Osteogenesis imperfecta tooth level phenotype analysis: Cross-sectional study

Skeletal and Non-skeletal Phenotypes in Children with Osteogenesis Imperfecta

Although fractures are the defining characteristic of osteogenesis imperfecta (OI), the disorder affects many tissues. Here we discuss three facets of the OI phenotype, skeletal growth and development, skeletal muscle weakness and the dental and craniofacial characteristics. Short stature is almost universal in the more severe forms of OI and is probably caused by a combination of direct effects of the underlying genetic defect on growth plates and indirect effects of fractures, bone deformities and scoliosis. Recent studies have developed OI type-specific growth curves, which allow determining whether a given child with OI grows as expected for OI type. Impaired muscle function is an important OI-related phenotype in severe OI. Muscles may be directly affected in OI by collagen type I abnormalities in muscle connective tissue and in the muscle-tendon unit. Indirect effects like bone deformities and lack of physical activity may also contribute to low muscle mass and function. Dental and craniofacial abnormalities are also very common in severe OI and include abnormal tooth structure (dentinogenesis imperfecta), malocclusion, and deformities in the bones of the face and the skull. It is hoped that future treatment approaches will address these OI-related phenotypes.

Genetic Evaluation for Monogenic Disorders of Low Bone Mass and Increased Bone Fragility: What Clinicians Need to Know

PURPOSE OF REVIEW

The purpose of this review is to outline the principles of clinical genetic testing and to provide practical guidance to clinicians in navigating genetic testing for patients with suspected monogenic forms of osteoporosis.

RECENT FINDINGS

Heritability assessments and genome-wide association studies have clearly shown the significant contributions of genetic variations to the pathogenesis of osteoporosis. Currently, over 50 monogenic disorders that present primarily with low bone mass and increased risk of fractures have been described. The widespread availability of clinical genetic testing offers a valuable opportunity to correctly diagnose individuals with monogenic forms of osteoporosis, thus instituting appropriate surveillance and treatment. Clinical genetic testing may identify the appropriate diagnosis in a subset of patients with low bone mass, multiple or unusual fractures, and severe or early-onset osteoporosis, and thus clinicians should be aware of how to incorporate such testing into their clinical practices.

Craniofacial dysmorphism of osteogenesis imperfecta mouse and effect of cathepsin K knockout: Preliminary craniometry observations

OBJECTIVES

In addition to bone fragility, patients with osteogenesis imperfecta (OI) type III have typical craniofacial abnormalities, such as a triangular face and maxillary micrognathism. However, in the osteogenesis imperfecta mouse (oim), a validated model of OI type III, few descriptions exist of craniofacial phenotype. Treatment of OI mostly consists of bisphosphonate administration. Cathepsin K inhibition has been tested as a promising therapeutic approach for osteoporosis and positive results were observed in long bones of cathepsin K knocked out oim (oim/CatK-/-). This craniometry study aimed to highlight the craniofacial characteristics of oim and Cathepsin K KO mouse.

MATERIALS AND METHODS

We analyzed the craniofacial skeleton of 51 mice distributed in 4 genotype groups: Wt (control), oim, CatK-/-, oim/CatK-/-. The mice were euthanized at 13 weeks and their heads were analyzed using densitometric (pQCT), X-ray cephalometric, and histomorphometric methods.

RESULTS

The craniofacial skeleton of the oim mouse is frailer than the Wt one, with a reduced thickness and mineral density of the cranial vault and mandibular ramus. Different cephalometric data attest a dysmorphism similar to the one observed in humans with OI type III. Those abnormalities were not improved in the oim/CatK-/- group.

CONCLUSION

These results suggest that oim mouse could serve as a complete model of the human OI type III, including the craniofacial skeleton. They also suggest that invalidation of cathepsin K has no impact on the craniofacial abnormalities of the oim model.

Cranio-cervical abnormalities in moderate-to-severe osteogenesis imperfecta - Genotypic and phenotypic determinants

INTRODUCTION

Cranio-cervical anomalies are significant complications of osteogenesis imperfecta (OI), a rare bone fragility disorder that is usually caused by mutations in collagen type I encoding genes.

