Generalized pustular psoriasis in a toddler with IL36RN mutation: a case report.

Generalized Pustular Psoriasis (GPP) is a dermatological autoinflammatory disease that rarely occurs in children and is associated with complex genetic factors. GPP pathogenesis has been associated with mutations in IL36RN gene, which encodes an interleukin-36 receptor antagonist. GPP usually occurs without a history of psoriasis in the patients or their family members. This case report describes the clinical course of a 3-year-old toddler with GPP. The diagnosis of GPP was confirmed through a comprehensive series of examinations, and genetic testing revealed an IL36RN mutation, providing further insight into the genetic basis of the condition. This case highlights the importance of a genetic perspective for diagnosing GPP, particularly in children.

Identification of the BTN3A3 Gene as a Molecule Implicated in Generalized Pustular Psoriasis in a Chinese Population.

The discovery of pathogenic variants provided biological insight into the role of host genetic factors in generalized pustular psoriasis (GPP). However, not all those affected by GPP carry variants in the reported genes. To comprehensively explore the molecular pathogenesis of GPP, whole-exome sequencing was performed, and two loci were identified with exome-wide significance through single variant association analysis: rs148755083 in the IL36RN gene (Pcombined = 1.19 × 10-18, OR = 8.26) and HLA-C∗06:02 within the major histocompatibility complex region (Pcombined = 8.38 × 10-12, OR = 2.98). Gene burden testing revealed that BTN3A3 correlated with GPP (Pcombined = 1.14 × 10-10, OR = 5.59). Subtype analysis showed that IL36RN and BTN3A3 were both significantly associated with GPP alone and GPP with psoriasis vulgaris, whereas a correlation with HLA-C∗06:02 was only observed in GPP with psoriasis vulgaris. Functional analysis revealed that BTN3A3 regulated cell proliferation and inflammatory balance in GPP. In particular, loss of function of BTN3A3 activated NF-κB and promoted the production of inflammatory cytokines by inhibiting IL-36Ra expression to disturb the IL-1/IL-36 inflammatory axis and enhance the TNF-α-mediated pathway. Our findings identify BTN3A3 as, to our knowledge, a previously unreported pathogenic determinant, expanding our understanding of the genetic basis of GPP.

Different Clinical Features of Pediatric Generalized Pustular Psoriasis in Patients with or without IL36RN Variants.

BACKGROUND: Generalized pustular psoriasis (GPP) is a rare and life-threatening autoinflammatory dermatological disease. IL36RN was reported to be the main pathogenetic basis for GPP. Only a few studies have reported on the correlation analysis of IL36RN variants and the phenotype of pediatric-onset GPP. METHODS: IL36RN was screened in 60 children diagnosed with GPP from January 2013 to January 2020, and their detailed clinical profiles were obtained. RESULTS: Forty-six out of 60 (76.67%) patients harbored IL36RN variants, and six IL36RN variants were found, of which two were novel variants that were reported for the first time. The frequency of IL36RN variants was significantly different among the subtypes of GPP (GPP with acrodermatitis continua of Hallopeau group (ACH), 100%; GPP without plaque psoriasis (PV) and ACH, 78.05%; GPP with PV group, 44.44%) (p = 0.018), while the percentage of IL36RN variants in the GPP with ACH group was higher than that in the GPP with PV group (p < 0.05). IL36RN variants were associated with a lower percentage of PV, longer length of hospitalization, and longer time to reach normal body temperature after treatment (p < 0.05). After treatment, marked responses, moderate responses, and no responses were recorded in 75.00%, 8.33%, and 16.67% of patients, respectively. No significant difference was observed during efficacy assessment in patients with or without IL36RN variants (χ2 = 1.122, p > 0.05). CONCLUSIONS: IL36RN variants are associated with GPP with ACH subtypes, an absence of concurrent PV, and a greater extent of severe inflammation. Acitretin was an effective treatment for patients in our study and mostly resulted in a marked response in our cohort.

Treatment Options and Goals for Patients with Generalized Pustular Psoriasis.

