Metabolic Bone Diseases Practice Questions

Q: Paget's disease of bone is a chronic disease of which skeleton?

Adult skeleton. **Explanation:** **Paget’s Disease of Bone (Osteitis Deformans)** is a chronic skeletal disorder characterized by excessive and disorganized bone remodeling. The correct answer is the **Adult skeleton** because this condition is almost exclusively seen in individuals over the age of 40, with its prevalence increasing significantly with advancing age (affecting up to 3% of the population over 55). * **Why Option D is correct:** Paget’s disease involves an initial phase of overactive osteoclasts (resorption) followed by compensatory, chaotic osteoblastic activity. This process requires a mature, fully formed skeleton. It is a disease of aging and is rarely, if ever, diagnosed in patients under 20. * **Why Options A, B, and C are incorrect:** These options refer to the developing or immature skeleton. Metabolic bone diseases affecting these stages are typically related to mineralization defects (like **Rickets**) or genetic collagen disorders (like **Osteogenesis Imperfecta**). Paget’s disease does not occur in infants or during the pubertal growth spurt. **High-Yield Clinical Pearls for NEET-PG:** * **Pathology:** The hallmark is the **"Mosaic pattern"** of bone (thickened trabeculae with irregular cement lines). * **Markers:** Characterized by **isolated elevation of Serum Alkaline Phosphatase (ALP)** with normal Calcium and Phosphate levels. * **Radiology:** Look for **"Blade of grass"** or "Flame-shaped" lytic lesions and **"Cotton wool"** appearance of the skull. * **Complications:** The most feared late complication is **Osteosarcoma** (seen in <1% of cases). * **Treatment:** **Bisphosphonates** (e.g., Zoledronic acid) are the drug of choice to inhibit osteoclast activity.

Q: All of the following are seen in rickets except:

Frenkels line. In Rickets, the primary pathology is a failure of mineralization of the osteoid matrix at the growth plate. This leads to characteristic radiological changes primarily seen at the metaphysis of long bones. **Explanation of the Correct Answer:** * **A. Fraenkel’s Line (White line of Fraenkel):** This is a dense, radiopaque line seen at the zone of provisional calcification. It is a hallmark of **Scurvy (Vitamin C deficiency)**, not rickets. In Scurvy, there is a failure of osteoid formation, but the calcification of existing cartilage continues, leading to this dense line. In Rickets, the zone of provisional calcification is lost or blurred. **Explanation of Incorrect Options:** * **B. Widening of epiphysis-diaphysis distance:** In rickets, the non-mineralized osteoid and hypertrophic cartilage accumulate, causing the radiolucent gap between the epiphysis and the shaft to increase. * **C. Cupping and splaying of metaphysis:** Due to the weight-bearing load on softened, uncalcified bone, the metaphysis expands laterally (**splaying**) and develops a concave, saucer-like appearance (**cupping**). * **D. Rarefaction:** This refers to a generalized decrease in bone density (osteopenia) due to poor mineralization of the bone trabeculae, a consistent finding in rickets. **NEET-PG High-Yield Pearls:** * **Rickets Triad on X-ray:** Cupping, Splaying, and Fraying (shaggy margins) of the metaphysis. * **Scurvy Signs (for differential):** Wimberger’s ring (dense epiphysis), Pelkan spur (metaphyseal spurs), and Trummerfeld zone (scurvy zone/lucent line). * **Earliest Sign of Rickets:** Fraying of the metaphysis (best seen at the lower end of the radius and ulna). * **Biochemical Profile:** Low/Normal Calcium, Low Phosphate, and **Elevated Alkaline Phosphatase (ALP)**.

Q: Which of the following is NOT seen in osteopetrosis?

