G(s)alpha mutations in fibrous dysplasia and McCune-Albright syndrome

Wnt pathway inhibition with the porcupine inhibitor LGK974 decreases trabecular bone but not fibrosis in a murine model with fibrotic bone

G protein-coupled receptors (GPCRs) mediate a wide spectrum of physiological functions, including the development, remodeling, and repair of the skeleton. Fibrous dysplasia (FD) of the bone is characterized by fibrotic, expansile bone lesions caused by activating mutations in GNAS. There are no effective therapies for FD. We previously showed that ColI(2.3)+/Rs1+ mice, in which Gs-GPCR signaling was hyper-activated in osteoblastic cell lineages using an engineered receptor strategy, developed a fibrotic bone phenotype with trabecularization that could be reversed by normalizing Gs-GPCR signaling, suggesting that targeting the Gs-GPCR or components of the downstream signaling pathway could serve as a promising therapeutic strategy for FD. The Wnt signaling pathway has been implicated in the pathogenesis of FD-like bone, but the specific Wnts and which cells produce them remain largely unknown. Single-cell RNA sequencing on long-bone stromal cells of 9-wk-old male ColI(2.3)+/Rs1+ mice and littermate controls showed that fibroblastic stromal cells in ColI(2.3)+/Rs1+ mice were expanded. Multiple Wnt ligands were up- or downregulated in different cellular populations, including in non-osteoblastic cells. Treatment with the porcupine inhibitor LGK974, which blocks Wnt signaling broadly, induced partial resorption of the trabecular bone in the femurs of ColI(2.3)+/Rs1+ mice, but no significant changes in the craniofacial skeleton. Bone fibrosis remained evident after treatment. Notably, LGK974 caused significant bone loss in control mice. These results provide new insights into the role of Wnt and Gs-signaling in fibrosis and bone formation in a mouse model of Gs-GPCR pathway overactivation.

A Rare Case of Monostotic Fibrous Dysplasia of the Femoral Neck With Pathological Fracture: A Case Report

Fibrous dysplasia is a rare benign bone disorder characterized by the replacement of normal bone with fibroblastic and osteoblastic tissue. We present a case of monostotic fibrous dysplasia in a 25-year-old male patient. The case highlights the clinical presentation, radiographic features, and management approach for this condition. This report aims to contribute to the understanding of fibrous dysplasia and its management options. A 25-year-old male presented with a chief complaint of persistent left hip pain. The pain was described as a dull ache, associated with difficulty in weight-bearing activities. There was no history of trauma or constitutional symptoms. Physical examination revealed externally rotated left lower limb. Range of motion of the left hip could not be assessed due to pain, with no neurological deficits noted. Initial imaging included plain radiographs of the right femur, which demonstrated a radiolucent lesion with a ground-glass appearance and cortical thinning. Magnetic resonance imaging of both hip joints reveals an irregular T2 hyperintense and T1 hypointense lesion involving the left femoral neck; moreover, few tiny cystic spaces are seen within the lesion. Part of the lesion is extending into the superior-lateral aspect of the femoral head and surrounding bone marrow edema with minimal left hip joint effusion, features suggestive of a primary bony tumour. Plain computed tomography (CT) of the hip joint and pelvis was suggestive of an expansile lytic lesion with thin bony septation within and thick sclerotic margin in the left femoral head and greater trochanter associated with sub-capital femoral neck fracture suggestive of bone neoplasm (? giant cell tumour > simple bone cyst). A bone biopsy was performed, and histopathological examination confirmed the diagnosis of fibrous dysplasia, with characteristic woven bone and fibrous stroma. In this case, after confirming the diagnosis, the patient was managed with total hip arthroplasty on the left side. Monostotic fibrous dysplasia is a rare benign bone disorder that can present with various clinical manifestations. Timely diagnosis through a combination of clinical, radiographic, and histopathological assessments is crucial. Management should be tailored to the patient's symptoms.

A Rare Skeletal Disorder, Fibrous Dysplasia: A Review of Its Pathogenesis and Therapeutic Prospects

Fibrous dysplasia (FD) is a rare, non-hereditary skeletal disorder characterized by its chronic course of non-neoplastic fibrous tissue buildup in place of healthy bone. A myriad of factors have been associated with its onset and progression. Perturbation of cell-cell signaling networks and response outputs leading to disrupted building blocks, incoherent multi-level organization, and loss of rigid structural motifs in mineralized tissues are factors that have been identified to participate in FD induction. In more recent years, novel insights into the unique biology of FD are transforming our understandings of its pathology, natural discourse of the disease, and treatment prospects. Herein, we built upon existing knowledge with recent findings to review clinical, etiologic, and histological features of FD and discussed known and potential mechanisms underlying FD manifestations. Subsequently, we ended on a note of optimism by highlighting emerging therapeutic approaches aimed at either halting or ameliorating disease progression.

Current concepts of craniofacial fibrous dysplasia: pathophysiology and treatment

Fibrous dysplasia is an uncommon genetic disorder in which bone is replaced by immature bone and fibrous tissue, manifesting as slowgrowing lesions. Sporadic post-zygotic activating mutations in GNAS gene result in dysregulated GαS-protein signaling and elevation of cyclic adenosine monophosphate in affected tissues. This condition has a broad clinical spectrum, ranging from insignificant solitary lesions to severe disease. The craniofacial area is the most common site of fibrous dysplasia, and nine out of 10 patients with fibrous dysplasia affecting the craniofacial bones present before the age of 5. Surgery is the mainstay of treatment, but the technique varies according to the location and severity of the lesion and associated symptoms. The timing and indications of surgery should be carefully chosen with multidisciplinary consultations and a patient-specific approach.

Structural and Functional Implication of Natural Variants of Gαs

Heterotrimeric guanine nucleotide-binding proteins (G proteins) are among the most important cellular signaling components, especially G protein-coupled receptors (GPCRs). G proteins comprise three subunits, Gα, Gβ, and Gγ. Gα is the key subunit, and its structural state regulates the active status of G proteins. Interaction of guanosine diphosphate (GDP) or guanosine triphosphate (GTP) with Gα switches G protein into basal or active states, respectively. Genetic alteration in Gα could be responsible for the development of various diseases due to its critical role in cell signaling. Specifically, loss-of-function mutations of Gαs are associated with parathyroid hormone-resistant syndrome such as inactivating parathyroid hormone/parathyroid hormone-related peptide (PTH/PTHrP) signaling disorders (iPPSDs), whereas gain-of-function mutations of Gαs are associated with McCune-Albright syndrome and tumor development. In the present study, we analyzed the structural and functional implications of natural variants of the Gαs subtype observed in iPPSDs. Although a few tested natural variants did not alter the structure and function of Gαs, others induced drastic conformational changes in Gαs, resulting in improper folding and aggregation of the proteins. Other natural variants induced only mild conformational changes but altered the GDP/GTP exchange kinetics. Therefore, the results shed light on the relationship between natural variants of Gα and iPPSDs.

Hyperfunctioning parathyroid gland and skeletal involvement on [18F]fluorocholine PET/CT: one look with two views

Hyperparathyroidism is an endocrine disorder that may be associated with other metabolic diseases. Non-invasive imaging techniques including [^99mTc]Tc-sestamibi single-photon emission computed tomography (SPECT) and [¹⁸F]fluorocholine positron emission tomography (PET)/computed tomography (CT) play a key role on management of patients with hyperparathyroidism. We report for the first time a case of a patient with evidence of both hyperfunctioning parathyroid tissue and multiple lytic bone lesions on [¹⁸F]fluorocholine PET/CT imaging. The present case report highlights the potential role of whole-body [¹⁸F]fluorocholine PET/CT for the identification of both parathyroid adenoma and multiple bone lesions in a single diagnostic setting.

