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Investigation of genetic determinants of Mendelian skin disorders has substantially advanced understanding of epidermal biology. Here we show that mutations in PERP, encoding a crucial component of desmosomes, cause both dominant and recessive human keratoderma. Heterozygosity for a C-terminal truncation, which produces a protein that appears to be unstably incorporated into desmosomes, causes Olmsted syndrome with severe periorificial and palmoplantar keratoderma in multiple unrelated kindreds. Homozygosity for an N-terminal truncation ablates expression and causes widespread erythrokeratoderma, with expansion of epidermal differentiation markers. Both exhibit epidermal hyperproliferation, immature desmosomes lacking a dense midline observed via electron microscopy, and impaired intercellular adhesion upon mechanical stress. Localization of other desmosomal components appears normal, which is in contrast to other conditions caused by mutations in genes encoding desmosomal proteins. These discoveries highlight the essential role of PERP in human desmosomes and epidermal homeostasis and further expand the heterogeneous spectrum of inherited keratinization disorders.

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OBJECTIVES Hidradenitis suppurativa (HS) is an inflammatory skin disease typically localized in the axillae and inguinal and perineal areas. In the absence of standardized medical treatment, severe HS patients present chronic suppurative lesions with polymicrobial anaerobic abscesses. Wide surgery is the cornerstone treatment of severe HS, but surgical indications are limited by the extent of lesions. Intravenous broad-spectrum antibiotics may help control HS, but their efficacy is not documented. This study was designed to assess the efficacy of a 6 week course of ertapenem (1 g daily) and of antibiotic consolidation treatments for 6 months (M6) in severe HS. PATIENTS AND METHODS Thirty consecutive patients with severe HS were retrospectively included in this study. The clinical severity of HS was assessed using the Sartorius score, which takes into account the number and severity of lesions. RESULTS The median (IQR) Sartorius score dropped from 49.5 (28-62) at baseline to 19.0 (12-28) after ertapenem (P < 10(-4)). Five patients were lost to follow-up thereafter. At M6 the Sartorius score further decreased for the 16 patients who received continuous consolidation treatments, since 59% of HS areas reached clinical remission at M6 (i.e. absence of any inflammatory symptoms, P < 10(-4)). Nine patients interrupted or received intermittent consolidation treatments due to poor observance or irregular follow-up. Their Sartorius score stopped improving or returned to baseline. No major adverse event occurred. CONCLUSIONS Ertapenem can dramatically improve severe HS. Consolidation treatments are needed to further improve HS and are mandatory to prevent relapses. Combined with surgery, optimized antibiotic treatments may be promising in severe HS.

Inherited epidermolysis bullosa (EB) comprises rare heterogeneous disorders characterized by cutaneous and mucosal fragility. Most of the 20 proteins affected have structural functions. Recently, a previously undescribed type of EB simplex (EBS), caused by gain-of-function mutations in KLHL24, encoding KLHL24 has been identified (He et al., 2016, Lin et al., 2016). This protein seems to be involved in protein ubiquitination. Patients carrying monoallelic mutations in the translation initiation codon of KLHL24 have a characteristic clinical phenotype, showing skin defects and blistering at birth and unusual stellate scarring, skin fragility, and whorled or macular hyperpigmentation or hypopigmentation in childhood (Figure 1a–e). Although skin fragility improves by adulthood, nail dystrophy, anetoderma, and hair loss may occur (Figure 1f–h).

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Erythrokeratodermia variabilis et progressiva (EKVP) is a genodermatosis with clinical and genetic heterogeneity, most often transmitted in an autosomal dominant manner, caused by mutations in GJB3 and GJB4 genes encoding connexins (Cx)31 and 30.3, respectively. In this issue, Boyden et al. (2015) report for the first time de novo dominant mutations in GJA1 encoding the ubiquitous Cx43 in patients with EKVP. These results expand the genetic heterogeneity of EKVP and the human disease phenotypes associated with GJA1 mutations. They disclose that EKVP is allelic to oculo-dento-digital dysplasia, a rare syndrome previously known to be caused by dominant GJA1 mutations.

Background Hidradenitis suppurativa (HS) is a frequent and severe disease of the skin, characterized by recurrent or chronic skinfold suppurative lesions with a high impact on quality of life. Although considered inflammatory, antimicrobial treatments can improve or lead to clinical remission of HS, suggesting triggering microbial factors. Indeed, mixed anaerobic microbiota are associated with a majority of HS lesions. Our aim in this study was to characterize the landscape of anaerobic infections in HS using high-throughput sequencing. Methods We sampled and cultured 149 lesions and 175 unaffected control skinfold areas from 65 adult HS patients. The microbiome of 80 anaerobic lesions was compared to that of 88 control samples by 454 high-throughput sequencing after construction of 16S ribosomal RNA gene libraries. Results Bacterial cultures detected anaerobes in 83% of lesions vs 53% of control samples, combined with milleri group streptococci and actinomycetes in 33% and 26% of cases, respectively. High-throughput sequencing identified 43 taxa associated with HS lesions. Two gram-negative anaerobic rod taxa, Prevotella and Porphyromonas, predominated, contrasting with a reduced abundance of aerobic commensals. These rare taxa of normal skinfold microbiota were associated with lesions independently of gender, duration and familial history of HS, body mass index, and location. Two main additional taxa, Fusobacterium and Parvimonas, correlated with the clinical severity of HS. Conclusions In this study we reveal the high prevalence and particular landscape of mixed anaerobic infection in HS, paving the way for rationale targeted antimicrobial treatments.

