Metabolic Bone Diseases Practice Questions

Q: Splaying and cupping of the metaphysis is seen in which condition?

Rickets. **Explanation:** **Rickets** is the correct answer because it is characterized by a failure of mineralization of the osteoid matrix at the growth plate. In Rickets, the zone of provisional calcification fails to form, leading to an accumulation of hypertrophic chondrocytes. This results in a softened, widened, and disorganized epiphyseal plate. Under the stress of weight-bearing or muscle pull, the weakened metaphysis expands laterally (**Splaying**) and develops a concave, hollowed-out appearance (**Cupping**). Additionally, the margins appear irregular and fuzzy (**Fraying**). **Why other options are incorrect:** * **Scurvy:** Caused by Vitamin C deficiency, it affects collagen synthesis. Radiographic hallmarks include the **White line of Frankel** (dense zone of provisional calcification), **Wimberger’s ring** (sclerotic margin of epiphysis), and **Pelkan spurs**, rather than cupping. * **Paget’s Disease:** A disorder of bone remodeling characterized by excessive resorption and disorganized formation. Key findings include cortical thickening, **coarse trabeculae**, and "Picture frame" vertebrae. * **Lead Poisoning:** Characterized by **Lead lines**, which are dense transverse radiopaque bands at the metaphysis due to impaired resorption of calcified cartilage. **High-Yield Clinical Pearls for NEET-PG:** * **Earliest sign of Rickets:** Fraying and cupping at the distal ends of the radius and ulna. * **Rachitic Rosary:** Palpable/visible enlargement of the costochondral junctions (rounded in Rickets, angular in Scurvy). * **Harrison’s Sulcus:** A horizontal groove along the lower border of the thorax corresponding to the diaphragmatic attachment. * **Looser’s Zones:** Pseudofractures seen in Osteomalacia (the adult counterpart of Rickets).

Q: According to Sillence classification of osteogenesis imperfecta, which is the most common and mildest form?

Type 1. **Explanation:** Osteogenesis Imperfecta (OI), or "Brittle Bone Disease," is a genetic disorder characterized by defects in **Type 1 Collagen** synthesis. The **Sillence Classification** categorizes OI into four primary types based on clinical severity and genetic transmission. * **Type 1 (Correct Answer):** This is the **most common** and **mildest** form. It is inherited in an Autosomal Dominant (AD) pattern. Patients have a near-normal stature and minimal bone deformity. A classic high-yield feature is the presence of **distinct blue sclera** throughout life. Fractures typically occur during childhood but decrease after puberty. **Analysis of Incorrect Options:** * **Type 2:** This is the **most severe and lethal** form (Perinatal lethal). It results in stillbirth or death in early infancy due to extreme bone fragility and respiratory failure. * **Type 3:** This is the **most severe non-lethal** form. It is characterized by "progressive deforming" bones, short stature, and significant scoliosis. Sclera may be blue at birth but often turns white with age. * **Type 4:** This is of intermediate severity. It is similar to Type 1 but is distinguished by having **normal (white) sclera**. **NEET-PG High-Yield Pearls:** * **Genetic Defect:** Mutations in **COL1A1** and **COL1A2** genes. * **Clinical Triad:** Fragile bones, Blue sclera, and Early-onset Otosclerosis (conductive hearing loss). * **Radiological Sign:** "Zebra stripe sign" (seen in patients treated with cyclic Bisphosphonates). * **Wormian Bones:** Often seen on skull X-rays of OI patients.

Q: What is the most common site of osteoporosis?

