Tricho-dento-osseous syndrome: diagnosis and dental management

Fixed prosthodontic rehabilitation using a facially driven fully digital workflow of a patient with syndromic amelogenesis imperfecta associated with a rare form of ectodermal dysplasia, tricho-dento-osseous (TDO) syndrome

Tricho-dento-ossseous (TDO) syndrome is a rare form of ectodermal dysplasia (ED) characterized by defects in the hair, bones, nails, and teeth. Dental findings consistently seen in patients with TDO syndrome include amelogenesis imperfecta and taurodontism, but additional findings such as periapical abscesses, mandibular prognathism, and impacted teeth have been reported. Because of the rarity of this disorder, the prevalence is unknown and limited research is available regarding its dental management. This clinical report describes the fixed prosthodontic implant rehabilitation of an adult patient with TDO syndrome by using a facially driven fully digital workflow. The facially driven digital workflow streamlined the rehabilitation and allowed for functional, esthetic, and psychosocial improvements in a timely manner.

Dentofacial manifestations in a child with Jalili syndrome

Jalili syndrome (JS) (MIM#217080) is a rare autosomal recessive disorder with oculo-dental malformations. The clinical phenotype is characterized by the presence of Cone-Rod Dystrophy (CRD) and Amelogenesis Imperfecta (AI). Genetic mechanism entails a mutation in the CNNM4, a metal transporter gene located on Chromosome 2q11.2. A high fluoride concentration in groundwater has also been identified as an epigenetic factor in this syndrome. JS draws the attention of dentists due to its distinct oral manifestations. To the best of our knowledge, this is the first genetically confirmed pediatric case report from the Indian subcontinent emphasizing the clinical and radiographic features of this condition and its management in a 6-year-old child.

The odontoblastic differentiation of dental mesenchymal stem cells: molecular regulation mechanism and related genetic syndromes

Dental mesenchymal stem cells (DMSCs) are multipotent progenitor cells that can differentiate into multiple lineages including odontoblasts, osteoblasts, chondrocytes, neural cells, myocytes, cardiomyocytes, adipocytes, endothelial cells, melanocytes, and hepatocytes. Odontoblastic differentiation of DMSCs is pivotal in dentinogenesis, a delicate and dynamic process regulated at the molecular level by signaling pathways, transcription factors, and posttranscriptional and epigenetic regulation. Mutations or dysregulation of related genes may contribute to genetic diseases with dentin defects caused by impaired odontoblastic differentiation, including tricho-dento-osseous (TDO) syndrome, X-linked hypophosphatemic rickets (XLH), Raine syndrome (RS), hypophosphatasia (HPP), Schimke immuno-osseous dysplasia (SIOD), and Elsahy-Waters syndrome (EWS). Herein, recent progress in the molecular regulation of the odontoblastic differentiation of DMSCs is summarized. In addition, genetic syndromes associated with disorders of odontoblastic differentiation of DMSCs are discussed. An improved understanding of the molecular regulation and related genetic syndromes may help clinicians better understand the etiology and pathogenesis of dentin lesions in systematic diseases and identify novel treatment targets.

A novel DSPP frameshift mutation causing dentin dysplasia type 2 and disease management strategies

The present study aims to investigate the mutation in a Chinese family with dentin dysplasia type II (DD-II) and to summarize mutation hotspots, clinical manifestations, and disease management strategies. Phenotype analysis, clinical intervention, mutation screening, and cosegregation analysis within the enrolled family were performed. A summary of the reported mutations in the dentin phosphoprotein (DPP) region of dentin sialophosphoprotein (DSPP) was analyzed. Pathogenicity prediction analysis of the physical properties and function of DSPP variants was performed by bioinformatic processing. Clinical management strategies are discussed. A novel pathogenic mutation (c.2035delA) in the DPP region of DSPP was identified, which was cosegregated in the family. The immature permanent teeth of patients with DD-II presented with X-shaped root canal phenotypes. Most of the identified mutations for DD-II were clustered in the DPP region between nucleotides 1686-2134. Points of differential diagnosis, clinical interventions, and management strategies are proposed. This study revealed a novel DSPP frameshift mutation and presented new clinical features of DD-II. The locus involving nucleotides 1686-2134 of DSPP may represent a mutational hotspot for the disease. Appropriate management of DD-II at different stages is important to avoid the development of secondary dental lesions.

Case report: Enamel renal syndrome: a case series from sub-Saharan Africa

Enamel Renal Syndrome (ERS) (OMIM # 204690) is a rare genetic condition characterised by hypoplastic amelogenesis imperfecta, failed tooth eruption, intra-pulpal calcifications, gingival enlargement and occasionally nephrocalcinosis. In this case series, we report on four unrelated patients with a confirmed molecular diagnosis of ERS (FAM20A pathogenic variants) from Sub-Saharan Africa. The pathognomonic oral profile of ERS was mostly fulfilled in these patients, with the notable addition of an odontoma in one patient. The cases presented a spectrum of phenotypic severity both dentally and systemically. One patient presented with nephrocalcinosis and abnormal kidney function, one had reduced kidney size with normal kidney function, and two had no renal abnormalities. Patients presenting with the oral profile of ERS should receive a prompt referral to a nephrologist and a geneticist. They should receive long-term management from a multidisciplinary medical and dental team.

