Metabolic Bone Diseases Practice Questions

Q: Increased bone density is seen in all of the following conditions EXCEPT?

Primary hyperparathyroidism. **Explanation:** The core concept behind this question is the balance between bone formation and bone resorption. **Increased bone density (Osteosclerosis)** occurs when there is either excessive bone formation or defective bone resorption. **1. Why Primary Hyperparathyroidism is the Correct Answer:** In **Primary Hyperparathyroidism**, there is an excess of Parathyroid Hormone (PTH). PTH stimulates osteoclasts (via the RANKL pathway), leading to increased bone resorption. This results in **decreased bone density (Osteopenia/Osteoporosis)**. Classic radiological features include subperiosteal bone resorption (most common in phalanges), "Salt and Pepper" skull, and Brown tumors (Osteitis Fibrosa Cystica). **2. Analysis of Incorrect Options (Conditions with Increased Density):** * **Osteopetrosis (Marble Bone Disease):** Caused by a functional defect in osteoclasts. Since bone is not resorbed/remodeled, it becomes excessively dense, chalky, and brittle. * **Fluorosis:** Chronic fluoride toxicity stimulates osteoblastic activity and replaces hydroxyapatite with fluoroapatite, leading to dense, sclerotic bones, especially in the axial skeleton. * **Hypoparathyroidism:** A deficiency of PTH leads to decreased osteoclast activity. While not as dramatic as osteopetrosis, it often results in increased bone mineral density (BMD) because the normal "remodeling markers" are low. **High-Yield Clinical Pearls for NEET-PG:** * **Rugger Jersey Spine:** Characterized by sclerotic bands at the endplates; seen in **Chronic Renal Failure (Renal Osteodystrophy)**. * **Erlenmeyer Flask Deformity:** Seen in **Osteopetrosis**, Gaucher’s disease, and Thalassemia. * **Most common site of bone resorption in Hyperparathyroidism:** Radial aspect of the middle phalanx of the index and middle fingers.

Q: Marble bone disease is also known as which of the following?

Osteopetrosis. **Explanation:** **Osteopetrosis**, also known as **Marble Bone Disease** or Albers-Schönberg disease, is a rare genetic disorder characterized by a functional defect in **osteoclasts**. Due to the failure of normal bone resorption, bones become pathologically dense, thick, and sclerotic (resembling marble on X-ray). However, despite the increased density, the bone is structurally weak and prone to "chalk-like" fractures. **Analysis of Options:** * **Osteoporosis (A):** This is characterized by decreased bone mass and density (porous bones), the exact opposite of the dense bones seen in osteopetrosis. * **Osteochondritis (B):** This refers to a group of disorders involving inflammation or necrosis of the bone and cartilage at the joints (e.g., Perthes disease), not a generalized increase in bone density. * **Osteogenesis Imperfecta (D):** Also known as "Brittle Bone Disease," this is a connective tissue disorder caused by defective Type I collagen synthesis. It typically presents with blue sclera and multiple fractures, but bones appear osteopenic (translucent) on X-ray, not dense. **High-Yield Clinical Pearls for NEET-PG:** * **Pathophysiology:** Deficiency of **Carbonic Anhydrase II** enzyme is a common cause, leading to a failure of the acidic environment required for osteoclasts to dissolve bone. * **Radiological Signs:** Look for **"Bone within a bone"** appearance (Endobone) and **"Erlenmeyer flask deformity"** of the distal femur. * **Complications:** Obliteration of the marrow cavity leads to **pancytopenia** and extramedullary hematopoiesis (hepatosplenomegaly). Cranial nerve palsies may occur due to the narrowing of cranial foramina. * **Treatment:** Bone marrow transplant is the definitive treatment for the infantile (malignant) form to provide functional osteoclasts.

Q: Shepherd's crook deformity is a characteristic radiological feature of which of the following conditions?

