Pediatric Osteoporosis

Updated: May 19, 2020
  • Author: Manasa Mantravadi, MD, MS; Chief Editor: Jatinder Bhatia, MBBS, FAAP  more...
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Overview

Practice Essentials

Pediatric osteoporosis is defined by the occurrence of one or more vertebral compression fractures in the absence of local disease or high-energy trauma or the presence of both low bone density for age and a significant fracture history, according to the International Society for Clinical Densitometry. [1]  Dual-energy x-ray absorptiometry (DXA) is the most widely used method for measurement of bone density in children and adolescents. The main goals of treatment of pediatric osteoporosis are to prevent fractures and scoliosis, to improve function and mobility, and to alleviate pain.

Signs and symptoms

Patients with low bone mineral density for age may be asymptomatic or may present with bone pain. Peripubertal children with idiopathic juvenile osteoporosis often experience a gradual onset of pain, primarily in the hips, ankles, knees, and feet.

A history of axial skeletal fractures or multiple fractures from low biomechanical force may indicate skeletal fragility and should raise concern for osteoporosis.

Physical examination findings are often normal in children with osteoporosis. Abnormal findings may include the following:

  • Joint hypermobility or hypomobility
  • Spinal deformities (eg, kyphosis, kyphoscoliosis)
  • Pectus deformities (both carinatum and excavatum)
  • Long bone deformities (associated with more severe forms of metabolic bone disease)
  • Limping due to pain

See Presentation for more detail.

Diagnosis

Laboratory studies

Baseline laboratory studies include the following:

  • Basic chemistry panel, including serum calcium (total or ionized), phosphorus, creatinine, and parathyroid hormone concentrations
  • Spot measurements of urine calcium and creatinine
  • Alkaline phosphatase (total or bone-specific) and osteocalcin levels
  • Magnesium levels

Imaging studies and other tests

In children and adolescents, bone densitometry based on DXA is the most widely used method to quantify the amount of calcium in bone. According to the American Academy of Pediatrics, DXA is recommended for children with the following conditions [2] :

  • Primary bone disorders such as idiopathic juvenile osteoporosis and osteogenesis imperfecta
  • Secondary conditions known to increase fracture risk (eg, chronic inflammatory diseases, immobilization for long periods, endocrine or hematologic diseases, cancer and associated treatments that adversely affect bone)
  • A history of clinically significant fracture

DXA may also be indicated based on risk factors including patient’s age at fracture, severity of underlying conditions, exposures to radiation or drugs detrimental to bone, and family history.

Other diagnostic methods under investigation include calcaneal and phalangeal ultrasonography and quantitative computed tomography. Because of the availability of blood and urine biochemical markers of bone turnover, the use of bone histology obtained by iliac crest bone biopsy is no longer routine.

See Workup for more detail.

Management

The primary goals of the management of pediatric osteoporosis are prevention of fractures, including vertebral fractures, and scoliosis and improvement in function, mobility, and pain. Therapy includes antiresorptive agents such as bisphosphonates as well as calcium and vitamin D supplementation. Hormone replacement therapy does not have a role in pediatric management unless the low bone mass is attributable to hypogonadism.

See Treatment and Medication for more detail.

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Background

There are several commonly used definitions for osteoporosis. At the National Institutes of Health (NIH) Consensus Conference, osteoporosis was defined as a skeletal disorder characterized by compromised bone strength that predisposes to an increased risk of fracture. [3] The World Health Organization (WHO) defines osteoporosis in adults as a bone mineral density (BMD) at least 2.5 standard deviations (SD) below peak (defined as the BMD achieved by healthy young adults of the same race and gender aged 18-30 years). For adults, BMD is commonly expressed in T-scores, defined by SD from the mean peak BMD, with T-scores at the lumbar spine or hip of < -2.5 defining osteoporosis.

Although this definition is functionally valid for adults, it is not appropriate for children because they have not yet attained peak bone mass. Because the T-score is a measure of BMD compared with early adulthood, its use in children whose BMD and bone mineral content (BMC, in grams) have not yet reached peak will generally yield a low value. Instead, Z-scores are used in children because they reflect SD scores from the mean in comparison to BMD and BMC of healthy children of the same age, gender, and body size. Some but not all Z-score measures also incorporate race.

