Nagashima-type Palmoplantar Keratosis Research Articles

Coincidence of acral peeling skin syndrome and Nagashima-type palmoplantar keratosis in a Japanese pedigree with acral skin peeling.

Acral peeling skin syndrome (APSS; MIM 609796) is a rare genodermatosis characterized by painless focal cutaneous exfoliation of the dorsal hands and feet, typically displaying autosomal recessive inheritance. While cases associated with a founder mutation in TGM5 are relatively common in European Caucasian populations, no APSS cases have been reported from Japan or other East Asian countries. In contrast, Nagashima-type palmoplantar keratosis (NPPK; MIM 615598), caused by variants in SERPINB7, is relatively common in East Asia due to founder mutations. We describe a 27-year-old Japanese woman with spontaneous focal cutaneous exfoliation of the dorsal hand following prolonged glove use, indicative of APSS. Histopathological examination revealed a cleft between the stratum corneum and stratum granulosum and within the horny layer of the epidermis, supporting this diagnosis. However, her mother and maternal uncle exhibited similar symptoms, and there was no reported consanguinity in the patient's parents or grandparents, prompting suspicion of an autosomal dominant genodermatosis. Whole-genome sequencing (WGS) revealed compound heterozygous variants in TGM5 (c.1037G>A and c.684 + 1G>A) as suspected causative variants in the patient, leading to an APSS diagnosis, the first reported in East Asia. On the other hand, her mother and maternal uncle were diagnosed with NPPK due to compound heterozygous pathogenic variants in SERPINB7 (c.796C>T and c.455-1G>A). This case highlights the complexity of diagnosing skin disorders when multiple genodermatoses with similar phenotypes exist within a pedigree. Comprehensive genetic analyses, such as whole-exome sequencing and WGS, are invaluable for identifying causative variants in such complex cases.

Application of topical gentamicin ointment in the treatment of Nagashima-type palmoplantar keratosis in children with a nonsense mutation.

Nagashima-type palmoplantar keratosis (NPPK) is a hereditary dermatosis mostly caused by a nonsense mutation in SERPINB7. Despite the increasing interest in readthrough gentamicin treatment of NPPK, clinical evidence for this treatment is limited. This study aimed to provide further evidence for the use of topical gentamicin in the treatment of NPPK in children with nonsense mutations. We designed a bilaterally controlled study of topical gentamicin ointment. Children diagnosed with NPPK carrying nonsense mutations were enrolled in this study. A 0.1% gentamicin ointment was applied to one hand and an emollient to the other for 3 months. A bilateral comparison of the visual analog scale scores for clinical manifestations and safety was performed. Ten children with NPPK were included in this study. In comparison with the emollient side, the topical gentamicin side showed significant improvements in hyperkeratosis, erythema, maceration, and desquamation after 1 and 3 months of treatment (P < 0.05). However, hyperhidrosis and odor did not improve significantly. No adverse events were observed during the systemic safety monitoring examinations. Topical gentamicin ointment showed good safety in the treatment of NPPK with nonsense mutations, indicating that it is a promising therapeutic choice in children with NPPK.

863 The application of topical gentamicin ointment in treatment of nagashima-type palmoplantar keratosis in children with nonsense mutation

863 The application of topical gentamicin ointment in treatment of nagashima-type palmoplantar keratosis in children with nonsense mutation

SERPINB7 mutation causes Nagashima-type palmoplantar keratosis and its spatiotemporal expression in zebrafish.