Fibrous dysplasia. **Explanation:** **Fibrous Dysplasia (Correct Answer):** Fibrous dysplasia is a condition where normal bone is replaced by fibrous connective tissue and haphazardly arranged trabeculae (often described as **"Chinese letter" patterns**). The **Shepherd’s crook deformity** refers to a severe coxa vara deformity of the proximal femur. It occurs because the dysplastic bone is weak and undergoes progressive bowing under the stress of body weight, causing the femoral neck to bend downward and the shaft to lateralize, mimicking the shape of a staff used by a shepherd. This is most commonly seen in the **polyostotic** form of the disease. **Incorrect Options:** * **Osteosarcoma:** A primary malignant bone tumor characterized by the production of osteoid. Radiological hallmarks include the **Sunburst appearance** and **Codman’s triangle**. * **Chondrosarcoma:** A malignant cartilage-forming tumor. It typically presents with **"popcorn calcification"** or endosteal pocketing, not gross structural bowing like a shepherd’s crook. * **Vertebral Hemangioma:** A benign vascular tumor of the spine. Its classic radiological feature is the **"Jail-bar" or "Corduroy cloth" appearance** due to thickened vertical trabeculae. **NEET-PG High-Yield Pearls:** * **Ground-glass appearance:** The classic radiological description of the bone density in fibrous dysplasia. * **McCune-Albright Syndrome:** A triad of polyostotic fibrous dysplasia, precocious puberty, and café-au-lait spots (with irregular "Coast of Maine" borders). * **Mazabraud Syndrome:** Association of fibrous dysplasia with soft tissue myxomas. * **Treatment:** Bisphosphonates may help with pain; surgery (like intramedullary nailing) is required for deformities or fractures.

Q: What is the most common site of metastasis in osteosarcoma?

Lungs. **Explanation:** **Osteosarcoma** is the most common primary malignant bone tumor in children and adolescents. It is characterized by the production of osteoid (immature bone) by malignant cells. **Why Lungs are the Correct Answer:** Osteosarcoma is a highly aggressive mesenchymal tumor that spreads primarily via the **hematogenous route** (through the bloodstream). Because the venous drainage from the extremities (where most osteosarcomas arise, such as the distal femur) passes directly into the systemic circulation and reaches the pulmonary capillary bed first, the **lungs** are the most common site of distant metastasis. Approximately 80% of all metastases in osteosarcoma occur in the lungs. **Why Other Options are Incorrect:** * **Brain & Liver:** While hematogenous spread can theoretically reach any organ, these are rare primary sites for osteosarcoma metastasis. Brain involvement is usually a terminal event. * **Bladder:** This is not a recognized site for osteosarcoma spread. **High-Yield Clinical Pearls for NEET-PG:** * **Skip Metastasis:** This refers to a second smaller lesion within the same bone but separate from the primary tumor. It is a poor prognostic factor. * **Second Most Common Site:** After the lungs, the most common site of spread is **other bones**. * **Radiology:** Look for the "Sunburst appearance" and "Codman’s triangle" on X-ray. * **Investigation of Choice:** Chest CT is the most sensitive test to detect early pulmonary nodules (micrometastases). * **Treatment:** Neoadjuvant chemotherapy followed by limb-salvage surgery and postoperative chemotherapy.

Q: A classical expansile lytic lesion in the transverse process of a vertebra is seen in:

Aneurysmal bone cyst. **Explanation:** The correct answer is **Aneurysmal Bone Cyst (ABC)**. **1. Why Aneurysmal Bone Cyst is correct:** An ABC is a benign but locally aggressive, blood-filled reactive bone lesion. In the spine, it has a strong predilection for the **posterior elements** (lamina, pedicles, and transverse processes). Radiologically, it presents as a **"blow-out" expansile lytic lesion** with a thin shell of cortical bone. The classic description of an expansile lesion specifically involving the transverse process is a hallmark of ABC. **2. Analysis of Incorrect Options:** * **Osteosarcoma:** This is a highly malignant primary bone tumor characterized by osteoid formation and a "sunburst" periosteal reaction. It typically affects the metaphysis of long bones and rarely presents as an isolated expansile lesion of the transverse process. * **Osteoblastoma:** While it also involves the posterior elements of the spine, it is usually more sclerotic or contains calcified matrix. It is less likely to be described as a purely "expansile lytic" lesion compared to the "blow-out" appearance of ABC. * **Metastasis:** Spinal metastases most commonly involve the **vertebral body** (due to high vascularity) rather than the transverse process alone. They are usually destructive and lack the characteristic well-defined expansile shell of an ABC. **3. NEET-PG High-Yield Pearls:** * **Location:** 80% of ABCs occur in patients under 20 years of age. * **Imaging Gold Standard:** MRI is the investigation of choice to visualize **Fluid-Fluid levels** (caused by settling of RBCs within the blood-filled cavities). * **Spinal Predilection:** ABC and Osteoblastoma are the two most common benign tumors involving the posterior elements of the spine. * **Treatment:** Curettage and bone grafting is the standard treatment.

