eMedicine Specialties > Pediatrics: General Medicine > Nutrition
Osteoporosis: Differential Diagnoses & Workup
Updated: Aug 21, 2008
- Overview
- Differential Diagnoses & Workup
- Treatment & Medication
- Follow-up
Differential Diagnoses
Other Problems to Be Considered
In children, low bone density (formerly termed osteoporosis) can develop because of low bone formation (low bone turnover) or high bone resorption (high bone turnover).
The following conditions elicit low bone formation:
- Medication-induced osteopenia (prominently corticosteroids and cyclosporine)
- Immobilization or prolonged bed rest
- Burn injury
- Hypoparathyroidism that results in hypercalciuria
- Hepatic osteodystrophy with chronic cholestasis (all causative syndromes and conditions)
- Aluminum toxicity in association with TPN or renal osteodystrophy
- Prolonged TPN
- Corticosteroid-induced osteopenia
Conditions giving rise to high bone turnover include the following:
- Corticosteroid-induced bone loss
- Immobilization or bed rest
- Paget disease
- Primary and secondary hyperparathyroidism
- Rickets due to vitamin D deficiency or calcium deficiency
- Idiopathic juvenile osteoporosis
Workup
Laboratory Studies
- Serum calcium, phosphorus, magnesium, creatinine levels
- High or normal serum calcium levels and normal or low phosphorus levels suggest secondary hyperparathyroidism.
- Low serum calcium levels and high or normal phosphorus levels suggest hypoparathyroidism.
- Creatinine levels provide an indication of renal disease.
- Magnesium levels provide an index of total body magnesium status and can be affected in perturbations of the parathyroid.
- Serum parathyroid hormone (PTH) levels
- High PTH levels confirm hyperparathyroidism.
- Low PTH levels confirm hypoparathyroidism.
- Serum or urinary cross-links of type I collagen (deoxypyridinoline), N-telopeptide of type I collagen (NTx) or C-telopeptide of type I collagen (CTx), urine creatinine
- Deoxypyridinoline, an index of bone resorption, is high in the urine of children who have rapid bone turnover.
- Obtain biochemical markers of bone resorption (NTx) and formation (osteocalcin) to clarify the nature of what is occurring in the bone.
- Serum osteocalcin or bone-specific alkaline phosphatase: Values may vary between assays. No expected results are reported. Osteopenia can develop from either high-turnover or low-turnover conditions. These tests help define which condition may be active.
- Pediatric reference ranges for osteocalcin
- Younger than 12 years - 10-25 ng/mL
- Older than 13 years - 2-8 ng/mL
- Pediatric reference ranges for bone specific alkaline phosphatase
- Preadolescents - 50-150 IU/L
- Adolescents - 10-50 IU/L
- Pediatric reference ranges for osteocalcin
Imaging Studies
- Dual energy x-ray absorptiometry scan
- The amount of calcium in bone can be quantified in several ways. Bone densitometry based on dual energy x-ray absorptiometry (DEXA) is the most widely used method. DEXA provides 2-dimensional imaging of a region of bone, such as the lumbar spine, hip, or radius.
- DEXA provides a computerized printout of bone calcium content, which is measured in grams; the bone area is measured in cm2; and the 2-dimensional bone density is measured in g/cm2.
- Pediatric reference ranges are taken from large studies using DEXA and are incorporated into the software that provides the printout; thus, actual individual bone density and its comparison to age-related normal values (Z score) is printed out as part of the report. The main drawback is that DEXA does not measure changes in bone volume and, therefore, changes in bone strength. It also tends to over-read bone density in larger patients and under-read it in smaller patients. Criteria for pediatric DEXA reporting are now available on the Web site of the International Society for Clinical Densitometry as well as the January 2008 issue of the Journal of Clinical Densitometry.9
- Investigational methods
- Other methods under investigation include calcaneal and phalangeal ultrasonography and quantitative CT (qCT), which involves the most radiation of any of the tests. Reference range values for phalangeal ultrasonography results are now available.
- Peripheral qCT (pqCT), which usually involves a foot or a lower limb and much less radiation than the qCT scan, can also provide an indirect assessment of bone density. However, DEXA is by far the most commonly used technique. Criteria for performing and reporting pQCT imaging are also found on the Web site of the International Society for Clinical Densitometry and the January 2008 issue of the Journal of Clinical Densitometry.9
Histologic Findings
Because of the availability of kits to measure biochemical markers of bone turnover, the use of bone histology obtained by iliac crest bone biopsy is no longer routine. Histology for bone biopsies is generally carried out using quantitative histomorphometry. For patients older than 10 years, administer tetracycline or one of its analogs 14 days before biopsy and then 2 days prior to biopsy. Using one of several specialized orthopedic needles, obtain a biopsy sample consisting of a 6-mm core of trabecular bone tissue.
When processed, the amounts of mineralized bone, unmineralized bone, and bone surface can be quantitated. In addition, the tetracycline binds to newly calcified bone at the mineralization front, which is the boundary between mineralized bone and unmineralized matrix where new bone forms. Each time a dose of tetracycline is administered, it forms a band at the mineralization front that can be detected under a fluorescent microscope. The distance between the 2 fluorescent bands can be quantitated. When divided by the time interval between doses and multiplied by the length of bone surface taking up the tetracycline yields, the rate of new bone formation is achieved. The eroded or resorbed bone surface also can be quantitated, and all can be compared to reference values for age.
Perform these studies if analysis of bone markers and other biochemical determinations are inconclusive regarding the nature of the activity of the bone in a particular condition. These studies also form the basis for validating the biochemical bone marker analyses.
More on Osteoporosis |
| Overview: Osteoporosis |
 Differential Diagnoses & Workup: Osteoporosis |
| Treatment & Medication: Osteoporosis |
| Follow-up: Osteoporosis |
| References |
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Further Reading
Keywords
osteoporosis, low bone mass, pediatric osteoporosis, juvenile osteoporosis, fracture, compromised bone strength, osteopenia, chronic liver disease, burn injuries, Paget disease, hyperparathyroidism, hypophosphatemic metabolic bone disease, idiopathic juvenile osteoporosis, bony deformities, cardiopulmonary compromise, reduced bone density, kyphosis, kyphoscoliosis, short stature, long bone deformities, lordosis, scoliosis, pigeon breast deformity, hip fractures, inflammatory bowel disease, rheumatoid arthritis, trauma
