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Nagashima-type palmoplantar keratosis (NPPK) is a relatively common autosomal recessive dermatosis characterized by well-defined diffuse erythema and non-destructive hyperkeratosis on the palmoplantar areas, with swelling and whitening when exposed to water. The pathogenesis of NPPK can be attributable to altered structure and function of SERPINB7, environmental factors, barrier dysfunction and inflammatory response. There is no specific and standardized therapy for this disorder. Topical treatment is primary therapy although systemic drugs or surgery can be used for severe cases. Gentamicin, a targeted therapy for the disease, has shown some potential, but more clinical studies are still needed to verify its efficacy and safety. The aim of this review is to summarize the causative gene, pathogenesis and therapeutic strategies of NPPK.

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Nagashima-type palmoplantar keratosis (NPPK) is a relatively common autosomal recessive dermatosis characterized by well-defined diffuse erythema and non-destructive hyperkeratosis on the palmoplantar areas, with swelling and whitening when exposed to water. The pathogenesis of NPPK can be attributable to altered structure and function of SERPINB7, environmental factors, barrier dysfunction and inflammatory response. There is no specific and standardized therapy for this disorder. Topical treatment is primary therapy although systemic drugs or surgery can be used for severe cases. Gentamicin, a targeted therapy for the disease, has shown some potential, but more clinical studies are still needed to verify its efficacy and safety. The aim of this review is to summarize the causative gene, pathogenesis and therapeutic strategies of NPPK. [ABSTRACT FROM AUTHOR]

Nagashima‐type palmoplantar keratoderma (NPPK) is an autosomal recessive form of diffuse palmoplantar keratoderma (PPK) characterized by thickening and redness of palms and/or soles. In this report, we describe a female patient of Korean descent who had clinical remission of her adult‐onset NPPK. To our knowledge, she is the first reported heterozygous SERBINB7 mutation carrier to present with classic NPPK who achieved spontaneous clinical remission. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Nagashima‐type palmoplantar keratoderma (NPPK) is the most prevalent hereditary palmoplantar keratoderma (PPK) in China, but there is a paucity of epidemiological data on the Chinese population. To explore the clinical and genetic characteristics, evaluate the demographic distribution, and estimate the burden of disease of NPPK. A total of 234 Chinese patients with NPPK were enrolled from two medical centers and an online PPK support group. Next‐generation sequencing and Sanger sequencing were performed to screen out and confirm pathogenic mutations in SERPINB7. Clinical features and quality of life (QOL) were evaluated using self‐completed questionnaires. In total, 14 pathogenic mutations were identified in SERPINB7 from the cohort. The top four recurrent mutations were c.796C>T (355, 75.9%), c.522dupT (66, 14.1%), c.650_653delCTGT (24, 5.1%), and c.455G>T (12, 2.6%), accounting for 97.6% of Chinese NPPK patients. Other mutations (11, 2.4%) include c.455‐1G>T, c.336+2T>G, c.635delG and seven novel mutations c.2T>C, c.434delG, c.455‐16A>G, c.656T>C, c.745‐553T>G, c.832C>T, c.1036G>T. The estimated prevalence of NPPK in China was found to be 0.975/10 000 based on Chinese databases. Clinically, there were no apparent genotype–phenotype correlations in NPPK patients. Pediatric patients mainly presented with palmoplantar peeling, while adults presented with scale (p < 0.001). The most common comorbidities in NPPK patients were onychomycosis (40.0%), eczema (36.8%), and tinea pedis (30.3%). As for burden of disease, NPPK patients' QOL was decreased by a moderate degree. In this study, pathogenic mutations' allele frequencies in SERPINB7 were updated, and prevalence of NPPK in China was estimated. This large‐scale cohort study provides evidence‐based recommendations for patient management. Identification of new mutations are important for timely diagnosis of NPPK. Palmoplantar peeling in children can be used as a hallmark for early recognition of NPPK. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Nagashima-type palmoplantar keratosis (NPPK) is a diffuse, non-syndromic (isolated), autosomal recessive palmoplantar keratoderma (PPK) with transgredients. It is characterized by non-progressive mild to moderate transgredient PPK. The mutation in SERPINB7 is reported to underlie the condition. Though many case reports/series have demonstrated various mutations in SERPINB7, the genotype-phenotype correlation in this disorder is still lacking. We herein report two brothers with NPPK. Both patients were found to be compound heterozygous for c.796C>T and c.650_653delCTGT in the SERPINB7 gene. We then summarize the previously reported cases of different mutations in SERPINB7 along with their clinical phenotypes in an attempt to shed some light on this correlation. Further investigations and systematic data collection are still needed to clarify this issue.

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. [ABSTRACT FROM AUTHOR]

Inherited ichthyosis comprises a series of heterogeneous dermal conditions; it mainly manifests as widespread hyperkeratosis, xerosis and scaling of the skin. At times, overlapping symptoms require differential diagnosis between ichthyosis and several other similar disorders. The present study reports seven patients with confirmed or suspected to be associated with ichthyosis by conducting a thorough clinical and genetic investigation. Genetic testing was conducted using whole-exome sequencing, with Sanger sequencing as the validation method. The MEGA7 program was used to analyze the conservation of amino acid residues affected by the detected missense variants. The enrolled patients exhibited ichthyosis-like but distinct clinical manifestations. Genetic analysis identified diagnostic variations in the FLG, STS, KRT10 and SERPINB7 genes and clarified the carrying status of each variant in the respective family members. The two residues affected by the detected missense variants remained conserved across multiple species. Of note, the two variants, namely STS: c.452C>T(p.P151L) and c.647_650del(p.L216fs) are novel. In conclusion, a clear genetic differential diagnosis was made for the enrolled ichthyosis-associated patients; the study findings also extended the mutation spectrum of ichthyosis and provided solid evidence for the counseling of the affected families. [ABSTRACT FROM AUTHOR]

