Ectodermal dysplasias: Clinical and molecular review

Assessment and Comparison of Early Developmental Toxicity of Six Per- and Polyfluoroalkyl Substances with Human Embryonic Stem Cell Models

Per- and polyfluoroalkyl substances (PFAS) are extensively utilized in varieties of products and tend to accumulate in the human body including umbilical cord blood and embryos/fetuses. In this study, we conducted an assessment and comparison of the potential early developmental toxicity of perfluorooctanoic acid (PFOA), undecafluorohexanoic acid (PFHxA), heptafluorobutyric acid, perfluorooctanesulfonate (PFOS), perfluorohexanesulfonate, and perfluorobutyric acid at noncytotoxic concentrations relevant to human exposure using models based on human embryonic stem cells in both three-dimensional embryoid body (EB) and monolayer differentiation configurations. All six compounds influenced the determination of cell fate by disrupting the expression of associated markers in both models and, in some instances, even led to alterations in the formation of cystic EBs. The expression of cilia-related gene IFT122 was significantly inhibited. Additionally, PFOS and PFOA inhibited ciliogenesis, while PFOA specifically reduced the cilia length. Transcriptome analysis revealed that PFOS altered 1054 genes and disrupted crucial signaling pathways such as WNT and TGF-β, which play integral roles in cilia transduction and are critical for early embryonic development. These results provide precise and comprehensive insights into the potential adverse health effects of these six PFAS compounds directly concerning early human embryonic development.

Ectodermal Dysplasia - An Overview and Update

Ectodermal dysplasias are a heterogeneous group of disorders that are characterized by abnormal development of ectodermal structures like hair, teeth, nails, and sweat glands. Alhough they were earlier classified according to the structures affected and hence the clinical manifestations, recent developments inch towards a genetic basis for classification. They are currently divided into four groups of disorders based on the pathway involved, which includes the ectodysplasin/nuclear factor-kappa B (NFKB) pathway, wingless-type MMTV integration site family, member 10 ([wingless related integration site] WNT10), tumor protein p63 (TP63), and the structural group. In spite of attempts at the segregation of the various disorders, there is a great degree of overlap in clinical features among the conditions, which makes a thorough history-taking and clinical examination important in helping us arrive at a diagnosis and judge the various systems involved. A multidisciplinary approach forms the crux of the management of patients with ectodermal dysplasias and their families, with a focus on education, counseling, prosthesis, and an overall rehabilitative outlook. Special attention must also be paid to screening family members for varying severities of the disorders, and an attempt must be made at a genetic diagnosis with genetic counseling.

Congenital nail abnormalities

Congenital nail disorders are an uncommon presenting symptom which can be difficult to diagnose and manage. Nail diseases in the pediatric population differ from those in adults in terms of diagnosis, approach and management. In most cases, they do not require treatment and resolve with growth. Physicians need to be able to recognize them, to reassure the parents. The most frequently encountered pathologies associated with nail disorder are syndactyly, acrosyndactyly, symbrachydactyly, macrodactyly, Wassel I thumb duplication, Kirner's deformity and congenital onychodysplasia of the index finger. Treatment usually consists in surgical correction of the deformity. Nail malformation can also be an aspect of a systemic disease. It may provide a clue for screening, and should not be overlooked. Nail conditions can be the first sign of nail-patella syndrome, ectodermal dysplasia, dyskeratosis congenita, epidermolysis bullosa, pachyonychia congenita or lung disease. Medical treatment is therefore discussed on a case-by-case basis.

Understanding the effects of per- and polyfluoroalkyl substances on early skin development: Role of ciliogenesis inhibition and altered microtubule dynamics

Per- and polyfluoroalkyl substances (PFAS) are a class of highly stable chemicals, widely used in everyday products, and widespread in the environment, even in pregnant women. While epidemiological studies have linked prenatal exposure to PFAS with atopic dermatitis in children, little is known about their toxic effects on skin development, especially during the embryonic stage. In this study, we utilized human embryonic stem cells to generate non-neural ectoderm (NNE) cells and exposed them to six PFAS (perfluorooctanoic acid (PFOA), undecafluorohexanoic acid (PFHxA), heptafluorobutyric acid (PFBA), perfluorooctane sulfonate (PFOS), perfluorohexane sulfonate (PFHxS) and perfluorobutyric acid (PFBS)) during the differentiation process to assess their toxicity to early skin development. Our results showed that PFOS altered the spindle-like morphology of NNE cells to a pebble-like morphology, and disrupted several NNE markers, including KRT16, SMYD1, and WISP1. The six PFAS had a high potential to cause hypohidrotic ectodermal dysplasia (HED) by disrupting the expression levels of HED-relevant genes. Transcriptomic analysis revealed that PFOS treatment produced the highest number (1156) of differentially expressed genes (DEGs) among the six PFAS, including the keratinocyte-related genes KRT6A, KRT17, KRT18, KRT24, KRT40, and KRT81. Additionally, we found that PFOS treatment disturbed several signaling pathways that are involved in regulating skin cell fate decisions and differentiation, including TGF-β, NOTCH, Hedgehog, and Hippo signaling pathways. Interestingly, we discovered that PFOS inhibited, by partially interfering with the expression of cytoskeleton-related genes, the ciliogenesis of NNE cells, which is crucial for the intercellular transduction of the above-mentioned signaling pathways. Overall, our study suggests that PFAS can inhibit ciliogenesis and hamper the transduction of important signaling pathways, leading potential congenital skin diseases. It sheds light on the underlying mechanisms of early embryonic skin developmental toxicity and provides an explanation for the epidemiological data on PFAS. ENVIRONMENTAL IMPLICATION: We employed a model based on human embryonic stem cells to demonstrate that PFOS has the potential to elevate the risk of hypohidrotic ectodermal dysplasia. This is achieved by targeting cilia, inhibiting ciliogenesis, and subsequently disrupting crucial signaling pathways like TGF-β, NOTCH, Hedgehog, and Hippo, during the early phases of embryonic skin development. Our study highlights the dangers and potential impacts of six PFAS pollutants on human skin development. Additionally, we emphasize the importance of closely considering PFHxA, PFBA, PFHxS, and PFBS, as they have shown the capacity to modify gene expression levels, albeit to a lesser degree.

Compound heterozygous WNT10A missense variations exacerbated the tooth agenesis caused by hypohidrotic ectodermal dysplasia

BACKGROUND

The aim of this study was to analyse the differences in the phenotypes of missing teeth between a pair of brothers with hypohidrotic ectodermal dysplasia (HED) and to investigate the underlying mechanism by comparing the mutated gene loci between the brothers with whole-exome sequencing.

METHODS

The clinical data of the patients and their mother were collected, and genomic DNA was extracted from peripheral blood samples. By Whole-exome sequencing filtered for a minor allele frequency (MAF) ≤0.05 non-synonymous single-nucleotide variations and insertions/deletions variations in genes previously associated with tooth agenesis, and variations considered as potentially pathogenic were assessed by SIFT, Polyphen-2, CADD and ACMG. Sanger sequencing was performed to detect gene variations. The secondary and tertiary structures of the mutated proteins were predicted by PsiPred 4.0 and AlphaFold 2.