Inhibition of IL-6 in the treatment of fibrous dysplasia of bone: The randomized double-blind placebo-controlled TOCIDYS trial

Increased interleukin-6 (IL-6) has been observed in the bone tissue of fibrous dysplasia of bone/McCune-Albright syndrome (FD/MAS) and is possibly involved in the increased bone destruction and bone pain characterizing this disease. The TOCIDYS trial was a randomized, placebo-controlled, 1 year, cross-over, proof-of-concept trial, conducted in patients not responding to bisphosphonates, using monthly intra-venous tocilizumab (a monoclonal antibody to the IL-6 receptor) at 8 mg/kg or a matching placebo for 6 months. Over the following 6 months, they received tocilizumab if they first had placebo, and vice-versa. We measured change in serum CTX after 6 months of treatment, compared with baseline (primary endpoint). Other endpoints were the change in bone pain, change in P1NP, bone alkaline phosphatase, osteocalcin and ICTP, and variation of quality of life. The analysis relied on ANOVA, with sequence of treatment, period and treatment as factors and accounting for a potential carry-over effect. We have randomized 8 patients with FD/MAS in each sequence who all completed the first 6 months treatment period. During the second 6 months period, 3 patients stopped therapy, so the efficacy analysis set included 13 patients. We observed no significant change in serum CTX and other biochemical markers of bone turnover between the tocilizumab and placebo groups. There was no significant change in the level of bone pain on tocilizumab, although 3 patients had a sharp decrease in pain while on active drug, with progressive relapse on placebo for 2 of them, but with some degree of improvement in a few patients while on placebo. The SF-36 quality of life scale was not significantly changed. We conclude that tocilizumab does not decrease bone turnover in FD/MAS when administered in patients who fail to respond to bisphosphonates. Tocilizumab does not reduce bone pain in most patients, but a substantial effect in a subset cannot be ruled out in this trial powered for markers but not for pain.

Coexistence of craniopharyngioma and cranial fibrous dysplasia: a case series of clinicopathological study

Background

Craniopharyngioma (CP) and cranial fibrous dysplasia (CFD) are rare embryonic benign cranial diseases that most commonly present during childhood or adolescence. The coexistence of CP and CFD is extremely rare and has not yet been reported.

Methods

We retrospectively reviewed the data of five patients with concomitant CP and CFD treated at Beijing Tiantan Hospital from January 2003 to January 2021 and summarized their clinicopathological features, treatment modalities, and outcomes. We also performed a comprehensive literature review, tested the patients for characteristic GNAS gene mutations related to CFD, and tested the CP specimens for corresponding Gsα protein to explore the potential connection leading to the coexistence of CP and CFD.

Results

The cohort comprised four men and one woman (median age, 39 years). The symptoms mainly included headache, dizziness, fatigue, polyuria/polydipsia, hypogonadism, and blurred vision. CFD most commonly involved the sphenoid bone (n = 4). Four patients underwent surgery to remove the CP (one trans-sphenoidal and three transcranial resections); complete and subtotal resection were achieved in two patients, respectively. The tumor subtype was adamantinomatous in three patients and unknown in one. The common postoperative complications were panhypopituitarism, diabetes insipidus, and hypothyroidism. The mean follow-up duration was 57.2 months. Two patients required postoperative hormone replacement therapy. Three patients underwent genetic study of the tumor specimens; GNAS mutations were not detected, but these patients were positive for Gsα protein.

Conclusions

Although a definite causative relationship has not been proved, the coexistence of CP and CFD means that potential interplay or an atypical fibrous dysplasia course as uncommon manifestations of CP cannot be excluded. It is more challenging to initiate prompt diagnosis and appropriate treatment for concomitant CP and CFD than for solitary CP because of skull base deformations. Current management strategies are aimed at surgical treating the CP and regularly monitoring the CFD.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13023-022-02281-1.

Fibrous dysplasia animal models: A systematic review

BACKGROUND

Fibrous dysplasia (FD) is a rare genetic bone disorder resulting in an overproduction of cAMP leading to a structurally unsound tissue, caused by a genetic mutation in the guanine nucleotide-binding protein gene (GNAS). In order to better understand this disease, several animal models have been developed with different strategies and features.

OBJECTIVE

Conduct a systematic review to analyze and compare animal models with the causative mutation and features of FD.

METHODS

A PRISMA search was conducted in Scopus, PubMed, and Web of Science. Studies reporting an in vivo model of FD that expressed the causative mutation were included for analysis. Models without the causative mutation, but developed an FD phenotype and models of FD cell implantation were included for subanalysis.

RESULTS

Seven unique models were identified. The models were assessed and compared for their face validity, construct validity, mosaicism, and induction methods. This was based on the features of clinical FD that were reported within the categories of: macroscopic features, imaging, histology and histomorphometry, histochemical and cellular markers, and blood/urine markers.

LIMITATIONS

None of the models reported all features of FD and some features were only reported in one model. This made comparing models a challenge, but indicates areas where further research is necessary.

CONCLUSION

The benefits and disadvantages of every model were assessed from a practical and scientific standpoint. While all published reports lacked complete data, the models have nonetheless informed our understanding of FD and provided meaningful information to guide researchers in bench and clinical research.

Co-existing of craniofacial fibrous dysplasia and cerebrovascular diseases: a series of 22 cases and review of the literature

Background

Craniofacial fibrous dysplasia is a fairly rare condition. Some literature have reported a few patients with craniofacial fibrous dysplasia suffering from vascular abnormalities. This study aimed to describe the possible coexistence of craniofacial fibrous dysplasia and cerebrovascular diseases for the first time.

Method

We retrospectively reviewed the 1175 patients with craniofacial fibrous dysplasia in Beijing Tiantan Hospital and the information of the 22 patients coexisted with cerebrovascular diseases were described. In addition, we performed a systematic review for cases of craniofacial fibrous dysplasia with vascular abnormalities.

Result

22 out of 1175 patients (1.9%) were diagnosed with craniofacial fibrous dysplasia and cerebrovascular diseases including 9 intracranial aneurysms, 4 venous malformations, 2 arteriovenous malformations, 1 moyamoya disease, 2 intracranial venous stenosis and 4 cerebral ischemia with a mean age of 38.18 years old. Only 2 patients were managed surgically for craniofacial fibrous dysplasia and 6 patients were treated with neurosurgery for cerebrovascular diseases. 8 patients were closely followed and only 1 patient’s symptoms worsened.

Conclusion

Craniofacial fibrous dysplasia might cause constriction of the intracranial vessels and alteration of the overall hemodynamics of the intracranial vasculature resulting in various cerebrovascular diseases. Multimodal screening and examinations seems reasonable for patients with craniofacial fibrous dysplasia for throughout treatment and prognosis evaluations.

Could the burden of pancreatic cancer originate in childhood?

The presence of pancreatic cancer during childhood is extremely rare, and physicians may be tempted to overlook this diagnosis based on age criteria. However, there are primary malignant pancreatic tumors encountered in pediatric patients, such as pancreatoblastoma, and tumors considered benign in general but may present a malignant potential, such as the solid pseudo-papillary tumor, insulinoma, gastrinoma, and vasoactive intestinal peptide secreting tumor. Their early diagnosis and management are of paramount importance since the survival rates tend to differ for various types of these conditions. Many pediatric cancers may present pancreatic metastases, such as renal cell carcinoma, which may evolve with pancreatic metastatic disease even after two or more decades. Several childhood diseases may create a predisposition for the development of pancreatic cancer during adulthood; hence, there is a need for extensive screening strategies and complex programs to facilitate the transition from pediatric to adult healthcare. Nevertheless, genetic studies highlight the fact the specific gene mutations and family aggregations may be correlated with a special predisposition towards pancreatic cancer. This review aims to report the main pancreatic cancers diagnosed during childhood, the most important childhood diseases predisposing to the development of pancreatic malignancies, and the gene mutations associates with pancreatic malignant tumors.

Rare Diseases of the Middle Ear and Lateral Skull Base

Otalgia, otorrhea and hearing loss are the most common ear-related symptoms that lead to the consultation of an otolaryngologist. Furthermore, balance disorders and affections of the cranial nerve function may play a role in the consultation. In large academic centres, but also in primary care, the identification of rare diseases of the middle ear and the lateral skull base is essential, as these diseases often require interdisciplinary approaches to establish the correct diagnosis and to initiate safe and adequate treatments. This review provides an overview of rare bone, neoplastic, haematological, autoimmunological and infectious disorders as well as malformations that may manifest in the middle ear and the lateral skull base. Knowledge of rare disorders is an essential factor ensuring the quality of patient care, in particular surgical procedures. Notably, in untypical, complicated, and prolonged disease courses, rare differential diagnoses need to be considered.