Q: All of the following can cause osteopenia EXCEPT:

Osteopetrosis. **Explanation:** The term **osteopenia** refers to a decrease in bone mineral density (BMD) or bone mass, making the bones appear more radiolucent (darker) on X-rays. **Why Osteopetrosis is the correct answer:** **Osteopetrosis** (Marble Bone Disease) is characterized by a functional defect in **osteoclasts**, leading to impaired bone resorption. Since bone is constantly being formed but not broken down, there is a pathological **increase in bone density**. On imaging, bones appear "chalky white" or radiopaque, which is the exact opposite of osteopenia. **Analysis of incorrect options:** * **Rickets:** Occurs in children due to Vitamin D deficiency, leading to failure of mineralization of the osteoid at the growth plates. This results in decreased bone density (osteopenia). * **Osteomalacia:** The adult counterpart of Rickets. It involves inadequate mineralization of the bone matrix, leading to soft bones and generalized osteopenia. * **Osteonecrosis (Avascular Necrosis):** In the early stages of bone death, the surrounding viable bone undergoes hyperemia and disuse, leading to localized **disuse osteopenia**. While the necrotic segment itself may eventually appear dense (relative sclerosis), osteopenia is a recognized radiographic feature of the affected region. **High-Yield Clinical Pearls for NEET-PG:** * **Osteopetrosis Hallmark:** "Bone-within-a-bone" appearance (Endobone) and "Rugger-Jersey Spine." * **Rickets Hallmark:** Cupping, splaying, and fraying of the metaphysis. * **Osteomalacia Hallmark:** Looser’s zones (Pseudofractures or Milkman’s fractures). * **Key Distinction:** Osteoporosis is a quantitative defect (less bone), while Osteomalacia is a qualitative defect (poorly mineralized bone). Both present as osteopenia on X-ray.

Q: Which condition is characterized by nasal stiffness, pancytopenia, and hypertelorism?

Osteoporosis. **Explanation:** The correct answer is **Osteopetrosis** (Note: The option provided as "Osteoporosis" is a common typographical error in exams for **Osteopetrosis**, also known as Marble Bone Disease). **1. Why Osteopetrosis is correct:** Osteopetrosis is caused by **defective osteoclast function**, leading to failure of bone resorption. This results in excessively dense, brittle bones that encroach upon internal spaces: * **Pancytopenia:** Dense bone replaces the medullary cavity (myelophthisis), leading to bone marrow failure. * **Nasal Stiffness:** Overgrowth of facial bones (craniofacial hyperostosis) leads to narrowing of the nasal passages and paranasal sinuses. * **Hypertelorism:** Increased distance between the eyes occurs due to the expansion of the sphenoid bone and frontal bossing. **2. Why other options are incorrect:** * **Fibrous Dysplasia:** Characterized by the replacement of bone with fibrous tissue (Ground-glass appearance). While it can cause facial asymmetry (Leontiasis ossea), it does not typically cause pancytopenia. * **Marfan Syndrome:** A connective tissue disorder (Fibrillin-1 mutation) characterized by arachnodactyly, ectopia lentis, and aortic root dilation, not increased bone density. * **Apert Syndrome:** A craniosynostosis syndrome featuring midface hypoplasia and syndactyly (mitten hands), but not marrow failure or generalized bone density increase. **NEET-PG High-Yield Pearls:** * **Radiology:** "Bone within bone" appearance and "Erlenmeyer flask deformity." * **Complications:** Pathological fractures (chalk-stick fractures) and cranial nerve palsies (due to narrowing of foramina). * **Treatment:** Bone marrow transplant is the definitive treatment for the infantile (malignant) form to provide functional osteoclasts.