Delayed healing of fractures. **Explanation:** **Osteopetrosis** (Marble Bone Disease) is a genetic disorder characterized by **defective osteoclast function**, leading to failure of bone resorption. While the bones appear dense on X-ray, they are structurally weak and "chalk-like." 1. **Why "Delayed healing of fractures" is the correct answer:** In osteopetrosis, fractures actually **heal at a normal rate** or sometimes even faster. This is because fracture healing primarily depends on **osteoblastic activity** (callus formation), which is preserved or even hyperactive in this condition. The defect lies in the remodeling phase (osteoclasts), not the initial repair phase. 2. **Analysis of Incorrect Options:** * **Pancytopenia:** The failure of bone resorption leads to the obliteration of the medullary canal by calcified cartilage and bone. This "crowding out" of the bone marrow results in myelophthisic anemia and pancytopenia. * **Compression of cranial nerves:** Failure of remodeling prevents the enlargement of cranial foramina. As the skull thickens, nerves (especially II, VII, and VIII) are compressed, leading to blindness, facial palsy, or deafness. * **Osteomyelitis of mandible:** Despite the high density, the bone is relatively **avascular**. This poor blood supply, combined with dental caries (common in these patients), makes the mandible highly susceptible to refractory osteomyelitis. **High-Yield Clinical Pearls for NEET-PG:** * **Radiological Signs:** "Bone-within-a-bone" appearance (Endobone), "Sandwich vertebrae" (Rugger-Jersey spine appearance), and "Erlenmeyer flask deformity" of the distal femur. * **Most Common Type:** Autosomal Dominant (Albers-Schönberg disease) is the benign adult form; Autosomal Recessive is the malignant infantile form. * **Treatment:** Bone Marrow Transplant is the definitive treatment for the infantile form to provide functional osteoclasts.

Q: A child presents with long bone pain, weakness, lethargy, and bow legs. Radiographic findings include increased bone density, osteophytes, and a distorted joint space. What is the most likely diagnosis?

Fluorosis. **Explanation:** The clinical presentation of long bone pain, lethargy, and bow legs in a child, combined with specific radiographic findings of **increased bone density (osteosclerosis)** and **osteophyte formation**, is characteristic of **Fluorosis**. 1. **Why Fluorosis is correct:** Chronic ingestion of high levels of fluoride leads to its deposition in bones and teeth. Unlike most pediatric metabolic bone diseases that cause osteopenia, fluorosis causes **osteosclerosis** (increased density). It stimulates osteoblastic activity and leads to the calcification of ligaments and tendons. This results in bony outgrowths (osteophytes), joint space distortion, and physical deformities like **genu varum (bow legs)**. 2. **Why other options are incorrect:** * **Rickets:** While it presents with bow legs and weakness, the hallmark radiographic finding is **decreased bone density** (osteopenia) with cupping, splaying, and fraying of the metaphysis, not increased density. * **Scurvy:** Characterized by subperiosteal hemorrhage and specific signs like the **Wimberger ring sign** and **Frankel’s line**. It presents with osteopenia, not sclerosis. * **Caffey’s Disease (Infantile Cortical Hyperostosis):** Presents with irritability, soft tissue swelling, and new bone formation (periosteal reaction), typically involving the **mandible**, ribs, and clavicle in infants under 6 months. **NEET-PG High-Yield Pearls:** * **Fluorosis Hallmark:** Increased bone density + Calcification of the **interosseous membrane** (especially in the forearm). * **Dental Fluorosis:** Presents as mottling of enamel (chalky white patches or brownish discoloration). * **Safe Limit:** Fluoride in drinking water should ideally be **<1.0 mg/L (1 ppm)**. Skeletal fluorosis typically occurs when levels exceed 3-8 mg/L.

Q: All of the following are true about Osteomalacia, EXCEPT:

