High bone mineral density

A high bone mineral density is one where the bone mineral density (BMD) is usually greater than two standard deviations above what is expected for age. This can sometimes be seen on routine DXA scan assessment. Some authors advocate a definition of a high BMD where the Z-score is >+2.5 to highlight to clinicians the potential for underlying pathology.

Pathology

A high bone mineral density can result from a number of varied mechanisms. It may be associated with conditions with increased fracture risk, or artefacts that themselves do not affect fracture risk but may mask low bone mineral density or in situation where fracture risk may be reduced but other comorbidities may occur.

Etiology

Focal

• Paget disease of bone
• malignancy: sclerotic skeletal metastases
• tuberous sclerosis
• SAPHO syndrome

Generalized

• for adults: see generalized increased bone density in adults
• for children: see generalized increased bone density in children

Generalized acquired

• fluorosis
• renal osteodystrophy
• acromegaly
• hepatitis C associated osteosclerosis (HCAO)
• myelofibrosis
• mastocytosis
• estrogen implants

Generalized inherited

• decreased bone resorption
  • autosomal dominant osteopetrosis II
  • pycnodysostosis
• increased bone formation
  • LRP5 high bone mass
  • sclerosteosis
  • van Buchem disease
  • unexplained high bone mass

Artifactual causes

• osteoarthritis: degenerative disease
• diffuse idiopathic skeletal hyperostosis
• ankylosing spondylitis
• vertebral fractures
• extrinsic artifact