Q: A 40-year old man presented with acute onset pain and swelling of the left great toe. On X-ray, a punched-out lytic lesion is seen on the phalanx with sclerotic margins and overhanging bony edges. What is the most likely diagnosis?

Gout. ### Explanation The clinical presentation and radiographic findings are classic for **Gouty Arthritis**. **1. Why Gout is Correct:** The patient presents with **Podagra** (acute involvement of the first metatarsophalangeal joint), which is the most common site for gout. The X-ray description is pathognomonic: * **Punched-out lytic lesions:** These represent intraosseous tophi (monosodium urate crystals). * **Martel’s Sign (Overhanging edges):** The sclerotic, "rat-bite" erosions with overhanging bony margins are highly characteristic of chronic tophaceous gout. Unlike other inflammatory arthritides, the joint space in gout is often preserved until late stages. **2. Why Other Options are Incorrect:** * **Rheumatoid Arthritis (RA):** Typically presents with symmetrical involvement of small joints (MCP, PIP). Radiologically, it shows **periarticular osteopenia** and marginal erosions without sclerotic borders or overhanging edges. * **Psoriatic Arthritis:** While it can affect the distal phalanges, it is characterized by the "pencil-in-cup" deformity and periosteal new bone formation, not isolated punched-out lesions with sclerotic margins. * **Reiter’s Syndrome (Reactive Arthritis):** Usually follows a GI or GU infection and presents as an asymmetric oligoarthritis, often involving the heel (Achilles tendonitis) or sacroiliac joints. **3. High-Yield Pearls for NEET-PG:** * **Gold Standard Diagnosis:** Polarized light microscopy showing **needle-shaped, negatively birefringent** crystals (Yellow when parallel to the axis). * **Martel’s Sign:** The radiographic hallmark of gout (overhanging edges). * **Drug of Choice:** NSAIDs are first-line for acute attacks; **Colchicine** is an alternative. **Allopurinol** (Xanthine oxidase inhibitor) is used for chronic management but should *never* be started during an acute attack. * **Dietary triggers:** High purine foods (red meat, seafood) and alcohol.

Q: Which of the following conditions is not associated with osteoporosis?

Hypoparathyroidism. **Explanation:** **Hypoparathyroidism** is the correct answer because it is characterized by a deficiency of Parathyroid Hormone (PTH). PTH is a major regulator of bone remodeling; it stimulates both osteoblastic and osteoclastic activity. In its absence, bone turnover is significantly reduced, leading to an **increase in bone mineral density (BMD)** rather than a decrease. Therefore, it is not associated with osteoporosis. **Analysis of Incorrect Options:** * **Immobilization:** Lack of mechanical loading leads to "disuse osteoporosis." According to Wolff’s Law, bone adapts to the loads under which it is placed. Immobilization triggers rapid bone resorption by osteoclasts. * **Thyrotoxicosis:** Excess thyroid hormone (T3/T4) shortens the bone remodeling cycle, leading to a high-turnover state where bone resorption exceeds formation, resulting in secondary osteoporosis. * **Turner’s Syndrome:** This condition is associated with primary ovarian failure (hypogonadism). Estrogen deficiency leads to increased cytokine activity (IL-1, IL-6, TNF-α), which stimulates osteoclasts, causing significant bone loss. **High-Yield Clinical Pearls for NEET-PG:** * **Hyperparathyroidism** (specifically primary) is associated with osteoporosis and the classic "Salt and Pepper" skull appearance. * **Drug-induced Osteoporosis:** Long-term use of Glucocorticoids (most common cause), Heparin, and Phenytoin are frequent NEET-PG topics. * **Gold Standard Investigation:** DEXA Scan (Dual-Energy X-ray Absorptiometry). A **T-score of ≤ -2.5** defines osteoporosis. * **Bisphosphonates** (e.g., Alendronate) are the first-line treatment; they act by inhibiting osteoclast-mediated bone resorption.

Q: Diffuse multiple bone involvement, cafe-au-lait pigmentation, and endocrine disturbances are the features of which condition?