Increased calcium. **Explanation:** Osteomalacia is a metabolic bone disease characterized by **defective mineralization** of the organic bone matrix (osteoid), most commonly due to Vitamin D deficiency. **1. Why "Increased Calcium" is the correct answer (The Exception):** In Osteomalacia, serum calcium is **never increased**. Because Vitamin D is essential for intestinal calcium absorption, its deficiency leads to **low (hypocalcemia)** or **low-normal** serum calcium levels. An increase in calcium would instead suggest conditions like primary hyperparathyroidism or malignancy. **2. Analysis of other options:** * **Normal serum calcium (Option C):** This is a common finding due to **Secondary Hyperparathyroidism**. When calcium levels drop, the parathyroid glands secrete PTH, which mobilizes calcium from bones to maintain a low-normal serum level. * **Increased serum phosphate (Option B):** *Note: In classic Osteomalacia, phosphate is usually low due to PTH-induced renal wasting. However, in the context of this specific question format, "Increased Calcium" is the most definitive physiological impossibility, making it the primary exception.* * **Osteosclerotic lesions and pseudofractures (Option D):** **Looser’s zones** (pseudofractures) are the hallmark radiologic feature of osteomalacia. While the bone is generally osteopenic, some variants (like Renal Osteodystrophy) can present with osteosclerosis (e.g., "Rugger-Jersey spine"). **High-Yield NEET-PG Pearls:** * **Biochemical Profile:** ↓/Normal Ca²⁺, ↓ Phosphate, **↑ Alkaline Phosphatase (ALP)**, and ↑ PTH. * **Radiology:** Look for **Looser’s Zones** (Milkman’s fractures)—transverse lucent lines perpendicular to the cortex, typically found in the femoral neck, ribs, and scapula. * **Histology:** Increased thickness of **unmineralized osteoid seams**. * **Clinical Sign:** Proximal muscle weakness (waddling gait) and bone pain.

Q: A 10-year-old child presents with anemia and recurrent fractures. The X-ray shows diffuse hyper density of bone. What is the most likely diagnosis?

Osteopetrosis. ### **Explanation** The clinical presentation of recurrent fractures, anemia, and diffuse hyperdensity on X-ray is classic for **Osteopetrosis** (also known as Marble Bone Disease or Albers-Schönberg disease). **1. Why Osteopetrosis is Correct:** The underlying pathology is **defective osteoclast function** (failure of bone resorption). While bones appear dense ("marble-like") on X-ray, they are structurally weak, brittle, and prone to fractures. The excessive bone formation encroaches upon the medullary cavity, leading to **bone marrow failure**, which manifests as **anemia**, thrombocytopenia, and hepatosplenomegaly (due to extramedullary hematopoiesis). **2. Why Other Options are Incorrect:** * **Osteogenesis Imperfecta:** Characterized by defective Type I collagen. While it presents with recurrent fractures and "brittle bones," the X-ray typically shows **osteopenia** (radiolucent/thin bones) rather than hyperdensity. Blue sclera is a common associated finding. * **Osteochondroma:** This is a benign bone tumor (exostosis) presenting as a bony outgrowth near the growth plate. It does not cause diffuse hyperdensity or systemic anemia. * **Hyperparathyroidism:** Increased PTH leads to excessive osteoclast activity, resulting in **osteopenia**, subperiosteal resorption, and "Brown tumors." It is characterized by decreased bone density, not hyperdensity. **3. High-Yield Clinical Pearls for NEET-PG:** * **X-ray Signs:** "Bone-within-a-bone" appearance and "Sandwich vertebrae" (sclerosis of endplates). * **Erlenmeyer Flask Deformity:** Seen at the distal femur due to defective remodeling. * **Cranial Nerve Palsies:** Narrowing of cranial foramina can lead to blindness or deafness. * **Treatment:** Bone Marrow Transplant is the definitive treatment for the infantile (malignant) form to provide functional osteoclasts.

Q: Serum alkaline phosphatase level is normal in which of the following conditions?

Multiple myeloma.. **Explanation:** The correct answer is **Multiple Myeloma**. **1. Why Multiple Myeloma is the correct answer:** Serum Alkaline Phosphatase (ALP) is a marker of **osteoblastic (bone-forming) activity**. In Multiple Myeloma, the bone lesions are purely **osteolytic**. The malignant plasma cells produce "Osteoclast Activating Factors" (like IL-6 and RANKL) which stimulate osteoclasts to resorb bone, while simultaneously secreting substances (like DKK-1) that inhibit osteoblasts. Because there is no compensatory osteoblastic activity or new bone formation, the ALP levels remain characteristically **normal**, despite extensive bone destruction. **2. Why the other options are incorrect:** * **Paget’s Disease:** This condition is characterized by excessive and disorganized bone remodeling. The osteoblastic phase is very active, leading to significantly **elevated ALP** levels (often the highest seen in clinical practice), while calcium and phosphate remain normal. * **Fibrous Dysplasia:** This is a condition where normal bone is replaced by fibrous connective tissue. During periods of active bone turnover or in extensive polyostotic forms, **ALP levels are frequently elevated**. **3. High-Yield Clinical Pearls for NEET-PG:** * **The "Normal" Rule in Myeloma:** In Multiple Myeloma, despite "punched-out" lytic lesions on X-ray, the **ALP, Calcium (initially), and PSA** are typically normal. However, Calcium may rise later due to massive bone resorption (Hypercalcemia). * **ALP as a Marker:** Always associate elevated ALP with **osteoblasts**. If a bone disease is purely lytic (like Myeloma or some purely lytic metastases), ALP will not rise. * **Paget’s Triad:** High ALP + Normal Calcium + Normal Phosphate. * **Osteoblastic Metastases:** (e.g., Prostate cancer) will show very high ALP levels.

