Idiopathic juvenile osteoporosis: evidence of normal osteoblast function by 1,25-dihydroxyvitamin D3 stimulation test

Osteoporosis in children and adolescents: etiology and management

Bone mass increases progressively during childhood, but mainly during adolescence when approximately 40% of total bone mass is accumulated. Peak bone mass is reached in late adolescence, and is a well recognised risk factor for osteoporosis later in life. Thus, increasing peak bone mass can prevent osteoporosis. The critical interpretation of bone mass measurements is a crucial factor for the diagnosis of osteopenia/osteoporosis in children and adolescents. To date, there are insufficient data to formally define osteopenia/osteoporosis in this patient group, and the guidelines used for adult patients are not applicable. In males and females aged <20 years the terminology 'low bone density for chronologic age' may be used if the Z-score is less than -2. For children and adolescents, this terminology is more appropriate than osteopenia/osteoporosis. Moreover, the T-score should not be used in children and adolescents. Many disorders, by various mechanisms, may affect the acquisition of bone mass during childhood and adolescence. Indeed, the number of disorders that have been identified as affecting bone mass in this age group is increasing as a consequence of the wide use of bone mass measurements. The increased survival of children and adolescents with chronic diseases or malignancies, as well as the use of some treatment regimens has resulted in an increase in the incidence of reduced bone mass in this age group. Experience in treating the various disorders associated with osteoporosis in childhood is limited at present. The first approach to osteoporosis management in children and adolescents should be aimed at treating the underlying disease. The use of bisphosphonates in children and adolescents with osteoporosis is increasing and their positive effect in improving bone mineral density is encouraging. Osteoporosis prevention is a key factor and it should begin in childhood. Pediatricians should have a fundamental role in the prevention of osteoporosis, suggesting strategies to achieve an optimal peak bone mass.

Osteoporosis in children and adolescent girls: case report of idiopathic juvenile osteoporosis and review of the literature

The diagnosis and treatment of osteoporosis is an important aspect of gynecologic training and practice. Idiopathic juvenile osteoporosis (IJO) is a rare disease of children and adolescents that resolves after the onset of puberty. A case report is presented and current methods of diagnosis and treatment of IJO are discussed as well as the differential diagnosis. A MEDLINE search was performed of the following terms: idiopathic juvenile osteoporosis, pediatric osteoporosis, adolescent osteoporosis, bisphosphonates pediatric adolescent, and pregnancy osteoporosis, and references from bibliographies of selected papers were used as well. All papers in English, French, and German are considered in this review. There were 114 papers selected as relevant to the topic. Data relevant to the diagnosis, pathogenesis, methods of imaging, laboratory evaluation, differential diagnosis, and treatment of IJO are presented. IJO is a diagnosis of exclusion in the pediatric and adolescent patient with osteoporosis. Although bone density gradually improves after the onset of puberty, treatment of currently affected children and adolescents involves activity restriction, calcium, vitamin D, and bisphosphonate therapy. Future reproductive concerns are discussed and areas requiring additional study are reviewed.

TARGET AUDIENCE

Obstetricians & Gynecologists, Family Physicians

LEARNING OBJECTIVES

After completion of this article, the reader will be able to describe the condition idiopathic juvenile osteoporosis, compare the clinical features of this condition to other similar conditions, outline the diagnostic workup of a child with this condition, and list the potential therapeutic options for a patient with idiopathic juvenile osteoporosis.

Osteoporosis in children and adolescents: diagnosis, risk factors, and prevention

Bone mass acquired during childhood and adolescence is a key determinant of adult bone health. Peak bone mass, which is achieved in late adolescence, is a main determinant of osteoporosis in adulthood. Therefore, any factor adversely impacting on bone acquisition during childhood or adolescence can potentially have long-standing detrimental effects on bone health predisposing to osteoporosis and fracture risk. Thus, osteoporosis can well have its origin in childhood and adolescence. Pediatricians should be playing an active role in osteoporosis diagnosis and prevention. It is increasingly recognized that osteoporosis may occur in some disorders of children and adolescents. In this paper we review the diagnostic criteria of osteopenia/osteoporosis by densitometric assessment of bone mineral density, the contributing factors, and the mechanisms whereby several disorders may affect the acquisition of bone mass in children and adolescents. Finally, some recommendations to optimize peak bone mass in order to prevent osteopenia/osteoporosis are suggested.

