Australian Dental Council (ADC) Practice Test

Marble bone disorder, known as osteopetrosis, is characterized by an abnormal increase in bone density due to a failure in the normal resorption process of bone. This condition results from genetic mutations affecting the osteoclasts, the cells responsible for breaking down bone tissue. As a result, bones become overly dense but also brittle, leading to a higher risk of fractures despite the increased density.

Osteopetrosis typically presents with symptoms such as pain, frequent fractures, and various complications due to compressed nerves and bone marrow failure. The abnormal accumulation of bone tissue results in a "marble-like" appearance on X-rays, hence the name marble bone disorder.

Other conditions like osteoporosis, osteogenesis imperfecta, and fibrous dysplasia have distinct etiology and pathology that do not align with the characteristics of marble bone disorder. Osteoporosis involves a reduction in bone density and mass, osteogenesis imperfecta is primarily a disorder of collagen formation leading to brittle bones, and fibrous dysplasia involves the replacement of normal bone with fibrous tissue but does not lead to the excessive density seen in osteopetrosis.