Serine protease inhibitor B7 (SERPINB7) mutations have been reported to cause Nagashima-type palmoplantar keratosis (NPPK), but their biological effects are largely unknown. We conducted whole-exome sequencing and identified a c.796C>T (p.Arg266Ter) mutation in SERPINB7 in a Chinese pedigree, which presented as an autosomal recessive inheritance pattern. We assessed the function of SERPINB7 in homozygous and heterozygous mutation carriers, and the results suggested that the single c.796C>T mutation may alter the subcellular localization of SERPINB7. One of the homozygous mutation patients (II-3) was treated with ixekizumab and showed moderate improvement in keratinization. In addition, we analysed the spatiotemporal expression of serpinb1l1 and serpinb1l3, the zebrafish homologue of human SERPINB7, which is expressed in larvae and adults. In larvae, both serpinb1l1 and serpinb1l3 were expressed in the digestive tract. Then, we performed RT-PCR on adult fins based on similarity to the site of NPPK expression in humans and found that the genes were expressed in five fins (pectoral, pelvic, dorsal, anal and caudal) of the zebrafish distal extremity. Taken together, our results demonstrated that the single c.796C>T (p.Arg266Ter) mutation may alter the location of SERPINB7-encoded protein in the skin, while zebrafish SERPINB7 homologue was expressed in adult fins. These findings will enable us to construct knock-out models to explore the pathogenesis of palmoplantar keratosis.

Noninvasive fetal genotyping of single nucleotide variants and linkage analysis for prenatal diagnosis of monogenic disorders

BackgroundHigh-cost, time-consuming and complex processes of several current approaches limit the use of noninvasive prenatal diagnosis (NIPD) for monogenic disorders in clinical application. Thus, a more cost-effective and easily implementable approach is required.MethodsWe established a low-cost and convenient test to noninvasively deduce fetal genotypes of the mutation and single nucleotide polymorphisms (SNPs) loci by means of targeted amplification combined with deep sequencing of maternal genomic and plasma DNA. The sequential probability ratio test was performed to detect the allelic imbalance in maternal plasma. This method can be employed to directly examine familial pathogenic mutations in the fetal genome, as well as infer the inheritance of parental haplotypes through a group of selected SNPs linked to the pathogenic mutation.ResultsThe fetal mutations in 17 families with different types of monogenic disorders including hemophilia A, von Willebrand disease type 3, Duchenne muscular dystrophy, hyper-IgM type 1, glutaric acidemia type I, Nagashima-type palmoplantar keratosis, and familial exudative vitreoretinopathy were identified in the study. The mutations included various forms: point mutations, gene inversion, deletions/insertions and duplication. The results of 12 families were verified by sequencing of amniotic fluid samples, the accuracy of the approach in fetal genotyping at the mutation and SNPs loci was 98.85% (172/174 loci), and the no-call rate was 28.98% (71/245 loci). The overall accuracy was 12/12 (100%). Moreover, the approach was successfully applied in plasma samples with a fetal fraction as low as 2.3%.ConclusionsWe have shown in this study that the approach is a cost-effective, less time consuming and accurate method for NIPD of monogenic disorders.

Two novel mutations of SERPINB7 in eight cases of Nagashima-type palmoplantar keratosis in the Chinese population.

Nagashima‐type palmoplantar keratosis (NPPK) is a diffuse, autosomal recessive, and non‐epidermolytic palmoplantar keratosis caused by mutations in the SERPINB7 gene, a member of the serine protease inhibitor superfamily. Genetic studies and case reports suggest that NPPK is the most common palmoplantar keratosis in East Asia but rare in Western countries. This study reports eight NPPK patients in seven pedigrees of the Chinese Han ethnicity with two novel (c.530T>C and c.643A>G) and two recurrent mutations (c.796C>T and c.455G>T) in SERPINB7. The diagnosis of NPPK is now well‐defined because of the typical manifestations and pathogenic gene tests. However, its pathomechanism is still obscure, and treatment remains a challenge. This study reviewed all 15 pathogenic mutations and related data in the 1000 Genomes Project to elucidate the founder effect of SERPINB7. Also, several latest cases of NPPK in areas outside East Asia are presented, including France, Finland, and Thailand. Further clinical investigation and genetic studies are crucial for identifying the pathomechanism of NPPK. Also, large‐scale control studies are required to determine the safety and curative effects of available therapies.

Application of topical gentamicin-a new era in the treatment of genodermatosis.

