Treatment of Paget's disease--taming the wild osteoclast

Osteonecrosis of the Jaws and Bisphosphonate Therapy

Bisphosphonates are a class of agents used to treat osteoporosis and malignant bone metastases. The efficacy of these agents in treating and preventing the significant skeletal complications associated with these conditions has had a major positive impact for patients and is responsible for their widespread use in medicine. Despite these benefits, osteonecrosis of the jaws has recently emerged as a significant complication in a subset of patients receiving these drugs. Based on a growing number of case reports and institutional reviews, bisphosphonate therapy may cause exposed and necrotic bone that is isolated to the jaw. This complication usually presents following simple dento-alveolar surgery, and can cause a significant adverse effect on the quality of life for most patients. The pathogenesis for this complication appears to be related to the profound inhibition of osteoclast function and bone remodeling.

The ever-expanding conundrum of primary osteoporosis: aetiopathogenesis, diagnosis, and treatment

In recent years, as knowledge regarding the etiopathogenetic mechanisms of bone involvement characterizing many diseases has increased and diagnostic techniques evaluating bone health have progressively improved, the problem of low bone mass/quality in children and adolescents has attracted more and more attention, and the body evidence that there are groups of children who may be at risk of osteoporosis has grown. This interest is linked to an increased understanding that a higher peak bone mass (PBM) may be one of the most important determinants affecting the age of onset of osteoporosis in adulthood. This review provides an updated picture of bone pathophysiology and characteristics in children and adolescents with paediatric osteoporosis, taking into account the major causes of primary osteoporosis (PO) and evaluating the major aspects of bone densitometry in these patients. Finally, some options for the treatment of PO will be briefly discussed.

Paget's Disease of Bone: A Review of Epidemiology, Pathophysiology and Management

Paget's disease of bone is a common disorder which may affect one or many bones. Although many patients are asymptomatic, a variety of symptoms and complications may occur. Fortunately, effective pharmacologic therapy, primarily with potent bisphosphonates, is now available to treat patients with complications or symptoms. This review of Paget's disease of bone will include epidemiology and pathophysiology, complications and clinical findings, indications for treatment, and the drugs currently available to treat this condition.

Bisphosphonate-related osteonecrosis of the jaw: an overview

Bisphosphonates are widely used in the management of metastatic disease to bone and in diseases of altered bone turnover. Recently, multiple-case series and retrospective studies have established a relationship between necrotic bone lesions localized to the jaw and the use of chronic bisphosphonate therapy. This condition has been named bisphosphonate-related osteonecrosis of the jaw (BRONJ). To evaluate the potential risks associated with this new and emerging complication, stage-specific management strategies and guidelines have been developed. In view of the widespread use of chronic bisphosphonate therapy, the observation of an associated risk of osteonecrosis of the jaw should alert practitioners to monitor for this previously unrecognized complication and to reevaluate the indications for and the duration of bisphosphonate therapy in patients with osteopenia/osteoporosis and cancer. Morbidity associated with BRONJ might be prevented or reduced by implementing prevention strategies and establishing early diagnostic procedures. The current widespread use of bisphosphonates as an inhibitor of bone resorption is directly attributable to their efficacy in improving the quality of life for patients with metastatic bone cancer, osteoporosis, and Paget's disease.

Paget's disease of bone: emphasis on treatment with zoledronic acid

The treatment of Paget's disease of bone (PDB) aims at suppression of abnormal bone turnover and bisphosphonates (BPs) are currently the drugs of choice. Zoledronic acid, a third-generation nitrogen-containing BPs, is the newest BP approved for PDB and is administered by a single intravenous infusion. In vitro zoledronic acid has higher binding affinity for hydroxyapatite and is a stronger inhibitor of farnesyl pyrophosphate synthase compared with other BPs. In vivo zoledronic acid improves symptoms, normalizes bone turnover markers and scintigraphic imaging in the majority of patients, and maintains remission of PDB longer than other BPs. This review summarizes available data on the pathogenesis, epidemiology, clinical manifestation, biochemical assessment and management of PDB, giving special attention to the treatment of PDB with zoledronic acid, based on current evidence.