Dental management of tricho-dento-osseous syndrome in adolescent patients: Literature review and case presentation

Tricho-dento-osseous syndrome (TDO) is a rare autosomal dominant disorder with complete penetrance. Common clinical features include abnormalities of hair, teeth, and skull. Dental management of TDO patients is quite challenging in terms of existing dental and skeletal problems. The current article presents a 12-year-old girl suffering TDO, followed by a review on the published literature pertaining to the dental management of TDO patients. Patient history included, rejected corneal transplantation, stone-forming kidneys, and several previous dental treatments. She was noted to have signs of mandibular prognatia, frontal bossing of the skull, mild bilateral tibial bowing, microstomia, and labial fissures. Dental findings included severe generalized enamel defects, discolored teeth, microdontia, anterior open-bite, posterior cross-bite, deep periodontal pockets, hyperplastic inflamed gingiva, taurodontism of permanent molars, dental periapical radiolucencies, and missing teeth. She was the only child of healthy, nonconsanguineous parents with no familial history of similar congenital syndrome or dental abnormalities. A treatment plan was established based on medical/dental history and findings, using a team-based approach. This article emphasizes the importance of a multidisciplinary approach for the dental management of patients suffering TDO.

An unusual case of tricho-dento-osseous syndrome

Tricho-dento-osseous (TDO) syndrome is a multisystem congenital disorder that is known by bone, skin, and hair abnormalities. Primitive studies show different varieties of manifestations related to this disorder, which involve sclerotic bones, nail involvement, enamel hypoplasia, mandibular prognathism, and taurodontism. Although exploring different TDO cases revealed genetic mutations in all of them, they have many variations in phenotypic view. In this study, we report a case whose primary diagnosis was alopecia and came for extraction of her third molars, but after clinical and radiographic examination, it was found that the cause of her disease was something different.

Genodermatoses with teeth abnormalities

Many genodermatoses exhibit abnormal teeth findings. Studies examining these entities are scarce and narrow in their scope. This paper reviews the evolution, development, and structure of the tooth and provides a summary of genodermatoses with aberrant dental findings. The latter are classified according to the abnormal dental findings: periodontal disease, anodontia/oligodontia/hypodontia, polydontia, enamel hypoplasia, natal teeth, dental pits, and others. Finally, we provide an algorithm that dermatologists and dentists can follow to better recognize genodermatoses with dental involvement.

Trichodentoosseous syndrome: a case report and review of literature

Trichodentoosseous (TDO) syndrome is a rare autosomal dominant condition characterized by various dental and non-dental findings such as taurodontism, amelogenesis imperfecta, osseous dysplasia, mandibular prognathism, curly hair, dysplastic nails, which may be symptomatic or asymptomatic. TDO syndrome is divided into three subtypes that helps to categorize different features seen in patients. There are very few cases reported in the literature of TDO syndrome. We present a case of a young adult male showing interesting Type I and II clinical and radiographic findings of the TDO syndrome. Amelogenesis imperfecta hypomaturation-hypoplastic type and TDO syndrome overlaps in their dental findings such as taurodontism and enamel hypoplasia and makes the diagnosis of TDO crucial. TDO syndrome was noted as an incidental finding on cone beam CT. This case report highlights the pathognomonic radiographic findings, treatment plan, and the clues to diagnosis this rare disorder. Management of TDO requires a proper diagnosis, multidisciplinary approach with comprehensive treatment plan including periodic follow up. Knowledge of this condition along with thorough interpretation of the entire cone beam CT volume are critical to understand this syndrome better due to its rarity.

Novel DLX3 variants in amelogenesis imperfecta with attenuated tricho-dento-osseous syndrome

OBJECTIVES

Variants in DLX3 cause tricho-dento-osseous syndrome (TDO, MIM #190320), a systemic condition with hair, nail and bony changes, taurodontism and amelogenesis imperfecta (AI), inherited in an autosomal dominant fashion. Different variants found within this gene are associated with different phenotypic presentations. To date, six different DLX3 variants have been reported in TDO. The aim of this paper was to explore and discuss three recently uncovered new variants in DLX3.

SUBJECTS AND METHODS

Whole-exome sequencing identified a new DLX3 variant in one family, recruited as part of an ongoing study of genetic variants associated with AI. Targeted clinical exome sequencing of two further families revealed another new variant of DLX3 and complete heterozygous deletion of DLX3. For all three families, the phenotypes were shown to consist of AI and taurodontism, together with other attenuated features of TDO.

