Identification of a novel ANO5 missense mutation in a Chinese family with familial florid osseous dysplasia

Familial gigantiform cementoma with recurrent ANO5 p.Cys356Tyr mutations: Clinicopathological and genetic study with literature review

BACKGROUND

Familial gigantiform cementoma (FGC) is a rare tumor characterized by the early onset of multi-quadrant fibro-osseous lesions in the jaws, causing severe maxillofacial deformities. Its clinicopathological features overlap with those of other benign fibro-osseous lesions. FGC eventually exhibits progressively rapid growth, but no suspected causative gene has been identified.

METHODS

In this study, three patients with FGC were recruited, and genomic DNA from the tumor tissue and peripheral blood was extracted for whole-exome sequencing.

RESULTS

Results showed that all three patients harbored the heterozygous mutation c.1067G > A (p.Cys356Tyr) in the ANO5 gene. Furthermore, autosomal dominant mutations in ANO5 at this locus have been identified in patients with gnathodiaphyseal dysplasia (GDD) and are considered a potential causative agent, suggesting a genetic association between FGC and GDD. In addition, multifocal fibrous bone lesions with similar clinical presentations were detected, including five cases of florid cemento-osseous dysplasia, five cases of polyostotic fibrous dysplasia, and eight cases of juvenile ossifying fibromas; however, none of them harbored mutations in the ANO5 gene.

CONCLUSION

Our findings indicate that FGC may be an atypical variant of GDD, providing evidence for the feasibility of ANO5 gene testing as an auxiliary diagnostic method for complex cases with multiple quadrants.

Introduction of a Cys360Tyr Mutation in ANO5 Creates a Mouse Model for Gnathodiaphyseal Dysplasia

Gnathodiaphyseal dysplasia (GDD) is a rare autosomal dominant genetic disease characterized by the osteosclerosis of tubular bones and the formation of cemento-osseous lesions in mandibles. Although genetic mutations for GDD have been identified in the ANO5/TMEM16E gene, the cellular and molecular mechanisms behind the pathogenesis of GDD remain unclear. Here, we generated the first knock-in mouse model for GDD with the expression of human mutation p.Cys360Tyr in ANO5. Homozygous Ano5 knock-in mice (Ano5^KI/KI ) replicated GDD-like skeletal features, including massive jawbones, bowing tibia, bone fragility, sclerosis, and cortical thickening of the femoral and tibial diaphysis. Serum alkaline phosphatase (ALP) levels were elevated in Ano5^KI/KI mice as in GDD patients with p.Cys360Tyr mutation. Calvaria-derived Ano5^KI/KI osteoblast cultures showed increased osteoblastogenesis, including hypermineralized bone matrix and enhanced bone formation-related factors expression. Interestingly, Ano5^KI/KI bone marrow-derived macrophage cultures showed decreased osteoclastogenesis, and Ano5^KI/KI osteoclasts exhibited disrupted actin ring formation, which may be associated with some signaling pathways. In conclusion, this new mouse model may facilitate elucidation of the pathogenesis of GDD and shed more light on its treatment. © 2021 American Society for Bone and Mineral Research (ASBMR).

Florid Cemento-osseous Dysplasia: A Report of Two Cases and Literature Review

AIM

This report aims to provide the clinical and radiographic features of two symptomatic Indian patients with florid cemento-osseous dysplasia (FCOD), along with a discussion of the differential diagnosis, potential challenges, and therapeutic implications.

BACKGROUND

FCOD is a rare, multifocal, periapical, and bilateral condition involving the premolar and molar region of the posterior mandible and sometimes the maxilla.

CASE DESCRIPTION

The first patient is a 30-year-old female with a recent history of dental pain. The patient was otherwise healthy and the medical history was unremarkable. The second patient is a 50-year-old female with a history of orthodontic therapy. Radiographic evaluation using cone-beam computed tomography (CBCT) revealed bilateral involvement of the posterior mandible, sparing the entire maxilla in both patients Clinical significance: For a pathognomonic condition like FCOD, a radiology survey alone is often sufficient to arrive at the final diagnosis, and therefore surgical interventions should ideally be avoided.

Familial florid cemento-osseous dysplasia: a report of three cases and review of the literature

Familial cases of benign fibro-osseous lesions of the jaws are rare and have been described under numerous terms including familial gigantiform cementoma, multiple cemento-ossifying fibromas, sclerotic cemental masses and familial florid cemento-osseous dysplasia. The synonymous and interchangeable use of these terms to describe distinct entities with overlapping features has resulted in confusion and inaccurate categorisation of these lesions. This study highlights three family members with diffuse fibro-osseous jaw lesions with areas of significant expansion. In the pursuit of finding the best clinicopathological categorisation for the reported cases, familial florid cemento-osseous dysplasia and familial gigantiform cementoma were investigated. The final consensus of these three cases was that of familial florid cemento-osseous dysplasia, and one patient presented with a concurrent "ossifying fibromatoid lesion". A literature review on the above entities was performed in an attempt to provide clarification and delineate distinguishing features of the individual diseases.