replaces deficient end products and prevents accumulation of potentially toxic precursors.

[Eruptive disseminated superficial porokeratosis associated with acute hepatitis E]

BACKGROUND

Porokeratosis (PK) is a rare form of dermatosis characterized by a keratinization disorder of unknown etiology. Herein we describe the first case associated with hepatitis E virus infection.

PATIENTS AND METHODS

A 69-year-old patient with colorectal cancer treated with radiation and chemotherapy followed by surgery in April 2017 presented two months later with jaundice associated with annular keratotic lesions of the skin with a raised border. Blood tests revealed elevated liver enzymes and hyperbilirubinemia. Viral hepatitis E was diagnosed based on serology and viral PCR after other aetiologies such as obstruction, auto-immune disease and other viruses (HAV, HBV, HCV, HSV, HIV, EBV and CMV) had been ruled out. A skin biopsy showed a cornoid lamella. Disseminated superficial porokeratosis associated with hepatitis E infection was then diagnosed.

DISCUSSION

The mechanism of PK is unknown and probably involves a combination of different factors. PK has been described in patients with treatment-induced immunosuppression, solid cancer or AIDS, sometimes promoted by HCV viral infection, but never with concomitant HEV infection. A combination of immunosuppression induced by radio-chemotherapy and HEV infection could have prompted the development of PK in our patient.

CONCLUSION

We report the first case of eruptive disseminated superficial porokeratosis associated with hepatitis E infection. The exact role of hepatitis E infection in the development of PK is still unclear.

Update on the Genetics of Autoinflammatory Disorders

PURPOSE OF THE REVIEW

This review aims at presenting the most significant data obtained in the field of the genetics of autoinflammatory disorders (AID) over the last past 5 years.

RECENT FINDINGS

More than 15 genes have been implicated in AID since 2014, unveiling new pathogenic pathways. Recent data have revealed atypical modes of transmission in several inherited AID, such as somatic mosaicism and digenism. First pieces of evidence showing an involvement of epigenetic modifications in the pathogenesis of AID have also been brought to light. Novel genetic data have been obtained on the molecular bases of genetically complex AID. The development of next-generation sequencing in routine clinical practice has led to an explosion in the identification of new AID genes. Advances in the knowledge of AID further blur the limits between monogenic and multifactorial forms of these syndromes, and between autoinflammatory and autoimmune conditions.

Clonal Expansion of Second-Hit Cells with Somatic Recombinations or C>T Transitions Form Porokeratosis in MVD or MVK Mutant Heterozygotes

Patients with disseminated superficial actinic porokeratosis (DSAP) and linear porokeratosis (LP) exhibit monoallelic germline mutations in genes encoding mevalonate pathway enzymes, such as MVD or MVK. Here, we showed that each skin lesion of DSAP exhibited an individual second hit genetic change in the wild-type allele of the corresponding gene specifically in the epidermis, indicating that a postnatal second hit triggering biallelic deficiency of the gene is required for porokeratosis to develop. Most skin lesions exhibited one of two principal second hits, either somatic homologous recombinations rendering the monoallelic mutation biallelic or C>T transition mutations in the wild-type allele. The second hits differed among DSAP lesions but were identical in those of congenital LP, suggesting that DSAP is attributable to sporadic postnatal second hits and congenital LP to a single second hit in the embryonic period. In the characteristic annular skin lesions of DSAP, the central epidermis featured mostly second hit keratinocytes, and that of the annular ring featured a mixture of such cells and naïve keratinocytes, implying that each lesion reflects the clonal expansion of single second hit keratinocytes. DSAP is therefore a benign intraepidermal neoplasia, which can be included in the genetic tumor disorders explicable by Knudson's two-hit hypothesis.

