Juvenile osteoporosis

Juvenile osteoporosis is osteoporosis in children and adolescents. Osteoporosis is rare in children and adolescents. When it occurs, it is usually secondary to some other condition, e.g. osteogenesis imperfecta, rickets, eating disorders or arthritis. In some cases, there is no known cause and it is called idiopathic juvenile osteoporosis. Idiopathic juvenile osteoporosis usually goes away spontaneously.

Also, child abuse should be suspected in recurring cases of bone fracture.

Cause

• Mutations in the LRP5 gene can cause juvenile primary osteoporosis.
• This gene provides instructions for making a protein that participates in a chemical signaling pathway that affects the way cells and tissues develop. In particular, the LRP5 protein is involved in the regulation of bone mineral density.

Gene mutations

• LRP5 gene mutations that cause juvenile primary osteoporosis result in an LRP5 protein that cannot transmit signals along the pathway.
• The resulting reduction in signaling impairs proper bone development, causing decreased bone mineral density and osteoporosis at a young age.
• Many people with childhood-onset osteoporosis do not have a mutation in the LRP5 gene. (When its cause is unknown, the condition is often called idiopathic juvenile osteoporosis).
• It is likely that mutations in other genes that have not been identified are involved in this condition.

Inheritance

Autosomal dominant pattern, a 50/50 chance.

This condition is inherited in an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to cause the disorder.

Onset

Symptoms typically develop just before puberty.

Signs and symptoms

• The first sign of IJO is usually pain in the lower back, hips, and feet, often accompanied by difficulty walking.
• Knee and ankle pain and fractures of the lower extremities also may occur.
• Physical malformations include abnormal curvature of the upper spine (kyphosis), loss of height, a sunken chest, or a limp.
• These physical malformations are sometimes reversible after IJO has run its course.

For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed. 80%-99% of people have these symptoms

• Bone pain
• Osteoporosis
• Recurrent fractures(Increased fracture rate)

30%-79% of people have these symptoms

• Gait disturbance(Abnormal gait)
• Vertebral compression fractures(Compression fracture)

5%-29% of people have these symptoms

• Kyphosis(Hunched back)

Diagnosis

• X-rays of children with IJO often show low bone density, fractures of weight-bearing bones, and collapsed or misshapen vertebrae.
• However, conventional x-rays may not be able to detect osteoporosis until significant bone mass already has been lost.
• Newer methods such as dual energy x-ray absorptiometry (DXA), dual photon absorptiometry (DPA), and quantitative computed tomography (CAT scans) allow for earlier and more accurate diagnosis of low bone mass.
• These noninvasive, painless tests are a bit like x-rays.

Treatment

• There is no established medical or surgical therapy for juvenile osteoporosis.
• In some cases, treatment is not necessary, as the condition resolves spontaneously.
• Early diagnosis may allow for preventive steps, including physical therapy, avoidance of weight-bearing activities, use of crutches and other supportive care.
• A well-balanced diet rich in calcium and vitamin D is also important.
• In severe, long-lasting cases, medications such as bisphosphonates may be used. In most cases, complete recovery of bone occurs.

Further reading

• Juvenile Osteoporosis - NIH Osteoporosis and Related Bone Diseases ~ National Resource Center

External links

Classification	ICD-10: M81.5 OMIM: 259750
External resources	Orphanet: 85193