Esclerosis bilateral de huesos largos: enfermedad de Erdheim-Chester. Reporte de un caso / Bilateral long bone sclerosis: Erdheim-Chester disease. Case report

La enfermedad de Erdheim-Chester (EEC) es una patología poco frecuente, caracterizada por presentar infiltración xantogranulomatosa sistémica, con afección de diversos sistemas incluido el óseo. La EEC se encuentra descripta dentro de las enfermedades osteocon-densantes (EO), las cuales se reconocen por presentar aumento de la masa ósea y compromiso tanto de huesos largos como planos. La presentación clínica de la EEC es variada: puede presentar desde un curso indolente hasta manifestaciones multisistémicas. Las características radiológicas son de gran importancia para establecer su diagnóstico. Presentamos una paciente con EEC, con esclerosis bilateral de huesos largos, que exhibe algunas características diferenciales con relación a otros casos reportados: a) afectación exclusivamente ósea a 10 años de evolución, b) compromiso bilateral y simétrico de distinta magnitud, c) esclerosis cortical endóstica y perióstica, d) signos radiológicos sugestivos de periostitis, d) ausencia de compromiso metafisario, e) ausencia de actividad metabólica de las lesiones en las imágenes de 18F-FDG PET/CT.Conclusión: la presencia de lesiones osteocondensantes bilaterales exclusivamente en huesos largos deben hacer sospechar EEC. La ausencia de compromiso metafisario y de actividad metabólica en 18F-FDG PET/CT ha sido raramente descripta. (AU)

Erdheim - Chester disease (ECD) is a rare disease, characterized by systemic xanthogranulomatous infiltration, with involvement of various organs including bone. ECD is described within the sclerosing bone disorders, which are recognized for presenting increased bone mass and involvement of both long and flat bones. The clinical presentation of ECD is diverse, ranging from an asymptomatic course to multisystemic manifestations. Radiological features are of great importance to establish the diagnosis. We describe here a patient with ECD, with bilateral sclerosis of long bones that presents some differential characteristics in relation to other reported cases: a) exclusively bone involvement at 10 years of evolution, b) bilateral and symmetric involvement of different magnitude, c) endosteal and periosteal cortical sclerosis d) radiological signs suggestive of periostitis, d) absence of metaphyseal involvement, e) absence of metabolic activity of the lesions in 18F-FDG PET/CT.Conclusion: the presence of bilateral osteosclerosis exclusively in long bones should lead to suspect ECD. The absence of metaphyseal involvement and metabolic activity in 18F-FDG PET/CT have been rarely described. (AU)

Sclerosing bone dysplasias.

The group of sclerosing bone dysplasia's is a clinically and genetically heterogeneous group of rare bone disorders which, according to the latest Nosology and classification of genetic skeletal disorders (2015), can be subdivided in three subgroups; the neonatal osteosclerotic dysplasias, the osteopetroses and related disorders and the other sclerosing bone disorders. Here, we give an overview of the most important radiographic and clinical symptoms, the underlying genetic defect and potential treatment options of the different sclerosing dysplasias included in these subgroups.

Human Genetics of Sclerosing Bone Disorders.

PURPOSE OF REVIEW: The group of sclerosing bone disorders encompasses a variety of disorders all marked by increased bone mass. In this review, we give an overview of the genetic causes of this heterogeneous group of disorders and briefly touch upon the value of these findings for the development of novel therapeutic agents. RECENT FINDINGS: Advances in the next-generation sequencing technologies are accelerating the molecular dissection of the pathogenic mechanisms underlying skeletal dysplasias. Throughout the years, the genetic cause of these disorders has been extensively studied which resulted in the identification of a variety of disease-causing genes and pathways that are involved in bone formation by osteoblasts, bone resorption by osteoclasts, or both processes. Due to this rapidly increasing knowledge, the insights into the regulatory mechanisms of bone metabolism are continuously improving resulting in the identification of novel therapeutic targets for disorders with reduced bone mass and increased bone fragility.

Reversing LRP5-dependent osteoporosis and SOST deficiency-induced sclerosing bone disorders by altering WNT signaling activity.

The bone formation inhibitor sclerostin encoded by SOST binds in vitro to low-density lipoprotein receptor-related protein (LRP) 5/6 Wnt co-receptors, thereby inhibiting Wnt/ß-catenin signaling, a central pathway of skeletal homeostasis. Lrp5/LRP5 deficiency results in osteoporosis-pseudoglioma (OPPG), whereas Sost/SOST deficiency induces lifelong bone gain in mice and humans. Here, we analyzed the bone phenotype of mice lacking Sost (Sost(-/-) ), Lrp5 (Lrp5(-/-) ), or both (Sost(-/-) ;Lrp5(-/-) ) to elucidate the mechanism of action of Sost in vivo. Sost deficiency-induced bone gain was significantly blunted in Sost(-/-) ;Lrp5(-/-) mice. Yet the Lrp5 OPPG phenotype was fully rescued in Sost(-/-) ;Lrp5(-/-) mice and most bone parameters were elevated relative to wild-type. To test whether the remaining bone increases in Sost(-/-) ;Lrp5(-/-) animals depend on Lrp6, we treated wild-type, Sost(-/-) , and Sost(-/-) ;Lrp5(-/-) mice with distinct Lrp6 function blocking antibodies. Selective blockage of Wnt1 class-mediated Lrp6 signaling reduced cancellous bone mass and density in wild-type mice. Surprisingly, it reversed the abnormal bone gain in Sost(-/-) and Sost(-/-) ;Lrp5(-/-) mice to wild-type levels irrespective of enhancement or blockage of Wnt3a class-mediated Lrp6 activity. Thus, whereas Sost deficiency-induced bone anabolism partially requires Lrp5, it fully depends on Wnt1 class-induced Lrp6 activity. These findings indicate: first, that OPPG syndrome patients suffering from LRP5 loss-of-function should benefit from principles antagonizing SOST/sclerostin action; and second, that therapeutic WNT signaling inhibitors may stop the debilitating bone overgrowth in sclerosing disorders related to SOST deficiency, such as sclerosteosis, van Buchem disease, and autosomal dominant craniodiaphyseal dysplasia, which are rare disorders without viable treatment options.

Enfermedades osteocondensantes con compromiso de huesos largos: presentación de dos casos y revisión de la literatura / Sclerosing bone diseases with involvement of long bones: report of two cases and literature review

Las enfermedades osteocondensantes son un grupo de patologías poco frecuentes que se caracterizan por aumento de la masa ósea, comprometiendo tanto a huesos largos como a huesos planos. Tradicionalmente, la radiología simple ha permitido su diagnóstico al identificar patrones de afectación ósea característicos de cada enfermedad. Actualmente, la caracterización molecular y genética ha facilitado la comprensión del sustrato fisiopatológico y la expresión fenotípica de estás patologías, sin embargo, la radiología simple continua teniendo un valor inconmesurable en el reconocimiento de las enfermedades osteocondensantes.

Sclerosing bone disorders are a rare group of diseases characterized by increased bone mass in both long and flat bones. Traditionally, plain radiography has allowed the diagnosis of these diseases identifying characteristic patterns of bone involvement. At present, the molecular and genetic characterization of these diseases has provided a better understand of their pathophysiology and phenotypic expression, however plain radiography continues to have an important role in the recognition of sclerosing bone disorders.