It is also important to note that BMD is derived from an areal measure, defined as the BMC in grams per selected bone area measured in centimeters squared. It therefore is not a true volumetric density. Unlike adult patients in whom the bone volume does not change over time, a child’s bones grow and model over time, with the growth of individual bones not happening uniformly in 3 dimensions. Sufficient population-based data correlating BMD measures with fracture rates in healthy children are also not available. For all these reasons, the official WHO definition of osteoporosis cannot pertain to children.

At the first Pediatric Consensus Development Conference (sponsored by the International Society for Clinical Densitometry [ISCD]) an official position on the use and interpretation of densitometric studies in children based on expert opinion was released; it was subsequently updated several times. [1, 4, 5]  The following are the most recent pediatric osteoporosis definitions and fracture risk positions in children [1] :

  • “The diagnosis of osteoporosis in children and adolescents should not be made on the basis of densitometric criteria alone.”

  • “The finding of one or more vertebral compression (crush) fractures is indicative of osteoporosis, in the absence of local disease or high-energy trauma. In such children and adolescents, measuring BMD (bone mineral density) adds to the overall assessment of bone health.”

  • “In the absence of vertebral compression (crush) fractures, the diagnosis of osteoporosis is indicated by the presence of both a clinically significant fracture history and BMD Z-score ≤ -2.0. A clinically significant fracture history is one or more of the following: 1) two or more long bone fractures by age 10 years; 2) three or more long bone fractures at any age up to age 19 years.”

  • “A BMC/BMD Z-score > -2.0 does not preclude the possibility of skeletal fragility and increased fracture risk.”

The ISCD guidelines additionally stipulate that dual-energy x-ray absorptiometry (DXA) is the preferred method for assessing BMC and areal BMD (aBMD) in children and adolescents. [1]   Although population-based data on the relationship between BMD and fracture are still limited, population-based reference curves for DXA assessments of BMC and aBMD for total body less head (TBLH), lumbar spine, hip, femoral neck, and distal one-third radius for black and nonblack children in the United States are available from the Bone Mineral Density in Childhood Study (BMDCS). [6]

Unlike in adults, in whom osteopenia is defined as a T-score between -1 and -2.5, use of the word “osteopenia” is not appropriate when referring to pediatric BMC/BMD values. Instead, low BMCs or aBMDs are defined by Z-scores of -2.0 or less adjusted for age, sex and body size (height z-score). "Low bone mineral mass or bone mineral density" is the phrase that is recommended for low BMC or aBMD in the absence of a fracture history suggestive of osteoporosis. [5, 1]

See Osteoporosis for information on non-pediatric osteoporosis.

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Pathophysiology

Low BMD in adults is generally due to net bone loss after peak accrual. In children low BMD can result from loss of bone or, more commonly, failure to accrue adequate bone mineral for the bone size. Some causes of low BMD are also due to inherited conditions, particularly ones that affect collagen amount or function (such as osteogenesis imperfecta).

DXA provides aBMD measures, which are 2-dimensional measurements derived by dividing BMC measured in grams in a specified bone region (eg, lumbar spine) by the bone area (BA) in cm2.  Since it does not account for the depth of the bone, it gives “density” as a reading in g/cm2. This method of assessing BMD is limited because changes in bone volume are not accounted for. This can result in inaccurate estimations of the degree of bone loss or the skeletal response to treatment. 

Low BMD in children results when there is an imbalance between the rates of bone formation and resorption. Low-turnover conditions, characterized by low bone formation, include chronic liver disease, burn injuries, and conditions that affect the bone marrow (eg, leukemias) or their treatments. High-turnover states, such as hyperparathyroidism or hyperthyroidism, can result in an increase in bone resorption.

Bone will not accrue normally when there are deficits of calcium, phosphate, and/or vitamin D or when bone is not exposed to normal physical/mechanical stresses and strains. One population particularly at risk for failure to accrue bone are infants born prematurely. Because most calcium is transmitted from mother to fetus during the third trimester, premature infants do not receive in utero all the calcium their bodies need to normally mineralize. With rapid postnatal increases in bone turnover, fewer opportunities are available for the bones to mineralize. [7]

Furthermore, most of these children receive parenteral nutrition (first as intravenous [IV] fluids and then later as total parenteral nutrition [TPN]) for the first several weeks of life. Calcium and phosphorus requirements are generally not able to be met by TPN in any age group, and infants, especially the very premature infant, can present with poor bone mass and metabolic bone disease.

