Pachyonychia congenita is an uncommon autosomal dominant skin disorder characterized by hypertrophic nail dystrophy, palmoplantar keratoderma, oral leukokeratosis, and cutaneous cysts. And fissured tongue is rarely reported in patients with pachyonychia congenita. The disease is primarily associated with mutations in five keratin genes, namely KRT6A, KRT6B, KRT6C, KRT16 or KRT17. Herein we report a 9-year-old Chinese girl who has thickened nails, keratinized plaques, and fissured tongue since birth. To investigate the underlying genetic cause, whole-exome sequencing and Sanger sequencing were performed in this patient and her family members. We identified a candidate variant c.1460-2_1460del (p.S487Lfs*21) in the KRT6A gene (NM_005554.4) by whole-exome sequencing. Sanger sequencing revealed the absence of the mutation in both parents, indicating that it is a de novo variant. Thus, the novel heterozygous frameshift mutation c.1460-2_1460del (p.S487Lfs*21) within exon 9 of KRT6A was identified as the genetic cause of the patient. Our study identified a rare de novo heterozygous frameshift mutation in the KRT6A gene in a patient with pachyonychia congenita presenting fissured tongue. Our findings expand the KRT6A gene mutation spectrum of Pachyonychia congenita, and will contribute to the future genetic counseling and gene therapy for this disease.

Botulinum toxin is a superfamily of neurotoxins produced by the bacterium Clostridium Botulinum with well-established efficacy and safety profile in focal idiopathic hyperhidrosis. Recently, botulinum toxins have also been used in many other skin diseases, in off label regimen. The objective of this manuscript is to review and analyze the main therapeutic applications of botulinum toxins in skin diseases. A systematic review of the published data was conducted, following Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. Botulinum toxins present several label and off-label indications of interest for dermatologists. The best-reported evidence concerns focal idiopathic hyperhidrosis, Raynaud phenomenon, suppurative hidradenitis, Hailey-Hailey disease, epidermolysis bullosa simplex Weber-Cockayne type, Darier\'s disease, pachyonychia congenita, aquagenic keratoderma, alopecia, psoriasis, notalgia paresthetica, facial erythema and flushing, and oily skin. Further clinical trials are still needed to better understand the real efficacy and safety of these applications and to standardize injection and doses protocols for off label applications.

Pachyonychia congenita (PC) describes a group of genodermatoses manifesting as thickened nails, palmoplantar keratoderma (PPK) and increased risk of cutaneous infections. PC tarda (PCT) describes late-onset PC, and associated genetic polymorphisms have been identified. There has been discussion that PCT may not be a distinct entity but rather misdiagnosed ectodermal dysplasia (ED) or PPK. Clarification of this is important for appropriate diagnosis, management and patient and genetic counselling. We aimed to conduct a systematic review of all reported cases of PCT in the published literature and collate evidence of genetic polymorphisms and clinical features to compare with known features of PC, ED and PPK. PubMed (1946 to 1 July 2018), Scopus (1955 to 1 July 2018) and Web of Science (1990 to 1 July 2018) databases were searched for case reports of PCT with no search restrictions on date or language. The search strategy included the terms pachyonychia congenita tarda OR pachyonychia congenita AND (late onset OR delayed OR PCT). In total, 13 reports describing 19 individual cases of PCT were identified. Of the three identified genetic polymorphisms, the earliest identified has been shown to be highly probably pathogenic, with the second likely to result in a benign amino acid change, while the third has since been shown to be nonpathogenic,. No epigenetic studies have been performed on any reported cases. Previous authors have suggested that a number of cases of PCT may be misdiagnosed ED or PPK. The findings of our review cannot refute this suggestion, and highlight the need for thorough clinical documentation of suspected cases of PCT and thorough genetic screening of kindred to identify causative genetic polymorphisms. Further high-quality datasets and reporting are needed to give further insight into the nature of PCT as a unique entity.