Nagashima-type palmoplantar keratoderma (NPPK) is characterized by non-progressive, diffuse, and cross-gradient hyperkeratosis caused by mutations in the SERPINB7 gene on chromosome 18q21.33. Chromosome 18q deletion syndrome (18q- syndrome) is a terminal deletion or microdeletion syndrome characterized by intellectual disability and congenital malformations. This paper describes an 18-year-old man with palmoplantar keratoderma and diffuse white matter abnormalities in the brain. Trio-based exome sequencing (ES) revealed a suspected mosaic compound heterozygous mutation for c.796C>T (p.Arg266∗) in exon 8 inherited from the mother and a de novo exons 4–6 deletion of SERPINB7. Additional copy number variant (CNV) analysis of the ES data indicated a heterozygous gross deletion of 18q22.3-q23. The two SERPINB7 gene variants were verified by Sanger sequencing and quantitative real-time polymerase chain reaction (qRT-PCR). Finally, low-coverage whole-genome sequencing (WGS) confirmed the 18q22.3-q23 deletion and additionally detected a mosaic 18q21.33-q22.3 deletion, together explaining NPPK and the neurological phenotypes of the proband. The gross deletion of all exons of SERPINB7 was revealed for the first time. More rarely, c.796C>T (p.Arg266∗) was likely to be mosaic, while the exon deletion was mosaic. In conclusion, the combination of multiple molecular genetic testing methods provides comprehensive informative molecular findings and promotes the diagnosis of complex diseases, as in this case.

Nagashima-type palmoplantar keratoderma (NPPK) is characterized by non-progressive, diffuse, and cross-gradient hyperkeratosis caused by mutations in the SERPINB7 gene on chromosome 18q21.33. Chromosome 18q deletion syndrome (18q- syndrome) is a terminal deletion or microdeletion syndrome characterized by intellectual disability and congenital malformations. This paper describes an 18-year-old man with palmoplantar keratoderma and diffuse white matter abnormalities in the brain. Trio-based exome sequencing (ES) revealed a suspected mosaic compound heterozygous mutation for c.796C>T (p.Arg266∗) in exon 8 inherited from the mother and a de novo exons 4–6 deletion of SERPINB7. Additional copy number variant (CNV) analysis of the ES data indicated a heterozygous gross deletion of 18q22.3-q23. The two SERPINB7 gene variants were verified by Sanger sequencing and quantitative real-time polymerase chain reaction (qRT-PCR). Finally, low-coverage whole-genome sequencing (WGS) confirmed the 18q22.3-q23 deletion and additionally detected a mosaic 18q21.33-q22.3 deletion, together explaining NPPK and the neurological phenotypes of the proband. The gross deletion of all exons of SERPINB7 was revealed for the first time. More rarely, c.796C>T (p.Arg266∗) was likely to be mosaic, while the exon deletion was mosaic. In conclusion, the combination of multiple molecular genetic testing methods provides comprehensive informative molecular findings and promotes the diagnosis of complex diseases, as in this case. [ABSTRACT FROM AUTHOR]

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., (© 2024 The Author(s). The Journal of Dermatology published by John Wiley & Sons Australia, Ltd on behalf of Japanese Dermatological Association.)

Nagashima-type palmoplantar keratosis (NPPK) is a diffuse, non-syndromic (isolated), autosomal recessive palmoplantar keratoderma (PPK) with transgredients. It is characterized by non-progressive mild to moderate transgredient PPK. The mutation in SERPINB7 is reported to underlie the condition. Though many case reports/series have demonstrated various mutations in SERPINB7, the genotype-phenotype correlation in this disorder is still lacking. We herein report two brothers with NPPK. Both patients were found to be compound heterozygous for c.796C>T and c.650_653delCTGT in the SERPINB7 gene. We then summarize the previously reported cases of different mutations in SERPINB7 along with their clinical phenotypes in an attempt to shed some light on this correlation. Further investigations and systematic data collection are still needed to clarify this issue. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Atopic dermatitis (AD) is a common chronic inflammatory skin disease with high heritability. Previous genome-wide association studies have identified several loci predisposing to AD. These findings explain approximately 30% of the variance in AD susceptibility, suggesting that further work is required to fully understand the genetic underpinnings. We sought to gain additional understanding of the genetic contribution to AD risk by using biobank resources. We completed a genome-wide meta-analysis of AD in 796,661 individuals (N cases = 22,474) from the FinnGen study, the Estonian Biobank, and the UK Biobank. We further performed downstream in silico analyses to characterize the risk variants at the novel loci. We report 30 loci associating with AD (P < 5 × 10−8), 5 of which are novel. In 2 of the novel loci, we identified missense mutations with deleterious predictions in desmocollin 1 and serpin family B member 7, genes encoding proteins crucial to epidermal strength and integrity. These findings elucidate novel genetic pathways involved in AD pathophysiology. The likely involvement of desmocollin 1 and serpin family B member 7 in AD pathogenesis may offer opportunities for the development of novel treatment strategies for AD in the future. [ABSTRACT FROM AUTHOR]