The clinical use of gentamicin always lies in its antimicrobial activity in the past as an aminoglycoside antibiotic. However, in the past decade, there were considerable interests in therapeutic approaches in treating hereditary diseases. Some of the genodermatosis is caused by nonsense mutations that create premature termination codons and lead to the production of truncated or non-functional proteins. Gentamicin could induce readthrough of nonsense mutations and enable the synthesis of full-length proteins. We focus on previous publications on topical application of gentamicin and review its utility in genetic skin diseases. We search the MEDLINE through PubMed, EMBASE databases, and the Clinical Trials Registry Platform from January 1960 to July 2020 using the key search terms "gentamicin, topical gentamicin, genodermatosis, genetic skin diseases". The application of gentamicin in genodermatosis yielded promising results, both in vivo and in vitro, including Nagashima-type palmoplantar keratosis, epidermolysis bullosa, Hailey-Hailey disease, hereditary hypotrichosis simplex of the scalp, etc. CONCLUSIONS: Topical gentamicin is a potential treatment option for genodermatosis caused by nonsense mutation.

172 Discovery of small molecule compounds with readthrough potency at premature termination codon

Nagashima-type palmoplantar keratosis (NPPK) is the most common palmoplantar keratoderma in the East Asian populations. NPPK is caused by biallelic loss-of-function mutations in SERPINB7. Notably, almost all NPPK patients carry the TGAA nonsense mutation c.796C>T (p.Arg266Ter) in SERPINB7, which creates a premature termination codon (PTC) and leads to highly reduced production of full-length, functional SERPINB7 polypeptides. The suppression of a PTC, also known as ‘readthrough’, is able to restore the full-length protein. As the currently available drugs, including topical vitamin D3 and topical keratolytic, yield very limited improvement of NPPK skin phenotypes, we sought to tackle the disease by the readthrough therapy. We first performed a high- throughput screening of 19,992 small molecule compounds for readthrough activity using firefly luciferase assay. A total of 64 compounds survived retest screening and were shortlisted as potential readthrough candidates. Next, we generated a FLAG-tagged mutant SERPINB7 cDNA vector which contains the nonsense mutation c.796C>T and perform single and multiple concentrations screening using this vector for the selected 64 compounds. 2 hit compounds were identified with readthrough efficiency at their optimal concentration. Additional small molecule compounds with similar chemical structures of the 2 hit compounds were purchased for hit expansion; the process in which derivatives with similar chemical structure are selected from databases. Along with the hit expansion compounds, they have shown to induce a higher readthrough potency than the currently available drugs such as gentamicin and ataluren (Translarna®). As approximately 10% of all described gene lesions in genetic diseases are caused by nonsense mutations, the discovery of potent hit compounds can benefit not only NPPK patients but also patients who suffer from diseases caused by nonsense mutations.

Acral peeling in Nagashima type palmo-plantar keratosis patients reveals the role of serine protease inhibitor B 7 in keratinocyte adhesion.

Acral peeling skin syndrome (APSS) is a heterogenous group of genodermatoses, manifested by peeling of palmo-plantar skin and occasionally associated with erythema and epidermal thickening. A subset of APSS is caused by mutations in protease inhibitor encoding genes, resulting in unopposed protease activity and desmosomal degradation and/or mis-localization, leading to enhanced epidermal desquamation. We investigated two Arab-Muslim siblings with mild keratoderma and prominent APSS since infancy. Genetic analysis disclosed a homozygous mutation in SERPINB7, c.796C>T, which is the founder mutation in Nagashima type palmo-plantar keratosis (NPPK). Although not previously formally reported, APSS was found in other patients with NPPK. We hypothesized that loss of SERPINB7 function might contribute to the peeling phenotype through impairment of keratinocyte adhesion, similar to other protease inhibitor mutations that cause APSS. Mis-localization of desmosomal components was observed in a patient plantar biopsy compared with a biopsy from an age- and gender-matched healthy control. Silencing of SERPINB7 in normal human epidermal keratinocytes led to increased cell sheet fragmentation upon mechanical stress. Immunostaining showed reduced expression of desmoglein 1 and desmocollin 1. This study shows that in addition to stratum corneum perturbation, loss of SERPINB7 disrupts desmosomal components, which could lead to desquamation, manifested by skin peeling.

