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Generalized pustular psoriasis (GPP) is a rare form of psoriasis, which is characterized by sudden onset of repeated erythema and pustule formation with generalized inflammation. Recent advances in molecular genetics have led to the identification of several genes associated with GPP, including IL36RN, CARD14, AP1S3, SERPINA3, and MPO. Of these, only limited cases of GPP have been reported to carry mutations in the AP1S3, SERPINA3, or MPO to date. In the present study, we investigated a Japanese patient with GPP and found a homozygous missense mutation c.1769GT (p.Arg590Leu) in the MPO gene. Structural analysis predicted that the mutant MPO protein would abolish its ability to bind with heme protein. In vitro studies using cultured cells revealed that the mutant MPO was stably expressed, but completely lost its myeloperoxidase activity. Immunohistochemistry (IHC) using an anti-MPO antibody showed markedly reduced expression of MPO protein in the patient's skin, suggesting that the mutation would lead to an instability of the MPO protein in vivo. Finally, IHC with an anti-citrullinated Histone H3 antibody demonstrated a sparse formation of neutrophil extracellular traps within a Kogoj's spongiform pustule of the patient's skin. Collectively, we conclude that the c.1769GT (p.Arg590Leu) in the MPO is a complete loss-of-function mutation associated with GPP in the patient. Our data further underscore critical roles of the MPO gene in the pathogenesis of GPP.

BackgroundEpidermolytic ichthyosis (EI) is a major form of nonsyndromic inherited ichthyosis, characterized by erythroderma, marked hyperkeratosis and scale, bulla and erosion at birth, associated with KRT1/KRT10 mutations. The cytokine and chemokine profiles in EI are poorly understood, and specific treatment options have not been established.AimTo explore novel biomarkers and therapeutic targets in patients with EI.MethodsWe analysed cytokine levels in serum and skin samples from 10 patients with inherited ichthyosis, including seven patients with EI. Wild-type and mutant KRT1 constructs were established and transfected into HaCaT cells, an immortalized keratinocyte cell line, for in vitro immunoblotting and immunocytochemistry analyses.ResultsMultiplex cytokine/chemokine analysis revealed that 10 cytokines/chemokines [interleukin (IL)-1β, IL-4, IL-17A, IL-16, IL-18, IL-1 receptor-α, macrophage colony-stimulating factor, interferon-α2, basic fibroblast growth factor and monocyte chemotactic protein-3] were significantly increased in patients with EI. Furthermore, IL-18 levels were significantly higher in patients with EI [n = 7; 2714.1 (1438.0) pg mL−1] than in healthy controls [n = 11; 218.4 (28.4) pg mL−1, P < 0.01]. Immunohistochemical analyses showed that IL-18 expression was elevated in skin samples from patients with EI. Serum IL-18 levels correlated with the severity of ichthyosis, as measured by the Ichthyosis Scoring System. Immunoblotting analysis revealed that mature IL-18 levels were increased in the supernatant of mutant KRT1 expressing HaCaT cells. Additionally, these cells showed NLRP3 aggregation in the cytoplasm and ASC clustered around mutant keratin aggregations. These findings suggest that mutant keratin might promote the activation of the NLRP3 inflammasome and its downstream caspase-1-mediated IL-18 release in keratinocytes from patients with EI.ConclusionsOur results suggest that serum IL-18 is a severity marker released from the skin of patients with EI. Blockade of IL-18 may be a useful novel therapeutic option for patients with EI.

Background Baricitinib, an oral, selective, reversible Janus kinase (JAK)1/JAK2 inhibitor, is an approved treatment for adults with severe alopecia areata (AA) in the USA, European Union and Japan. Objectives To report safety data for baricitinib in patients with severe AA from two clinical trials including long-term extension periods. Methods This analysis includes pooled patient-level safety data from two trials, an adaptive phase II/III trial (BRAVE-AA1) and a phase III trial (BRAVE-AA2) (ClinicalTrials.gov, NCT03570749 and NCT03899259). Data are reported in three datasets: (i) the placebo-controlled dataset (up to week 36): baricitinib 2 mg and 4 mg vs. placebo; (ii) the extended dataset (up to the data cutoff): patients remaining on continuous treatment with baricitinib 2 mg or 4 mg from baseline; and (iii) the all-baricitinib dataset (all-BARI, up to the data cutoff): all patients receiving any dose of baricitinib at any time during the trials. Safety outcomes include treatment-emergent adverse events (TEAEs), adverse events of special interest and abnormal laboratory changes. Proportions of patients with events and incidence rates (IR) were calculated. Results Data were collected for 1303 patients who were given baricitinib, reflecting 1868 patient-years of exposure (median 532 days). The most frequently reported TEAEs during the placebo-controlled period (based on the baricitinib 4-mg group) were upper respiratory tract infection, nasopharyngitis, headache, acne and elevated blood creatine phosphokinase (CPK). During the placebo-controlled period, the frequency of acne was higher with baricitinib than placebo, and elevated CPK was higher with baricitinib 4 mg than placebo and baricitinib 2 mg. In all-BARI, the IR of serious infections was low (n = 16, IR 0.8). There was one opportunistic infection (IR 0.1), and 34 cases of herpes zoster (IR 1.8). There was one positively adjudicated major adverse cardiovascular event (myocardial infarction) (IR 0.1), one pulmonary embolism (IR 0.1), three malignancies other than nonmelanoma skin cancer (IR 0.2) and one gastrointestinal perforation (IR 0.1). No deaths were reported. Conclusions This integrated safety analysis in patients with severe AA is consistent with the overall safety profile of baricitinib. Some differences with atopic dermatitis were noted that may be attributable to the disease characteristics of AA.