RESULTS

Both brothers were clinically diagnosed with HED, but the younger brother had more teeth than the elder brother. An EDA variation (c.878 T > G) was identified in both brothers. Additionally, compound heterozygous variations of WNT10A (c.511C > T and c.637G > A) were identified in the elder brother. Digenic variations in EDA (c.878 T > G) and WNT10A (c.511C > T and c.637G > A) in the same patient have not been reported previously. The secondary structure of the variant WNT10A protein showed changes in the number and position of α-helices and β-folds compared to the wild-type protein. The tertiary structure of the WNT10A variant and molecular simulation docking showed that the site and direction where WNT10A binds to FZD5 was changed.

CONCLUSIONS

Compound heterozygous WNT10A missense variations may exacerbate the number of missing teeth in HED caused by EDA variation.

Novel frameshift variant of WNT10A in a Japanese patient with hypodontia

Congenital tooth agenesis is caused by the impairment of crucial genes related to tooth development, such as Wnt signaling pathway genes. Here, we investigated the genetic causes of sporadic congenital tooth agenesis. Exome sequencing, followed by Sanger sequencing, identified a novel single-nucleotide deletion in WNT10A (NC_000002.12(NM_025216.3):c.802del), which was not found in the healthy parents of the patient. Thus, we concluded that the variant was the genetic cause of the patient's agenesis.

Meibomian gland development: Where, when and how?

The Meibomian gland (MG) is an indispensable adnexal structure of eye that produces meibum, an important defensive component for maintaining ocular homeostasis. Normal development and maintenance of the MGs is required for ocular health since atrophic MGs and disturbances in composition and/or secretion of meibum result in major ocular pathologies, collectively termed as Meibomian gland dysfunction (MGD). Currently available therapies for MGD merely provide symptomatic relief and do not treat the underlying deficiency of the MGs. Hence, a thorough understanding of the timeline of MG development, maturation and aging is required for regenerative purposes along with signaling molecules & pathways controlling proper differentiation of MG lineage in mammalian eye. Understanding the factors that contribute to the development of MGs, developmental abnormalities of MGs, and changes in the quality & quantity of meibum with developing phases of MGs are essential for developing potential treatments for MGD. In this review, we compiled a timeline of events and the factors involved in the structural and functional development of MGs and the associated developmental defects of MGs during development, maturation and aging.

Molecular Pathway-Based Classification of Ectodermal Dysplasias: First Five-Yearly Update

To keep pace with the rapid advancements in molecular genetics and rare diseases research, we have updated the list of ectodermal dysplasias based on the latest classification approach that was adopted in 2017 by an international panel of experts. For this purpose, we searched the databases PubMed and OMIM for the term "ectodermal dysplasia", referring mainly to changes in the last 5 years. We also tried to obtain information about those diseases on which the last scientific report appeared more than 15 years ago by contacting the authors of the most recent publication. A group of experts, composed of researchers who attended the 8th International Conference on Ectodermal Dysplasias and additional members of the previous classification panel, reviewed the proposed amendments and agreed on a final table listing all 49 currently known ectodermal dysplasias for which the molecular genetic basis has been clarified, including 15 new entities. A newly reported ectodermal dysplasia, linked to the gene LRP6, is described here in more detail. These ectodermal dysplasias, in the strict sense, should be distinguished from syndromes with features of ectodermal dysplasia that are related to genes extraneous to the currently known pathways involved in ectodermal development. The latter group consists of 34 syndromes which had been placed on the previous list of ectodermal dysplasias, but most if not all of them could actually be classified elsewhere. This update should streamline the classification of ectodermal dysplasias, provide guidance to the correct diagnosis of rare disease entities, and facilitate the identification of individuals who could benefit from novel treatment options.

A novel mutation in the collagen domain of EDA results in hypohidrotic ectodermal dysplasia by impacting the receptor‐binding capability

BACKGROUND

Hypohidrotic ectodermal dysplasia (HED) mainly results from gene mutations in the EDA/EDAR/NF-κB pathway. Function analysis of the mutations in the collagen domain of ectodysplasin A (EDA)result in HED has been rarely studied. This study aimed at determining the mechanism by which the novel collagen domain mutation of EDA results in HED.

METHODS

We analyzed the DNAs from a Chinese family with HED and performed bioinformatics analysis. A new three-dimensional structure model of the EDA trimer was built and used to predict the effect of the mutations on EDA. We performed a western blot to detect EDA1 proteins in cell lysates and supernatants. We then performed coimmunoprecipitation to determine whether the mutation would affect the interaction of EDA1 with the EDA receptor (EDAR). Dual luciferase reporter assay and immunofluorescence were performed to detect the effect of the mutant EDA1 protein on nuclear factor kappa B (NF-κB) activation.

RESULTS

A novel missense mutation (c.593G > A, p. Gly198Glu) in the collagen domain of EDA was detected. The mutation was predicted to be disease-causing. A three-dimensional structure model of the EDA trimer was first built in this study, in which the mutation site is located around the receptor binding domain. Functional studies showed that there was no difference in the secretion activity between the mutant EDA1 and the wild-type EDA1. However, the receptor-binding activity and the transcription activation of NF-κB were impaired by the mutation.

CONCLUSION

We identified a novel mutation (c.593G > A, p. Gly198Glu) in the collagen domain of EDA. Bioinformatics analysis and functional studies showed this mutation was damaging, indicating that mutations in the collagen domain of EDA could result in HED by affecting the receptor-binding activity of EDA and the transcriptional activity of NF-κB.

Rare X-Linked Hypohidrotic Ectodermal Dysplasia in Females Associated with Ectodysplasin-A Variants and the X-Chromosome Inactivation Pattern

The goal of this study was to identify the pathogenic gene variants in female patients with severe X-linked hypohidrotic ectodermal dysplasia (XLHED). Whole-exome sequencing (WES) and Sanger sequencing were used to screen for the pathogenic gene variants. The harmfulness of these variations was predicted by bioinformatics. Then, skewed X-chromosome inactivation (XCI) was measured by PCR analysis of the CAG repeat region in the human androgen receptor (AR) gene in peripheral blood cells. Two novel Ectodysplasin-A (EDA) heterozygous variants (c.588_606del19bp and c.837G>A) and one heterozygous variant (c.1045G>A, rs132630317) were identified in the three female XLHED patients. The bioinformatics analysis showed that these variants might be pathogenic. The tertiary structure analysis showed that these variants could cause structural damage to EDA proteins. Analysis of the skewed X-chromosome inactivation revealed that extreme skewed X-chromosome inactivation was found in patient #35 (98:2), whereas it was comparatively moderate in patients #347 and #204 (21:79 and 30:70). Our results broaden the variation spectrum of EDA and the phenotype spectrum of XLHED, which could help with clinical diagnosis, treatment, and genetic counseling.

