Marble bone is characteristic of?
**Core Concept**
Marble bone, also known as osteopetrosis, is a rare genetic disorder characterized by an increase in bone density due to impaired osteoclast function. This leads to a reduction in bone resorption and an accumulation of compact, dense bone tissue.
**Why the Correct Answer is Right**
The correct answer is related to the pathophysiology of osteopetrosis. Osteopetrosis is caused by mutations in genes encoding proteins involved in osteoclast function, such as RANKL, RANK, and OPG. Impaired osteoclast activity results in a failure to resorb bone, leading to an accumulation of dense, compact bone tissue. This gives the bone a characteristic "marble-like" appearance on radiographs.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as osteogenesis imperfecta is a different genetic disorder characterized by fragile bones and blue sclerae due to defects in collagen production.
**Option B:** This option is incorrect as fibrous dysplasia is a non-genetic disorder characterized by abnormal fibrous tissue replacing normal bone tissue.
**Option C:** This option is incorrect as osteomalacia is a condition of softening of bones due to deficiency of vitamin D, calcium, or phosphate.
**Clinical Pearl / High-Yield Fact**
A key feature of osteopetrosis is the characteristic "marble-like" appearance of the bone on radiographs, which is due to the accumulation of compact, dense bone tissue.
**Correct Answer:** C. Osteomalacia