Other populations of children experience secondary bone loss from adaptations to trauma and infection or threat of infection. These include bone loss due to immobilization as well as loss due to the stress response, in which endogenous glucocorticoids act in the same manner as exogenously administered steroids. These compounds cause an initial increase in osteoblast production of the receptor activator of nuclear transcription factor kappa B ligand (RANKL), which stimulates marrow to produce osteoclastic cells, increasing bone resorption. However, steroids also promote osteoblast apoptosis and reduce marrow cell osteoblast differentiation, eventually leading to a low-turnover bone loss or adynamic bone.

Another mechanism linked to bone loss is the inflammatory response. This involves the production of the cytokines interleukin (IL)–1 beta and IL-6, as well as tumor necrosis factor (TNF) alpha. These can increase bone resorption via stimulation of osteoblast production of RANKL.

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Etiology

Bone mass and, for children, the ultimate achievement of young adult peak bone mass are predominately determined by genetics. Adequate dietary intake and absorption of calcium, phosphorus, and vitamin D are also critical for normal bone accrual.

Phosphorus is relatively plentiful in most Western diets, and therefore dietary phosphorus deficiency that is significant enough to cause bone disease is very rare. Calcium intake is much more likely to be deficient in children, particularly young adolescent girls. The NIH Consensus Conference on Osteoporosis recommended that preadolescent and young adolescent girls have a calcium intake that is 50% more than the intake recommended for younger children and older adults. [8] Dietary calcium supplementation in the preadolescent years may be a key factor in optimizing peak bone mass. However, when dietary calcium supplementation is stopped, data suggest that the increase in bone mass is not maintained.

Another critical factor for optimal bone accrual is exercise. Results from the Bone Mineral Density in Childhood Study showed that self-reported weight-bearing physical activity contributed to significantly greater BMC accrual after adjustment for age, height velocity, Tanner stage, prior visit BMC, and calcium intake in both sexes and both racial subgroups (defined as blacks and non-blacks in this study). [9]

Conditions that adversely affect bone mineralization and strength can result in pediatric osteoporosis. Primary osteoporosis occurs because of an intrinsic skeletal defect of genetic or idiopathic origin. Osteogenesis imperfecta (OI) is the most common of the genetic conditions. Secondary osteoporosis stems from chronic systemic illnesses in children due to either the effects of the disease process on the skeleton or their treatment. Causes of secondary osteoporosis include immobility, leukemia, inflammatory conditions, glucocorticoid therapy, hypogonadism and poor nutrition. [10]

The following table lists some of the most frequent conditions that result in reduced bone mass in children. [11]

Table 1. Conditions Associated with Reduced Bone Mass in Children and Adolescents (Open Table in a new window)

Genetic conditions
   Osteogenesis imperfecta
   Idiopathic juvenile osteoporosis
   Turner syndrome
Chronic illness
   Cystic fibrosis
   Connective tissue disorders (lupus, juvenile idiopathic arthritis, juvenile dermatomyositis)
   Inflammatory bowel disease, celiac disease
   Chronic renal failure
   Childhood cancer
   Cerebral palsy
   Chronic immobilization

Eating disorders, including anorexia nervosa, bulimia nervosa, eating disorders not otherwise specified, and the female athlete triad

Endocrine disorders
   Cushing syndrome
   Hypogonadism
   Hyperthyroidism
   Hyperparathyroidism
   Growth hormone deficiency
   Diabetes mellitus
Medications
   Glucocorticoids
   Anticonvulsants
   Chemotherapy
   Leuprolide acetate
   Proton pump inhibitors
   Selective serotonin reuptake inhibitors
   Depot medroxyprogesterone acetate (DMPA)

Table from: Golden NH, Abrams SA, Committee on Nutrition. Optimizing bone health in children and adolescents. Pediatrics. 2014 Oct. 134 (4):e1229-43.

OI, a rare genetic disorder of type 1 collagen, is perhaps the most studied form of primary osteoporosis. Individuals with OI present with varying degrees of fracture, blue sclerae, dentinogenesis imperfecta, ligament laxity, and hearing impairment. [12] Bone biopsy shows decreased cortical and cancellous bone mass. [13] Dominant mutations in COL1A1 and COL1A2 account for 95% of OI cases. [14]

See Osteogenesis Imperfecta (OI) for more information.

Idiopathic juvenile osteoporosis (IJO) is another rare form of primary osteoporosis and is a diagnosis of exclusion. IJO typically presents before puberty and spontaneously remits after puberty. Its characteristic features are bone pain, difficulties in walking, and metaphyseal and vertebral fractures. [15]

Secondary forms of pediatric osteoporosis can be the result both of the primary disease and of the treatments for that disease or concomitant features. Sarcopenia, malnutrition, malabsorption, proinflammatory cytokines, sunlight avoidance, immobilization, endocrine dysfunction, and chronic glucocorticoid exposure are among the factors that contribute to the deleterious effects on bone.  