Ectodysplasin A (EDA) Signaling: From Skin Appendage to Multiple Diseases

Ectodysplasin A (EDA) signaling is initially identified as morphogenic signaling regulating the formation of skin appendages including teeth, hair follicles, exocrine glands in mammals, feathers in birds and scales in fish. Gene mutation in EDA signaling causes hypohidrotic ectodermal dysplasia (HED), a congenital hereditary disease with malformation of skin appendages. Interestingly, emerging evidence suggests that EDA and its receptors can modulate the proliferation, apoptosis, differentiation and migration of cancer cells, and thus may regulate tumorigenesis and cancer progression. More recently, as a newly discovered hepatocyte factor, EDA pathway has been demonstrated to be involved in the pathogenesis of nonalcoholic fatty liver disease (NAFLD) and type II diabetes by regulating glucose and lipid metabolism. In this review, we summarize the function of EDA signaling from skin appendage development to multiple other diseases, and discuss the clinical application of recombinant EDA protein as well as other potential targets for disease intervention.

Confirmation of a Phenotypic Entity for TSPEAR Variants in Egyptian Ectodermal Dysplasia Patients and Role of Ethnicity

Ectodermal dysplasia (ED) are hereditary disorders characterized by the disturbance of the ectodermal development of at least two of four ectodermal tissues: teeth, hair, nails and sweat glands. Clinical classification of ED is challenged by overlapping features, variable expressivity, and low number of patients, hindering full phenotypic spectrum identification. Disease-causing variants in elements of major developmental pathways, e.g., Ectodysplasin/NFκB, Wnt, and Tp63 pathways, have been identified in fewer than half of ED phenotypes. Whole-exome sequencing (WES) was performed for ten Egyptian ED patients presenting with tooth agenesis, normal sweating, scalp hypotrichosis, and sharing characteristic facial features. WES was followed by in silico analysis of the effects of novel detected genetic variants on mRNA and protein structure. The study identified four novel rare pathogenic and likely pathogenic TSPEAR variants, a gene which was recently found to be involved in ectodermal organogenesis. A novel in-frame deletion recurred in eight patients from six unrelated families. Comparing our cohort to previously reported TSPEAR cohorts highlighted the influence of ethnicity on TSPEAR phenotypic affection. Our study expands the clinical and mutational spectrum of the growing TSPEAR associated phenotypes, and pinpoints the influence of WES and in silico tools on identification of rare disease-causing variants.

Reproductive decision-making by women with X-linked hypohidrotic ectodermal dysplasia

BACKGROUND

In X-linked hypohidrotic ectodermal dysplasia (XLHED), ectodysplasin A1 (EDA1) deficiency results in malformation of hair, teeth, and sweat glands. Lack of sweating which can cause life-threatening hyperthermia is amenable to intrauterine therapy with recombinant EDA1.

OBJECTIVES

This study aimed at evaluating reproductive decision-making by women with XLHED and at clarifying the potential impact of a prenatal treatment option.

METHODS

In a retrospective cross-sectional analysis, a 75-item questionnaire filled in by 50 women with XLHED (age 19-49 years) was assessed.

RESULTS

16 women (32%) prevented pregnancies because of the risk to pass on XLHED, 15 considered assisted reproduction for the same reason. Twelve women had a history of miscarriage, stillbirth or abortion, three women reported on previous abortion of affected fetuses. When imagining to be pregnant, all except one showed interest in prenatal diagnosis of XLHED and in the possibility of treatment before birth. In 13 out of 50 women (26%), XLHED if detected prenatally would have impact on the continuation of pregnancy. Among 35 mothers of at least one affected child, XLHED had rarely been diagnosed during the first pregnancy (17%) but regularly during subsequent pregnancies (77%). Becoming aware of the condition before birth had caused a moral conflict for 50% of these women. Subjects with an affected child less frequently considered assisted reproduction to prevent XLHED (p<0.05). In more than 66% of the women who reported an effect of XLHED on family planning, a prenatal treatment option for this disease would influence their decision-making.

CONCLUSIONS

Many pregnant XLHED carriers who seek prenatal diagnosis experience moral conflicts. A prenatal treatment option would have strong impact on reproductive decisions, underlining the importance of adequate professional counselling.

Potential Risks of Corneal Refractive Surgery in Patients with Ectodermal Dysplasia

Ectodermal dysplasia (ED) involves the aberrant development of at least two ectodermal derivatives, such as skin, teeth, hair, sweat glands, and ocular tissue. The group of over 200 conditions is commonly classified into two major types: hypohidrotic/anhidrotic ED, in which sweat glands are either absent or significantly reduced, and hidrotic ED, in which sweat glands are normal. Ocular manifestations pertinent to patients undergoing corneal vision correction surgery include multifaceted dry eye syndrome, corneal pathology, such as recurrent erosions, scars, neovascularization, and limbal stem cell deficiency, and early-onset cataracts and glaucoma. In this article we discuss the current understanding of ED and offer factors to consider when these patients are seeking corneal refractive surgery.

Ectodysplasin pathogenic variants affecting the furin-cleavage site and unusual clinical features define X-linked hypohidrotic ectodermal dysplasia in India

Hypohidrotic ectodermal dysplasia (HED) is a rare genetic disorder caused by mutational inactivation of a developmental pathway responsible for generation of tissues of ectodermal origin. The X-linked form accounts for the majority of HED cases and is caused by Ectodysplasin (EDA) pathogenic variants. We performed a combined analysis of 29 X-linked hypohidrotic ectodermal dysplasia (XLHED) families (including 12 from our previous studies). In addition to the classical triad of symptoms including loss (or reduction) of ectodermal structures, such as hair, teeth, and sweat glands, we detected additional HED-related clinical features including facial dysmorphism and hyperpigmentation in several patients. Interestingly, global developmental delay was identified as an unusual clinical symptom in many patients. More importantly, we identified 22 causal pathogenic variants that included 15 missense, four small in-dels, and one nonsense, splice site, and large deletion each. Interestingly, we detected 12 unique (India-specific) pathogenic variants. Of the 29 XLHED families analyzed, 11 (38%) harbored pathogenic variant localized to the furin cleavage site. A comparison with HGMD revealed significant differences in the frequency of missense pathogenic variants; involvement of specific exons and/or protein domains and transition/transversion ratios. A significantly higher proportion of missense pathogenic variants (33%) localized to the EDA furin cleavage when compared to HGMD (7%), of which p.R155C, p.R156C, and p.R156H were detected in three families each. Therefore, the first comprehensive analysis of XLHED from India has revealed several unique features including unusual clinical symptoms and high frequency of furin cleavage site pathogenic variants.

Update of recent findings in genetic hair disorders

Genetic hair disorders, although unusual, are not very rare, and dermatologists often have opportunities to see patients. Significant advances in molecular genetics have led to identifying many causative genes for genetic hair disorders, including the recently identified causative genes, such as LSS and C3ORF52. Many patients have been detected with autosomal recessive woolly hair/hypotrichosis in the Japanese population caused by founder mutations in the LIPH gene. Additionally, many patients with genetic hair disorders caused by other genes have been reported in East Asia including Japan. Understanding genetic hair disorders is essential for dermatologists, and the findings obtained from analyzing these diseases will contribute to revealing the mechanisms of hair follicle morphogenesis and development in humans.

