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Update on Osteopetrosis

Osteopetrosis is a hardening of the bone that leads to problems with fractures, arthritis, and osteomyelitis (bone infection). In this update and review of osteopetrosis, classification (type), pathology (what went wrong), and signs and symptoms are presented. Treatment is also discussed.

Osteopetrosis is caused by genetic mutations and is an inherited condition. There are three main forms including malignant, intermediate, and benign. Most cases are the benign form.

The pathology behind this bone condition is a problem with the osteoclasts. Osteoclasts are bone cells that remove bone tissue. This process is known as bone resorption.

Bone resorption is part of a normal building up and tearing down of bone cells. But in osteopetrosis, the osteoclasts can't remodel bone during growth. Instead, the bone stays thick with bone cells in a disorganized pattern. The poor bone quality leads to hard but brittle bones that fracture easily.

Symptoms can be mild to severe depending on the type of osteopetrosis present. The malignant form occurs in the first year of life. Most children with this type do not survive.

The intermediate form occurs later in life. Fractures are the first sign of a problem. Bone growth around cranial nerves can cause neurologic problems. Cranial nerves come directly from the brain instead of the spinal cord. They send and receive motor and sensory messages in the head and neck region. Hearing loss and blindness can develop.
This type of osteopetrosis is less severe than the malignant form.

The most common type (benign) can occur at any age. Frequent fractures that don't heal well affect 60 per cent of these patients. The fractures lead to bone deformity, which can result in osteoarthritis (OA). Spine problems such as scoliosis (curvature of the spine) and low back pain have also been reported. The remaining 40 per cent of patients with benign osteopetrosis may not have any symptoms.

References: Joshua Landa, MD, et al. Orthopaedic Management of the Patient with Osteopetrosis. In Journal of the American Academy of Orthopaedic Surgeons. November 2007. Vol. 15. No. 11. Pp. 654-662.

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