Bisphosphonates for the treatment of fibrous dysplasia of bone

INTRODUCTION

Fibrous dysplasia of bone (FD) is a rare congenital bone disease, due to a somatic mutation of GNAS. This mutation results in a defect of osteoblast differentiation and mineralization and also an increase in bone resorption by large active osteoclasts. Bone pain is present in half of patients and is the main determinant of quality of life of patients with FD. Bisphosphonates are known to reduce bone pain and reduce the risk of fracture in patients with bone metastases or Paget's disease. Bisphosphonates may have similar effects in FD. In this article, we have reviewed the therapeutic potential of bisphosphonates to reduce bone pain due to FD, improve bone strength and reduce the occurrence of fracture.

MATERIAL AND METHODS

We have reviewed 234 articles examining the effect of bisphosphonates on FD/McCune Albright Syndrome with no date limit, in PubMed and selected the articles with highest quality of methodology.

RESULTS

Pamidronate therapy significantly decreased bone pain and bone resorption (urinary NTX, urinary and serum CTX). Pamidronate may improve radiological lesions of FD patients (filling of osteolytic lesion and/or cortical thickening). This data with intravenous pamidronate, however, has been obtained from observational studies and no randomized controlled trial is available. Randomized placebo-controlled trials of oral bisphosphonates (alendronate or risedronate) have failed to demonstrate a significant decrease in bone pain over placebo. Several studies including one randomized controlled trial have shown an increase in bone mineral density (BMD) at FD sites with oral and intravenous bisphosphonate treatment. No effect on occurrence of fracture has been reported.

CONCLUSION

In conclusion, intravenous bisphosphonates may be proposed to treat persistent, moderate to severe bone pain of FD, e.g., according to the guidelines from the FD/MAS International Consortium. Oral bisphosphonates should not be used in this indication.

A Signature of Circulating miRNAs Associated With Fibrous Dysplasia of Bone: the mirDys Study

Fibrous dysplasia (FD) is a rare bone disease caused by activating mutations of GNAS encoding the Gsα protein, enhancing cyclic adenosine monophosphate (cAMP) production by overstimulation of adenylyl cyclase and impairing osteoblastic differentiation. The clinical presentation ranges from asymptomatic to polyostotic forms with severe disability, explained by the mosaic distribution of the GNAS mutation. Physicians have to deal with the gap of knowledge in FD pathogenesis, the absence of prognostic markers and the lack of specific treatment. The identification of specific biomarkers for FD is an important step to improve the clinical and therapeutic approaches. An epigenetic regulation driven by microRNAs (miRNAs), known as promising biomarkers in bone disease, could be involved in FD. We have sought circulating miRNAs that are differentially expressed in FD patients compared to controls and would reflect dysregulations of osteogenesis-related genes and bone disorder. The global miRNA profiling was performed using Next Generation Sequencing in patient serum collected from a discovery cohort of 20 patients (10 polyostotic and 10 monostotic) and 10 controls. From these, we selected 19 miRNAs for a miRNA validation phase from serum of 82 patients and 82 controls, using real-time qPCR. Discovery screening identified 111 miRNAs differentially expressed in patient serum, after adjusting for the false discovery rate (FDR). Among the 82 patients, 55% were polyostotic, and 73% were women with a mean age of 42 years. Six miRNAs (miR-25-3p, miR-93-5p, miR-182-5p, miR-324-5p, miR-363-3p, and miR-451a) were significantly overexpressed in serum, with FDR <0.05. The expression level of these six miRNAs was not associated with the FD severity. In conclusion, we identified a signature of circulating miRNAs associated with FD. These miRNAs are potential negative regulators of gene expression in bone cell progenitors, suggesting their activity in FD by interfering with osteoblastic and osteoclastic differentiation to impair bone mineralization and remodeling processes. © 2020 American Society for Bone and Mineral Research.

PET Imaging of Phosphodiesterase-4 Identifies Affected Dysplastic Bone in McCune-Albright Syndrome, a Genetic Mosaic Disorder

McCune-Albright syndrome (MAS) is a mosaic disorder arising from gain-of-function mutations in the GNAS gene, which encodes the 3',5'-cyclic adenosine monophosphate (cAMP) pathway-associated G-protein, G_sα. Clinical manifestations of MAS in a given individual, including fibrous dysplasia, are determined by the timing and location of the GNAS mutation during embryogenesis, the tissues involved, and the role of G_sα in the affected tissues. The G_sα mutation results in dysregulation of the cAMP signaling cascade, leading to upregulation of phosphodiesterase type 4 (PDE4), which catalyzes the hydrolysis of cAMP. Increased cAMP levels have been found in vitro in both animal models of fibrous dysplasia and in cultured cells from individuals with MAS but not in humans with fibrous dysplasia. PET imaging of PDE4 with ¹¹C-(R)-rolipram has been used successfully to study the in vivo activity of the cAMP cascade. To date, it remains unknown whether fibrous dysplasia and other symptoms of MAS, including neuropsychiatric impairments, are associated with increased PDE4 activity in humans. Methods: ¹¹C-(R)-rolipram whole-body and brain PET scans were performed on 6 individuals with MAS (3 for brain scans and 6 for whole-body scans) and 9 healthy controls (7 for brain scans and 6 for whole-body scans). Results: ¹¹C-(R)-rolipram binding correlated with known locations of fibrous dysplasia in the periphery of individuals with MAS; no uptake was observed in the bones of healthy controls. In peripheral organs and the brain, no difference in ¹¹C-(R)-rolipram uptake was noted between participants with MAS and healthy controls. Conclusion: This study is the first to find evidence for increased cAMP activity in areas of fibrous dysplasia in vivo. No differences in brain uptake between MAS participants and controls were detected-a finding that could be due to several reasons, including the limited anatomic resolution of PET. Nevertheless, the results confirm the usefulness of PET scans with ¹¹C-(R)-rolipram to indirectly measure increased cAMP pathway activation in human disease.

Response to Zoledronic Acid Infusion in Children With Fibrous Dysplasia

Objective: This retrospective study evaluated the outcome and safety of long-term treatment with zoledronic acid, in both polyostotic and mono-ostotic fibrous dysplasia (FD) of children. Methods: The case records of children and adolescents with symptomatic FD who received zoledronic acid (0.1 mg/kg IV infusion over 1 h) and have completed at least 2 years follow-up were analyzed. The relevant details were recorded in a predesigned chart. Clinical assessment [pain assessment by visual analog scale (VAS) and incidence of new fracture], radiological changes (cortical thickening, ossification, and decrease in the diameter of the osteolytic lesions) and biochemical parameters [alkaline phosphatase (ALP)] were used to evaluate the improvement. Results: The mean age of presentation was 9.1 years, with four males and six females. All patients had symptomatic FD in the lower limb with complaints of pain, tenderness, swelling, or deformity. Four children had associated pathological fracture. The radiological evaluation with bone scan revealed polyostotic involvement in eight patients and mono-ostotic involvement in two patients. Three patients had associated systemic features like café-au-lait spots or precocious puberty. The fracture united within 3 months and the radiological improvement was evident in the form of filling of the osteolytic defect. The pain score in six patients showed significant improvement (VAS < 3). The ALP level decreased to 544.12 ± 47.35 IU/L from an initial value of 895.75 ± 79.64 IU/L (p = 0.04) at 12 months. One patient had symptomatic hypocalcaemia after zoledronic acid infusion. Conclusion: The clinical and radiological response of zoledronic acid treatment in FD of children is promising. Further randomized control trials with a larger sample size are required to establish this drug as a first-line medical treatment in FD.

Auxological and Endocrinological Features in Children With McCune Albright Syndrome: A Review

McCune-Albright syndrome is a rare and challenging congenital sporadic disease involving the skin and skeletal and endocrine systems with a prevalence ranges from one in 100,000 to 1,000,000. In addition to the classical triad of fibrous dysplasia of bone, café au lait pigmented skin lesions and precocious puberty, other multiple endocrinological features, including hyperthyroidism, growth hormone excess, hypercortisolism, and hypophosphatemic rickets, have been reported. A brief review of the syndrome in children is here reported.