Clinical studies in familial VCP myopathy associated with Paget disease of bone and frontotemporal dementia

Inclusion body myopathy with Paget disease of the bone (PDB) and/or frontotemporal dementia (IBMPFD, OMIM 167320), is a progressive autosomal dominant disorder caused by mutations in the Valousin-containing protein (VCP, p97 or CDC48) gene. IBMPFD can be difficult to diagnose. We assembled data on a large set of families to illustrate the number and type of misdiagnoses that occurred. Clinical analysis of 49 affected individuals in nine families indicated that 42 (87%) of individuals had muscle disease. The majority were erroneously diagnosed with limb girdle muscular dystrophy (LGMD), facioscapular muscular dystrophy, peroneal muscular dystrophy, late adult onset distal myopathy, spinal muscular atrophy, scapuloperoneal muscular dystrophy, or amyotrophic lateral sclerosis (ALS) among others. Muscle biopsies showed rimmed vacuoles characteristic of an inclusion body myopathy in 7 of 18 patients (39%), however, inclusion body myopathy was correctly diagnosed among individuals in only families 5 and 15. Frontotemporal dementia (FTD) was diagnosed in 13 individuals (27%) at a mean age of 57 years (range 48.9-60.2 years); however, several individuals had been diagnosed with Alzheimer disease. Histopathological examination of brains of three affected individuals revealed a pattern of ubiquitin positive neuronal intranuclear inclusions and dystrophic neurites. These families expand the clinical phenotype in IBMPFD, a complex disorder caused by mutations in VCP. The presence of PDB in 28 (57%) individuals suggests that measuring serum alkaline phosphatase (ALP) activity may be a useful screen for IBMPFD in patients with myopathy.

Effect of inappropriate and continuous therapy with alendronate for ten years on skeletal integrity - observations in two elderly patients

Alendronate is a potent aminobisphosphonate that has been used worldwide to decrease fracture risk in millions of post-menopausal women with and without osteoporosis, men with low bone mass, and in those with glucocorticoid- induced osteoporosis. A recent report of 9 patients with spontaneous atypical non-vertebral fractures during treatment with alendronate for up to 8 yr raised questions suggesting the possibility of severe suppression of bone turnover and resultant susceptibility to fracture. Our recent observations in 2 elderly women with inactive monostotic Paget's disease of bone who had been treated elsewhere continuously for this disease with alendronate for 10 yr at doses overall of 2 and 4 times the osteoporotic dose provided an opportunity to engage in the ongoing controversy over long-term safety of bisphosphonate therapy. Despite such therapy, skeletal integrity was maintained with normal bone densities and the absence of skeletal fractures. These observations do not support the suggestion of deleterious effects with longterm alendronate therapy.

Serum OPG and RANKL levels before and after intravenous bisphosphonate treatment in Paget's disease of bone

Paget's disease of bone (PDB) is a focal disorder of bone remodeling characterized by increased osteoclast-mediated bone resorption. Even though increasing evidence indicates enhanced nuclear factor-kB (NF-kB) signaling as a common mechanism involved in PDB and other related disorders, few studies investigated circulating osteoprotegerin (OPG) and receptor of activator of NF-kB-ligand (RANKL) levels in PDB patients. In this study we explored the relationships between OPG or RANKL levels and bone turnover markers in a group of patients with PDB, before and after intravenous bisphosphonate treatment (pamidronate 60 mg). Both OPG and RANKL were markedly elevated in PDB patients with respect to control groups (healthy or osteoporotic postmenopausal women and elderly men) and were positively associated with bone turnover markers. Higher levels of these cytokines were observed in polyostotic than monostotic PDB cases. The ratio between RANKL and OPG was more than 3-fold higher in PDB patients than in controls. Interestingly, in the group of patients treated with pamidronate, we found an increase in OPG levels that become statistically significant after 3 and 6 months from treatment. A trend toward a decrease in RANKL levels after treatment was also observed. The RANKL/OPG ratio was significantly reduced after 3 and 6 months of therapy. In contrast, in patients classified as non-responders, OPG and RANKL levels after pamidronate infusion did not significantly differ with respect to pre-treatment values. Thus, the positive effect of amino bisphosphonates in the treatment of PDB may be due to either direct or indirect suppression of RANKL-induced bone resorption through decreased RANKL and increased OPG production.

Zoledronic Acid

The third-generation, nitrogen-containing bisphosphonate zoledronic acid (Aclasta) is approved in the EU for the treatment of Paget's disease of bone. Results of well designed trials show that a single intravenous dose of zoledronic acid 5 mg is effective and well tolerated in the treatment of Paget's disease of bone. A single intravenous dose of zoledronic acid was associated with a significantly higher therapeutic response rate and a more rapid reduction in bone turnover than that achieved with 60 days of oral risedronic acid. Moreover, biochemical remission was sustained after 24 months of follow-up in zoledronic acid recipients. Preliminary results suggest that zoledronic acid is a cost-effective option in Paget's disease of bone. Thus, zoledronic acid is an important first-line treatment for Paget's disease of bone.