Association between tooth agenesis and cancer: a systematic review

The congenital absence of multiple teeth may share the same genetic background of the development of some types of cancer. Objective: This systematic review aimed to investigate the possible association between dental agenesis and cancer, and the perspective of agenesis as an early predictor for cancer risk. Methodology: The electronic databases PubMed, Scopus, Web of Science, Cochrane Library, LILACS, and OpenGrey were searched and the risk of bias was evaluated using the Newcastle-Ottawa tool. The GRADE tool was used to evaluate the certainty of the evidence. Results: Six studies met the eligibility criteria. A positive co-occurrence between ovarian cancer and hypodontia was found in two articles. Three studies evaluated the association between dental agenesis and colorectal cancer and only one showed common genes for these conditions. One paper found individuals with hypodontia had a higher risk of family history of cancer. Five studies had a fair quality and one a good quality. The certainty of evidence was classified as very low. Conclusion: Notwithstanding the limited scientific evidence, there may be a possible association between dental agenesis and cancer due to genes involved in both conditions. Agenesis of multiple teeth could be an early indicator of cancer risk. Nevertheless, studies with a better level of evidence are needed to confirm this possible association.

Consecutive tooth agenesis patterns in non-syndromic oligodontia

Agenesis of two or more consecutive adjacent permanent teeth (consecutive tooth agenesis, CTA) is a serious manifestation of oligodontia requiring long-term, multi-disciplinary treatment. Therefore, the present study investigated the characteristics of the CTA pattern in orthodontic patients with non-syndromic oligodontia. Using panoramic radiographs, the number of agenetic permanent teeth excluding third molars in non-syndromic orthodontic patients was evaluated, and patients with six or more agenetic teeth (oligodontia group, n = 97) and with one to five agenetic teeth (hypodontia group, n = 107) were selected. The numbers of CTA including third molars in each quadrant and in each patient were compared between the groups. Each quadrant with CTA of patients was categorized into one of the following four types: (I) involves anterior teeth only; (II) involves posterior teeth only; (IIIA) includes anterior and posterior teeth; and (IIIB) separate in the anterior and posterior teeth. CTA in at least one quadrant was found in 91.8 and 4.7% of patients in the oligodontia and hypodontia groups, respectively. The highest frequency CTA patterns included agenesis of the first and second premolars and of the second and third molars in the oligodontia and hypodontia groups, respectively. In the oligodontia group, type IIIA was significantly more frequent in the maxillary than in the mandibular quadrant. Most oligodontia patients who visit orthodontic clinics have CTA. A rare but severe CTA pattern that continues from the anterior to posterior segments is more frequent in the maxillary than in the mandibular quadrant.

A novel homozygous RIPK4 variant in a family with severe Bartsocas-Papas syndrome

Bartsocas-Papas syndrome (BPS) is a rare autosomal recessive disorder characterized by popliteal pterygia, syndactyly, ankyloblepharon, filiform bands between the jaws, cleft lip and palate, and genital malformations. Most of the BPS cases reported to date are fatal either in the prenatal or neonatal period. Causative genetic defects of BPS were mapped on the RIPK4 gene encoding receptor-interacting serine/threonine kinase 4, which is critical for epidermal differentiation and development. RIPK4 variants are associated with a wide range of clinical features ranging from milder ectodermal dysplasia to severe BPS. Here, we evaluated a consanguineous Turkish family, who had two pregnancies with severe multiple malformations compatible with BPS phenotype. In order to identify the underlying genetic defect, direct sequencing of the coding region and exon-intron boundaries of RIPK4 was carried out. A homozygous transversion (c.481G>C) that leads to the substitution of a conserved aspartic acid to histidine (p.Asp161His) in the kinase domain of the protein was detected. Pathogenicity predictions, molecular modeling, and cell-based functional assays showed that Asp161 residue is required for the kinase activity of the protein, which indicates that the identified variant is responsible for the severe BPS phenotype in the family.

Subjective Oral Health-Related Quality of Life and Objective Oral Health in People with Ectodermal Dysplasia

Ectodermal dysplasia (ED) refers to a heterogeneous group of genetic diseases of the skin, skin appendages, and teeth. People with ED experience a poorer oral health-related quality of life (OHRQoL) compared to the general population. The aim of this study was to examine the OHRQoL of people with ED and to measure their objective physical oral health to confirm or disprove evidence of poorer oral health in this population. To determine OHRQoL, the German version of the 14-item Oral Health Impact Profile (OHIP-14G) was used. All the participants in the study were clinically examined, and the measured parameters were recorded using the Physical Oral Health Index (PhOX). In total, 10 male and 11 female participants, with an average age of 22.0 ± 9.0 years, were included in this study. The OHIP-14G summary score was 23.9 (±15.2) points (range: 0–56 points). The PhOX summary score was 61.2 (±5.1) points (range: 22–80 points). The findings indicated that both the OHRQoL and physical oral health of the participants were highly impaired and that their objective and subjective oral health were worse than those of the general population in Germany.

Cleft Lip and Palate in Ectodermal Dysplasia

OBJECTIVE

Ectodermal dysplasia (ED) comprises multiple syndromes that affect skin, hair, nails, and teeth, and sometimes are associated with orofacial clefting. The purpose of this study is to (1) identify the prevalence and characteristics of cleft lip and/or palate (CL/P) in patients with ED and (2) describe the management and outcomes.

DESIGN

Retrospective review from 1990 to 2019.

PATIENTS

All patients with ED treated at Boston Children's Hospital.

MAIN OUTCOMES MEASURES

Prevalence of CL/P was calculated and clinical details recorded: phenotypic anomalies, cleft type, operative treatment, and results of repair.

RESULTS

Of 170 patients with a purported diagnosis of ED, 24 (14%) had CL/P. Anatomic categories were bilateral CL/P (67%), unilateral CL/P (8%), and cleft palate only (25%). The most common ED syndrome (37%) was ectrodactyly, ectodermal dysplasia, and cleft lip/palate (EEC). Pathogenic variants in TP63 were the most frequent finding in the 11 patients who had genetic testing. Aberrations from a typical clinical course included failure of presurgical dentofacial orthopedics, dehiscence of nasolabial adhesion, and total palatal absence requiring free-flap construction. Two patients had prolonged postoperative admission for respiratory infection. High fistula (8%) and velopharyngeal insufficiency (33%) rates reflected the predominance of bilateral complete forms.

CONCLUSIONS

As in other types of syndromic CL/P, cleft phenotypic expression in ED is more severe than the general cleft population. Further studies are needed to correlate genotype and phenotype for the distinct syndromes included in the ED spectrum.