Craniofacial fibrous dysplasia associated with McCune-Albright syndrome: challenges in diagnosis and treatment: case reports

Background

McCune-Albright syndrome (MAS) is a rare multisystem disorder that classically was defined by the triad of polyostotic fibrous dysplasia of bone, café-au-lait skin pigmentation, and precocious puberty. It is a condition that has a gradual onset, slow growth rate and remain painless throughout. The clinical phenotype of MAS is highly variable and no definite treatment is available.

Case presentation

This article describes two cases, a 10-year-old girl and an 11-year-old boy, both with MAS comprising deforming craniofacial FD. Challenges related to diagnosis and management included late reporting with big lesions, involvement of multiple craniofacial bones, mutilating surgeries and ultimately high degree of morbidity.

Conclusion

Delayed diagnosis and management of MAS results in devastating physical disabilities and severe morbidity after treatment.

Serum periostin levels and severity of fibrous dysplasia of bone

Fibrous dysplasia of bone (FD) is a rare congenital bone disease, characterized by a fibrous component in the bone marrow. Periostin has been extensively researched because of its implication in various fibrotic or inflammatory diseases. Periostin may be associated with the burden or the severity of FD. The case control PERIOSDYS study aimed at assessing serum periostin levels in FD patients. Sixty four patients with monostotic or polyostotic disease were included, in order to evaluate whether the concentrations were greater in patients than in 128 healthy age, BMI and sex-matched controls and if they were more elevated in patients with the more severe phenotypes. We found that periostin levels were greater in patients with FD compared to controls (mean = 1085 vs 958 pmol/l, p = 0.026), especially in those with a history of fracture (mean = 1475 vs 966 pmol/l, p = 0.0005), polyostotic forms (mean = 1214 vs 955 pmol/l, p = 0.004) or McCune-Albright syndrome (mean = 1585 vs 1023 pmol/l, p = 0.0048). In contrast, high pain levels were not associated with periostin levels (mean = 1137 vs 1036 pmol/l, p = 0.445). Furthermore, patients undergoing bisphosphonate therapy had significantly lower levels than treatment naïve patients (mean = 953 vs 1370 pmol/l, p = 0.002). In conclusion, periostin may be a biochemical marker indicative of the most severe forms of FD and could be used to monitor patients treated with bisphosphonates.

Gαs signaling in skeletal development, homeostasis and diseases

Skeletal development is exquisitely controlled both spatially and temporally by cell signaling networks. Gα_s is the stimulatory α-subunit in a heterotrimeric G protein complex transducing the signaling of G-protein-coupled receptors (GPCRs), responsible for controlling both skeletal development and homeostasis. Gα_s, encoded by the GNAS gene in humans, plays critical roles in skeletal development and homeostasis by regulating commitment, differentiation and maturation of skeletal cells. Gα_s-mediated signaling interacts with the Wnt and Hedgehog signaling pathways, both crucial regulators of skeletal development, remodeling and injury repair. Genetic mutations that disrupt Gα_s functions cause human disorders with severe skeletal defects, such as fibrous dysplasia of bone and heterotopic bone formation. This chapter focuses on the crucial roles of Gα_s signaling during skeletal development and homeostasis, and the pathological mechanisms underlying skeletal diseases caused by GNAS mutations.

Clinical and Radiographic Gastrointestinal Abnormalities in McCune-Albright Syndrome

CONTEXT

McCune-Albright syndrome (MAS) is a rare disorder characterized by fibrous dysplasia of bone, café-au-lait macules, and hyperfunctioning endocrinopathies. It arises from somatic gain-of-function mutations in GNAS, which encodes the cAMP-regulating protein Gαs. Somatic GNAS mutations have been reported in intraductal papillary mucinous neoplasms (IPMNs) and various gastrointestinal (GI) tumors. The clinical spectrum and prevalence of MAS-associated GI disease is not well established.

OBJECTIVE

Define the spectrum and prevalence of MAS-associated GI pathology in a large cohort of patients with MAS.

DESIGN

Cross-sectional study.

SETTING

National Institutes of Health Clinical Center and The Johns Hopkins Hospital.

METHODS

Fifty-four consecutive subjects with MAS (28 males; age range, 7 to 67 years) were screened with magnetic resonance cholangiopancreatography (MRCP).

RESULTS

Thirty of 54 subjects (56%) had radiographic GI abnormalities. Twenty-five (46%) of the screened subjects had IPMNs (mean age of 35.1 years). Fourteen of the 25 had IPMNs alone, and 11 had IPMNs and abnormal hepatobiliary imaging. The 30 patients with MAS-associated GI pathology had a higher prevalence of acute pancreatitis, diabetes mellitus, and skeletal disease burden of fibrous dysplasia than patients without GI disease.

CONCLUSIONS

A broad spectrum of GI pathology is associated with MAS. IPMNs are common and occur at a younger age than in the general population. Patients with MAS should be considered for screening with a focused GI history and baseline MRCP. Further determination of the natural history and malignant potential of IPMNs in MAS is needed.

Phosphate homeostasis disorders

Our understanding of the regulation of phosphate balance has benefited tremendously from the molecular identification and characterization of genetic defects leading to a number of rare inherited or acquired disorders affecting phosphate homeostasis. The identification of the key phosphate-regulating hormone, fibroblast growth factor 23 (FGF23), as well as other molecules that control its production, such as the glycosyltransferase GALNT3, the endopeptidase PHEX, and the matrix protein DMP1, and molecules that function as downstream effectors of FGF23 such as the longevity factor Klotho and the phosphate transporters NPT2a and NPT2c, has permitted us to understand the complex interplay that exists between the kidneys, bone, parathyroid, and gut. Such insights from genetic disorders have allowed not only the design of potent targeted treatment of FGF23-dependent hypophosphatemic conditions, but also provide clinically relevant observations related to the dysregulation of mineral ion homeostasis in health and disease.

Constitutive stimulatory G protein activity in limb mesenchyme impairs bone growth

GNAS mutations leading to constitutively active stimulatory G protein alpha-subunit (Gsα) cause different tumors, fibrous dysplasia of bone, and McCune-Albright syndrome, which are typically not associated with short stature. Enhanced signaling of the parathyroid hormone/parathyroid hormone-related peptide receptor, which couples to multiple G proteins including Gsα, leads to short bones with delayed endochondral ossification. It has remained unknown whether constitutive Gsα activity also impairs bone growth. Here we generated mice expressing a constitutively active Gsα mutant (Gsα-R201H) conditionally upon Cre recombinase (cGsα^R201H mice). Gsα-R201H was expressed in cultured bone marrow stromal cells from cGsα^R201H mice upon adenoviral-Cre transduction. When crossed with mice in which Cre is expressed in a tamoxifen-regulatable fashion (CAGGCre-ER™), tamoxifen injection resulted in mosaic expression of the transgene in double mutant offspring. We then crossed the cGsα^R201H mice with Prx1-Cre mice, in which Cre is expressed in early limb-bud mesenchyme. The double mutant offspring displayed short limbs at birth, with narrow hypertrophic chondrocyte zones in growth plates and delayed formation of secondary ossification center. Consistent with enhanced Gsα signaling, bone marrow stromal cells from these mice demonstrated increased levels of c-fos mRNA. Our findings indicate that constitutive Gsα activity during limb development disrupts endochondral ossification and bone growth. Given that Gsα haploinsufficiency also leads to short bones, as in patients with Albright's hereditary osteodystrophy, these results suggest that a tight control of Gsα activity is essential for normal growth plate physiology.

