Metabolic Bone Diseases — MCQs

Q: Osteonecrosis is seen in all except

Paget's disease. ***Paget's disease*** - **Paget's disease of bone (osteitis deformans)** is a localized disorder of bone remodeling, characterized by excessive and disorganized bone formation, leading to enlarged, softened, and misshapen bones, but not directly causing osteonecrosis. - While complications like **pathological fractures** and **osteosarcoma** can occur, primary osteonecrosis is not a typical feature of Paget's disease itself. *Fracture neck femur* - **Fractures of the femoral neck** can disrupt the blood supply to the femoral head, particularly the medial circumflex femoral artery, leading to **avascular necrosis** (osteonecrosis) of the femoral head. - This is a well-known and common complication, especially in displaced fractures. *Sickle cell anemia* - **Sickle cell anemia** causes sickling of red blood cells, leading to **vaso-occlusion** and impaired blood flow to bones, resulting in **bone infarcts** (osteonecrosis). - This can affect various bones, including the femoral head, humeral head, and vertebrae. *Perthe's disease* - **Perthe's disease** (Legg-Calvé-Perthes disease) is a childhood condition characterized by **idiopathic osteonecrosis** of the femoral head. - It involves the collapse and subsequent re-ossification of the femoral epiphysis due to an interruption of its blood supply.

Q: Which of the following is not typically associated with osteogenesis imperfecta?

Bilateral Hip dislocation. ***Bilateral Hip dislocation*** - While hip dislocations can occur in severe cases due to bone fragility, **bilateral hip dislocation** is not a characteristic or typical primary association with osteogenesis imperfecta. - The underlying issue is primarily **bone fragility** leading to fractures, not inherent joint instability or malformation causing bilateral dislocation. *Blue sclera* - **Blue sclera** is a classic sign of osteogenesis imperfecta, caused by the thinness of the sclera allowing the underlying choroid vessels to show through. - This is due to a defect in **Type I collagen** synthesis, which affects not only bones but also other connective tissues including the sclera. *Lax ligament* - **Lax ligaments** are common in osteogenesis imperfecta due to the generalized **connective tissue defect**, particularly involving Type I collagen. - This can contribute to joint instability, *hypermobility*, and an increased risk of sprains. *Osteoporosis* - **Osteoporosis** with reduced bone mineral density is a hallmark feature of osteogenesis imperfecta, leading to **fragile bones** and recurrent fractures. - The genetic defect in **Type I collagen** impairs bone matrix formation, resulting in weak and brittle bones.

Q: A patient complains of loss of visual acuity, deafness, and enlargement of the maxilla.

Paget's disease. ***Paget's disease*** [1] - Characterized by abnormal **bone remodeling**, leading to an increase in bone size and deformity, particularly in the **maxilla**, causing enlargement [1]. - Associated with complications such as **loss of visual acuity** (due to involvement of the skull) and **deafness** from auditory canal changes [1][2], making this the most fitting diagnosis. *Fibrous dysplasia* - Typically presents with **fibrous replacement** of bone, not specifically causing deafness or visual acuity loss. - Customarily involves the **classic "ground glass" appearance** on imaging, not the structural enlargement seen in Paget's disease. *Osteogenesis imperfecta* - Mainly causes **brittle bones** and frequent fractures, not associated with **maxillary enlargement** or changes in auditory function. - Rarely causes visual acuity loss, which is not a feature of this condition. *Osteomalacia* - Primarily characterized by **softening of bones** due to vitamin D deficiency, leading to weakness rather than structural changes like maxillary enlargement. - Symptoms like **bone pain** or **muscle weakness** occur, but not specifically loss of auditory function or visual acuity. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Bones, Joints, and Soft Tissue Tumors, pp. 1192-1194. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Osteoarticular And Connective Tissue Disease, pp. 669-670.

Practice by Chapter

Osteoporosis

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Osteomalacia and Rickets

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Paget's Disease of Bone

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Hyperparathyroidism

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Renal Osteodystrophy

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Fluorosis

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Osteogenesis Imperfecta

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Bone Mineral Density Assessment

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Pharmacological Management of Metabolic Bone Diseases

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Surgical Considerations in Metabolic Bone Diseases

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Fragility Fractures

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Prevention Strategies

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