Fibrous dysplasia (FD) is an uncommon and debilitating skeletal disorder resulting in fractures, deformity, functional impairment and pain. It arises from postzygotic somatic activating mutations in GNAS, in the cAMP-regulating transcript α-subunit, Gsα. Constitutive Gs signaling results in activation of adenylyl cyclase and dysregulated cAMP production. In the skeleton this leads to the development of FD lesions with abnormal bone matrix, trabeculae, and collagen, produced by undifferentiated mesenchymal cells. FD may occur in isolation or in combination with extraskeletal manifestations, including hyperfunctioning endocrinopathies and café-au-lait macules, termed McCune-Albright syndrome (MAS). This review summarizes current clinical and translational perspectives in FD/MAS, with an emphasis on FD pathogenesis, natural history, pre-clinical and clinical investigation, and future directions.

Blocking the action of FSH genetically or pharmacologically in mice reduces body fat, lowers serum cholesterol, and increases bone mass, making an anti-FSH agent a potential therapeutic for three global epidemics: obesity, osteoporosis, and hypercholesterolemia. Here, we report the generation, structure, and function of a first-in-class, fully humanized, epitope-specific FSH blocking antibody with a KD of 7 nM. Protein thermal shift, molecular dynamics, and fine mapping of the FSH–FSH receptor interface confirm stable binding of the Fab domain to two of five receptor-interacting residues of the FSHβ subunit, which is sufficient to block its interaction with the FSH receptor. In doing so, the humanized antibody profoundly inhibited FSH action in cell-based assays, a prelude to further preclinical and clinical testing.

McCune-Albright Syndrome (MAS) is a rare sporadic syndrome caused by post-zygotic mutations in the GNAS oncogene, leading to constitutional mosaicism for these alterations. Somatic activating GNAS mutations also commonly occur in several gastrointestinal and pancreatic neoplasms, but the spectrum of abnormalities in these organs in patients with MAS has yet to be systematically described. We report comprehensive characterization of the upper gastrointestinal tract in seven patients with MAS and identify several different types of polyps, including gastric heterotopia/metaplasia (7/7), gastric hyperplastic polyps (5/7), fundic gland polyps (2/7), and a hamartomatous polyp (1/7). In addition, one patient had an unusual adenomatous lesion at the gastroesophageal junction with high-grade dysplasia. In the pancreas, all patients had endoscopic ultrasound findings suggestive of intraductal papillary mucinous neoplasm (IPMN), but only 2 patients met the criteria for surgical intervention. Both of these patients had IPMNs at resection, one with low-grade dysplasia and one with high-grade dysplasia. GNAS mutations were identified in the majority of lesions analyzed, including both IPMNs and the adenomatous lesion from the gastroesophageal junction. These studies suggest that there is a broad spectrum of abnormalities in the gastrointestinal tract and pancreas in patients with MAS, and that patients with MAS should be evaluated for gastrointestinal pathology, some of which may warrant clinical intervention due to advanced dysplasia.

Purpose Tumor-induced osteomalacia (TIO) is a rare paraneoplastic syndrome of abnormal phosphate and vitamin D metabolism caused by typically small endocrine tumors that secrete fibroblast growth factor 23 (FGF23). TIO is characterized clinically by progressive musculoskeletal pain, fatigue, proximal muscle weakness, and multiple fractures, leading to long-term disability. Misdiagnosis and delayed diagnosis are common because of the non-specific symptoms, and several years may elapse before patients receive an accurate diagnosis and appropriate treatment. Thus, it is vital that awareness of the appropriate recognition and management of TIO is increased among healthcare professionals who may encounter patients with suspected TIO. Methods A roundtable meeting was held on 10 January 2020 in Dallas, TX, USA to gather perspectives on the diagnosis and treatment of TIO. The following topics were considered: clinical presentation, patient history, differential diagnosis, laboratory assessment, imaging, venous sampling, and treatment. Results This report provides a summary of our collective experiences in the management of TIO. Main conclusions Laboratory tests are mandatory to expedite TIO diagnosis and should include measurement of fasting serum phosphorus, renal phosphate reabsorption, serum 1,25-dihydroxyvitamin D, and serum FGF23 levels. Functional and anatomical imaging are essential to locate the FGF23-secreting tumor(s) causing TIO. Surgical resection is often a curative treatment when the tumor can be localized; however, better management of non-operable patients with targeted therapies is needed. Further efforts to increase awareness of TIO within the medical community, and education on recommended diagnostic and treatment pathways are required to improve the management of this debilitating disease.

Background Survivors of childhood leukemia/lymphoma are at increased risk for reduced bone mineral density (BMD). The authors sought to determine the frequency of reduced BMD detected by off‐therapy surveillance, factors associated with reduced BMD, and the association of reduced BMD with fractures. Methods This cross‐sectional study included childhood leukemia/lymphoma survivors attending 2 survivorship clinics who received guideline‐recommended BMD surveillance ≥2 years post‐therapy with dual‐energy x‐ray absorptiometry (from January 1, 2004 to August 31, 2016). Lumbar spine BMD z‐scores were height‐for‐age–adjusted. Low and very low BMD were >1 SD and >2 SDs below norms, respectively. Treatment, chronic conditions, and fractures were abstracted from medical records. Logistic regression was used to examine the association of low BMD with patient/treatment factors and fractures. Results In total, 542 patients (51.5% female) with a mean age of 15.5 years (range, 4.4‐52.2 years) who were 6 years post‐therapy (range, 2.0‐35.1 years) were evaluated, including 116 who reported post‐therapy fractures. Lumbar spine low BMD was identified in 17.2% of survivors, and very low BMD was identified in 3.5% of survivors, but frequencies varied considerably between subgroups; 10.8% of survivors aged 15 to 19 years at diagnosis had very low BMD. In multivariable analyses, older age at diagnosis, white race, and being underweight were significantly associated with low BMD. Survivors with low BMD had greater odds of nondigit fractures (odds ratio, 2.2; 95% CI, 1.3‐3.7) and specifically long‐bone fractures (odds ratio, 2.7; 95% CI, 1.5‐4.7). Conclusions In this study of childhood leukemia/lymphoma survivors undergoing guideline‐recommended dual‐energy x‐ray absorptiometry surveillance, patients who were older at diagnosis, white, and underweight were at the highest risk for lumbar spine low BMD. Low BMD was associated with a greater risk of fractures, emphasizing the clinical importance of surveillance.

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.

Postoperative fever in spine surgery patients is associated with a delay in patient discharge and increases in hospital charges. Postoperative fever discharge guidelines should be regularly and publicly subjected to appropriate cost-benefit analysis.

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