BACKGROUND: Pachyonychia congenita (PC), a rare autosomal dominant disorder, is featured by significant hypertrophic nail, palmoplantar keratoderma, and plantar pain. It is caused by the mutation of KRT6A, KRT6B, KRT6C, KRT16, or KRT17.
OBJECTIVE: To identify the gene mutation caused the PC in a Chinese family.
METHODS: Genomic DNA was extracted from peripheral blood samples of five patients and six healthy individuals. Genomic DNA of three patients was sequenced by whole-exome sequencing (WES). Then, exons 6 of KRT16 of all samples were amplified by polymerase chain reaction (PCR), and PCR products were sequenced to identify potential mutations.
RESULTS: We identified the proline substitution mutation p.Leu421Pro (c.1262T>C) in the 2B domain of K16 that is associated with PC in a Chinese family. The same mutation was not found in the six healthy individuals of the family.
CONCLUSIONS: The mutation found in this study is the first report in China. So far, 25 mutations in KRT16 have been reportedly associated with PC. Twenty-one mutations are located on exon 1, and four mutations on exon 6.

BACKGROUND: Pachyonychia congenita (PC) is a group of autosomal dominant keratinizing disorders caused by a mutation in one of 4 keratin genes. Previous classification schemes have relied on data from case series and case reports. Most patients in these reports were not genetically tested for PC.
OBJECTIVE: We sought to clarify the prevalence of clinical features associated with PC.
METHODS: We surveyed 254 individuals with confirmed keratin mutations regarding their experience with clinical findings associated with PC. Statistical comparison of the groups by keratin mutation was performed using logistic regression analysis.
RESULTS: Although the onset of clinical symptoms varied considerably among our patients, a diagnostic triad of toenail thickening, plantar keratoderma, and plantar pain was reported by 97% of patients with PC by age 10 years. Plantar pain had the most profound impact on quality of life. Other clinical findings reported by our patients included fingernail dystrophy, oral leukokeratosis, palmar keratoderma, follicular hyperkeratosis, hyperhidrosis, cysts, hoarseness, and natal teeth. We observed a higher likelihood of oral leukokeratosis in individuals harboring KRT6A mutations, and a strong association of natal teeth and cysts in carriers of a KRT17 mutation. Most keratin subgroups expressed a mixed constellation of findings historically reported as PC-1 and PC-2.
CONCLUSIONS: Data were obtained through questionnaires, not by direct examination. Patients were self- or physician-referred.
CONCLUSIONS: We propose a new classification for PC based on the specific keratin gene affected to help clinicians improve their diagnostic and prognostic accuracy, correct spurious associations, and improve therapeutic development.

We report the results of the first systematic review of the worldwide literature on eruptive vellus hair cysts (EVHC). It is likely that EVHC are less rare than it may appear from the scarcity of related publications in the literature. EVHC may be present at birth and may appear at any age, although they show a clear trend towards occurring during the first 3 decades of life. A strong clue to the heavy influence of genes on the occurrence of EVHC is provided by the numerous reports of families in whom two or more members were affected. EVHC lesions present clinically in a rather monomorphous fashion, i.e. round, dome-shaped, skin-colored, asymptomatic, soft-tender papules with a smooth surface and grouped or disseminated in a symmetric pattern. EVHC may affect any cutaneous area, even if the upper part of the body and some distribution patterns are particularly frequent and recognizable, i.e. cephalic, upper trunk around the midline, upper limb including axillae, and proximal lower limb. Such a distribution is likely not random and seems to grossly overlap with that of pilosebaceous and apocrine units. Like clinical morphology, the histologic features of EVHC papules are rather monomorphous, indeed, the diagnostic hallmark being the presence of vellus hair shafts within the cystic space. Peculiar subgroups (familial, late-onset, unilesional, and associated with steatocystoma multiplex) are also identified and discussed. In conclusion, EVHC are basically a cosmetic concern to patients but represent a chronic and difficult-to-treat condition. On the basis of our review, future studies are warranted, mainly concerning (i) further nosographic framing involving genetic and tissue analysis, (ii) implementation of non-invasive diagnostic procedures, and (iii) therapeutic trials of interventions shown to achieve some effectiveness.

Milia are frequently encountered as a primary or secondary patient concern in pediatric and adult clinics, and in general or surgical dermatology practice. Nevertheless, there are few studies on the origin of milia and, to our knowledge, there is no previous comprehensive review of the subject. We review the various forms of milia, highlighting rare variants including genodermatosis-associated milia, and present an updated classification.

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