RESULTS

c.574delG p.(E192Rfs*66), c.476G>T (p.R159L) and a heterozygous deletion of the entire DLX3 coding region were identified in our families.

CONCLUSION

These previously unreported variants add to the growing literature surrounding AI, allowing for more accurate genetic testing and better understanding of the associated clinical consequences.

Genome-wide detection of copy number variation in Chinese indigenous sheep using an ovine high-density 600 K SNP array

Copy number variants (CNVs) represent a form of genomic structural variation underlying phenotypic diversity. In this study, we used the Illumina Ovine SNP 600 K BeadChip array for genome-wide detection of CNVs in 48 Chinese Tan sheep. A total of 1,296 CNV regions (CNVRs), ranging from 1.2 kb to 2.3 Mb in length, were detected, representing approximately 4.7% of the entire ovine genome (Oar_v3.1). We combined our findings with five existing CNVR reports to generate a composite genome-wide dataset of 4,321 CNVRs, which revealed 556 (43%) novel CNVRs. Subsequently, ten novel CNVRs were randomly chosen for further quantitative real-time PCR (qPCR) confirmation, and eight were successfully validated. Gene functional enrichment revealed that these CNVRs cluster into Gene Ontology (GO) categories of homeobox and embryonic skeletal system morphogenesis. One CNVR overlapping with the homeobox transcription factor DLX3 and previously shown to be associated with curly hair in sheep was identified as the candidate CNV for the special curly fleece phenotype in Tan sheep. We constructed a Chinese indigenous sheep genomic CNV map based on the Illumina Ovine SNP 600 K BeadChip array, providing an important addition to published sheep CNVs, which will be helpful for future investigations of the genomic structural variations underlying traits of interest in sheep.

Taurodontism, Root Dilaceration, and Tooth Transposition: A Radiographic Study of a Population With Nonsyndromic Cleft Lip and/or Palate

OBJECTIVES

In an effort to contribute to proper dental planning and define possible dental phenotypes of nonsyndromic cleft lip and/or palate (CL/P), this study aimed to investigate the occurrence of taurodontism, root dilaceration, and tooth transposition in persons with nonsyndromic CL/P, specifically analyzing the differences among gender, cleft types, and the most affected teeth.

DESIGN

This retrospective study analyzed 974 panoramic x-rays from nonsyndromic Brazilians older than 16 years and categorized into the following four groups: group 1, 250 persons with unilateral cleft lip and palate; group 2, 250 persons with unilateral cleft lip; group 3, 224 persons with cleft palate; and a control group of 250 persons without clefts. Radiographs were digitalized with a scanner and analyzed.

RESULTS

In the Brazilian population studied, the prevalence of taurodontism was 60.4% in group 1, 62.4% in group 2, 67.0% in group 3, and 42.8% in the control group. Root dilacerations had a prevalence of 31.2% in group 1, 29.6% in group 2, 26.3% in group 3, and 27.2% in the control group. The teeth most affected by taurodontism were 17 and 27; whereas root dilacerations were most common in teeth 38 and 48. No tooth transpositions were found in any radiograph analyzed.

CONCLUSIONS

Taurodontism is significantly more prevalent in Brazilians with nonsyndromic CL/P than in persons without clefts; whereas the prevalence of root dilaceration no different from that in the control group. However, root dilacerations in anterior teeth were increased in groups 1 and 2 when compared to the control group.

Transcriptional factor DLX3 promotes the gene expression of enamel matrix proteins during amelogenesis

Mutation of distal-less homeobox 3 (DLX3) is responsible for human tricho-dento-osseous syndrome (TDO) with amelogenesis imperfecta, indicating a crucial role of DLX3 in amelogenesis. However, the expression pattern of DLX3 and its specific function in amelogenesis remain largely unknown. The aim of this study was to investigate the effects of DLX3 on enamel matrix protein (EMP) genes. By immunohistochemistry assays of mouse tooth germs, stronger immunostaining of DLX3 protein was identified in ameloblasts in the secretory stage than in the pre-secretory and maturation stages, and the same pattern was found for Dlx3 mRNA using Realtime PCR. In a mouse ameloblast cell lineage, forced expression of DLX3 up-regulated the expression of the EMP genes Amelx, Enam, Klk4, and Odam, whereas knockdown of DLX3 down-regulated these four EMP genes. Further, bioinformatics, chromatin immunoprecipitation, and luciferase assays revealed that DLX3 transactivated Enam, Amelx, and Odam through direct binding to their enhancer regions. Particularly, over-expression of mutant-DLX3 (c.571_574delGGGG, responsible for TDO) inhibited the activation function of DLX3 on expression levels and promoter activities of the Enam, Amelx, and Odam genes. Together, our data show that DLX3 promotes the expression of the EMP genes Amelx, Enam, Klk4, and Odam in amelogenesis, while mutant-DLX3 disrupts this regulatory function, thus providing insights into the molecular mechanisms underlying the enamel defects of TDO disease.