Werewolf, There Wolf: Variants in Hairless Associated with Hypotrichia and Roaning in the Lykoi Cat Breed

A variety of cat breeds have been developed via novelty selection on aesthetic, dermatological traits, such as coat colors and fur types. A recently developed breed, the lykoi (a.k.a. werewolf cat), was bred from cats with a sparse hair coat with roaning, implying full color and all white hairs. The lykoi phenotype is a form of hypotrichia, presenting as a significant reduction in the average numbers of follicles per hair follicle group as compared to domestic shorthair cats, a mild to severe perifollicular to mural lymphocytic infiltration in 77% of observed hair follicle groups, and the follicles are often miniaturized, dilated, and dysplastic. Whole genome sequencing was conducted on a single lykoi cat that was a cross between two independently ascertained lineages. Comparison to the 99 Lives dataset of 194 non-lykoi cats suggested two variants in the cat homolog for Hairless (HR) (HR lysine demethylase and nuclear receptor corepressor) as candidate causal gene variants. The lykoi cat was a compound heterozygote for two loss of function variants in HR, an exon 3 c.1255_1256dupGT (chrB1:36040783), which should produce a stop codon at amino acid 420 (p.Gln420Serfs*100) and, an exon 18 c.3389insGACA (chrB1:36051555), which should produce a stop codon at amino acid position 1130 (p.Ser1130Argfs*29). Ascertainment of 14 additional cats from founder lineages from Canada, France and different areas of the USA identified four additional loss of function HR variants likely causing the highly similar phenotypic hair coat across the diverse cats. The novel variants in HR for cat hypotrichia can now be established between minor differences in the phenotypic presentations.

A novel EDA1 missense mutation in X-linked hypohidrotic ectodermal dysplasia

A mutation in the epithelial morphogen gene ectodysplasin-A1 (EDA1) is responsible for the disorder X-linked hypohidrotic ectodermal dysplasia (XLHED), the most common form of ectodermal dysplasia. XLHED is characterized by impaired development of hair, eccrine sweat glands, and teeth. This study aimed to identify potentially pathogenic mutations in four Chinese XLHED families.Genomic DNA was extracted from the peripheral blood and sequenced. Sanger sequencing was used to carry out mutational analysis of the EDA1 gene, and the three-dimensional structure of the novel mutant residues in the EDA trimer was determined. Transcriptional activity of NF-κB was tested by Dual luciferin assay.We identified a novel EDA1 mutation (c.1046C>T) and detected 3 other previously-reported mutations (c.146T>A; c.457C>T; c.467G>A). Our findings demonstrated that novel mutation c.1046C>T (p.A349 V) resulted in XLHED. The novel mutation could cause volume repulsion in the protein due to enlargement of the amino acid side chain. Dual luciferase assay revealed that transcriptional NF-κB activation induced by XLHED EDA1 protein was significantly reduced compared with wild-type EDA1.These results extend the spectrum of EDA1 mutations in XLHED patients and suggest a functional role of the novel mutation in XLHED.

EDA, EDAR, EDARADD and WNT10A allelic variants in patients with ectodermal derivative impairment in the Spanish population

BACKGROUND

Ectodermal dysplasias (ED) are a group of genetic conditions affecting the development and/or homeostasis of two or more ectodermal derivatives. An attenuated phenotype is considered a non-syndromic trait when the patient is affected by only one impaired ectodermal structure, such as in non-syndromic tooth agenesis (NSTA) disorder. Hypohidrotic ectodermal dysplasia (HED) is the most highly represented ED. X-linked hypohidrotic ectodermal dysplasia (XLHED) is the most common subtype, with an incidence of 1/50,000-100,000 males, and is associated with the EDA gene (Xq12-q13.1); the dominant and recessive subtypes involve the EDAR (2q13) and EDARADD (1q42.3) genes, respectively. The WNT10A gene (2q35) is associated more frequently with NSTA. Our goal was to determine the mutational spectrum in a cohort of 72 Spanish patients affected by one or more ectodermal derivative impairments referred to as HED (63/72) or NSTA (9 /72) to establish the prevalence of the allelic variants of the four most frequently associated genes. Sanger sequencing of the EDA, EDAR, EDARADD and WNT10A genes and multiplex ligation-dependent probe amplification (MLPA) were performed.

RESULTS

A total of 61 children and 11 adults, comprising 50 males and 22 females, were included. The average ages were 5.4 and 40.2 years for children and adults, respectively. A molecular basis was identified in 51/72 patients, including 47/63 HED patients, for whom EDA was the most frequently involved gene, and 4/9 NSTA patients, most of whom had variants of WNT10A. Among all the patients, 37/51 had variants of EDA, 8/51 had variants of the WNT10A gene, 4/51 had variants of EDAR and 5/51 had variants of EDARADD. In 42/51 of cases, the variants were inherited according to an X-linked pattern (27/42), with the remaining showing an autosomal dominant (10/42) or autosomal recessive (5/42) pattern. Among the NSTA patients, 3/9 carried pathogenic variants of WNT10A and 1/9 carried EDA variants. A total of 60 variants were detected in 51 patients, 46 of which were different, and out of these 46 variants, 12 were novel.

CONCLUSIONS

This is the only molecular study conducted to date in the Spanish population affected by ED. The EDA, EDAR, EDARADD and WNT10A genes constitute the molecular basis in 70.8% of patients with a 74.6% yield in HED and 44.4% in NSTA. Twelve novel variants were identified. The WNT10A gene has been confirmed as the second molecular candidate that has been identified and accounts for one-half of non-EDA patients and one-third of NSTA patients. Further studies using next generation sequencing (NGS) will help to identify other contributory genes in the remaining uncharacterized Spanish patients.

Genetic Hair Disorders: A Review

Hair loss in early childhood represents a broad differential diagnosis which can be a diagnostic and therapeutic challenge for a physician. It is important to consider the diagnosis of a genetic hair disorder. Genetic hair disorders are a large group of inherited disorders, many of which are rare. Genetic hair abnormalities in children can be an isolated phenomenon or part of genetic syndromes. Hair changes may be a significant finding or even the initial presentation of a syndrome giving a clue to the diagnosis, such as Netherton syndrome and trichothiodystrophy. Detailed history including family history and physical examination of hair and other ectodermal structures such as nails, sweat glands, and sebaceous glands with the use of dermoscopic devices and biopsy all provide important clues to establish the correct diagnosis. Understanding the pathophysiology of genetic hair defects will allow for better comprehension of their treatment and prognosis. For example, in patients with an isolated hair defect, the main problem is aesthetic. In contrast, when the hair defect is associated with a syndrome, the prognosis will depend mainly on the associated condition. Treatment of many genetic hair disorders is focused on treating the primary cause and minimizing trauma to the hair.

