Gnathodiaphyseal dysplasia

Gnathodiaphyseal dysplasia: Diagnostic clues from two fetal cases and literature review

This article presents two fetal cases of gnathodiaphyseal dysplasia (GDD), a rare autosomal dominant disorder, and reviews the relevant literature. The cases involved two fetuses exhibiting bone bowing, which led to the diagnosis of GDD. Genetic testing revealed two de novo variants of the ANO5 gene, confirming the diagnosis. A literature review was conducted to explore GDD's clinical and paraclinical presentation, diagnosis, and management. GDD is a rare but frequently inherited cause of bone fragility and jaw lesions characterized by a gain-of-function variant within the ANO5 gene. Clinical manifestations range from recurrent dental infections with mild jaw lesions to severe bone fragility with several fractures associated with large jaw lesions requiring disfiguring surgeries. Diagnostic techniques depend on the context and include targeted genetic testing of ANO5, untargeted molecular analysis with whole-exome sequencing, or whole-genome sequencing. This case report highlights the importance of recognizing GDD as a novel cause of bone bowing and fractures during pregnancy. By summarizing the literature, this article contributes to healthcare professionals' knowledge and improves the recognition, diagnosis, and care of patients with GDD.

Genetic disruption of Ano5 leads to impaired osteoclastogenesis for gnathodiaphyseal dysplasia

OBJECTIVES

Gnathodiaphyseal dysplasia (GDD; OMIM#166260) is a rare skeletal genetic disorder characterized by sclerosis of tubular bones and cemento-osseous lesions in mandibles. TMEM16E/ANO5 gene mutations have been identified in patients with GDD. Here, Ano5 knockout (Ano5-/-) mice with enhanced osteoblastogenesis were used to investigate whether Ano5 disruption affects osteoclastogenesis.

SUBJECTS AND METHODS

The maturation of osteoclasts, formation of F-actin ring and bone resorption were detected by immunohistochemistry, TRAP, phalloidin staining and Coming Osteo assays. The expression of osteoclast-related factors was measured by qRT-PCR. Early signaling pathways were verified by western blot.

RESULTS

Ano5-/- mice exhibited inhibitory formation of multinucleated osteoclasts with a reduction of TRAP activity. The expression of Nfatc1, c-Fos, Trap, Ctsk, Mmp9, Rank and Dc-stamp was significantly decreased in bone tissues and bone marrow-derived macrophages (BMMs) of Ano5-/- mice. Ano5-/- osteoclasts manifested disrupted actin ring and less mineral resorption. RANKL-induced early signaling pathways were suppressed in Ano5-/- osteoclasts and Ano5 knockdown RAW264.7 cells. Moreover, the inhibitory effects of NF-κB signalling pathway on osteoclastogenesis were partially attenuated with NF-κB signalling activator.

CONCLUSIONS

Ano5 deficiency impairs osteoclastogenesis, which leads to enhanced osteogenic phenotypes mediated by bone homeostasis dysregulation.

Recurrent femoral shaft fractures in a child with gnathodiaphyseal dysplasia: a case report

Background

Gnathodiaphyseal dysplasia (GDD) is an extremely rare autosomal dominant disease characterized by cemento-osseous lesions in the jawbones, bone fragility, and diaphyseal sclerosis of the tubular bones. Patients with GDD are prone to sustain fractures by minor accidents. Although over 80 cases have been reported, detailed information about the orthopedic treatment of the fractures is limited.

Case presentation

A 9-year-old Japanese girl with a known history of GDD presented with pain and deformity in the left thigh after a minor fall. She had a displaced transverse fracture in the mid-shaft of the left femur and underwent a closed reduction and external fixation. In the 25th week after the initial surgery, she had another fracture in the left femur at one of the half-pin insertion sites. She underwent an external fixation again. After this operation, the patient sustained another refracture at the same fracture site and one supracondylar fracture at the distant site of the femur. The supracondylar fracture occurred without any triggering activity before beginning a weight-bearing exercise. The supracondylar fracture was successfully treated conservatively, but she sustained two more diaphyseal fractures at half-pin insertion sites one after another. She eventually underwent a revision surgery with a flexible intramedullary nail. At 3 months postoperatively, the fracture was healed and the patient maintained her ambulatory status without further refracture.

Conclusions

Patients with GDD might have narrower safety ranges of biomechanical and physiological drawbacks, which are considered to be acceptable in ordinary cases. The choice of treatment should be aimed at minimizing these negative effects. We recommend intramedullary devise as the first-choice implant for the treatment of isolated femoral shaft fracture in GDD patients in this age group.

Gnathodiaphyseal dysplasia: Severe atypical presentation with novel heterozygous mutation of the anoctamin gene (ANO5)

Gnathodiaphyseal dysplasia (GDD; OMIM #166260) is an ultra-rare autosomal dominant disorder caused by heterozygous mutation in the anoctamin 5 (ANO5) gene and features fibro-osseous lesions of the jawbones, bone fragility with recurrent fractures, and bowing/sclerosis of tubular bones. The physiologic role of ANO5 is unknown. We report a 5-year-old boy with a seemingly atypical and especially severe presentation of GDD and unique ANO5 mutation. Severe osteopenia was associated with prenatal femoral fractures, recurrent postnatal fractures, and progressive bilateral enlargement of his maxilla and mandible beginning at ~2months-of-age that interfered with feeding and speech and required four debulking operations. Histopathological analysis revealed benign fibro-osseous lesions resembling cemento-ossifying fibromas of the jaw without psammomatoid bodies. A novel, de novo, heterozygous, missense mutation was identified in exon 15 of ANO5 (c.1553G>A; p.Gly518Glu). Our findings broaden the phenotypic and molecular spectra of GDD. Fractures early in life with progressive facial swelling are key features. We assessed his response to a total of 7 pamidronate infusions commencing at age 15months. Additional reports must further elucidate the phenotype, explore any genotype-phenotype correlation, and evaluate treatments.

Gnathodiaphyseal Dysplasia: Surgical Treatment and Prosthetic Rehabilitation of 2 Members of the Same Family

Gnathodiaphyseal dysplasia (GDD) is a rare hereditary syndrome characterized by cemento-ossifying fibromas of the maxillary bones, fragile bones, curvature and cortical thinning of the tubular bones, and diaphyseal sclerosis of the long bones. In this study, 2 complex clinical cases of 2 members of the same family had GDD and were treated in the authors' odonto-stomatology department. The first was treated with a block bone graft and implant-prosthetic therapy; the other, who had extensive osteomyelitis of the second quadrant, was managed with extraction of the involved teeth, surgical revision of the site, and a graft of autologous platelet concentrate.

Gnathodiaphyseal dysplasia: report of a family with a novel mutation of the ANO5 gene

Gnathodiaphyseal dysplasia (GDD) is a rare autosomal dominant disorder characterized by florid osseous dysplasia of the jaws, bone fragility, and diaphyseal cortical thickening and bowing of long bones. We present a family with previously undiagnosed GDD. The disorder was identified by the characteristic gnathic and skeletal manifestations in the father. Clinical and radiologic examination of the patient's son also revealed the characteristic features of GDD. Gene sequencing revealed a novel mutation (c. 1067 G>A, p. Cys356 Tyr) in the ANO5 gene, which is causative for GDD. This mutation was predicted to be detrimental by computational analyses and by structural modeling of the protein. The implications for recognition and management of this disease are discussed.