Osteopenic syndromes in the adolescent female

Low bone density in growing girls and mature young women is usually a finding that needs an explanation and further clinical investigation. Population-based epidemiologic studies on osteoporosis in young persons do not exist. As a disease, osteoporosis among children and adolescents is rate, and since 1965 only 100 cases of idiopathic juvenile osteoprososis have been reported. When osteoporosis occurs in children, it is usually secondary to an underlying medical disorder (e.g., anorexia nervosa, leukemia) or to medications, but occasionally no identifiable primary cause can be detected. It may also be the result of a genetic disorder such as osteogenesis imperfecta. On the other hand, osteopenia in growing and young persons seems much commoner and needs further investigation. Adolescence is a period of increased calcium requirement, and girls with an underlying bone disease are at higher risk for bone demineralization. An additional point of interest is the changes in the geometry of bones through their continuous adaptation to simultaneous skeletal and muscular growth. Bones, through the mechanostat mechanism, adapt to mechanical loading by differentiating their geometry. A recent finding in this direction is that before and during the teenage years there is an environmental effect of physical activity and nutrition on hip geometry. Another important finding is an age-dependent increase in bone cross-sectional area and bone strength index in the absence of an increase in volumetric spongiosa bone density and cortical bone density. Girls, in comparison to boys, deposit more calcium in their bones during puberty, thus probably preparing their skeleton for the forthcoming events of pregnancy and lactation.

Deficient bone formation in idiopathic juvenile osteoporosis: a histomorphometric study of cancellous iliac bone

Idiopathic juvenile osteoporosis (IJO), a rare cause of osteoporosis in children, is characterized by the occurrence of vertebral and metaphyseal fractures. Little is known about the histopathogenesis of IJO. We analyzed by quantitative histomorphometry iliac crest biopsies from 9 IJO patients (age, 10.0-12.3 years; 7 girls) after tetracycline labeling. Results were compared with identically processed samples from 12 age-matched children without metabolic bone disease and 11 patients with osteogenesis imperfecta type I. Compared with healthy controls, cancellous bone volume (BV) was markedly decreased in IJO patients (mean [SD]: 10.0% [3.1%] vs. 24.4% [3.8%]), because of a 34% reduction in trabecular thickness (Tb.Th) and a 37% lower trabecular number (Tb.N; p < 0.0001 each; unpaired t-test). Bone formation rate (BFR) per bone surface was decreased to 38% of the level in controls (p = 0.0006). This was partly caused by decreased recruitment of remodeling units, as shown by a trend toward lower activation frequency (54% of the control value; p = 0.08). Importantly, osteoblast team performance also was impaired, as evidenced by a decreased wall thickness (W.Th; 70% of the control value; p < 0.0001). Reconstruction of the formative sites revealed that osteoblast team performance was abnormally low even before mineralization started at a given site. No evidence was found for increased bone resorption. Compared with children with osteogenesis imperfecta (OI), IJO patients had a similarly decreased cancellous BV but a much lower bone turnover. These results suggest a pathogenetic model for IJO, in which impaired osteoblast team performance decreases the ability of cancellous bone to adapt to the increasing mechanical needs during growth. This will finally result in load failure at sites where cancellous bone is essential for stability.

[Idiopathic juvenile osteoporosis: a new observation]

Idiopathic juvenile osteoporosis is a rare form of bone demineralization which occurs during childhood. The mechanism of disease remains unknown. We report a new case which illustrates the main difficulties of diagnosis and treatment.

CASE REPORT

A 7 year old girl was admitted because of painful disability of her lower limbs. Diagnosis was based on radiological signs, total bone density and bone histologic pattern. Plasma levels of calcium, phosphorus, alkaline phosphatases, 25-OH D3 and parathormone were within the normal range value. Other diseases associated with bone demineralization, such as enteric malabsorption, endocrine or tumoral diseases, were excluded. Recovery occurred after some months of treatment with calcium, vitamin D and rehabilitation, but we could not establish a clear causal relationship.

CONCLUSION

The relative role of increased bone resorption or defective osteoblast function remain to be discussed. Recovery often occurs with or without treatment, but sequelae can lead to disability.