OBJECTIVE

To assess cranio-cervical anomalies and associated clinical findings in patients with moderate-to-severe OI using 3D cone beam computed tomography (CBCT) scans.

METHODS

Cross-sectional analysis of CBCT scans in 52 individuals with OI (age 10-37 years; 32 females) and 40 healthy controls (age 10-32 years; 26 females). Individuals with a diagnosis of OI type III (severe, n = 11), type IV (moderate, n = 33) and non-collagen OI (n = 8) were recruited through the Brittle Bone Disorders Consortium. Controls were recruited through the orthodontic clinic of the University of Missouri-Kansas City (UMKC).

RESULTS

OI and control groups were similar in mean age (OI: 18.4 [SD: 7.2] years, controls: 18.1 [SD: 6.3] years). The cranial base angle was increased in the OI group (OI: mean 148.6° [SD: 19.3], controls: mean 130.4° [SD: 5.7], P = .001), indicating a flatter cranial base. Protrusion of the odontoid process into the foramen magnum (n = 7, 14%) and abnormally located odontoid process (n = 19, 37%) were observed in the OI group but not in controls. Low stature, expressed as height z-score (P = .01), presence of DI (P = .04) and being male (P = .04) were strong predictors of platybasia, whereas height z-score (P = .049) alone was found as positive predictor for basilar impression as per the Chamberlain measurement.

CONCLUSION

The severity of the phenotype in OI, as expressed by the height z-score, correlates with the severity of cranial base anomalies such as platybasia and basilar impression in moderate-to-severe OI. Screening for cranial base anomalies is advisable in individuals with moderate-to-severe OI, with special regards to the individuals with a shorter stature and DI.

Dental anomalies in individuals with osteogenesis imperfecta: a systematic review and meta-analysis of prevalence and comparative studies

BACKGROUND

Osteogenesis imperfecta (OI) is a rare genetic disorder primarily caused by mutations in the genes involved in the production of type 1 collagen. OI is also known as brittle bone disease.

OBJECTIVE

This study aims to describe the prevalence of dental anomalies (except dentinogenesis imperfecta) in individuals with OI, and compare the prevalence of dental anomalies between individuals with and without OI and between individuals with different types of OI.

SEARCH METHODS

Searches in PubMed, Web of Science, Scopus, Ovid, and gray literature were performed in October 2022.

SELECTION CRITERIA

Observational studies (with or without a comparison group) that evaluated the prevalence of dental anomalies in individuals with OI. Data collection and analysis: Data items were extracted by two authors. Quality assessment employing the Joanna Briggs Institute checklists and meta-analyses was conducted. Results were provided in prevalence values and odds ratio (OR) / 95% confidence interval (CI). Strength of evidence was determined.

RESULTS

Eighteen studies were included. Most prevalent dental anomalies in individuals with OI included pulp obliteration (46.4%), dental impaction (33.5%), dental impaction of second molars (27%), and tooth agenesis (23.9%). Individuals with OI type III/IV had 20.16-fold greater chance of exhibiting tooth discoloration in comparison with individuals with OI type I (CI: 1.10-370.98). In comparison with the group without OI, the individuals with OI had 6.90-fold greater chance of exhibiting dental impaction (CI: 1.54-31.00). High methodological quality was found in 47% of the studies. Strength of evidence was low or very low.

CONCLUSIONS

Pulp obliteration, dental impaction, and tooth agenesis were the most prevalent dental anomalies in the OI group. Individuals with OI were more likely to have dental impaction than individuals without OI. Individuals with OI type III/IV (severe-moderate) are more likely to have tooth discoloration than individuals with OI type I (mild).