GNAS mutations and heterotopic ossification

GNAS is a complex imprinted gene encoding the alpha-subunit of the stimulatory heterotrimeric G protein (Gsα). GNAS gives rise to additional gene products that exhibit exclusively maternal or paternal expression, such as XLαs, a large variant of Gsα that shows exclusively paternal expression and is partly identical to the latter. Gsα itself is expressed biallelically in most tissues, although the expression occurs predominantly from the maternal allele in a small set of tissues, such as renal proximal tubules. Inactivating mutations in Gsα-coding GNAS exons are responsible for Albright's hereditary osteodystrophy (AHO), which refers to a constellation of physical and developmental disorders including obesity, short stature, brachydactyly, cognitive impairment, and heterotopic ossification. Patients with Gsα mutations can present with AHO in the presence or absence of end-organ resistance to multiple hormones including parathyroid hormone. Maternal Gsα mutations lead to AHO with hormone resistance (i.e. pseudohypoparathyroidism type-Ia), whereas paternal mutations cause AHO alone (i.e. pseudo-pseudohypoparathyroidism). Heterotopic ossification associated with AHO develops through intramembranous bone formation and is limited to dermis and subcutis. In rare cases carrying Gsα mutations, however, ossifications progress into deep connective tissue and skeletal muscle, a disorder termed progressive osseous heteroplasia (POH). Here I briefly review the genetic, clinical, and molecular aspects of these disorders caused by inactivating GNAS mutations, with particular emphasis on heterotopic ossification.

Treatment of precocious puberty in a McCune–Albright syndrome patient using Chinese medicinal herbs combined with megestrol acetate: A case report

Introduction: McCune–Albright Syndrome (MAS) is a rare congenital sporadic disorder characterized by fibrous bone dysplasia, café-au-lait pigmented spots on the skin, and non-gonadotropin dependent precocious puberty (PP), which is caused by a postzygotic somatic activating mutation in the GNAS gene encoding the alpha subunit of Gs protein. In our case study, we recorded a girl with the onset of MAS and treated her with Chinese medicinal herbs combined with megestrol acetate. We aim to provide a method for the treatment of children with this rare form of precocious puberty.

Case Presention: A 4-year-old girl presented with vaginal bleeding and enlarged breasts. The activating mutation of GNAS was not detected in the patient’s peripheral blood samples, as some had reported. Because of peripheral PP and fibrous dysplasia of the diagnosed bone, the patient was considered as MAS. We chose the Chinese medicinal herbs combined with megestrol acetate for treatment, and the patient was effectively treated.

Conclusion: The combination therapy of Chinese medicinal herbs plus megestrol acetate in managing PP in an MAS is one of the useful treatments.

Acute development of cortical porosity and endosteal naïve bone formation from the daily but not weekly short-term administration of PTH in rabbit

Teriparatide [human parathyroid hormone (1–34)], which exerts an anabolic effect on bone, is used for the treatment of osteoporosis in patients who are at a high risk for fracture. That the once-daily administration of teriparatide causes an increase in cortical porosity in animal models and clinical studies has been a matter of concern. However, it is not well documented that the frequency of administration and/or the total dose of teriparatide affect the cortical porosity. The present study developed 4 teriparatide regimens [20 μg/kg/day (D20), 40 μg/kg/day (D40), 140 μg/kg/week (W140) and 280 μg/kg/week (W280)] in the rabbit as a model animal with a well-developed Haversian system and osteons. The total weekly doses were equivalent in the low-dose groups (D20 and W140) and in the high-dose groups (D40 and W280). After the short-term (1 month) administration of TPDT, micro-CT, histomorphometry and three-dimensional second harmonic generation (3D-SHG) imaging to visualize the bone collagen demonstrated that daily regimens but not weekly regimens were associated with the significant development of cortical porosity and endosteal naïve bone formation by marrow fibrosis. We concomitantly monitored the pharmacokinetics of the plasma teriparatide levels as well as the temporal changes in markers of bone formation and resorption. The analyses in the present study suggested that the daily repeated administration of teriparatide causes more deleterious changes in the cortical microarchitecture than the less frequent administration of higher doses. The findings of the present study may have some implications for use of teriparatide in clinical treatment.

Pro-fibrotic effects of PFKFB4-mediated glycolytic reprogramming in fibrous dysplasia

Fibrous dysplasia (FD) caused by a mosaic somatic mutation of GNAS is characterized by replacement of the affected bone with abnormal fibrous tissue. Herein, we present novel disease models for FD developed with pairs of isogenic wild-type and GNAS(R201H)-mutated induced pluripotent stem cells (iPSCs) and their derivative mesenchymal stem cells (MSCs). Both 2D and 3D MSC culture models for FD successfully reflect FD's typical molecular characteristics, such as enhanced cAMP level, PKA activity, CREB1 phosphorylation and the pathologic fibrotic phenotype. The fibrotic features of GNAS(R201H) FD model cells were closely linked to augmented glycolysis and depended on glycolytic PFKFB4 and the activation of pro-fibrotic TGFβ signalling. Either depletion of PFKFB4 or inhibition of glycolysis or TGFβ signalling potentially blocked fibrosis progression in GNAS(R201H) FD model cells. Our FD models could facilitate a better mechanistic understanding of FD and help develop effective therapeutics for FD and other fibrosis diseases.

Clinical and endocrine characteristics and genetic analysis of Korean children with McCune-Albright syndrome: a retrospective cohort study

Background

McCune–Albright syndrome (MAS) is a rare disease defined by the triad of fibrous dysplasia (FD), café au lait spots, and peripheral precocious puberty (PP). Because of the rarity of this disease, only a few individuals with MAS have been reported in Korea. We describe the various clinical and endocrine manifestations and genetic analysis of 14 patients with MAS in Korea.

Methods

Patients’ clinical data—including peripheral PP, FD, and other endocrine problems—were reviewed retrospectively. In addition, treatment experiences of letrozole in five patients with peripheral PP were described. Mutant enrichment with 3′-modified oligonucleotides - polymerase chain reaction (MEMO-PCR) was performed on eight patients to detect mutation in GNAS using blood. MEMO-PCR is a simple and practical method that enables the nondestructive selection and enrichment of minor mutant alleles in blood.

Results

The median age at diagnosis was 5 years 2 months (range: 18 months to 16 years). Eleven patients were female, and three were male. Thirteen patients showed FD. All female patients showed peripheral PP at onset, and three patients subsequently developed central PP. There was a significant decrease in estradiol levels after two years of letrozole treatment. However, bone age was advanced in four patients. Two patients had clinical hyperthyroidism, and two patients had growth hormone (GH) excess with pituitary microadenoma. c.602G > A (p.Arg201His) in GNAS was detected in two patients in blood, and c.601C > T (p.Arg201Cys) in GNAS was detected in one patient in pituitary adenoma.

Conclusions

This study described the various clinical manifestations of 14 patients with MAS in a single center in Korea. This study first applied MEMO-PCR on MAS patients to detect GNAS mutation. Because a broad spectrum of endocrine manifestations could be found in MAS, multiple endocrinopathies should be monitored in MAS patients. Better treatment options for peripheral PP with MAS are needed.

Diagnosis and management of benign fibro-osseous lesions of the jaws: a current review for the dental clinician

Benign fibro-osseous lesions of the maxillofacial skeleton constitute a heterogeneous group of disorders that includes developmental, reactive (dysplastic) and neoplastic lesions. Although their classification has been reviewed multiple times in the past, the most common benign fibro-osseous lesions are fibrous dysplasia, osseous dysplasia and ossifying fibroma. For the dental clinician, the challenges involve diagnosis and treatment (or lack thereof). A careful correlation of all clinical, radiologic and microscopic features is essential to establish a proper diagnosis and a clear treatment plan. This article aimed to review the clinical, radiologic and histopathologic characteristics of benign fibro-osseous lesions of the jaws, with emphasis on their differential diagnoses. With a deeper understanding of benign fibro-osseous lesions, clinicians will be better prepared to manage these lesions in their practice.