Hereditary angio-oedema (HAE) is a rare genetic disease characterised by repeated episodes of temporary organ swelling. Three types of HAE are known, of which HAE with normal C1 inactivator is difficult to be diagnosed due to its lack of laboratory abnormalities. Here, we describe a case of HAE with normal C1 inactivator and recurrent acute abdomen following low-dose oestrogen–progestin therapy. Notably, genetic analysis by Sanger sequencing led to the identification of a recurrent heterozygous missense mutation c.988A > G (p.K330E) in the plasminogen (PLG) gene of the patient. Prophylactic tranexamic acid and on-demand selective bradykinin B2 receptor blockers are used to treat her symptoms.

Hh signaling has been shown to be activated in intact and injured peripheral nerve. However, the role of Hh signaling in peripheral nerve is not fully understood. In the present study, we observed that Hh signaling responsive cells [Gli1(+) cells] in both the perineurium and endoneurium. In the endoneurium, Gli1(+) cells were classified as blood vessel associated or non-associated. After injury, Gli1(+) cells around blood vessels mainly proliferated to then accumulate into the injury site along with endothelial cells. Hh signaling activity was retained in Gli1(+) cells during nerve regeneration. To understand the role of Hedgehog signaling in Gli1(+) cells during nerve regeneration, we examined mice with Gli1(+) cells-specific inactivation of Hh signaling (Smo cKO). After injury, Smo cKO mice showed significantly reduced numbers of accumulated Gli1(+) cells along with disorganized vascularization at an early stage of nerve regeneration, which subsequently led to an abnormal extension of the axon. Thus, Hh signaling in Gli1(+) cells appears to be involved in nerve regeneration through controlling new blood vessel formation at an early stage.

Genetic hair disorders, although unusual, are not very rare, and dermatologists often have opportunities to see patients. Significant advances in molecular genetics have led to identifying many causative genes for genetic hair disorders, including the recently identified causative genes, such as LSS and C3ORF52. Many patients have been detected with autosomal recessive woolly hair/hypotrichosis in the Japanese population caused by founder mutations in the LIPH gene. Additionally, many patients with genetic hair disorders caused by other genes have been reported in East Asia including Japan. Understanding genetic hair disorders is essential for dermatologists, and the findings obtained from analyzing these diseases will contribute to revealing the mechanisms of hair follicle morphogenesis and development in humans.

Hypohidrotic ectodermal dysplasia (HED) is a genetic disorder characterized by hypohidrosis, hypodontia, and hypotrichosis. Autosomal forms of the disease are caused by mutations in either EDAR or EDARADD. To date, the underlying pathomechanisms for HED resulting from EDARADD mutations have not fully been disclosed. In this study, we performed detailed in vitro analyses in order to characterize three dominantly inherited missense mutations, p.D120Y, p.L122R, and p.D123N, and one recessively inherited missense mutation, p.E152K, in the EDARADD gene. Nuclear factor (NF)-κB reporter assays demonstrated that all the mutant EDARADD showed reduction in activation of NF-κB. Importantly, p.D120Y-, p.L122R-, and p.D123N-mutant EDARADD slightly reduced the NF-κB activity induced by wild-type EDARADD in a dominant negative manner. Co-immunoprecipitation assays showed that all of the mutant EDARADD were capable of binding to EDAR and wild-type EDARADD. Additional co-immunoprecipitation assays revealed that p.D120Y-, p.L122R-, and p.D123N-mutant EDARADD markedly prevented the interaction between EDAR and wild-type EDARADD, which further indicated a dominant negative effect by these mutations. Finally, we found that p.D120Y-, p.L122R-, and p.D123N-mutant EDARADD completely lost the ability to bind with TRAF6, while p.E152K-mutant EDARADD showed a mild reduction in the affinity. Our findings will provide crucial information toward unraveling the molecular mechanisms how EDARADD gene mutations cause the disease.