Generalized pustular psoriasis (GPP) is a rare, severe neutrophilic skin disorder characterized by sudden widespread eruption of superficial sterile pustules with or without systemic inflammation. GPP flares can be life-threatening if untreated due to potential severe complications such as cardiovascular failure and serious infections. Currently, there are no GPP-specific therapies approved in the USA or Europe. Retinoids, cyclosporine, and methotrexate are the most commonly used non-biologic therapies for GPP. The evidence that supports the currently available treatment options is mainly based on case reports and small, open-label, single-arm studies. However, recent advances in our understanding of the pathogenic mechanisms of GPP and the identification of gene mutations linked to the disease have paved the way for the development of specific targeted therapies that selectively suppress the autoinflammatory and autoimmune mechanisms induced during GPP flares. Several biologic agents that target key cytokines involved in the activation of inflammatory pathways, such as tumor necrosis factor-α blockers and interleukin (IL)-17, IL-23, and IL-12 inhibitors, have emerged as potential treatments for GPP, with several being approved in Japan. The evidence supporting the efficacy of these agents is mainly derived from small, uncontrolled trials. A notable recent advance is the discovery of IL36RN mutations and the central role of IL-36 receptor ligands in the pathogenesis of GPP, which has defined key therapeutic targets for the disease. Biologic agents that target the IL-36 pathway have demonstrated promising efficacy in patients with GPP, marking the beginning of a new era of targeted therapy for GPP.

Targeting heat shock proteins 90 and 70: A promising remedy for both autoimmune bullous diseases and COVID-19.

Heat shock proteins (Hsps), including Hsp90 and Hsp70, are intra- and extracellular molecules implicated in cellular homeostasis and immune processes and are induced by cell stress such as inflammation and infection. Autoimmune bullous disorders (AIBDs) and COVID-19 represent potentially life-threatening inflammatory and infectious diseases, respectively. A significant portion of AIBDs remain refractory to currently available immunosuppressive therapies, which may represent a risk factor for COVID-19, and suffer from treatment side-effects. Despite advances in vaccination, there is still a need to develop new therapeutic approaches targeting SARS-CoV-2, especially considering vaccine hesitancy, logistical distribution challenges, and breakthrough infections. In this mini review, we briefly summarize the role of targeting Hsp90/70 as a promising double-edged sword in the therapy of AIBDs and COVID-19.

Congenital atrichia with papular lesions.

Congenital atrichia with papular lesions is a rare, autosomal recessive and irreversible form of total alopecia of the body hair characterized by hair loss soon after birth and the development of keratinfilled cysts or horny papules over extensive areas of the body. The condition is associated with a mutation of the human hairless gene on chromosome region 8p12. We report a 1-year-old boy presenting with the absence of scalp and body hair since birth. On examination, he had complete absence of hair on the scalp, eyebrows, and eyelashes. Multiple, discrete, pearly-to-skin-colored papules of 1-3mm in size were present over the scalp. The skin biopsy from a scalp papule revealed normal overlying epidermis with multiple keratin cysts and hypoplastic hair follicles in the upper dermis.

A Comparative Analysis of CD32A and CD16A Polymorphisms in Relation to Autoimmune Responses in Pemphigus Diseases and Subepithelial Autoimmune Blistering Disorders.

Autoimmune blistering dermatoses (ABDs) are characterized by autoantibodies to keratinocyte surface antigens and molecules within the dermal-epidermal junction causing disruption of skin integrity. The affinity of Fc receptors (FcRs) causing an autoimmune response in ABDs may vary based on single-nucleotide polymorphisms (SNPs) in FcRs determining the course of disease. This study aimed to explore the effects of CD16A and CD32A SNPs on the autoimmune response in several ABDs. In total, 61 ABDs patients were investigated. ELISA tests, direct immunofluorescence (DIF), TaqMan SNP Genotyping Assays, and statistical analyses were performed. The CA genotype (composed of allele C and A) of rs396991 in CD16A had a higher affinity for tissue-bound IgG1 in pemphigus and for C3 in subepithelial ABDs, showing statistical significance. The greatest relative risk (odds ratio) was reported for AA (rs396991 of CD16A) and CC (rs1801274 of CD32A) homozygotes. There were no statistically significant differences between certain genotypes and specific circulating autoantibodies (anti-DSG1, anti-DSG3 IgG in pemphigus; anti-BP180, anti-BP230 IgG) in subepithelial ABDs. Our findings indicated that rs396991 in CD16A may be of greater importance in ABDs development. Moreover, FcR polymorphisms appeared to have a greater impact on tissue-bound antibodies detected using DIF than circulating serum antibodies in ABDs.