Effective treatment of disseminated superficial actinic porokeratosis with chemical peels - customary treatment for a rare disease

Background: Disseminated superficial actinic porokeratosis (DSAP) is a rare dermatologic disorder of the epidermis. Often misdiagnosed as chronic UV-damage or actinic keratoses, patients are treated for years with different therapeutic options with little success. Current treatment options include imiquimod, ingenol mebutate, cryosurgery, photodynamic therapy and topical or systemic therapy with retinoids. Since those approaches show only little success or come along with major side effects, therapeutic alternatives are strongly requested. Methods: We report a series of five female patients with history of DSAP that were successfully treated with chemical peels. Results: All patients suffered from the disease for 14.4 years on average and all were refractory to at least two therapeutic options, mostly imiquimod and topical tretinoin. Patients were treated with glycolic acid 50% and salicylic acid 25% in a two-layer-technique. After a mean of three cycles every 6 weeks a clear reduction in lesion was assessed by physicians. Patients were highly satisfied with outcome and rare occurrence of side effects as assessed by TSQM questionnaire. Conclusion: Chemical peels are safe and well tolerated treatment options for patients with refractory porokeratosis. As characteristic for chronic diseases, frequent repetition of treatment is needed in order to control disease activity.

The forty years of medical genetics in China

Medical genetics is the newest cutting-edge discipline that focuses on solving medical problems using genetics knowledge and methods. In China, medical genetics research activities initiated from a poor inner basis but a prosperous outer environment. During the 40 years of reform and opening-up policy, Chinese scientists contributed significantly in the field of medical genetics, garnering considerable attention worldwide. In this review, we highlight the significant findings and/or results discovered by Chinese scientists in monogenic diseases, complex diseases, cancer, genetic diagnosis, as well as gene manipulation and gene therapy. Due to these achievements, China is widely recognized to be at the forefront of medical genetics research and development. However, the significant progress and development that has been achieved could not have been accomplished without sufficient funding and a well-constructed logistics network. The successful implementation of translational and precise medicine sourced from medical genetics will depend on an open ethics policy and intellectual property protection, along with strong support at the national industry level.

A clinical update on inflammasomopathies

Inflammasomes are important elements of the innate immune defense. The most common autoinflammatory syndromes, as well a number of rare ones, are due to hereditary defects in the inflammasomes, hence are called inflammasomopathies. The recent clinical advances in these diseases will be reviewed, with special emphasis on reflecting the international collaborative work in the field. Recent recommendations for familial Mediterranean fever, cryopyrin-associated periodic syndromes and hyper-IgD syndrome/mevalonate kinase deficiency will be presented and diagnostics tests, treatment alternatives and follow-up recommendations will be summarized. The other rare inflammasomopathies will be briefly discussed based on clinical features; these diseases are pyogenic arthritis, pyoderma gangrenosum and acne, NLRC4-related macrophage-activation syndrome of enterocolitis, mutations in NLRP12 that cause hereditary periodic fever syndromes (familial cold inflammatory syndrome 2) and NLRP1-associated autoinflammation with arthritis and dyskeratosis.

Mutations in mevalonate pathway genes in patients with familial or sporadic porokeratosis

Porokeratosis comprises heterogeneous keratinization disorders that are characterized by one or more atrophic patches surrounded by a ridge-like cornoid lamella. In this study, we evaluated seven families affected by porokeratosis and five sporadic patients of the disease in a Chinese population. We performed Sanger sequencing of exons and flanking intron-exon boundaries of mevalonate pathway genes (MVD, MVK, PMVK and FDPS) and of SLC17A9. In five familial and three sporadic patients, we detected six variations, including four novel mutations (MVD c.1A>G; p.Met1?, c.916G>A; p.Ala306Thr, c.1013+1G>A, and PMVK c.65A>G; p.Lys22Arg) and two recurrent mutations (MVD c.746T>C; p.Phe249Ser, and MVK c.1028T>C; p.Leu343Pro). We then applied I-TASSER and iGEMDOCK to assess these variants for probable functional impacts. The findings of this study extend the mutation spectrum of porokeratosis and provide further evidence for the genetic basis of this disease.