McCune Albright syndrome. **Explanation:** The correct answer is **McCune Albright Syndrome (MAS)**. This condition is a specific, severe form of **Polyostotic Fibrous Dysplasia** caused by a post-zygotic mutation in the *GNAS1* gene. This mutation leads to constitutive activation of the G-protein signaling pathway, resulting in a classic clinical triad: 1. **Polyostotic Fibrous Dysplasia:** Multiple bones are replaced by fibrous tissue (often showing a "ground-glass" appearance on X-ray). 2. **Café-au-lait Pigmentation:** Large, irregular skin patches typically described as having "Coast of Maine" borders (jagged), unlike the smooth "Coast of California" borders seen in Neurofibromatosis. 3. **Endocrine Disturbances:** Most commonly **Precocious Puberty** (especially in girls), but can also include hyperthyroidism or growth hormone excess. **Analysis of Other Options:** * **Jaffe’s Syndrome:** This is also a form of Polyostotic Fibrous Dysplasia with Café-au-lait spots, but it **lacks** the endocrine disturbances. * **Mazabraud’s Syndrome:** This refers to the association of Fibrous Dysplasia (usually polyostotic) with **intramuscular myxomas**. **High-Yield Clinical Pearls for NEET-PG:** * **Monostotic vs. Polyostotic:** Monostotic (single bone) is more common (70-80%), but Polyostotic is associated with these systemic syndromes. * **Radiology:** Look for the "Ground Glass" appearance and "Shepherd’s Crook" deformity of the femur. * **Histology:** Characterized by "Chinese letter" patterns of trabecular bone without osteoblastic rimming. * **Treatment:** Bisphosphonates (like Pamidronate) are used to manage bone pain and strengthen the lesions; surgery is reserved for fractures or severe deformities.

Question 1

Increased bone density is seen in all of the following conditions EXCEPT?

Accepted Answer

Primary hyperparathyroidism

Answer

Osteopetrosis

Answer

Fluorosis

Answer

Hypoparathyroidism

Question 2

Marble bone disease is also known as which of the following?

Accepted Answer

Osteopetrosis

Answer

Osteoporosis

Answer

Osteochondritis

Answer

Osteogenesis imperfecta

Question 3

Shepherd's crook deformity is a characteristic radiological feature of which of the following conditions?

Accepted Answer

Fibrous dysplasia

Answer

Osteosarcoma

Answer

Chondrosarcoma

Answer

Vertebral hemangioma

Question 4

What is the most common site of metastasis in osteosarcoma?

Accepted Answer

Lungs

Answer

Brain

Answer

Liver

Answer

Bladder

Question 5

A classical expansile lytic lesion in the transverse process of a vertebra is seen in:

Accepted Answer

Aneurysmal bone cyst

Answer

Osteosarcoma

Answer

Osteoblastoma

Answer

Metastasis

Question 6

All of the following can cause osteopenia EXCEPT:

Accepted Answer

Osteopetrosis

Answer

Rickets

Answer

Osteomalacia

Answer

Osteonecrosis

Question 7

Which condition is characterized by nasal stiffness, pancytopenia, and hypertelorism?

Accepted Answer

Osteoporosis

Answer

Fibrous dysplasia

Answer

Marfan syndrome

Answer

Apert syndrome

Question 8

A 40-year old man presented with acute onset pain and swelling of the left great toe. On X-ray, a punched-out lytic lesion is seen on the phalanx with sclerotic margins and overhanging bony edges. What is the most likely diagnosis?

Accepted Answer

Gout

Answer

Rheumatoid arthritis

Answer

Psoriatic arthritis

Answer

Reiter's syndrome

Question 9

Which of the following conditions is not associated with osteoporosis?

Accepted Answer

Hypoparathyroidism

Answer

Immobilization

Answer

Thyrotoxicosis

Answer

Turner's syndrome

Question 10

Diffuse multiple bone involvement, cafe-au-lait pigmentation, and endocrine disturbances are the features of which condition?

Accepted Answer

McCune Albright syndrome

Answer

Jaffe's syndrome

Answer

Mazabrauds syndrome

Answer

All of the above

Metabolic Bone Diseases — MCQs

Metabolic Bone Diseases — MCQs

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