Clinical and genetic analysis of patients with cherubism

Loss-of-function OGFRL1 variants identified in autosomal recessive cherubism families

Cherubism (OMIM 118400) is a rare craniofacial disorder in children characterized by destructive jawbone expansion due to the growth of inflammatory fibrous lesions. Our previous studies have shown that gain-of-function mutations in SH3 domain-binding protein 2 (SH3BP2) are responsible for cherubism and that a knock-in mouse model for cherubism recapitulates the features of cherubism, such as increased osteoclast formation and jawbone destruction. To date, SH3BP2 is the only gene identified to be responsible for cherubism. Since not all patients clinically diagnosed with cherubism had mutations in SH3BP2, we hypothesized that there may be novel cherubism genes and that these genes may play a role in jawbone homeostasis. Here, using whole exome sequencing, we identified homozygous loss-of-function variants in the opioid growth factor receptor like 1 (OGFRL1) gene in 2 independent autosomal recessive cherubism families from Syria and India. The newly identified pathogenic homozygous variants were not reported in any variant databases, suggesting that OGFRL1 is a novel gene responsible for cherubism. Single cell analysis of mouse jawbone tissue revealed that Ogfrl1 is highly expressed in myeloid lineage cells. We generated OGFRL1 knockout mice and mice carrying the Syrian frameshift mutation to understand the in vivo role of OGFRL1. However, neither mouse model recapitulated human cherubism or the phenotypes exhibited by SH3BP2 cherubism mice under physiological and periodontitis conditions. Unlike bone marrow-derived M-CSF-dependent macrophages (BMMs) carrying the SH3BP2 cherubism mutation, BMMs lacking OGFRL1 or carrying the Syrian mutation showed no difference in TNF-ɑ mRNA induction by LPS or TNF-ɑ compared to WT BMMs. Osteoclast formation induced by RANKL was also comparable. These results suggest that the loss-of-function effects of OGFRL1 in humans differ from those in mice and highlight the fact that mice are not always an ideal model for studying rare craniofacial bone disorders.

Denosumab Therapy in Cherubism

Cherubism is a rare disorder characterized by proliferative fibro-osseous lesions that result in bilateral bony hyperplasia of the face. Management varies based on symptom severity and includes longitudinal follow-up, pharmacotherapy, and/or surgical debulking. Off-label treatment with denosumab, a human monoclonal antibody that binds RANKL and inhibits osteoclast function to reduce bone resorption, can be beneficial in suppressing the proliferation of bone to minimize the need for surgery and to control postoperative reproliferation. Close follow-up is needed to maintain appropriate electrolyte levels. The present case demonstrates the achievement of symptomatic control with denosumab in a child with severe refractory cherubism.

Treatment of Progressive Cherubism during the Second Dental Transitional Phase with Calcitonin

Cherubism is an autosomal dominant disease with variable expression. Aggressive forms of untreated cherubism may lead to severe malformation of the maxillofacial skeleton, developing tooth germs and teeth. Scarcely described and empirically applied interventional therapies during active stages of the disease try to limit the damage and deformation caused by progression of expanding intraosseous lesions. The final goal is to minimize the need for corrective surgeries once progressive growth has halted and disease enters its quiescent phase. New insights into the pathophysiology of cherubism hypothesize a potential role for dental development and jaw growth in the (hyper)activation of the disease. Theoretically, this could guide the ideal moment of pharmacological interventions. In this case report, the off-label use of systemic calcitonin treatment is described, stressing particularly the potential importance of its appropriate timing and duration of treatment.

Reconstruction of bilateral ramus-condyle unit defect using custom titanium prosthesis with preservation of both condyles

BACKGROUND

Novel technologies for management and reconstruction of complex bony defects regarding both function and facial appearance are interestingly used in maxillofacial surgery. In the current study, we demonstrated reconstruction of a bilateral ramus-condyle unit (RCU) defect while preserving both condyles by a novel designed titanium prosthesis using virtual surgical planning (VSP), computer-aided design and manufacturing (CAD/CAM), and Selective Laser Melting (SLM) technologies.

