Fused teeth, macrodontia and increased caries are characteristic features of neurofibromatosis type 1 patients with NF1 gene microdeletion

Dental Developmental Stages and Decayed, Missing, and Restored Teeth in Neurofibromatosis Type 1-affected Children and Adolescents

Background

Neurofibromatosis type 1 (NF1) is an autosomal dominant inherited tumor predisposition disease with a highly variable phenotype. The influence of the characteristic NF1 tumors (neurofibromas) on dentition has not yet been examined in detail. The aim of the study was to assess the dentition of NF1 children and adolescents, considering the symmetry of tooth development.

Material and Methods

The panoramic radiographs of 59 patients with a confirmed NF1 diagnosis were compared with 59 age-and-sex-matched controls. The stages of tooth development on the sides of the jaw, added to a score, were assessed. In addition, the number of filled or decayed teeth, and the number of retained or missing teeth were assessed.

Results

The tooth development of both study groups is symmetrical for almost all parameters and in the same developmental stage according to the sum score of the tooth development stages. Discrete developmental delays of teeth, in particular in the oral area of facial plexiform neurofibroma (PNF) are noticeable. NF1 patients' teeth showed less decay and more restorations than that of the control group. The facial PNF (FPNF) does not impair emergence of deciduous teeth.

Conclusions

Development of dentition of NF1 patients does not differ from the general population. However, FPNF with oral tumor components often prevent mesial movement of permanent molars and premolars, so these teeth do not develop contact (spacing), hardly emerge or may stay retained in bone. Oral PNF may have a low-retarding effect on some tooth root development (e.g., wisdom teeth). This effect is negligible when comparing the affected and unaffected sides of the jaw and is probably non-specific. Key words:Neurofibromatosis type 1, plexiform neurofibroma, dentition, mixed dentition, symmetry, oral health, tooth development.

Age-dependent oral manifestations of neurofibromatosis type 1: a case-control study

Introduction

Most craniofacial manifestations of neurofibromatosis type 1 (NF1) are considered as a result of tumor compression. We sought to determine salivary changes, caries, and periodontal complications in NF1 patients without tumors in the oral cavity.

Objective and methods

Eleven NF1 patients without tumors in the oral cavity and 29 matched controls without NF1 were enrolled in this case–control study. Demographic information, medical history, and data of intraoral examinations, including the Decayed, Missing, and Filled Teeth (DMFT) scores and Russel’s periodontal index (PI), were recorded. The functional salivary analysis was performed for sialometry, salivary pH values, and amylase activity. Ingenuity Systems Pathway Analysis (IPA) was conducted to identify mutually activated pathways for NF1-associated oral complications.

Results

NF1 patients were associated with periodontitis (OR = 1.40, 95% CI = 1.06–1.73, P = 0.04), gingivitis (OR = 1.55, 95% CI = 1.09–2.01, P = 0.0002), and decreased salivary flow rates (OR = 1.40, 95% CI = 1.05–1.76, P = 0.005). Periodontal destruction, salivary changes, and dental caries in NF1 patients were age-dependent. Subgroup analyses based on age stratification suggested that salivary flow rates and salivary amylase activities were significantly low in NF1 patients aged over 20 years and that salivary pH values, PI and DMFT scores were significantly high among NF1- controls aged over 20. All oral complications were not significantly presented in NF1 patients aged below 20 years. IPA analyses suggested that cellular mechanisms underlying NF1-associated oral complications involved chronic inflammatory pathways and fibrosis signaling pathway.

Conclusion

NF1 patients without tumors in the oral cavity presented a comparatively high prevalence of age-dependent oral complications, including periodontal destruction and salivary gland dysfunction, which were associated with chronic inflammatory pathogenesis.

Supernumerary Molars and Wisdom Tooth Shape Alterations in Patients with Neurofibromatosis Type 1

Objectives

The purpose of the present study was the systematic investigation of numerical and morphological aberrations of teeth in the wisdom teeth region in neurofibromatosis type 1 patients.

Material and Methods

The panoramic radiographs of 179 patients were analysed for supernumerary molars and dysplastic wisdom teeth with special reference to facial tumour type. The results were compared to radiographic findings obtained in panoramic radiographs of age- and sex-matched controls.

Results

The total number of dysplastic or supernumerary molars was 21 (17 individuals, 4.75%) and predominantly a finding of the maxilla (maxilla: 15, mandible: 1, maxilla and mandible: 1). Differences of dental findings between neurofibromatosis type 1 (NF1) patients (n = 15) and the control group (n = 2) were statistically significant (P < 0.01). All individuals with supernumerary molars were diagnosed as being affected with NF1. This difference achieved statistical significance when it was considered that the event may occur at least once per quadrant, and thus the individual potentially needs to be considered four times (P = 0.0038).

Conclusions

This investigation revealed that supernumerary molars and aberrations in wisdom tooth form are more common in patients than in age- and sex-matched controls. There is no association between these findings and a specific feature of the disease, id est facial manifestation of a trigeminal nerve sheath tumour (plexiform neurofibroma). The cause of this phenomenon is unknown. A review of these dental findings on other neurofibromatosis type 1 study groups should be attempted.

Emerging genotype-phenotype relationships in patients with large NF1 deletions

The most frequent recurring mutations in neurofibromatosis type 1 (NF1) are large deletions encompassing the NF1 gene and its flanking regions (NF1 microdeletions). The majority of these deletions encompass 1.4-Mb and are associated with the loss of 14 protein-coding genes and four microRNA genes. Patients with germline type-1 NF1 microdeletions frequently exhibit dysmorphic facial features, overgrowth/tall-for-age stature, significant delay in cognitive development, large hands and feet, hyperflexibility of joints and muscular hypotonia. Such patients also display significantly more cardiovascular anomalies as compared with patients without large deletions and often exhibit increased numbers of subcutaneous, plexiform and spinal neurofibromas as compared with the general NF1 population. Further, an extremely high burden of internal neurofibromas, characterised by >3000 ml tumour volume, is encountered significantly, more frequently, in non-mosaic NF1 microdeletion patients than in NF1 patients lacking such deletions. NF1 microdeletion patients also have an increased risk of malignant peripheral nerve sheath tumours (MPNSTs); their lifetime MPNST risk is 16–26%, rather higher than that of NF1 patients with intragenic NF1 mutations (8–13%). NF1 microdeletion patients, therefore, represent a high-risk group for the development of MPNSTs, tumours which are very aggressive and difficult to treat. Co-deletion of the SUZ12 gene in addition to NF1 further increases the MPNST risk in NF1 microdeletion patients. Here, we summarise current knowledge about genotype–phenotype relationships in NF1 microdeletion patients and discuss the potential role of the genes located within the NF1 microdeletion interval whose haploinsufficiency may contribute to the more severe clinical phenotype.