Identification of a recurrent nonsense mutation in HR gene responsible for atrichia with papular lesions in two Kashmiri families.

BACKGROUND: Congenital atrichia (CA) is a rare form of irreversible alopecia with an autosomal recessive mode of inheritance. This form of hair loss is mainly associated with mutations in the human hairless (HR) gene located at chromosome 8p21.3. An additional unique feature atrichia with papular lesions (APL) comprises keratin-filled cysts known as papules. The present study aimed to uncover the underlying genetic causes of APL in two consanguineous Kashmiri families. METHODS: In the present study, two consanguineous families of Kashmiri origin with APL displaying an autosomal recessive mode of inheritance were investigated. Whole exome and Sanger sequencing followed by bioinformatic studies, variant prioritization, Sanger validation and segregation analysis was performed to find the mutation. RESULTS: A recurrent nonsense (NM_005144: c.2818C > T:p.Arg940*) mutation was detected in exon 13 of the human HR gene. CONCLUSIONS: Whole exome sequencing analysis has widely been used in the screening of single gene disorders mutations, both in research and diagnostic laboratories. Sanger sequencing alone for genes such as HR becomes expensive and time consuming. Instead, it is recommended that a patient is to screen by whole exome sequencing and then special attention first focuses on known genes of the APL phenotype. This is helpful for intime diagnosis, being more efficient and economic. The results obtained in the present study may contribute to prenatal diagnosis, carrier secreening and the genetic counseling of families with the APL phenotype in Kashmiri poplution.

Collagen XVII Processing and Blistering Skin Diseases.

Collagen XVII (COL17) is a hemidesmosomal transmembrane protein in the skin, which, in several autoimmune blistering skin diseases, may be targeted by autoantibodies. In addition, loss-of-function mutations in the COL17A1 gene induce a subtype of junctional epidermolysis bullosa. The extracellular domain of COL17 can be physiologically cleaved from the cell surface by ADAM family proteins in a process known as ectodomain shedding. COL17 ectodomain shedding is thought to be associated with the migration and proliferation of keratinocytes. Furthermore, the C-terminal cleavage of COL17 may be associated with basement membrane formation. COL17 can be targeted by various proteases, including MMP9, neutrophil elastase, plasmin and granzyme B, which may be associated with blister formation in pemphigoid diseases. Interestingly, cleavage of COL17 may induce neoepitopes on the proteolysed fragments, and such induction is associated with dynamic structural changes. This review summarizes the current understanding of cleavage of COL17, and how such cleavage relates to blistering skin diseases.

Genetics and Omics Analysis of Autoimmune Skin Blistering Diseases.

Autoimmune blistering diseases (AIBDs) of the skin are characterized by autoantibodies against different intra-/extracellular structures within the epidermis and at the basement membrane zone (BMZ). Binding of the antibodies to their target antigen leads to inflammation at the respective binding site and degradation of these structures, resulting in the separation of the affected skin layers. Clinically, blistering, erythema and lesions of the skin and/or mucous membranes can be observed. Based on the localization of the autoantigen, AIBDs can be divided into pemphigus (intra-epidermal blistering diseases) and pemphigoid diseases (sub-epidermal blistering diseases), respectively. Although autoantigens have been extensively characterized, the underlying causes that trigger the diseases are still poorly understood. Besides the environment, genetic factors seem to play an important role in a predisposition to AIBDs. Here, we review currently known genetic and immunological mechanisms that contribute to the pathogenesis of AIBDs. Among the most commonly encountered genetic predispositions for AIBDs are the HLA gene region, and deleterious mutations of key genes for the immune system. Particularly, HLA class II genes such as the HLA-DR and HLA-DQ alleles have been shown to be prevalent in patients. This has prompted further epidemiological studies as well as unbiased Omics approaches on the transcriptome, microbiome, and proteome level to elucidate common and individual genetic risk factors as well as the molecular pathways that lead to the pathogenesis of AIBDs.

[Syndromes with skin fragility]. / Syndrome mit Hautfragilität.