In vivo real-time assessment of developmental defects in enamel of anti-Act1 mice using optical coherence tomography

The purpose of this study was to explore the feasibility of using optical coherence tomography (OCT) for real-time and quantitative monitoring of enamel development in gene-edited enamel defect mice. NF-κB activator 1, known as Act1, is associated with many inflammatory diseases. The antisense oligonucleotide of Act1 was inserted after the CD68 gene promoter, which would cover the start region of the Act1 gene and inhibit its transcription. Anti-Act1 mice, gene-edited mice, were successfully constructed and demonstrated amelogenesis imperfecta by scanning electron microscope (SEM) and energy dispersive X-ray (EDX) spectroscopy. Wild-type (WT) mice were used as the control group in this study. WT mice and anti-Act1 mice at 3 weeks old were examined by OCT every week and killed at eight weeks old. Their mandibular bones were dissected and examined by OCT, micro-computed tomography (micro-CT), and SEM. OCT images showed that the outer layer of enamel of anti-Act1 mice was obviously thinner than that of WT mice but no difference in total thickness. When assessing enamel thickness, there was a significant normal linear correlation between these methods. OCT could scan the imperfect developed enamel noninvasively and quickly, providing images of the enamel layers of mouse incisors.

Craniofacial and dental phenotype of two girls with osteogenesis imperfecta due to mutations in CRTAP

Mutations in CRTAP lead to an extremely rare form of recessive osteogenesis imperfecta (OI). CRTAP deficient mice have a brachycephalic skull, fusion of facial bones, midface retrusion and class III dental malocclusion, but in humans, the craniofacial and dental phenotype has not been reported in detail. Here, we describe craniofacial and dental findings in two 11-year-old girls with biallelic CRTAP mutations. Patient 1 has a homozygous c.472-1021C>G variant in CRTAP intron 1 and a moderately severe OI phenotype. The variant is known to create a cryptic splice site, leading to a frameshift and nonsense-mediated RNA decay. Patient 1 started intravenous bisphosphonate treatment at 2 years of age. At age 11 years, height Z-score was +0.6. She had a short and wide face, concave profile and class III malocclusion, with a prognathic mandible and an antero-posterior crossbite. A panoramic radiograph showed a poor angulation of the second upper right premolar, and no dentinogenesis imperfecta or dental agenesis. Cone-beam computed tomography confirmed these findings and did not reveal any other abnormalities. Patient 2 has a homozygous CRTAP deletion of two amino acids (c.804_809del, p.Glu269_Val270del) and a severe OI phenotype. As previously established, the variant leads to instability of CRTAP protein. Intravenous bisphosphonate treatment was started at the age of 15 months. At 11 years of age her height Z-score was -9.7. She had a long and narrow face and convex profile, maxillary retrusion leading to a class III malocclusion, an edge-to-edge overjet and lateral open bite. Panoramic radiographs showed no dental abnormalities. Cone-beam computed tomography showed occipital bossing, platybasia and wormian bones. In these two girls with CRTAP mutations, the severity of the skeletal phenotype was mirrored in the severity of the craniofacial phenotype. Class III malocclusion and antero-posterior crossbite were a common trait, while dental agenesis or dentinogenesis imperfecta were not detected.

Morphological Study of Dental Structure in Dentinogenesis Imperfecta Type I with Scanning Electron Microscopy

Background: Dentinogenesis imperfecta type I (DGI-I) is a hereditary alteration of dentin associated with osteogenesis imperfecta (OI). Aim: To describe and study the morphological characteristics of DGI-I with scanning electron microscopy (SEM). Material and methods: Twenty-five teeth from 17 individuals diagnosed with OI and 30 control samples were studied with SEM at the level of the enamel, dentin–enamel junction (DEJ) and four levels of the dentin, studying its relationship with clinical–radiographic alterations. The variables were analysed using Fisher’s exact test, with a confidence level of 95% and asymptotic significance. Results: OI teeth showed alterations in the prismatic structure in 56%, interruption of the union in the enamel and dentin in 64% and alterations in the tubular structure in all of the cases. There is a relationship between the severity of OI and the morphological alteration of the dentin in the superficial (p = 0.019) and pulpar dentin (p 0.004) regions. Conclusions: Morphological alterations of the tooth structure are found in OI samples in the enamel, DEJ and dentin in all teeth regardless of the presence of clinical–radiographic alterations. Dentin structural anomalies and clinical dental alterations were observed more frequently in samples from subjects with a more severe phenotype of OI.