Bone marrow fibrosis with fibrocytic and immunoregulatory responses induced by β-catenin activation in osteoprogenitors

Wnt/β-catenin signaling has been reported to contribute to the development of bone fibrous dysplasia. However, it remains unclear whether fibrocytes and immune cells are involved in this β-catenin-mediated bone marrow fibrosis. In this study, we showed that constitutive activation of β-catenin by Col1a1-Cre (3.6-kb) exhibited bone marrow fibrosis, featured with expanded populations of fibrocytes, myofibroblasts and osteoprogenitors. Lineage tracing and IHC examinations showed that Col3.6-Cre display Cre recombinase activity not only in osteoprogenitors, but also in monocyte-derived fibrocytes in the endosteal niches of bones. Additionally, β-catenin stimulated the secretion of cytokines and pro-fibrotic signals in bone marrow, including GM-CSF, TGFβ1 and VEGF. Consequently, the frequency of differentiated immature monocyte-derived dendritic cells and naïve T cells was markedly increased in the mutant bone marrow. These phenotypes were quite different from those following β-catenin activation in mature osteoblasts driven by Col1a1-Cre (2.3-kb). Our findings suggested that a conserved pro-fibrotic signal cascade might underlie β-catenin-mediated bone marrow fibrosis, involving TGFβ1-enhanced fibrocyte activation and immunoregulatory responses. This study might shed new light on the understanding and development of a therapeutic strategy for bone fibrous dysplasia.

Activation of Protein Kinase A in Mature Osteoblasts Promotes a Major Bone Anabolic Response

Protein kinase A (PKA) regulates osteoblast cell function in vitro and is activated by important bone mass modulating agents. We determined whether PKA activation in osteoblasts is sufficient to mediate a bone anabolic response. Thus, a mouse model conditionally expressing a constitutively active PKA (CA-PKA) in osteoblasts (CA-PKA-OB mouse) was developed by crossing a 2.3-kb α1 (I)-collagen promoter-Cre mouse with a floxed-CA-PKA mouse. Primary osteoblasts from the CA-PKA-OB mice exhibited higher basal PKA activity than those from control mice. Microcomputed tomographic analysis revealed that CA-PKA-OB female mice had an 8.6-fold increase in femoral but only 1.16-fold increase in lumbar 5 vertebral bone volume/total volume. Femur cortical thickness and volume were also higher in the CA-PKA-OB mice. In contrast, alterations in many femoral microcomputed tomographic parameters in male CA-PKA-OB mice were modest. Interestingly, the 3-dimensional structure model index was substantially lower both in femur and lumbar 5 of male and female CA-PKA-OB mice, reflecting an increase in the plate to rod-like structure ratio. In agreement, femurs from female CA-PKA-OB mice had greater load to failure and were stiffer compared with those of control mice. Furthermore, the CA-PKA-OB mice had higher levels of serum bone turnover markers and increased osteoblast and osteoclast numbers per total tissue area compared with control animals. In summary, constitutive activation of PKA in osteoblasts is sufficient to increase bone mass and favorably modify bone architecture and improve mechanical properties. PKA activation in mature osteoblasts is, therefore, an important target for designing anabolic drugs for treating diseases with bone loss.

Benign Fibro-Osseous Lesions of the Jaws

Fibro-osseous lesions are grouped together because histologically they show similar cellular and mineralization patterns. Despite the histologic ubiquity, their behaviors vary significantly. Because of the histologic similarity and the broad range of morbidity among them, it is important to be able to differentiate between them in the preliminary diagnostic process. The radiographic presentations along with the location of the bony changes are often extremely critical diagnostic features to help render a differential or working diagnosis in lieu of an automatic biopsy procedure. Therefore the unique and specific radiographic presentations may be one of the main criteria for preliminary diagnosis.

Loss of Gi G-Protein-Coupled Receptor Signaling in Osteoblasts Accelerates Bone Fracture Healing

G-protein-coupled receptors (GPCRs) are key regulators of skeletal homeostasis and are likely important in fracture healing. Because GPCRs can activate multiple signaling pathways simultaneously, we used targeted disruption of G(i) -GPCR or activation of G(s) -GPCR pathways to test how each pathway functions in the skeleton. We previously demonstrated that blockade of G(i) signaling by pertussis toxin (PTX) transgene expression in maturing osteoblastic cells enhanced cortical and trabecular bone formation and prevented age-related bone loss in female mice. In addition, activation of G(s) signaling by expressing the G(s) -coupled engineered receptor Rs1 in maturing osteoblastic cells induced massive trabecular bone formation but cortical bone loss. Here, we test our hypothesis that the G(i) and G(s) pathways also have distinct functions in fracture repair. We applied closed, nonstabilized tibial fractures to mice in which endogenous G(i) signaling was inhibited by PTX, or to mice with activated G(s) signaling mediated by Rs1. Blockade of endogenous G(i) resulted in a smaller callus but increased bone formation in both young and old mice. PTX treatment decreased expression of Dkk1 and increased Lef1 mRNAs during fracture healing, suggesting a role for endogenous G(i) signaling in maintaining Dkk1 expression and suppressing Wnt signaling. In contrast, adult mice with activated Gs signaling showed a slight increase in the initial callus size with increased callus bone formation. These results show that G(i) blockade and G(s) activation of the same osteoblastic lineage cell can induce different biological responses during fracture healing. Our findings also show that manipulating the GPCR/cAMP signaling pathway by selective timing of G(s) and G(i) -GPCR activation may be important for optimizing fracture repair.

Pagetoid polyostotic fibrous dysplasia

Fibrous dysplasia (FD) is a benign skeletal lesion occurring due to mutation of Gs α gene and involves one or multiple bones. We present a case of a 30-year-old female patient, with a 1-year history of swelling under her right eye that had gradually increased in size. Extraoral examination revealed a diffuse swelling extending anteroposteriorly from preauricular region to nasolabial fold, frontonasal region and superoinferiorly from zygoma to body of mandible, causing ipsilateral proptosis and contralateral deviation of nose. Intraoral examination showed obliteration of right upper and lower buccal vestibule. CT disclosed expansile lytic lesions involving multiple skull bones, jaws, sternum, rib and thoracic vertebrae. Histopathology displayed broad and interconnected trabeculae connected to the host bone exhibiting reversal lines resembling the mosaic pattern of Paget's disease. These features suggested pagetoid polyostotic FD. The patient underwent cosmetic recontouring and is under regular follow-up postoperatively.

Age-related mutations associated with clonal hematopoietic expansion and malignancies

Several genetic alterations characteristic of leukemia and lymphoma have been detected in the blood of individuals without apparent hematological malignancies. The Cancer Genome Atlas (TCGA) provides a unique resource for comprehensive discovery of mutations and genes in blood that may contribute to the clonal expansion of hematopoietic stem/progenitor cells. Here, we analyzed blood-derived sequence data from 2,728 individuals from TCGA and discovered 77 blood-specific mutations in cancer-associated genes, the majority being associated with advanced age. Remarkably, 83% of these mutations were from 19 leukemia and/or lymphoma-associated genes, and nine were recurrently mutated (DNMT3A, TET2, JAK2, ASXL1, TP53, GNAS, PPM1D, BCORL1 and SF3B1). We identified 14 additional mutations in a very small fraction of blood cells, possibly representing the earliest stages of clonal expansion in hematopoietic stem cells. Comparison of these findings to mutations in hematological malignancies identified several recurrently mutated genes that may be disease initiators. Our analyses show that the blood cells of more than 2% of individuals (5-6% of people older than 70 years) contain mutations that may represent premalignant events that cause clonal hematopoietic expansion.

Detection of SQSTM1/P392L post-zygotic mutations in Paget's disease of bone

Paget’s disease of bone (PDB) is transmitted, in one-third of cases, in an autosomal dominant mode of inheritance with incomplete penetrance. The SQSTM1/P392L germinal mutation is the most common mutation associated with PDB. Given the focal nature of PDB, one team of investigators showed that SQSTM1/P392L somatic mutations could occur in pagetic bone lesions in the absence of germinal mutations detectable in the peripheral blood. The objectives of this study were to develop a reliable method to detect SQSTM1/P392L post-zygotic mutations, by optimizing a polymerase chain reaction (PCR)-clamping method reported to be effective in detecting post-zygotic mutations in peripheral blood from patients with fibrous dysplasia; and to evaluate the frequency of this post-zygotic mutation in PDB patients. We used a locked nucleic acid (LNA) specifically designed for the SQSTM1/P392L mutation, which blocks the wild-type allele amplification during the PCR. DNA from 376 pagetic patients and 297 controls, all without any SQSTM1/P392L germinal mutation, was analyzed. We found that 4.8 % of PDB patients and 1.4 % of controls were carriers of this post-zygotic mutation [p = 0.013, OR 3.68 (1.23; 11.00)]. PDB patient carriers of a post-zygotic mutation had a lower number of affected bones and Renier’s index than patients carrying a germinal mutation, suggesting a lower disease extension. We also demonstrated that this post-zygotic mutation was restricted to the monocytic lineage. These results confirmed that LNA PCR clamping is effective for the detection of SQSTM1/P392L post-zygotic mutations, which may occur in patients with PDB.