Vertebrae. **Explanation:** **1. Why Vertebrae is the Correct Answer:** Osteoporosis is a systemic skeletal disorder characterized by low bone mass and micro-architectural deterioration. It primarily affects **trabecular (cancellous) bone** more than cortical bone because trabecular bone has a higher metabolic turnover rate and a larger surface area exposed to osteoclast activity. The **vertebral bodies** have the highest concentration of trabecular bone in the human body, making them the most common site for both asymptomatic bone loss and clinical fractures (vertebral compression fractures). **2. Analysis of Incorrect Options:** * **Humerus (A):** While proximal humerus fractures are common in osteoporotic elderly patients (part of the "fragility fracture" group), they occur less frequently than vertebral or hip fractures. * **Scapula (C):** The scapula is rarely affected by osteoporosis to a clinical degree because it is not a primary weight-bearing bone and has a different structural composition. * **Flat bones (D):** While some flat bones (like the pelvis) contain trabecular bone, the term is too broad. The vertebrae remain the statistically dominant site for osteoporotic changes. **3. NEET-PG High-Yield Pearls:** * **Most common site of fracture:** Vertebra (often asymptomatic/wedge fracture). * **Most common site of "Colles' fracture":** Distal Radius (often the first sign of osteoporosis in postmenopausal women). * **Most serious site of fracture:** Hip (Neck of femur/Intertrochanteric), associated with high mortality. * **Gold Standard Investigation:** DEXA Scan (Dual-Energy X-ray Absorptiometry). * **DEXA Sites:** Usually measured at the Lumbar Spine (L1-L4) and Hip (Total hip/Femoral neck). * **Diagnosis:** T-score ≤ -2.5 SD.

Q: Which of the following statements is WRONG regarding Hypophosphataemic Rickets?

Normal Alkaline Phosphatase (ALP). ### Explanation: Hypophosphataemic Rickets **Hypophosphataemic Rickets** (Vitamin D-resistant Rickets) is most commonly inherited as an X-linked dominant trait (XLH). The primary defect is a mutation in the **PHEX gene**, leading to increased levels of **FGF-23** (a phosphatonin). This results in renal phosphate wasting and impaired 1-alpha-hydroxylation of Vitamin D. #### 1. Why "Normal Alkaline Phosphatase" is the WRONG statement: In all forms of active rickets and osteomalacia, **Alkaline Phosphatase (ALP) is characteristically elevated**. ALP is a marker of osteoblastic activity; as the body attempts to mineralize the excessive unmineralized osteoid (the hallmark of rickets), ALP levels rise significantly. Therefore, a "Normal ALP" is clinically inconsistent with a diagnosis of active rickets. #### 2. Analysis of other options: * **Hypocalcemia:** While the primary defect is phosphate loss, serum calcium can be low or low-normal because the deficiency in 1,25-(OH)₂D (calcitriol) reduces intestinal calcium absorption. * **Elevated PTH:** Low serum calcium and low calcitriol levels trigger the parathyroid glands, leading to **Secondary Hyperparathyroidism**. * **Intestinal Malabsorption:** Due to the failure of the kidneys to convert Vitamin D to its active form (1,25-(OH)₂D), there is a secondary failure of calcium and phosphate absorption from the gut. #### 3. NEET-PG High-Yield Pearls: * **Biochemical Profile:** Low Serum Phosphate, Low/Normal Serum Calcium, **High ALP**, and Low/Normal 1,25-(OH)₂D. * **Hallmark:** "Phosphate wasting" despite low serum phosphate (decreased TmP/GFR). * **Clinical Feature:** Unlike nutritional rickets, these patients do **not** show signs of tetany (as calcium is rarely critically low) and do **not** respond to physiological doses of Vitamin D. * **Treatment:** Oral phosphate supplements and Calcitriol (active Vitamin D).

Q: Which of the following conditions is NOT associated with "Umbau Zones"?

Osteomyelitis. **Explanation:** **Umbau Zones** (also known as **Looser’s zones**, pseudofractures, or Milkman’s fractures) are radiolucent lines oriented perpendicular to the bone cortex. They represent stress fractures where the fractured bone is replaced by unmineralized osteoid rather than mature bone. **Why Osteomyelitis is the correct answer:** Osteomyelitis is an infectious inflammatory condition of the bone. Its hallmark radiological features include **sequestrum** (dead bone), **involucrum** (new bone formation), and **cloaca**. It does not involve the systemic defect in osteoid mineralization required to form Umbau zones. **Analysis of other options:** * **Osteomalacia:** This is the classic condition associated with Umbau zones. In adults, inadequate mineralization of the bone matrix leads to these characteristic pseudofractures, typically seen in the femoral neck, pubic rami, and axillary border of the scapula. * **Rickets:** As the pediatric counterpart to osteomalacia, severe rickets can also manifest with pseudofractures due to the same underlying pathology of defective mineralization. * **Osteogenesis Imperfecta (OI):** While OI is primarily a collagen defect, severe forms can present with "pseudo-Umbau zones" or actual stress fractures during the healing process of fragile bones. **NEET-PG High-Yield Pearls:** 1. **Common Sites for Umbau Zones:** Axillary border of the scapula (most classic), neck of the femur, pubic rami, and ribs. 2. **Radiological Appearance:** Transverse lucent bands that do NOT cross the entire bone width, often bilateral and symmetrical. 3. **Biochemical Profile in Osteomalacia:** Low/Normal Calcium, Low Phosphate, and **Elevated Alkaline Phosphatase (ALP)**. 4. **Milkman’s Syndrome:** A specific clinical entity characterized by multiple pseudofractures, often associated with Osteomalacia.