Syndromic disorders with skin fragility belong to different groups of genodermatoses: epidermolysis bullosa (EB), Ehlers-Danlos syndrome and porphyria. The genetic defects mainly concern structural proteins which assure the mechanical stability of the skin and other tissues. Depending on the expression pattern of the affected protein in the skin, cutaneous fragility may manifest as superficial erosions, blisters, wounds, wound healing defects or scars. Extracutaneous manifestations are manifold and involve the heart, skeletal muscles, intestine, kidneys, blood vessels or the skeleton. Syndromic types of EB include in addition to skin blistering: (i) cardiomyopathy in case of desmoplakin, plakoglobin, or kelch-like protein mutations; (ii) muscular dystrophy in case of plektin mutations; (iii) pyloric atresia in case of integrin α6ß4 or plectin mutations; (iv) nephrotic syndrome in case of CD151 or integrin α3 mutations. Lysyl hydroxylase 3 mutations affect posttranslational modifications of collagens and lead to a dystrophic epidermolysis bullosa-like multisystemic disorder. Ehlers-Danlos syndromes are due to defects of dermal collagens or their processing and affect the skin, joints and blood vessels. Finally porphyrias are complex metabolic disorders with photosensitivity and sometimes skin fragility, liver or neurologic problems. Their pathogenesis relies on the accumulation of precursors in the tissues. Although these syndromes are rare in clinical practice, knowledge of the syndromic constellation contributes to early diagnosis and detection of complications.

Phenotypic Spectrum of Epidermolysis Bullosa: The Paradigm of Syndromic versus Non-Syndromic Skin Fragility Disorders.

The heritable forms of epidermolysis bullosa (EB), a phenotypically heterogeneous group of skin fragility disorders, is currently associated with mutations in as many as 21 distinct genes. EB is primarily a disorder affecting the epithelial layers of skin and mucous membranes, without extracutaneous manifestations, and thus is nonsyndromic. However, recent demonstrations of skin blistering in multisystem disorders with single gene defects highlight the concept of syndromic EB. Here, we review the phenotypic and genotypic features of syndromic forms of EB to delineate the concept of syndromic versus nonsyndromic skin fragility disorders.

Mutation in IL36RN impairs the processing and regulatory function of the interleukin-36-receptor antagonist and is associated with DITRA syndrome.

The identification of loss-of-function mutations of the IL36RN gene encoding the interleukin-36 receptor antagonist (IL-36Ra) in generalized pustular psoriasis (GPP) emphasized the key role of this pathway in skin innate immunity and systemic inflammation. It has been previously shown in vitro that removal of the N-terminal amino acid IL36Ra (M1) is critical to its biological activity, but the in vivo contribution of this processing remains unknown. We report herein a new homozygous (c4G>T, pV2F) missense IL36RN mutation segregating in a family with three GPP-affected patients. The V2F mutation does not alter IL-36Ra protein expression but was devoid of any antagonist activity. Mass spectrometry showed that the V2F IL-36Ra mutant retains its first N-terminal methionine. These results provide the first in vivo demonstration that removal of N-terminal methionine of native IL-36Ra is a mandatory step to reach optimal antagonist activity and to prevent sustained skin and systemic inflammation in humans.

Human Hairless Protein Roles in Skin/Hair and Emerging Connections to Brain and Other Cancers.

The mammalian hairless protein (HR) is a 130 kDa nuclear transcription factor that is essential for proper skin and hair follicle function. Previous studies have focused on the role of HR in skin maintenance and hair cycling. However, the hairless gene (HR) is also expressed in brain and other tissues, where its role remains poorly understood. HR has been reported to contain functional domains that potentially serve in DNA binding, histone demethylation, nuclear translocation and protein-protein interactions. Indeed, HR has been shown to interact with and repress the action of the nuclear receptors for vitamin D and thyroid hormone as well as RAR-related orphan receptor alpha, possibly via recruitment of histone deacetylases. HR may also have important functions in non-skin tissues given that nearly 200 HR mutations have been identified in patients with various cancers, including prostate, breast, lung, melanoma, uterine, and glioma. This suggests that HR and/or mutants thereof have relevance to the growth and survival of cancer cells. For example, the reported intrinsic histone H3K9 demethylase activity of HR may activate dormant genes to contribute to carcinogenesis. Alternatively, the demonstrated ability of HR to interact with p53 and/or the p53 DNA response element to influence p53-regulated pathways may explain, at least in part, why many cancers express mutated HR proteins. In this review, we summarize the current knowledge of HR bioactions, how HR mutations may be contributing to alopecia as well as to cancer, and, finally, outline future directions in the study of this largely enigmatic nuclear protein. J. Cell. Biochem. 119: 69-80, 2018. © 2017 Wiley Periodicals, Inc.