Utilization of ancillary studies in the cytologic diagnosis of biliary and pancreatic lesions: The Papanicolaou Society of Cytopathology Guidelines

The Papanicolaou Society of Cytopathology has developed a set of guidelines for pancreatobiliary cytology including indications for endoscopic ultrasound guided fine needle aspiration, terminology and nomenclature of pancreatobiliary disease, ancillary testing and post-biopsy management. All documents are based on the expertise of the authors, a review of the literature, discussion of the draft document at several national and international meetings and synthesis of selected online comments of the draft document. This document presents the results of these discussions regarding the use of ancillary testing in the cytologic diagnosis of biliary and pancreatic lesions. Currently, fluorescence in-situ hybridization (FISH) appears to be the most clinically relevant ancillary technique for cytology of bile duct strictures. The addition of FISH analysis to routine cytologic evaluation appears to yield the highest sensitivity without loss in specificity. Loss of immunohistochemical staining for the protein product of the SMAD4 gene and positive staining for mesothelin support a diagnosis of ductal adenocarcinoma. Immunohistochemical markers for endocrine and exocrine differentiation are sufficient for a diagnosis of endocrine and acinar tumors. Nuclear staining for beta-catenin supports a diagnosis of solid-pseudopapillary neoplasm. Cyst fluid analysis for amylase and carcinoembryonic antigen aids in the pre-operative classification of pancreatic cysts. A number of gene mutations (KRAS, GNAS, von Hippel-Lindau, RNF43 and CTNNB1) may be of aid in the diagnosis of cystic neoplasms. Other ancillary techniques do not appear to improve diagnostic sensitivity sufficiently to justify their increased costs.

Disrupted bone remodeling leads to cochlear overgrowth and hearing loss in a mouse model of fibrous dysplasia

Normal hearing requires exquisite cooperation between bony and sensorineural structures within the cochlea. For example, the inner ear secretes proteins such as osteoprotegrin (OPG) that can prevent cochlear bone remodeling. Accordingly, diseases that affect bone regulation can also result in hearing loss. Patients with fibrous dysplasia develop trabecular bone overgrowth resulting in hearing loss if the lesions affect the temporal bones. Unfortunately, the mechanisms responsible for this hearing loss, which could be sensorineural and/or conductive, remain unclear. In this study, we used a unique transgenic mouse model of increased G_s G-protein coupled receptor (GPCR) signaling induced by expression of an engineered receptor, Rs1, in osteoblastic cells. These ColI(2.3)⁺/Rs1⁺ mice showed dramatic bone lesions that histologically and radiologically resembled fibrous dysplasia. We found that ColI(2.3)⁺/Rs1⁺ mice showed progressive and severe conductive hearing loss. Ossicular chain impingement increased with the size and number of dysplastic lesions. While sensorineural structures were unaffected, ColI(2.3)⁺/Rs1⁺ cochleae had abnormally high osteoclast activity, together with elevated tartrate resistant acid phosphatase (TRAP) activity and receptor activator of nuclear factor kappa-B ligand (Rankl) mRNA expression. ColI(2.3)⁺/Rs1⁺ cochleae also showed decreased expression of Sclerostin (Sost), an antagonist of the Wnt signaling pathway that normally increases bone formation. The osteocyte canalicular networks of ColI(2.3)⁺/Rs1⁺ cochleae were disrupted and showed abnormal osteocyte morphology. The osteocytes in the ColI(2.3)⁺/Rs1⁺ cochleae showed increased expression of matrix metalloproteinase 13 (MMP-13) and TRAP, both of which can support osteocyte-mediated peri-lacunar remodeling. Thus, while the ossicular chain impingement is sufficient to account for the progressive hearing loss in fibrous dysplasia, the deregulation of bone remodeling extends to the cochlea as well. Our findings suggest that factors regulating bone remodeling, including peri-lacunar remodeling by osteocytes, may be useful targets for treating the bony overgrowths and hearing changes of fibrous dysplasia and other bony pathologies.

Monostotic fibrous dysplasia of the proximal femur

Monostotic fibrous dysplasia of the proximal femur has a variable clinical course, despite its reported limited tendency to progress.

We investigated the natural history and predisposing factors for progression of dysplasia in a group of 76 patients with a mean follow-up of 8.5 years (2.0 to 15.2). Of these, 31 (41%) presented with an asymptomatic incidental lesion while 45 (59%) presented with pain or a pathological fracture. A group of 23 patients (30%) underwent early operative treatment for pain (19: 25%) or pathological fracture (4: 5%).

Of the 53 patients who were initially treated non-operatively, 45 (85%) remained asymptomatic but eight (15%) needed surgery because of pain or fracture. The progression-free survival of the observation group was 81% (sd 6.4%) at five-years follow-up. An initial presentation of pain (p < 0.001), a limp (p < 0.001), radiological evidence of microfracture (p = 0.001) and younger age (< 17 years) (p = 0.016) were significant predisposing factors for disease progression.

The risk of experiencing pain or pathological fracture is considerable in monostotic fibrous dysplasia of the proximal femur. Patients presenting with pain, a limp or radiological evidence of microfracture have a high chance of needing surgical treatment.

Cite this article: Bone Joint J 2014;96-B:673–6.

Utilization of ancillary studies in the cytologic diagnosis of biliary and pancreatic lesions: the Papanicolaou Society of Cytopathology guidelines for pancreatobiliary cytology

The Papanicolaou Society of Cytopathology has developed a set of guidelines for pancreatobiliary cytology including indications for endoscopic ultrasound-guided fine-needle aspiration, terminology and nomenclature of pancreatobiliary disease, ancillary testing, and post-biopsy management. All documents are based on the expertise of the authors, a review of the literature, discussions of the draft document at several national and international meetings, and synthesis of selected online comments of the draft document. This document presents the results of these discussions regarding the use of ancillary testing in the cytologic diagnosis of biliary and pancreatic lesions. Currently, fluorescence in situ hybridization (FISH) appears to be the most clinically relevant ancillary technique for cytology of bile duct strictures. The addition of FISH analysis to routine cytologic evaluation appears to yield the highest sensitivity without loss in specificity. Loss of immunohistochemical staining for the protein product of the SMAD4 gene and positive staining for mesothelin support a diagnosis of ductal adenocarcinoma. Immunohistochemical markers for endocrine and exocrine differentiation are sufficient for a diagnosis of endocrine and acinar tumors. Nuclear staining for beta-catenin supports a diagnosis of solid-pseudopapilary neoplasm. Cyst fluid analysis for amylase and carcinoembryonic antigen aids in the preoperative classification of pancreatic cysts. Many gene mutations (KRAS, GNAS, VHL, RNF43, and CTNNB1) may be of aid in the diagnosis of cystic neoplasms. Other ancillary techniques do not appear to improve diagnostic sensitivity sufficiently to justify their increased costs.

