Bone density disorders in children include a range of conditions that affect the density and strength of bones, leading to an increased risk of fractures and other skeletal issues. These disorders can arise from various factors, including genetic mutations, nutritional deficiencies, endocrine abnormalities, and underlying chronic diseases.
Bone density disorders are classified based on whether they are characterized by low or high bone density.
Low Bone Density Disorders in Children
Low bone density disorders are characterized by defective function of osteoblasts and clinically manifest with skeletal abnormalities and increased fracture risk.
Vitamin D and calcium deficiencies are among the most common causes of low bone density in children. Vitamin D deficiency impairs calcium absorption, leading to rickets and osteomalacia. Malabsorption resulting from celiac disease or chronic kidney disease may also lead to secondary vitamin D and calcium deficiencies. Other secondary causes include chronic glucocorticoid exposure, hypogonadism or delayed puberty, and growth hormone deficiency.
The main types of low bone density disorders in children include the following:
Inheritance of pediatric low bone density disorders varies by condition:
Osteogenesis imperfecta: Usually autosomal dominant (COL1A1 or COL1A2), but recessive forms exist
Primary osteoporosis (eg, osteoporosis-pseudoglioma syndrome): Often autosomal recessive
Rickets: Nutritional rickets is acquired; genetic rickets can be X-linked dominant (eg, XLH), autosomal recessive (eg, vitamin D–dependent rickets type 1 or 2), or autosomal dominant (rare forms of hypophosphatemic rickets).
Overall, symptoms of low bone density in children may include an increased risk of fractures, especially of the long bones and vertebrae. Patients may also have bone pain or back pain. Affected children may also present with reduced mobility due to prior fractures. Rarely, vertebral fractures can be asymptomatic but lead to indolent height loss or spinal deformity.
The diagnosis of low bone density is made by measurement of bone mineral density (bone mass per unit volume). Dual-energy x-ray absorptiometry (DXA) is the gold standard in children, and Z-scores (the number of standard deviations a patient’s bone density is above or below the average) are adjusted for age, sex, and body size.
The treatment of low bone density disorders is often directed to the underlying cause. Lifestyle changes and, in some cases, medications (eg, vitamin D, bisphosphonates) may also be helpful.The treatment of low bone density disorders is often directed to the underlying cause. Lifestyle changes and, in some cases, medications (eg, vitamin D, bisphosphonates) may also be helpful.
High Bone Density Disorders in Children
Osteopetroses are familial disorders caused by defective function of the osteoclasts and are characterized by increased bone density and skeletal modeling abnormalities.
Osteopetroses can be categorized based on whether sclerosis or defective skeletal modeling predominates. There are a number of different types, including the following:
Osteopetroses are all familial but have different inheritance patterns. Some types are comparatively benign, whereas others are progressive and fatal.
Bony overgrowth may severely distort the face, and malocclusion of the teeth can require specialized orthodontic measures.
Plain radiographs are typically diagnostic, showing diffuse bone sclerosis, “bone-in-bone” appearance, and metaphyseal flaring. The diagnostic evaluation should also include laboratory testing for cytopenias (due to loss of marrow space) as well as genetic testing to confirm the subtype, define inheritance, and guide prognosis and family counseling.
Surgical decompression may be required to relieve elevated intracranial pressure or to release a trapped facial or auditory nerve. Hematopoietic stem cell transplantation is a potential therapy for severe forms because replacing the hematopoietic compartment can correct intrinsic osteoclast defects.
Glucocorticoids may be used in the treatment of select craniotubular hyperostoses. They work by impairing bone formation and increasing bone resorption; intralesional glucocorticoids also serve to reduce local inflammation and pain.
Drugs Mentioned In This Article