The simian crease: Relationship to various genetic disorders

The creases of the palm have been of interest for clinicians, anthropologists, and palmists for hundreds of years, but the variations in them have only been studied during the past 50 years. The simian crease, aptly named for its resemblance to the palmar creases of nonhuman simian primates, has received recognition clinically and anthropologically owing to its abnormal appearance and confounding cytogenetic etiology. Given the rarity of these palmar creases but also their usefulness in diagnosing congenital disorders, discussion of cases of those disorders could provide clinicians with further helpful diagnostic knowledge. This review of the literature focuses on the history, embryology, genetic and hereditary origins, and clinical significance of simian creases for the benefit of the diagnosing clinician. Clin. Anat. 32:1042-1047, 2019. © 2019 Wiley Periodicals, Inc.

Self-Assessment of Oral Health-Related Quality of Life in People with Ectodermal Dysplasia in Germany

Background: Ectodermal dysplasia describes a heterogeneous group of hereditary, congenital malformations involving developmental dystrophies of ectodermal structures. The aim of this study was to analyse the oral health-related quality of life (OHRQoL) in people with ectodermal dysplasia and to evaluate the influence of different variables. Methods: The study was designed as an anonymous epidemiological survey study among people with ectodermal dysplasia to evaluate oral symptoms, satisfaction with the health system and their respective OHRQoL using the validated German version of the OHIP-14 (Oral Health Impact Profile) questionnaire. Results: When asked about oral symptoms, 110 of the participants provided responses, of which 109 (99.09%) described oral symptoms. The average age of the female participants at the time of diagnosis was 17.02 years (range: 0 to 48 years), the average age of men was 5.19 years (range: 0 to 43 years). The average OHIP-14 overall score for female participants was 12.23 points (SD: 12.39), for male participants an average OHIP score of 11.79 points was recorded (SD: 11.08 points). Difficulty in finding a dentist (p = 0.001), and the dissatisfaction with the health system (p = 0.007) showed a negative impact on the OHRQoL. Conclusion: People with ectodermal dysplasia rate their OHRQoL worse than is usually prevalent in the normal German population (4.09 points); women are diagnosed with “ectodermal dysplasia” later than men. Participants who reported difficulties in finding a dentist for treatment exhibited higher OHIP values. Likewise, dissatisfaction with the health system demonstrated a negative impact on the oral health-related quality of life.

Novel and Private EDA Mutations and Clinical Phenotypes of Korean Patients with X-Linked Hypohidrotic Ectodermal Dysplasia

X-linked hypohidrotic ectodermal dysplasia (XLHED; OMIM 305100) is the most common form of ectodermal dysplasia, presenting with the triad of hypotrichosis, hypodontia, and hypohidrosis. This disorder is caused by mutations in EDA, which encodes ectodysplasin A, a member of the tumor necrosis factor superfamily. In this study, we describe clinical and genetic characteristics of 10 Korean XLHED patients (9 males, 1 female) from 9 families. Nine out of the 10 patients manifested the cardinal triad of symptoms. Six patients had a positive family history, while 2 patients were brothers. The most common initial presentation was hypotrichosis or hypodontia, while 1 patient presented with recurrent high fever in early infancy. Sanger sequencing of the EDA gene was performed and revealed 9 different mutations. Three had been reported previously, and 6 were novel mutations. One female patient, carrying a previously reported missense mutation, might be affected by skewed X-inactivation. This is the first observational study investigating genetically confirmed XLHED patients in Korea. To provide appropriate supportive care and genetic counseling, clinicians should consider the possibility of XLHED in the differential diagnosis of recurrent fever in infants, as well as recognize the typical triad of symptoms.

[Genetics and dermatology]

Many types of genodermatosis exist, with numerous modes of transmission. The development of molecular genetic methods, in particular the most recent sequencing techniques, can be used to identify an increasing number of genes involved in these forms of genodermatosis while providing confirmation or more details regarding clinical diagnosis. Thanks to this approach, it is possible to determine risk of recurrence and to formulate an antenatal strategy. These technologies have led to improved molecular definition and to a better understanding of the physiopathological mechanisms involved in different genodermatoses such as bullous epidermolysis, keratinisation disorders, pigmentation disorders, potentially tumoral conditions, and epidermal and pilar dysplasia. The large amount of information provided by high-throughput sequencing makes it possible to study modifying genes as well as genotype-phenotype correlations. However, this genetic information in its turn poses problems of interpretation and of control of the resulting data. The use of genetics in dermatology for the purposes of diagnosis or research requires a consultation to provide patients with information regarding the genetic tests involved and the potential consequences thereof for them and their families. Furthermore, with pangenomic approaches there is a higher probability of fortuitous discovery of abnormalities such as variants associated with risks predisposing to cancer or neurodegenerative disease. Collaboration between dermatologists and geneticists enables optimisation of patient management in terms of diagnosis and genetic counselling in the event of such rare diseases. Therapeutic applications are beginning to be developed. The scope of therapeutic application includes gene therapy, replacement therapy (enzyme therapy) and targeted therapy.

Turkish Ectodermal Dysplasia Cohort: From Phenotype to Genotype in 17 Families

Hypohidrotic or anhidrotic ectodermal dysplasia (HED/EDA) is characterized by impaired development of the hair, teeth, or sweat glands. HED/EDA is inherited in an X-linked, autosomal dominant, or autosomal recessive pattern and caused by the pathogenic variants in 4 genes: EDA, EDAR, EDARADD, and WNT10A. The aim of the present study was to perform molecular screening of these 4 genes in a cohort of Turkish individuals diagnosed with HED/EDA. We screened for pathogenic variants of WNT10A, EDA, EDAR, and EDARADD through Sanger sequencing. We further assessed the clinical profiles of the affected individuals in order to establish phenotype-genotype correlation. In 17 (63%) out of 27 families, 17 pathogenic variants, 8 being novel, were detected in the 4 well-known ectodermal dysplasia genes. EDAR and EDA variants were identified in 6 families each, WNT10A variants in 4, and an EDARADD variant in 1, accounting for 35.3, 35.3, 23.5, and 5.9% of mutation-positive families, respectively. The low mutation detection rate of the cohort and the number of the EDAR pathogenic variants being as high as the EDA ones were the most noteworthy findings which could be attributed to the high consanguinity rate.

Rescue of recurrent deep intronic mutation underlying cell type-dependent quantitative NEMO deficiency

X-linked dominant incontinentia pigmenti (IP) and X-linked recessive anhidrotic ectodermal dysplasia with immunodeficiency (EDA-ID) are caused by loss-of-function and hypomorphic IKBKG (also known as NEMO) mutations, respectively. We describe a European mother with mild IP and a Japanese mother without IP, whose 3 boys with EDA-ID died from ID. We identify the same private variant in an intron of IKBKG, IVS4+866 C>T, which was inherited from and occurred de novo in the European mother and Japanese mother, respectively. This mutation creates a new splicing donor site, giving rise to a 44-nucleotide pseudoexon (PE) generating a frameshift. Its leakiness accounts for NF-κB activation being impaired but not abolished in the boys' cells. However, aberrant splicing rates differ between cell types, with WT NEMO mRNA and protein levels ranging from barely detectable in leukocytes to residual amounts in induced pluripotent stem cell-derived (iPSC-derived) macrophages, and higher levels in fibroblasts and iPSC-derived neuronal precursor cells. Finally, SRSF6 binds to the PE, facilitating its inclusion. Moreover, SRSF6 knockdown or CLK inhibition restores WT NEMO expression and function in mutant cells. A recurrent deep intronic splicing mutation in IKBKG underlies a purely quantitative NEMO defect in males that is most severe in leukocytes and can be rescued by the inhibition of SRSF6 or CLK.