Diagnostic value of investigating GNAS mutations in fibro-osseous lesions: a retrospective study of 91 cases of fibrous dysplasia and 40 other fibro-osseous lesions

GNAS (guanine nucleotide-binding protein/α-subunit) mutations that induce the activation of G-protein α-subunit participate in the pathogenesis of fibrous dysplasia. The aim of this study was to evaluate the sensitivity and specificity of GNAS mutations in fibrous dysplasia and other fibro-osseous lesions, to assess the value of investigating this mutation in the diagnosis of fibro-osseous lesions. We studied 91 cases of fibrous dysplasia. The quality and/or quantity of genomic DNA were suitable for molecular analysis for 51 cases of fibrous dysplasia. GNAS mutations were investigated by three techniques: high-resolution melting (exon 8), allele-specific PCR (exons 8 and 9) and/or direct DNA sequencing (exons 8 and 9). Fibrous dysplasia samples were classified blind to the GNAS mutation status into six histological subtypes as conventional, fibro-involutive, osteosclerosing, cementifying, osteocartilaginous and with prominent aneurysmal cystic changes. We also studied 14 cases of low-grade osteosarcoma, 21 cases of ossifying fibroma, 3 cases of osteofibrous dysplasia, 1 case of osseous dysplasia of the jawbone and 1 post-traumatic lesion of the ribs. Twenty-three cases of fibrous dysplasia (45%) showed mutations of codon 201 (exon 8, p.R201H or p.R201C). No mutation was found on codon 227 (exon 9). GNAS mutations in conventional fibrous dysplasia were detected in the same proportion (47%) as in the other histological subtypes (47%, P=0.96), regardless of sex (P=0.44), age (P=0.90) and location (P=1). GNAS mutations were not detected in any other fibro-osseous lesions. The GNAS mutation was thus specific to fibrous dysplasia in the context of fibro-osseous lesions. The particular mosaicism of mutant and non-mutant cells within the lesion or the existence of other mutations not already described could explain the lack of GNAS mutation in cases of fibrous dysplasia. Investigating this mutation may constitute a valuable complementary diagnostic tool, despite its low sensitivity, particularly in unconventional morphologically different subtypes of fibrous dysplasia.

Fibrous dysplasia and fibroblast growth factor-23 regulation

Fibrous dysplasia (FD) is a skeletal disorder caused by activating mutations in Gsα that result in elevations in cAMP. A feature of FD is elevated blood levels of the bone cell-derived phosphaturic hormone, fibroblast growth factor-23 (FGF23). FGF23 regulates serum phosphorus and active vitamin D levels by action on proximal renal tubule cells. An essential step in the production of biologically active FGF23 is glycosylation by the UDP-N-acetyl-α-D-galactosamine:polypeptide N-acetylgalactosaminyl transferase (ppGalNAc-T3). In the absence of glycosylation, FGF23 is processed into inactive N- and C-terminal proteins by a subtilisin proprotein convertase, probably furin. Normally, most if not all circulating FGF23 is intact. In FD, C-terminal levels are elevated, suggesting altered FGF23 processing. Altered processing in FD is the result of a cAMP-dependent, coordinated decrease in ppGalNAc-T3 and an increase in furin enzyme activity. These findings, and emerging data from other diseases, suggest regulation of FGF23 processing may be a physiologically important process.

An epidemiological and clinical analysis of craniomaxillofacial fibrous dysplasia in a Chinese population

BACKGROUND

Craniomaxillofacial fibrous dysplasia (FD) is a benign bone lesion characterized by facial disfigurement and functional impairment. The aim of this study was to characterize the epidemiological and clinical features of craniomaxillofacial FD by presenting data from a representative Chinese population during a 15-year period (1994-2009).

METHOD

The craniomaxillofacial disease registries of two Chinese tertiary referral hospitals (Shanghai Ninth People's Hospital and Stomatological hospital of Jiangsu Province) were searched and reviewed to collect relevant information for patients with craniomaxillofacial FD between Jan.1994 and Dec.2009. All included cases were further analyzed with regard to associated epidemiological and clinicopathological variables.

RESULTS

A total number of 266 cases with definitive diagnosis were identified with 219 primary cases and 47 recurrent cases. There were 111 males and 155 females with a male to female ratio of 0.716:1. They were clinically categorized into three groups: monostotic (71.1%), polysotic (27.4%) and Albright syndrome (1.5%). Maxilla alone or with adjacent bones was the most common affected site. The serum alkaline phosphatase (ALP) in patients was much higher than that in healthy control, whereas comparable between primary patients and recurrent ones. Three patients (3/266, 1.1%) with polysotic lesions underwent spontaneous malignant transformation into osteosarcoma. The majority of patients underwent conservative surgery, while the others received radical resection with or without reconstruction.

CONCLUSIONS

Craniomaxillofacial FD is a rare bony disorder with defined epidemiological and clinicopathological features in Chinese population. Further investigations are warranted to establish the optimized timing, treatment strategy and prognostic prediction for this clinical entity.

Mazabraud's syndrome. A case with multiple myxomas

Mazabraud's syndrome is defined as the combination of one or more intramuscular myxomas and fibrous dysplasia of bone. The diagnosis is important given the increased risk of malignant transformation of the bone lesions. We report a case in a 56-year-old patient with a 14-year follow-up during which multiple surgical procedures were required to remove myxomas (present at more than 15 sites). The resected myxomas were large and progressive. Unique features in this case include the long follow-up and the number of myxomas considerably above the average for this disease. Eighty other cases of Mazabraud's syndrome have been reported. The condition predominantly affects middle-aged women (mean age, 44 years). The bone lesions may be monostotic or polyostotic. Mazabraud's syndrome may be difficult to distinguish from soft-tissue sarcoma or neurofibromatosis. Identification of the underlying genetic abnormality provides diagnostic confirmation, as shown in our patient. The management consists in surgery to remove the myxomas and magnetic resonance imaging at regular intervals to monitor the lesions.

Fibro-Osseous Lesions

This article describes the clinical, radiographic, gross, microscopic, and histologic features; differential diagnosis; molecular pathology; treatment; and prognosis of fibrous dysplasia, osteofibrous dysplasia, and adamantinoma of long bones.

New mutations at the imprinted Gnas cluster show gene dosage effects of Gsα in postnatal growth and implicate XLαs in bone and fat metabolism but not in suckling

The imprinted Gnas cluster is involved in obesity, energy metabolism, feeding behavior, and viability. Relative contribution of paternally expressed proteins XLαs, XLN1, and ALEX or a double dose of maternally expressed Gsα to phenotype has not been established. In this study, we have generated two new mutants (Ex1A-T-CON and Ex1A-T) at the Gnas cluster. Paternal inheritance of Ex1A-T-CON leads to loss of imprinting of Gsα, resulting in preweaning growth retardation followed by catch-up growth. Paternal inheritance of Ex1A-T leads to loss of imprinting of Gsα and loss of expression of XLαs and XLN1. These mice have severe preweaning growth retardation and incomplete catch-up growth. They are fully viable probably because suckling is unimpaired, unlike mutants in which the expression of all the known paternally expressed Gnasxl proteins (XLαs, XLN1 and ALEX) is compromised. We suggest that loss of ALEX is most likely responsible for the suckling defects previously observed. In adults, paternal inheritance of Ex1A-T results in an increased metabolic rate and reductions in fat mass, leptin, and bone mineral density attributable to loss of XLαs. This is, to our knowledge, the first report describing a role for XLαs in bone metabolism. We propose that XLαs is involved in the regulation of bone and adipocyte metabolism.

A novel population of cells expressing both hematopoietic and mesenchymal markers is present in the normal adult bone marrow and is augmented in a murine model of marrow fibrosis

Bone marrow (BM) fibrosis is a feature of severe hyperparathyroidism. Consistent with this observation, mice expressing constitutively active parathyroid hormone (PTH)/PTH-related peptide receptors (PPR) in osteoblasts (PPR*Tg) display BM fibrosis. To obtain insight into the nature of BM fibrosis in such a model, a double-mutant mouse expressing constitutively active PPR and green fluorescent protein (GFP) under the control of the type I collagen promoter (PPR*Tg/GFP) was generated. Confocal microscopy and flow cytometry revealed the presence of a cell population expressing GFP (GFP(+)) that was also positive for the hematopoietic marker CD45 in the BM of both PPR*Tg/GFP and control animals. This cell population was expanded in PPR*Tg/GFP. The existence of cells expressing both type I collagen and CD45 in the adult BM was confirmed by IHC and fluorescence-activated cell sorting. An analysis of total RNA extracted from sorted GFP(+)CD45(+) cells showed that these cells produced type I collagen and PTH/PTH-related peptide receptor and receptor activator for NF-κB mRNAs, further supporting their features of being both mesenchymal and hematopoietic lineages. Similar cells, known as fibrocytes, are also present in pathological fibroses. Our findings, thus, indicate that the BM is a permissive microenvironment for the differentiation of fibrocyte-like cells and raise the possibility that these cells could contribute to the pathogenesis of BM fibrosis.