MATERIALS AND METHODS

A 3D customized titanium prosthesis was designed for a 49 -year-old patient with bilateral mandibular aggressive central giant cell granuloma (CGCG) according to mandibular normal anatomy and structure while preserving bilateral intact condyles. Finite element study was performed to investigate the effects of new design strength and the stress shielding phenomenon. The design of macro-pores inside the body of prosthesis allowed it to act as a scaffold for bone tissue engineering under load bearing conditions.

RESULTS

Analysis of the strength and stress shielding phenomenon demonstrated favorable outcomes regarding the novel design. For instance, there was no stress shielding in any of the preserved condyles with regard to the size and distribution of stresses. Also, the stress distribution around the pores showed that these pores had no effect on the strength of the prosthesis. Thirty month follow-ups after reconstruction of bilateral RCU defect showed normal jaw function with a favorable facial appearance and mandibular contour.

CONCLUSION

We design a novel patient-specific prosthesis with desirable biomechanical features for reconstruction of bilateral RCU defect after resection of the benign tumor with preservation of bilateral intact condyles.

Central giant cell granuloma of the head & neck: A case report and systematic review

PURPOSE

The purpose of this paper is to describe a recent case of central giant cell granuloma (CGCG) that rapidly progressed post corticosteroid treatment while also providing a review of the existing literature on CGCG of the head and neck (HNCGCG), with particular emphasis on extra-mandibular and maxillary cases.

MATERIALS AND METHODS

The investigators designed and implemented a 32-year review of literature, using the online databases: PubMed, Google Scholar, Medline, and Proquest. The total number of cases analyzed was 55 (42 case reports; 3 case series; 8 comparative studies; 1 retrospective cohort).

CASE PRESENTATION

We present a case of a CGCG in a 10-year old male. The lesion originated in the right anterior mandibular body and progressed after corticosteroid treatment. Diagnosis was made using a combination of imaging and histology. A timely debulking procedure of the hemi-mandible was performed and there was no recurrence of the lesion at follow up.

RESULTS

The average age at the time of diagnosis of CGCG was 27.5 years. HNCGCG was most commonly detected in the jaw (43.1%), but was also found in the temporal bone (33.3%). The most frequently employed treatment modality was complete surgical excision (76.9%). 93.2% of patients were alive with no evidence of disease at follow-up, while 6.8% of patients exhibited recurrence at follow-up. The median follow up was 13 months.

CONCLUSION

It is important for clinicians to recognize that CGCGs are capable of manifesting outside of the jaw. CGCG should be considered in the differential diagnosis of non-odontogenic radiolucent lesions, especially in young patients. CGCGs also need to be distinguished from brown tumor of hyperparathyroidism (BTH) and giant cell tumors, which are histologically similar.

Multiple versus solitary giant cell lesions of the jaw: Similar or distinct entities?

The majority of giant cell lesions of the jaw present as a solitary focus of disease in bones of the maxillofacial skeleton. Less frequently they occur as multifocal lesions. This raises the clinical dilemma if these should be considered distinct entities and therefore each need a specific therapeutic approach. Solitary giant cell lesions of the jaw present with a great diversity of symptoms. Recent molecular analysis revealed that these are associated with somatic gain-of-function mutations in KRAS, FGFR1 or TRPV4 in a large component of the mononuclear stromal cells which all act on the RAS/MAPK pathway. For multifocal lesions, a small group of neoplastic multifocal giant cell lesions of the jaw remain after ruling out hyperparathyroidism. Strikingly, most of these patients are diagnosed with jaw lesions before the age of 20 years, thus before the completion of dental and jaw development. These multifocal lesions are often accompanied by a diagnosis or strong clinical suspicion of a syndrome. Many of the frequently reported syndromes belong to the so-called RASopathies, with germline or mosaic mutations leading to downstream upregulation of the RAS/MAPK pathway. The other frequently reported syndrome is cherubism, with gain-of-function mutations in the SH3BP2 gene leading through assumed and unknown signaling to an autoinflammatory bone disorder with hyperactive osteoclasts and defective osteoblastogenesis. Based on this extensive literature review, a RAS/MAPK pathway activation is hypothesized in all giant cell lesions of the jaw. The different interaction between and contribution of deregulated signaling in individual cell lineages and crosstalk with other pathways among the different germline- and non-germline-based alterations causing giant cell lesions of the jaw can be explanatory for the characteristic clinical features. As such, this might also aid in the understanding of the age-dependent symptomatology of syndrome associated giant cell lesions of the jaw; hopefully guiding ideal timing when installing treatment strategies in the future.