Conservation analysis and pathogenicity prediction of mutant genes of ectodysplasin a

Background

Hypohidrotic ectodermal dysplasia (HED) is a common recessive X-linked hereditary disease that affects the development of ectoderm. Gene mutations of ectodysplasin A (EDA) play key roles in process of this disease. In our preliminary study, three unknown mutation sites (c.878 T > G, c.663-697del and c.587-615del) were detected from the pedigrees of HED.

Methods

Conservation analysis of the related homologous proteins in 3 unknown EDA gene mutation sites was conducted using the University of California Santa Cruz (UCSC) Genome Browser database. SIFT and PolyPhen-2, the online gene function prediction software, were utilized to predict the pathogenicity of point mutation of c.878 T > G.

Results

All three unknown mutation sites were located in the highly-conserved region of EDA and possessed strong amino acid conservation among different species. In addition, the results of the pathogenicity prediction of point mutation of c.878 T > G by SIFT (P = 0.00) and PolyPhen-2 (S = 0.997) demonstrated that the mutation site had considerable pathogenicity theoretically.

Conclusions

The EDA mutations of c.878 T > G, c.663-697del and c.587-615del may be responsible for the pathogenesis of HED in their pedigrees.

Reliability of prenatal detection of X-linked hypohidrotic ectodermal dysplasia by tooth germ sonography

OBJECTIVE

In X-linked hypohidrotic ectodermal dysplasia (XLHED), dysfunction of ectodysplasin A1 (EDA1) due to EDA mutations results in malformation of hair, teeth, and sweat glands. Hypohidrosis, which can cause life-threatening hyperthermia, is amenable to intrauterine therapy with recombinant EDA1. This study aimed at evaluating tooth germ sonography as a noninvasive means to identify affected fetuses in pregnant carrier women.

METHODS

Sonography, performed at 10 study sites between gestational weeks 18 and 28, led to the diagnosis of XLHED if fewer than six tooth germs were detected in mandible or maxilla. The assessment was verified postnatally by EDA sequencing and/or clinical findings. Estimated fetal weights and postnatal weight gain of boys with XLHED were assessed using appropriate growth charts.

RESULTS

In 19 of 38 sonographic examinations (23 male and 13 female fetuses), XLHED was detected prenatally. The prenatal diagnosis proved to be correct in 37 cases; one affected male fetus was missed. Specificity and positive predictive value were both 100%. Tooth counts obtained by clinical examination corresponded well with findings on panoramic radiographs. We observed no weight deficits of subjects with XLHED in utero but occasionally during infancy.

CONCLUSION

Tooth germ sonography is highly specific and reliable in detecting XLHED prenatally.

Basan gets a new fingerprint: Mutations in the skin-specific isoform of SMARCAD1 cause ectodermal dysplasia syndromes with adermatoglyphia

Basan syndrome is an autosomal dominant ectodermal dysplasia (ED) with congenital adermatoglyphia, transient neonatal acral bullae, and congenital facial milia. Autosomal dominant adermatoglyphia (ADG) is characterized as adermatoglyphia with hypohidrosis. Recently mutations in the skin-specific isoform of the gene SMARCAD1 have been found in both syndromes. This report proposes to unify these two previously distinct ED, into one syndrome. We offer a new acronym: SMARCAD syndrome (SMARCAD1-associated congenital facial Milia, Adermatoglyphia, Reduced sweating, Contractures, Acral Bullae, and Dystrophy of nails). Sanger sequencing was performed on genomic DNA from a patient with Basan syndrome using primers designed to flank SMARCAD1. Sanger sequencing revealed a novel variant, NM_001254949.1:c.-10 + 2 T > G, in the donor splice site of exon 1 of the skin-specific isoform. This variant and the other five previously reported variants in Basan syndrome and ADG are all within the same donor splice site. We conclude that Basan syndrome and ADG are on a phenotypic spectrum of a monogenic syndrome which is better described by the acronym SMARCAD syndrome.

Defective NaCl Reabsorption in Salivary Glands of Eda-Null X-LHED Mice

Mutations in the ectodysplasin A gene ( EDA) cause X-LHED (X-linked hypohidrotic ectodermal dysplasia), the most common human form of ectodermal dysplasia. Defective EDA signaling is linked to hypoplastic development of epithelial tissues, resulting in hypotrichosis, hypodontia, hypohidrosis, and xerostomia. The primary objective of the present study was to better understand the salivary gland dysfunction associated with ectodermal dysplasia using the analogous murine disorder. The salivary flow rate and ion composition of the 3 major salivary glands were determined in adult Eda-deficient Tabby hemizygous male (Ta/Y) and heterozygous female (Ta/X) mice. Submandibular and sublingual glands of Eda-mutant mice were smaller than wild-type littermates, while parotid gland weight was not significantly altered. Fluid secretion by the 3 major salivary glands was essentially unchanged, but the decrease in submandibular gland size was associated with a dramatic loss of ducts in Ta/Y and Ta/X mice. Reabsorption of Na+ and Cl-, previously linked in salivary glands to Scnn1 Na+ channels and Cftr Cl- channels, respectively, was markedly reduced at high flow rates in the ex vivo submandibular glands of Ta/Y mice (~60%) and, to a lesser extent, Ta/X mice (Na+ by 14%). Consistent with decreased Na+ reabsorption in Ta/Y mice, quantitative polymerase chain reaction analysis detected decreased mRNA expression for Scnn1b and Scnn1g, genes encoding the β and γ subunits, respectively. Moreover, the Na+ channel blocker amiloride significantly inhibited Na+ and Cl- reabsorption by wild-type male submandibular glands to levels comparable to those observed in Ta/Y mice. In summary, fluid secretion was intact in the salivary glands of Eda-deficient mice but displayed marked Na+ and Cl- reabsorption defects that correlated with the loss of duct cells and decreased Scnn1 Na+ channel expression. These results provide a likely mechanism for the elevated NaCl concentration observed in the saliva of affected male and female patients with X-LHED.