Early onset retinal degeneration associated with obesity can present a diagnostic challenge in paediatric ophthalmology practice. Clinical overlap between Bardet-Biedl syndrome (BBS) and Alström syndrome has been described, although the two entities are genetically distinct. To date, 16 genes are known to be associated with BBS (BBS1-16) and only one gene has been identified for Alström syndrome (ALMS1).In collaboration with the French National Center for Sequencing (CNS, Evry), all coding exons and flanking introns were sequenced for 27 ciliopathy genes (BBS1-12, MGC1203, TTC21b, AHI1, NPHP2-8 (NPHP6=BBS14), MKS1(BBS13), MKS3, C2ORF86, SDCCAG8, ALMS1) in 96 patients referred with a clinical diagnosis of BBS. ALMS1 gene analysis included sequencing of all coding exons.BBS known gene mutations were found in 44 patients (36 with two mutations and 8 heterozygous). ALMS1 mutations were found in four cases. The rate of ALMS1 mutations among patients suspected of having BBS was 4.2%.Clinically, all four patients presented early-onset severe retinal degeneration with congenital nystagmus associated with obesity. The difficult early differential diagnosis between the two syndromes is outlined. One mutation had already been reported (c.11310delAGAG/p.R3770fsX) and three were novel (c.2293CT/p.Q765X, c.6823insA/p.R2275fsX, c.9046delA/p.N3016fsX).Ciliopathy genes sequencing can be very helpful in providing a timely diagnosis in this group of patients, hence appropriate genetic counselling for families and adequate medical follow-up for affected children.

Keywords: anaerobes; hidradenitis suppurativa; inflammatory disease; microbiology; soft tissue and skin infections

Pyoderma gangrenosum, severe acne, and suppurative hidradenitis (PASH) syndrome can prove refractory to treatment and is characterized by relapses and recurrences. The combination of antibiotic therapy and surgery can produce success in the management of the syndrome. Acute treatment is required, but maintenance therapy is also necessary to prevent disease relapse. The response to antibiotic therapy is hypothesis generating, raising the issue of a modified host response. To date, anecdotal reports support the use of surgery and medical therapy, but controlled investigations with extended follow-up are necessary to substantiate preliminary data observed with individual cases.

or Africans. 4 The prevalence of FLG mutations is similar in Europeans and Asians. In contrast, FLG mutations seem to be less common in African populations, although they have been less extensively studied, with the consequent possibility of underestimating the frequency of distinct FLG mutations. The strongest associations have been reported between FLG mutations and the risk of early-onset, persistent, and severe AD. 4

Importance Olmsted syndrome (OS) is a rare keratinizing disorder characterized by excessive epidermal thickening of the palms and soles, with clinical and genetic heterogeneity. Approximately 50 cases have been reported, with the molecular basis described in only 9. Recently, TRPV3 (transient receptor potential vanilloid 3) mutations were identified in autosomal-dominant OS in 7 sporadic cases and 1 familial case, whereas an MBTPS2 (membrane-bound transcription factor protease, site 2) mutation was reported in X-linked recessive OS. We report a new sporadic case of severe, atypical OS and its underlying genetic basis. Observations Our patient is a young girl with severe nonmutilating (palmo)plantar keratoderma without periorificial keratotic plaques associated with intense acute flares of inflammation, itching, burning pain, vasodilatation, and redness of the extremities consistent with erythromelalgia. Whole exome sequencing of patient DNA identified a novel de novo heterozygous missense mutation within TRPV3 , p.Leu673Phe, predicted to be damaging. Conclusions and Relevance This case study further implicates TRPV3 in OS pathogenesis. In addition, previous reports of OS have not described erythromelalgia as a clinical feature. Its occurrence in our patient could be a chance event, but, if associated with OS, the features of erythromelalgia may expand the phenotypic spectrum of this rare syndrome.

Background The SCN5A gene encodes for the alpha-subunit of the cardiac sodium channel. The cardiac sodium current I Na is essential for generation and transmission of the action potential, and I Na dysfunction is responsible for multiple arrhythmias. Here, we characterized a distal truncating SCN5A mutation, R1860GfsX12, which was identified in a family with mixed clinical phenotypes of sick sinus syndrome, atrial fibrillation, atrial flutter, and AV block. Methods and Results Patch-clamp analysis performed in HEK 293 cells expressing the mutant channel showed a 70% reduction in I Na density compared to cells expressing the wild-type (WT) channels, consistent with western blot analysis showing a partial degradation of the mutant. In addition, the R1860Gfs12X mutation drastically altered the steady-state inactivation leading to a –25-mV shift, delayed the fast and slow inactivation, and increased the persistent current. Moreover, when mimicking the heterozygous state of the patients by coexpressing WT with R1860GfsX12, the biophysical properties were still altered. Loss of I Na density and alteration of the inactivation properties of this mutant channel are associated with a mix of atrial phenotype and AV block within the family. The variety of clinical phenotype seen in this family for the same mutation and the absence of a ventricular phenotype led us to investigate I Na density in HEK cells at membrane potentials mimicking a ventricular vs an atrial resting membrane potential (–86 and –83 mV, respectively). Surprisingly, despite an only 3-mV hyperpolarizing difference in the resting membrane potential of atria, we observed a further decrease in I Na density by 40% at the atrial resting membrane potential compared to the resting membrane potential of the ventricles. Conclusions Multiple mechanisms underlie functional consequences of SCN5A mutations. Here, we demonstrated that one mutation may have different clinical consequences in the atria or the ventricles due to their difference in resting membrane potential based on its biophysical defects. These results could explain how this mutation led to different atrial arrhythmias and conduction defect phenotype within the same family but to the absence of a Brugada phenotype.