Neurofibromatosis Type 1 With Cherubism-like Phenotype, Multiple Osteolytic Bone Lesions of Lower Extremities, and Alagille-syndrome: Case Report With Literature Survey

BACKGROUND/AIM

Neurofibromatosis type 1 (NF) is an autosomal dominant hereditary disease. The cardinal clinical findings include characteristic skeletal alterations. Difficulties in diagnosis and therapy can arise if an individual has further illnesses.

CASE REPORT

This is a case report of a 16-year-old patient affected by NF1. She also suffered from Alagille syndrome and the consequences of fetal alcohol exposure. The patient's facial phenotype showed findings that could be assigned to one or more of the known diseases. The patient was referred for treating a cherubism-like recurrent central giant cell granuloma (CGCG) of the jaw. The patient developed bilateral, multilocular non-ossifying fibromas (NOF) of the long bones of the lower extremity. Treatment of the skeletal lesions consisted of local curettage. While NOF regressed after surgery, the CGCG of the jaw remained largely unchanged. Extensive genetic tests confirmed a previously unknown germline mutation in the JAG1 gene, the germline mutation of the NF1 gene, and the somatic mutation in the NF1 gene in the diffuse plexiform neurofibroma, but not in the CGCG.

CONCLUSION

Assigning facial findings to a defined syndrome is ambiguous in many cases and especially difficult in patients who have multiple diseases that can affect the facial phenotype. Surgical therapy should be adapted to the individual findings.

Cherubism: a systematic literature review of clinical and molecular aspects

The purpose of this review was to integrate the clinical, radiological, microscopic, and molecular data of published cherubism cases, in addition to therapeutic approaches, to provide more concise information about the disease. An electronic search was undertaken in September 2019. Eligibility criteria included publications having enough clinical, radiological, and histological information to confirm the diagnosis. A total of 260 publications reporting 513 cherubism cases were included. Familial history was observed in 310/458 cases (67.7%). SH3BP2 mutations were reported in 101/108 cases (93.5%) and mainly occurred at protein residues 415, 418, 419, and 420. Retrospective clinical grading was possible in 175 cases. Advanced clinical grading was associated with tooth agenesis, but not with other clinical, radiological, and genetic features. Specific amino acid substitutions of SH3BP2 mutations were not associated with the clinical grading of the disease. 'Wait and see' was the most common therapeutic approach. In a small number of cases, drugs were used in the treatment, with variable response. In conclusion, there is no clear correlation between the genotype and the phenotype of the disease, but additional genomic and gene expression regulation information is necessary for a better understanding of cherubism.

Unusual Characteristics and Variable Expressivity in a Brazilian Family with Cherubism

Cherubism is a rare genetic condition characterized by a bone nonneoplastic disease. We aimed to report a 6-year-old girl with cherubism presenting similar cases in the maternal family. However, her mother and grandmother seemed to be asymptomatic. The patient had an enlarged and asymmetric jaw with multiple enlarged cervical lymph nodes that increased in size with time. Sanger sequencing revealed a heterozygous mutation in exon 9 of SH3BP2 not only in the patient but also in her mother. Thus, we observed a variable expression and a probably reduced penetrance within the family, as well as unusual characteristics of the patient (in this case, the asymmetrical involvement of the jaw).