Diagnosis and progress in the progressive symmetric erythrokeratodermia

Progressive symmetric erythrokeratodermia (PSEK) comprises a group of clinically and genetically heterogeneous diseases. Previous research have identified GJB3 and GJB4 as the leading genetic causes of this disorder. With the rapid development of genetics, GJA1, KDSR, KRT83 and TRPM4 have been identified as the new causative genes for PSEK, leading to a further understanding of its clinical features and genetic mechanisms. It's worth noting that Nagashima-type palmoplantar keratosis was often misdiagnosed as PSEK by our domestic dermatologists. Due to the identification of SERPINB7 as the causative gene of Nagashima-type palmoplantar keratosis recently, differentiation between the two disorders could be easily distinguished.

Nagashima-Type Palmoplantar Keratosis: Clinical Characteristics, Genetic Characterization, and Clinical Management.

Nagashima-type palmoplantar keratosis (NPPK) is the most prevalent palmoplantar keratoderma (PPK) in East Asia. Homozygous or compound heterozygous loss-of-function mutations in serpin peptidase inhibitor, clade B (ovalbumin), and member 70 (SERPINB7), which encodes members of the serine protease inhibitor superfamily, have been identified as the cause of NPPK. Clinical manifestations of NPPK include well-demarcated erythema, mild to moderate hyperkeratosis on the whole palm, and sole with transgrediens, extending to the dorsal surfaces of the hands and feet, inner wrists, ankles, and the Achilles tendon areas. In this study, we perform a review of relevant clinical cases aimed at elucidating the clinical characteristics, genetic characterization, differential diagnoses, and clinical management of NPPK. A better understanding of the clinical characteristics and pathogenic gene characterization of NPPK will enhance the diagnosis of NPPK, identify related diseases, and inform on the precise therapy and prognosis. Moreover, it will promote the awareness of NPPK in non-Asian regions.

Effect of Gentamicin Ointment in Patients with Nagashima-type Palmoplantar Keratosis: A Double-blind Vehicle-controlled Study.

Gentamicin ointment has potential in the treatment of Nagashima-type palmoplantar keratosis. However, there is a lack of reliable study data. The aim of this study was to perform a prospective, randomized, double-blinded, contralateral, vehicle-controlled clinical trial. A total of 20 subjects diagnosed with Nagashima-type palmoplantar keratosis by genetic test, who carried nonsense mutations, enrolled in the 30-day study. Gentamicin ointment was applied to the hand and foot on one side of the body, and vehicle ointment was applied to the hand and foot on the other side. The choice of hand and foot in each subject was randomly allocated. The severity of the patient’s skin lesions and quality of life were assessed by a blinded evaluator, using the Dermatology Life Quality Index, visual analogue scale scores and digital photography. Gentamicin ointment treatment resulted in a significant improvement in symptoms of hyperkeratosis and foul smell compared with vehicle. No difference was found in the effect on erythema between gentamicin and vehicle. In conclusion, gentamicin ointment demonstrated positive responses and good tolerance in treating Nagashima-type palmoplantar keratosis caused by nonsense mutations.

Nagashima-type palmoplantar keratosis in Finland caused by a SERPINB7 founder mutation

SERPINB7 mutations in NPPK are not confined to Asian populations. The presence of SERPINB7 mutations should be tested in patients with NPPK in non-Asian populations.

804 Readthrough and nonsense-mediated mRNA decay of SERPINB7 nonsense mutant transcripts in Nagashima-type palmoplantar keratosis

804 Readthrough and nonsense-mediated mRNA decay of SERPINB7 nonsense mutant transcripts in Nagashima-type palmoplantar keratosis

Topical Gentamicin for the Treatment of Genetic Skin Diseases

Clinical application of topical gentamicin is a worthwhile option to investigate further for Nagashima-type palmoplantar keratosis and other genetic skin diseases caused by nonsense mutations. It is especially interesting to study gentamicin 1B because it may be more efficacious than other gentamicin components. Topical gentamicin has an acceptable safety profile, although prospective tracking of antibiotic resistance is warranted.