Attenuation of Mammary Gland Dysplasia and Feeding Difficulties in Tabby Mice by Fetal Therapy

Hypohidrotic ectodermal dysplasias (HED) are hereditary differentiation disorders of multiple ectodermal structures including the mammary gland. The X-linked form of HED (XLHED) is caused by a lack of the secreted signaling molecule ectodysplasin A1 (EDA1) which is encoded by the gene EDA and belongs to the tumor necrosis factor (TNF) superfamily. Although male patients (hemizygous) are usually more severely affected by XLHED, heterozygous female carriers of an EDA mutation may also suffer from a variety of symptoms, in particular from abnormal development of their breasts. In Tabby mice, a well-studied animal model of XLHED, EDA1 is absent. We investigated the effects of prenatal administration of Fc-EDA, a recombinant EDA1 replacement protein, on mammary gland development in female Tabby mice. Intra-amniotic delivery of Fc-EDA to fetal animals resulted later in improved breastfeeding and thus promoted the growth of their offspring. In detail, such treatment led to a normalization of the nipple shape (protrusion, tapering) that facilitated sucking. Mammary glands of treated female Tabby mice also showed internal changes, including enhanced branching morphogenesis and ductal elongation. Our findings indicate that EDA receptor stimulation during development has a stable impact on later stages of mammary gland differentiation, including lactation, but also show that intra-amniotic administration of an EDA1 replacement protein to fetal Tabby mice partially corrects the mammary gland phenotype in female adult animals.

An ectodermal dysplasia patient treated with a small diameter implant supporting a single crown

Ectodermal dysplasia (EDD) is a developmental disorder that affects the skin, hair, and teeth among other organs generated in the ectoderm. Dental implants have been used to successfully treat partial edentulism in EDD patients, but the success rate is much lower for these patients. The report herein is a successful case of a single mini, small diameter, implant used to support a single crown of a mandibular right second premolar. A review of implant treatment in EDD patients is included.

Biallelic mutations of EGFR in a compound heterozygous state cause ectodermal dysplasia with severe skin defects and gastrointestinal dysfunction

Epidermal growth factor receptor (EGFR), a receptor that recognizes epidermal growth factor, is a very important regulator of cell proliferation and differentiation. To date, three cases of severe ectodermal dysplasia were reported to be caused by an inherited germline homozygous loss-of-function missense mutation of EGFR. This is the first report of a patient with biallelic compound heterozygous mutations in EGFR.

Hypohidrotic ectodermal dysplasia: clinical and molecular review

Hypohidrotic Ectodermal Dysplasia (HED) is a genetic human disorder which affects structures of ectodermal origin. Although there are autosomal recessive and dominant forms, X-linked (XL) is the most frequent form of the disease. This XL-HED phenotype is associated with mutations in the gene encoding the transmembrane protein ectodysplasin-1 (EDA1), a member of the TNFα-related signaling pathway. The proteins from this pathway are involved in signal transduction from ectoderm to mesenchyme leading to the development of ectoderm-derived structures in the fetus such as hair, teeth, skin, nails, and eccrine sweat glands. The aim of this review was to update the main clinical characteristics of HED regarding to recent molecular advances in the comprehension of all the possible genes involved in this group of disorders since it is known that Eda-A1-Edar signaling has multiple roles in ectodermal organ development, regulating their initiation, morphogenesis, and differentiation steps. The knowledge of the biological mechanisms that generate HED is needed for both a better detection of possible cases and for the design of efficient prevention and treatment approaches.

Nail Disorders in Children

Nail diseases in children do not account for a significant proportion of pediatric consultations, and most of the time the nails are not observed by the clinician, overlooking their importance. Specific examination of the nails is neglected, while localization to the nails could be an initial sign of a syndrome or a systemic disorder. Nail diseases in the pediatric population differ from those in adults in terms of diagnostic approach and management; some of them even are manifested mainly or exclusively in children. Pediatric patients with underlying systemic disorders are more likely to manifest acquired disorders of the nails. Although rare, nail diseases in children are a source of anxiety for the parents. Examination of the nails is an essential part of pediatric physical examination. A correct clinical history and careful examination help the clinician to distinguish the different conditions and to decide on the correct management of nail diseases in young patients. A classification of nail dystrophies according to age is somewhat arbitrary and a unique classification does not exist. Nail diseases in the pediatric population can be divided according to age groups where a predilection appears in most of the cases. Moreover, certain abnormalities may be lifelong once acquired, but their presentation may be modified by age, worsening or improving during life. This review describes many of the nail conditions that are seen in the pediatric population aging from newborn to toddler, starting with physiological aspects to better recognize the pathological conditions.

Let-7b regulates alpaca hair growth by downregulating ectodysplasin A

Hypohidrotic ectodermal dysplasia (HED), also known as anhidrotic ectodermal dysplasia, is characterized by the clinical manifestations of less sweat or no sweat, sparse or no hair, tooth agenesis and/or abnormal tooth morphology. The characteristics of alpaca ear hair differ from the back hair. The ectodysplasin A (EDA) signaling pathway has a regulatory effect on skin development and hair growth. The aim of the present study was to study the effects of EDA on alpaca hair growth by examining the mRNA and protein expression levels of EDA in alpaca ear and back skin by reverse transcription‑quantitative polymerase chain reaction and western blot analysis, respectively. Results indicated that EDA expression was higher in the ear skin compared with the back skin. The expression levels of let‑7b in the skin of healthy alpacas varies; the difference between let‑7b expression levels of the ear and back have been reported to be >2‑fold, suggesting a role for let‑7b in the development of adult alpaca skin and hair follicles. A dual‑luciferase reporter vector was constructed to verify the targeting relationship between microRNA let‑7b and EDA, and the results revealed that EDA was a target gene of let‑7b. Alpaca skin fibroblasts were transfected with a let‑7b eukaryotic expression vector to investigate the regulatory relationship between let‑7b and EDA. The expression of EDA was decreased in the transfected group; immunocytochemical results demonstrated that the EDA protein was abundantly expressed in the fibroblast cytoplasm. EDA protein expression was weaker in the transfected cells than in the untransfected cells. These results suggested that EDA may serve a role in alpaca hair growth and is probably a target gene of let‑7b; let‑7b downregulated EDA mRNA and protein expressions, which suggested that let‑7b may regulate alpaca hair growth. These conclusions suggested that let‑7b may be associated with HED.

Prevalence and Characteristics of Congenitally Missing Permanent Teeth among Orthodontic Patients in Southern Croatia

BACKGROUND

Congenitally missing permanent teeth (CMPT) was recognized as a clinical and public health problem in pediatric dentistry.

AIM

To determine the prevalence of CMPT among orthodontic patients in Southern Croatia.

MATERIALS AND METHODS

In a retrospective study, we analyzed CMPT in patients from three different regions in Southern Croatia (SC). Two orthodontic practices from each region were selected and a total of 4649 records of patients aged 6 - 15 years, who were clinically examined for orthodontic treatment between 2008 and 2015, were evaluated. We excluded 219 patients and 4430 patients remained for further analysis.

RESULTS

There was no difference in prevalence of CMPT among regions in Southern Croatia, and the whole sample was evaluated. CMPT was found in 345(7.8%) patients. The highest proportion of CMPT was with one or two missing teeth 122 (81.9%) and 158 (80.6%), followed by those with three to five missing teeth or moderate hypodontia, 25(16.8%) and 35(17.9%), in males, and females respectively. Bilateral hypodontia of the lower second premolars and upper second incisors was more common than unilateral hypodontia.

CONCLUSIONS

The obtained results of high prevalence of CMPT in Southern Croatia reinforce the need for a timely diagnostics and treatment of moderate and severe cases.