Q: Osteoporosis is characterized by?

Decreased bone density. **Explanation:** **Osteoporosis** is a metabolic bone disorder characterized by a **reduction in bone mass (density)** and the micro-architectural deterioration of bone tissue, leading to increased bone fragility and fracture risk. In osteoporosis, the chemical composition of the bone remains normal (the ratio of mineral to matrix is unchanged), but the total volume of bone tissue is decreased. **Analysis of Options:** * **Option B (Correct):** The hallmark of osteoporosis is **decreased bone mineral density (BMD)**. This is quantitatively assessed using a **DEXA scan**, where a T-score of **≤ -2.5** is diagnostic. * **Option A (Incorrect):** Serum calcium, phosphate, and **alkaline phosphatase (ALP) levels are typically normal** in primary osteoporosis. Elevated ALP is more characteristic of Paget’s disease, healing fractures, or Osteomalacia. * **Option C (Incorrect):** While sarcopenia (muscle loss) can coexist with osteoporosis in the elderly, muscle wasting is not a defining characteristic of the bone pathology itself. * **Option D (Incorrect):** **Looser’s zones** (pseudofractures) are the pathognomonic radiological feature of **Osteomalacia**, not osteoporosis. **High-Yield NEET-PG Pearls:** 1. **Most common site of fracture:** Vertebral body (compression fracture), followed by the neck of the femur and Colles' fracture. 2. **Gold Standard Investigation:** Dual-Energy X-ray Absorptiometry (DEXA). 3. **First-line Treatment:** Bisphosphonates (e.g., Alendronate), which inhibit osteoclast-mediated bone resorption. 4. **Singh’s Index:** Used to grade osteoporosis based on the disappearance of trabecular patterns in the proximal femur.

Q: Deficient mineralization in epiphysial growth cartilage is seen in?

Rickets. **Explanation:** The correct answer is **Rickets**. **1. Why Rickets is correct:** Rickets is a metabolic bone disease characterized by **deficient mineralization of the osteoid matrix and the epiphyseal growth plate** (physial cartilage) before the fusion of epiphyses. In children, the lack of Vitamin D, Calcium, or Phosphate leads to a failure of calcification in the zone of provisional calcification. This results in the accumulation of unmineralized cartilage, leading to the characteristic widening and cupping of the metaphysis seen on X-rays. **2. Why other options are incorrect:** * **Osteomalacia:** While this also involves deficient mineralization of the osteoid, it occurs in **adults** after the epiphyseal plates have fused. Therefore, it does not involve the growth cartilage. * **Scurvy:** This is caused by Vitamin C deficiency, which leads to defective **collagen synthesis** (osteoid formation), not a primary mineralization defect. The calcification of the growth plate is actually excessive (Zone of provisional calcification becomes dense—White line of Frankel). * **Hyperparathyroidism:** This involves increased **bone resorption** (osteoclastic activity) due to excess PTH, leading to "brown tumors" and subperiosteal resorption, rather than a primary defect in growth plate mineralization. **NEET-PG High-Yield Pearls:** * **Earliest sign of Rickets:** Craniotabes (softening of skull bones). * **Earliest Radiological sign:** Rarefaction/Cupping and fraying of the metaphysis (best seen at the lower end of the radius/ulna). * **Biochemical profile:** Low/Normal Calcium, Low Phosphate, and **Elevated Alkaline Phosphatase (ALP)**—ALP is the most sensitive marker for disease activity. * **Rachitic Rosary:** Palpable enlargement of costochondral junctions (rounded in Rickets, sharp/angular in Scurvy).