Hypohidrotic ectodermal dysplasia is a rare condition characterized by hypohidrosis, hypodontia, and hypotrichosis. The disease can show X-linked recessive, autosomal dominant or autosomal recessive inheritance trait. Of these, the autosomal forms are caused by mutations in either EDAR or EDARADD. To date, the underlying pathomechanisms or genotype-phenotype correlations for autosomal forms have not completely been disclosed. In this study, we performed a series of in vitro studies for four missense mutations in the death domain of EDAR protein: p.R358Q, p.G382S, p.I388T, and p.T403M. The results revealed that p.R358Q- and p.T403M-mutant EDAR showed different expression patterns from wild-type EDAR in both western blots and immunostainings. NF-κB reporter assays demonstrated that all the mutant EDAR showed reduced activation of NF-κB, but the reduction by p.G382S- and p.I388T-mutant EDAR was moderate. Co-immunoprecipitation assays showed that p.R358Q- and p.T403M-mutant EDAR did not bind with EDARADD at all, whereas p.G382S- and p.I388T-mutant EDAR maintained the affinity to some extent. Furthermore, we demonstrated that all the mutant EDAR proteins analyzed aberrantly bound with TRAF6. Sum of the data suggest that the degree of loss-of-function is different among the mutant EDAR proteins, which may be associated with the severity of the disease.

Data on the prevalence of alopecia areata (AA) in Japan is limited and the epidemiology of the disease there is not well understood; therefore, it is critical to examine the prevalence and severity of AA in Japan to inform the need for future treatments and research. A cross-sectional, web-based survey was conducted in Japan from January through March 2021. A total of 45 006 participants were identified through general population survey panels and asked about their experience with AA and hair loss. The Alopecia Assessment Tool and the Scalp Hair Assessment PRO

Hereditary angioedema (HAE) is a rare condition characterized by episodic local edema involving various organs, which can be life-threatening in some cases. Among the three subtypes of the disease, HAE types I and II are known to be caused by heterozygous mutations in the SERPING1 gene encoding C1 inhibitor (C1INH). Although a number of mutations in the SERPING1 gene have been identified to date, the mechanisms how these mutations cause HAE are not completely understood. We herein performed detailed in vitro studies for a missense SERPING1 gene mutation p.S150F which we recently identified in a Japanese patient with HAE type I. We showed that the p.S150F-mutant C1INH was stably expressed within the cultured cells, while it was not secreted into the medium at all. Furthermore, we demonstrated that the mutant C1INH significantly prevented secretion of wild-type C1INH. Finally, the results suggested that the wild-type protein was not only retained but also degraded within the cytoplasm through interacting with the mutant protein. Our study clearly revealed a dominant-negative effect of the p.S150F-mutant C1INH against the wild-type C1INH.

Discoid lupus erythematosus (DLE) is an autoimmune disorder with a poorly defined etiology. Despite epidemiologic gender and ethnic biases, a clear genetic basis for DLE remains elusive. In this study, we used exome and RNA sequencing technologies to characterize a consanguineous Lebanese family with four affected individuals who presented with classical scalp DLE and generalized folliculitis. Our results unraveled a novel biallelic variant c.1313C > A leading to a missense substitution p.(Thr438Asn) in TRAF3IP2(NM_147200.3). Expression studies in cultured cells revealed mis-localization of the mutated protein. Functional characterization of the mutated protein showed significant reduction in the physical interaction with the interleukin 17-A receptor (IL17RA), while interaction with TRAF6 was unaffected. By conducting a differential genome-wide transcriptomics analysis between affected and non-affected individuals, we showed that the hair follicle differentiation pathway is drastically suppressed, whereas cytokine and inflammation responses are significantly upregulated. Furthermore, our results were highly concordant with molecular signatures in patients with DLE from a public dataset. In conclusion, this is the first report on a new putative role for TRAF3IP2 in the etiology of DLE. The identified molecular features associated with this gene could pave the way for better DLE-targeted treatment.