Medications, such as tenofovir, corticosteroids, cyclosporine, and other cytotoxic agents, may contribute to bone loss. Long-term glucocorticoid use decreases bone formation and increases resorption. A study indicated that the risk of bone loss secondary to oral corticosteroid use is higher in boys than in girls, whereas cumulative inhaled corticosteroid use did not increase the risk of bone loss in either boys or girls. [16] However, more recent studies have shown that children with asthma receiving budesonide and beclomethasone dipropionate have decreased linear growth, and that children who receive long-term inhaled corticosteroid therapy for asthma have height deficits 1-2 years after treatment initiation that persist into adulthood. [17]

Thus, long-term therapy with inhaled corticosteroids is safer than frequent bursts of oral corticosteroids on bone mineral accretion. [17] However, an attempt to minimize any adverse effects with use of the lowest effective dose is recommended.

 

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Epidemiology

Highly powered studies do not exist for pediatric osteoporosis; thus, the data on the prevalence of pediatric osteoporosis are inadequate. For example, through 1991, the rare condition of idiopathic juvenile osteoporosis had been reported in only 60 cases. However, numerous observational studies have shown that survivors of pediatric and adolescent cancers are at risk for low bone mass after completion of therapy. Other studies have shown secondary bone fragility occurs early in the disease process, with 16% of children with acute lymphoblastic leukemia and 7% of children with a rheumatologic condition having evidence of vertebral compression fractures within 30 days of diagnosis. [18, 19]

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Prognosis

Prognosis depends on the underlying cause and the severity of the bone disease. While osteoporosis in children is not linked to increased mortality as in adults, it may have serious effects on a child’s quality of life, including pain, poor school performance, loss of function, and other long-term consequences. In extreme cases, including idiopathic juvenile osteoporosis and low BMD for age in immobile children with severe developmental delay, crippling bony deformities may lead to cardiopulmonary compromise.

Genetic conditions that lead to increased bone resorption may have a satisfactory prognosis if antiresorptive agents can eliminate further bone loss. (See Treatment.)

In the case of trauma-induced or burn-induced low BMD for age in which bone formation is primarily affected, prognosis depends on the patient’s genetically determined peak bone mass and the efficacy of clinically experimental therapies, such as anabolic steroids and pamidronate, along with correction of progressive vitamin D deficiency that is a consequence of the skin’s failure to make adequate vitamin D with ultraviolet light exposure, similar to what is seen in elderly persons. (See Treatment.)

Although theories suggest that early-onset bone loss may be overcome as new healthy bone replaces compromised bone, a long-term outcome study in 144 young adults with very low birth weight who were studied around the time of peak bone mass have significantly lower BMD at the lumbar spine and femoral neck compared with term-born peers. [20]  Studies have evaluated the impact of bone-involving diseases during childhood (anorexia nervosa, malignancy, and juvenile rheumatoid arthritis) on BMD and fracture risk in adult age. [21, 22, 23] These trials have demonstrated that even after resolution of some childhood diseases, permanent bone damage (in terms of reduced BMD and increased fracture risk) can be seen in adulthood.

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Patient Education

Use education as a means of prevention and treatment. As early as possible, inform patients of any age with low BMD for age or osteoporosis why bone loss has occurred and how to keep bone loss under control. Also inform patients with low BMD for age or osteoporosis of the consequences of bone loss. Instruct children, adolescents, and their families that the roots of adult-onset osteoporosis may begin in childhood.

The American Academy of Pediatrics (AAP) recommends that pediatricians assess children’s calcium and vitamin D consumption at ages 3 and 9 and then yearly in the preteen and teen years. Most children can get the recommended amount of calcium by eating 3 servings a day of low-fat dairy products (4 servings for adolescents). Infants less than 1 year old should receive 400 IU of vitamin D daily. Children older than age 1 year and adolescents should receive 600 IU of vitamin D daily through diet or supplements. The AAP also encourages physical activity, primarily weight-bearing exercise, as an important part of keeping bones healthy. [11]

For patient education resources, see the Osteoporosis Health Center and What Is Juvenile Osteoporosis?, as well as the slideshow A Visual Guide to Osteoporosis.

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