Q: Osteoporosis in postmenopausal women is defined by T-score of?

Below -2.5 SD. The diagnosis of osteoporosis is based on the **WHO criteria**, which utilize the **T-score** derived from Dual-energy X-ray Absorptiometry (DEXA) scans. The T-score compares a patient's Bone Mineral Density (BMD) to that of a healthy young adult (30-year-old) of the same sex. ### **Explanation of the Correct Answer** **Option D (Below -2.5 SD)** is correct because the WHO defines **Osteoporosis** as a BMD T-score of **≤ -2.5 standard deviations (SD)**. In postmenopausal women, the decline in estrogen leads to accelerated bone resorption, significantly increasing fracture risk when the density falls below this threshold. ### **Analysis of Incorrect Options** * **Option B (0 to -1 SD):** This range is considered **Normal** bone density. * **Option C (-1 to -2.5 SD):** This range defines **Osteopenia** (low bone mass), which is a precursor to osteoporosis but does not yet meet the diagnostic threshold for the disease. * **Option A (1 to 2.5 SD):** These are positive values indicating bone density that is higher than the young adult mean, which is not associated with osteoporosis. ### **NEET-PG High-Yield Pearls** * **Severe (Established) Osteoporosis:** Defined as a T-score ≤ -2.5 SD **plus** the presence of one or more fragility fractures. * **Z-score:** Compares the patient's BMD to an age-matched and sex-matched population. It is used primarily in children, premenopausal women, and men under 50. * **Gold Standard Site:** The hip (femoral neck) and lumbar spine are the preferred sites for DEXA scanning. * **Treatment Threshold:** Pharmacological intervention is usually initiated if the T-score is ≤ -2.5 or if the FRAX score indicates high 10-year fracture probability.

Question 1

Paget's disease of bone is a chronic disease of which skeleton?

Accepted Answer

Adult skeleton

Answer

Prepubertal skeleton

Answer

Pubertal skeleton

Answer

Infantile skeleton

Question 2

All of the following are seen in rickets except:

Accepted Answer

Frenkels line

Answer

Widening of epiphysis-diaphysis distance

Answer

Cupping and splaying of metaphysis

Answer

Rarefaction

Question 3

Which of the following is NOT seen in osteopetrosis?

Accepted Answer

Delayed healing of fractures

Answer

Pancytopenia

Answer

Compression of cranial nerve

Answer

Osteomyelitis of mandible

Question 4

A child presents with long bone pain, weakness, lethargy, and bow legs. Radiographic findings include increased bone density, osteophytes, and a distorted joint space. What is the most likely diagnosis?

Accepted Answer

Fluorosis

Answer

Rickets

Answer

Scurvy

Answer

Caffey's disease

Question 5

All of the following are true about Osteomalacia, EXCEPT:

Accepted Answer

Increased calcium

Answer

Increased serum phosphate

Answer

Normal serum calcium

Answer

Osteosclerotic lesions and pseudofractures are seen

Question 6

A 10-year-old child presents with anemia and recurrent fractures. The X-ray shows diffuse hyper density of bone. What is the most likely diagnosis?

Accepted Answer

Osteopetrosis

Answer

Osteogenesis imperfecta

Answer

Osteochondroma

Answer

Hyperparathyroidism

Question 7

Serum alkaline phosphatase level is normal in which of the following conditions?

Accepted Answer

Multiple myeloma.

Answer

Paget's disease.

Answer

Fibrous dysplasia.

Answer

All of the above.

Question 8

Osteoporosis is characterized by?

Accepted Answer

Decreased bone density

Answer

Increased serum alkaline phosphatase

Answer

Wasting of muscles

Answer

Looser's zone seen

Question 9

Deficient mineralization in epiphysial growth cartilage is seen in?

Accepted Answer

Rickets

Answer

Osteomalacia

Answer

Scurvy

Answer

Hyperparathyroidism

Question 10

Osteoporosis in postmenopausal women is defined by T-score of?

Accepted Answer

Below -2.5 SD

Answer

1 to 2.5 SD

Answer

0 to -1 SD

Answer

-1 to -2.5 SD

Metabolic Bone Diseases — MCQs

Metabolic Bone Diseases — MCQs

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