Gentamicin-Induced Readthrough and Nonsense-Mediated mRNA Decay of SERPINB7 Nonsense Mutant Transcripts

Nagashima-type palmoplantar keratosis (NPPK) is an autosomal recessive skin disorder with a high, unmet medical need that is caused by mutations in SERPINB7. Almost all NPPK patients carry the founder nonsense mutation c.796C>T (p.Arg266Ter) in the last exon of SERPINB7. Here we sought to determine whether topical nonsense-suppression (readthrough) therapy using gentamicin is applicable to NPPK. First, we demonstrated that gentamicin enhanced readthrough activity in cells transfected with SERPINB7 cDNA carrying the mutation and promoted full-length SERPINB7 protein synthesis in NPPK keratinocytes. We next conducted an investigator-blinded, randomized, bilaterally controlled compassionate use study of topical gentamicin in which five NPPK patients with c.796C>T were enrolled. Patients' self-reported improvement of hyperkeratosis was significantly greater on the gentamicin side than the control side (P= 0.0349). In two patients, hyperkeratosis was improved on the gentamicin side, as determined by a blinded-investigator assessment. These results indicate the therapeutic potential of topical gentamicin for NPPK. Unexpectedly, we also found that mutant SERPINB7 mRNAs harboring r.796c>u were degraded by nonsense-mediated mRNA decay. Furthermore, the truncated SERPINB7 protein was degraded via a proteasome-mediated pathway. These findings provide important insights into the mRNA/protein quality-control system in humans, which could be a potential therapeutic target for genetic diseases.

Gentamicin-induced restoration of SERPINB7 by readthrough of a prevalent nonsense mutation c.796C>T in Nagashima-type palmoplantar keratosis

Gentamicin-induced restoration of SERPINB7 by readthrough of a prevalent nonsense mutation c.796C>T in Nagashima-type palmoplantar keratosis

Nagashima-type palmoplantar keratosis in a Chinese Han population.

Nagashima-type palmoplantar keratosis (NPPK) is an autosomal recessive form of palmoplantar keratoderma (PPK), which is caused by mutations in the SERPINB7 gene. NPPK has only been reported in Japanese and Chinese populations. The present study was conducted on 12 unrelated Chinese patients who were clinically predicted to suffer from NPPK. Mutation screening was performed by direct sequencing of the entire coding regions of SERPINB7, SLURP1, AQP5, CSTA, KRT1 and KRT9 genes. Direct sequencing of SERPINB7 revealed five homozygous founder mutations (c.796C>T) and four compound heterozygous mutations in nine patients, including one novel mutation (c.122_127delTGGTCC). Nine out of the 12 patients were diagnosed with NPPK due to SERPINB7 pathogenic mutations, and the results expanded the known mutation spectrum of NPPK. Taking the other seven reported Chinese patients, who had been definitively diagnosed with NPPK by genetic testing, into account, the present study further demonstrated that NPPK is a common entity in Mainland China, and c.796C>T is the most prevalent mutation and exerts a founder effect. Furthermore, the NPPK cases described in the current study presented a consistently mild phenotype, as compared with the degrees of phenotypic variability associated with other types of relatively severe PPK, including Mal de Meleda and Olmsted syndrome.

Identification and Characterization of a Recessive Missense Mutation p.P277L in SERPINB7 in Nagashima-Type Palmoplantar Keratosis

Identification and Characterization of a Recessive Missense Mutation p.P277L in SERPINB7 in Nagashima-Type Palmoplantar Keratosis

Highly prevalent SERPINB7 founder mutation causes pseudodominant inheritance pattern in Nagashima-type palmoplantar keratosis.

Nagashima-type palmoplantar keratosis (NPPK) is a distinct autosomal recessive genodermatosis characterized by diffuse transgressive palmoplantar keratoderma (PPK). Very recently, putative loss-of-function mutations in SERPINB7, which encodes a member of the serine protease inhibitor superfamily and is abundantly expressed in the epidermis, have been identified as a cause of NPPK. To confirm further the role of SERPINB7 mutations in the pathogenesis of NPPK. We analysed 10 Japanese families with NPPK using Sanger and/or whole-exome sequencing. We identified one novel and three recurrent null mutations in SERPINB7. In all the families, the NPPK trait was inherited in an autosomal recessive manner; in one of the families, there was pseudodominant inheritance, which had not been described in NPPK. These data clearly provide further evidence that NPPK is caused by loss-of-function mutations in SERPINB7.