Synthesis of novel 2-benzothiopyran and 3-benzothiepin derivatives and their stimulatory effect on bone formation

In a search for therapeutic agents for the treatment of osteoporosis and bone fracture, we found that 2-benzothiopyran-1-carboxamide derivatives 1, derived from ipriflavone as a lead compound, increase cellular alkaline phosphatase activity in cultures of rat bone marrow stromal cells. Further modification of 1 has led to the discovery of more potent 3-benzothiepin-2-carboxamide derivatives 2. Of these, 3-benzothiepin derivatives bearing a 4-(dialkoxyphosphorylmethyl)phenyl group on the 2-carboxamide moiety such as 2h and 2q exhibited significant improvement of activity compared to ipriflavone. Asymmetric synthesis of 2h and 2q revealed that the (-)-isomers possessed activities superior to those of the (+)-isomers. Further evaluation of these compounds using the mouse osteoblastic cell line MC3T3-E1 revealed that (-)-2q enhanced the effect of bone morphogenetic protein. In addition, application of a sustained-release agent containing 2q increased the area of newly formed bone in a rat skull defect model. Based on these findings, (-)-2q was selected for further investigation as a new drug stimulating bone formation. Synthesis and structure-activity relationships for this novel series of 2-benzothiopyran and 3-benzothiepin derivatives are detailed.

Long-term effects of bisphosphonates on the growing skeleton. Studies of young patients with severe osteoporosis

Osteoporosis in children and adolescents is relatively uncommon and usually secondary to identifiable causal factors. There are no generally accepted therapies for patients with no treatable underlying cause of disease. Any treatment of young patients with bone-acting compounds should be not only effective but also devoid of adverse effects on bone growth and remodeling. For many years we have been studying the effects of bisphosphonates-an effective treatment of postmenopausal osteoporosis-on the growing skeleton. We review here our experience in the treatment of young patients with osteoporosis with special emphasis on issues of skeletal safety and effectiveness, and we discuss the available literature data. We studied 12 patients aged between 10.7 and 17.2 years with symptomatic osteoporosis and multiple fractures treated with the bisphosphonates pamidronate or olpadronate for periods between 2 and 8 years continuously. Linear growth continued normally on treatment; there was even a catch-up growth in prepubertal patients, and there was no excessive suppression of bone remodeling, assessed biochemically. Bone biopsies obtained at various stages during treatment showed bone of normal lamellar structure without mineralization defects. There was an increase in calcium balance, already evident within 10 days, the level of which was maintained for at least 3 years of treatment. This was associated with progressive increases in bone mineral density along a different slope from that of healthy peers as well as correction of vertebral deformities on X-rays in patients given bisphosphonates before puberty. Treatment was well tolerated and clinical improvement was remarkable. Our studies, supported by literature data, strongly suggest that bisphosphonate therapy can be beneficial to young patients with osteoporosis for whom no other options are currently available, and justify planning controlled studies in more common conditions for which no treatment is currently available, such as osteogenesis imperfecta.

Secondary osteoporosis

Osteoporosis with attendant increased fracture risk is a common complication of many other diseases. Indeed, almost all chronic diseases make some impact on life-style, usually by restricting physical activity and hence reducing the anabolic effect of exercise and gravitational strains on the skeleton. Restricted appetite and modified gastrointestinal tract function is another commonplace finding that has an impact on bone nutrition and synthesis, as on other systems. Sex hormone status is of particular importance for the maintenance of the normal skeleton, and the postmenopausal woman is at particular risk for most causes of secondary osteoporosis. In dealing with secondary osteoporosis in the hypo-oestrogenic woman, the question of giving hormone replacement therapy in addition to other disease-specific therapy should always be considered, as, for example, in a young amenorrhoeic woman with Crohn's disease. Similarly, in hypogonadal men the administration of testosterone is useful for bone conservation. The wider availability of bone densitometry ought to make us more aware of the presence of osteoporosis in the many disease states discussed above. This is particularly important as the life span of such patients is now increased by improved management of the underlying disease process in many instances. Even in steroid-induced osteoporosis--one of the commonest and most severe forms of osteoporosis--we now have some effective therapy in the form of the bisphosphonates and other anti-bone-resorbing drug classes. The possibility of prophylaxis against secondary osteoporosis has therefore become a possibility, although the very long-term effects of such drug regimens are still unknown. In some situations, such as thyrotoxicosis, Cushing's syndrome and immobilization, spontaneous resolution of at least part of the osteoporosis is possible after cure of the underlying problem. The shorter the existence of the basic problem, the more successful the restoration of the skeleton appears to be. A useful credo for clinicians with respect to secondary osteoporosis is: to think of it; to use specific therapy for the underlying disease; to reduce or remove completely any relevant drug or toxic material; to optimize physical activity and general nutrition; to treat hypogonadism if present and feasible; and to consider the use of specific anti-bone-resorbing or other bone active drugs.