Anhidrotic/hypohidrotic ectodermal dysplasia (A/HED) is a congenital disorder characterized by anhidrosis/hypohidrosis and inadequate hair and dental dysplasia. Large-scale case studies of patients with A/HED have already been conducted overseas, while there has been no large-scale study, but only a few case reports in Japan. Furthermore, an epidemiological study of this disease has not been conducted in Japan to date. The purpose of this study was to investigate the clinical characteristics of A/HED patients, the status of genetic aberrations and complications of A/HED in Japan. Initially, we conducted a physician-initiated questionnaire survey of A/HED patients who visited medical institutions across Japan to investigate their backgrounds, clinical symptoms, genotypes, diagnostic methods and complications of A/HED. We also investigated the presence or absence of various allergic diseases (atopic dermatitis-like skin manifestations, bronchial asthma and food allergies). Questionnaires were also obtained from 26 patients with ectodermal dysplasia (ED) who visited four medical institutions. We compared the incidence of allergic diseases in healthy controls in a similar study to that of patients. Twenty-four of those patients were considered to have A/HED, of which 18 had a confirmed genetic diagnosis and were genotyped. All patients had anhidrosis or hypohidrosis, hair and dental dysplasia, and unique facial appearance; 23 patients had several cutaneous manifestations and seven patients had periorbital pigmentation. In addition, there was a significantly higher incidence of atopic dermatitis-like cutaneous manifestations, bronchial asthma and food allergies in the A/HED patients than in healthy controls. We report the results from a questionnaire survey of 24 patients with A/HED. This is the first report of a large number of A/HED patients in Japan. This study clarifies the status of clinical diagnosis and genetic testing of A/HED patients in Japan, as well as the characteristics of their skin symptoms and allergic complications.

Hypohidrotic ectodermal dysplasia (HED) is a rare genetic disorder characterized by hypotrichosis, hypohidrosis and hypodontia. The disease shows X-linked recessive, autosomal dominant or autosomal recessive inheritance traits. The X-linked form of HED is caused by mutations in the EDA gene, while autosomal forms result from mutations in either EDAR or EDARADD genes. Regarding recessive mutations in the EDAR gene, the pathomechanisms have been well characterized. However, it has remained largely unknown how dominant mutations in the EDAR cause HED. In this study, we performed in vitro analyses for a dominant EDAR gene mutation, p.F398*, as a representative. We showed that the p.F398* mutant EDAR completely lost its affinity to EDARADD, and suppressed the downstream nuclear factor-κB activation induced by wild-type EDAR in a dominant-negative manner. Furthermore, we demonstrated that the mutant EDAR was capable of binding with the wild-type EDAR, which led to reduced interaction between the wild-type EDAR and EDARADD. Our findings not only underscore an essential role of the interaction between EDAR and EDARADD in ectodermal development, but also disclose, in part, the molecular basis of autosomal dominant HED.

Palmoplantar keratoderma (PPK) with deafness (OMIM:148350) is a well-known form of PPK characterised by palmoplantar hyperkeratosis and deafness, which is largely caused by mutations in GJB2 encoding connexin 26.1 The m.7445A>G mitochondrial DNA mutation also underlies deafness-associated PPK.2.

It has recently been shown that bi-allelic mutations in the lanosterol synthase (LSS) gene, which was originally reported as a causative gene for congenital cataracts, underlie a non-syndromic form of hypotrichosis. Furthermore, it has also been revealed that mutations in the LSS gene can cause syndromic forms of hypotrichosis. To date, however, clear genotype-phenotype correlations have not completely been characterized. In this study, we identified two Japanese patients who had severe congenital hypotrichosis without any other associated findings. Their scalp hairs were extremely short and thin, and were able to be plucked easily. Observation of the plucked hairs showed aberrantly-miniaturized anagen hair follicles. Genetic analysis demonstrated that both patients carried bi-allelic mutations in the LSS gene in a compound heterozygote state. Our findings further underscore the crucial roles of the LSS gene in hair follicle development and hair growth in humans.

Keratin-associated protein 8.1 (KAP8.1) is a hair protein whose structure, biochemical roles, and protein distribution patterns have not been well characterized. In this study, we generated a monoclonal antibody against human KAP8.1 to analyze the protein's roles and distribution in the human hair shaft. Using this antibody, we revealed that KAP8.1 was predominantly expressed in discrete regions of the keratinizing zone of the hair shaft cortex. The protein expression patterns paralleled the distribution of KAP8.1 mRNA and suggested that KAP8.1 plays a role associated with cells to control hair curvature. Cross-reactivity among species and epitope analysis indicated that the monoclonal antibody recognized a linear epitope shared among human, mouse, and sheep KAP8.1. The antibody failed to interact with sheep KAP8.1 in native conformation, suggesting that structural features of KAP8.1 vary among species.