Q: A 70-year-old woman with a history of vertebral crush fracture presents to the osteoporosis outpatient clinic. Which of the following investigations is most useful to assess the extent of her osteoporosis?

DEXA scan. ### Explanation **1. Why DEXA Scan is the Correct Answer:** Dual-Energy X-ray Absorptiometry (DEXA) scan is the **gold standard** for diagnosing osteoporosis and assessing its extent. It measures Bone Mineral Density (BMD) at clinically relevant sites like the lumbar spine and proximal femur. The diagnosis is based on the **T-score** (comparison to a young healthy adult). According to WHO criteria: * **Normal:** T-score ≥ -1.0 * **Osteopenia:** T-score between -1.0 and -2.5 * **Osteoporosis:** T-score ≤ -2.5 * **Severe Osteoporosis:** T-score ≤ -2.5 plus a fragility fracture (as seen in this patient). **2. Why Other Options are Incorrect:** * **Spinal X-rays:** While useful for identifying existing fractures (like the crush fracture mentioned), X-rays are insensitive for early diagnosis. Bone loss is only visible on plain radiographs after **30–50% of bone mass** has already been lost. * **Biochemistry (FBC, Bone/Liver profile):** In primary osteoporosis, serum calcium, phosphate, and alkaline phosphatase (ALP) levels are typically **normal**. These tests are used to rule out secondary causes (e.g., osteomalacia, hyperparathyroidism, or malignancy) rather than to quantify osteoporosis. * **Vitamin D levels:** While Vitamin D deficiency is a risk factor for bone loss, its level does not quantify the extent of bone density loss already present. **3. NEET-PG High-Yield Pearls:** * **Most common site** of osteoporotic fracture: Vertebra (Compression/Crush fracture). * **Most common site** for DEXA measurement: Neck of femur (best predictor of hip fracture) and Lumbar spine (L1–L4). * **Z-score:** Used for pre-menopausal women and men <50 years (compares density to age-matched controls). * **FRAX Tool:** Used to calculate the 10-year probability of a major osteoporotic fracture.

Q: Which of the following are features of Paget's disease?

All of the above.. **Explanation:** Paget’s disease (Osteitis Deformans) is a chronic disorder characterized by excessive and disorganized bone remodeling. It progresses through three stages: osteolytic, mixed, and osteosclerotic. * **Option A:** In the early **osteolytic phase**, the skull shows well-defined radiolucent areas known as **Osteoporosis Circumscripta**. As the disease progresses to the sclerotic phase, the bone thickens, leading to a progressive increase in head circumference (often described as the patient needing a larger hat size). * **Option B:** Histologically, the rapid, haphazard bone formation and resorption result in prominent cement lines. This creates a characteristic **"Mosaic" or "Jigsaw puzzle" appearance** of the lamellar bone, which is a pathognomonic finding. * **Option C:** When Paget’s disease involves the facial bones (maxilla and mandible), it causes massive bony overgrowth. This results in a lion-like facial appearance known as **Leontiasis Ossea**. Since all three descriptions are classic clinical and pathological hallmarks of the disease, **Option D** is the correct answer. **High-Yield Clinical Pearls for NEET-PG:** * **Marker of Choice:** Serum **Alkaline Phosphatase (ALP)** is markedly elevated, while Calcium and Phosphate levels typically remain normal. * **Radiological Signs:** "Cotton wool" appearance of the skull, "Picture frame" vertebrae, and "Ivory vertebra." * **Treatment:** **Bisphosphonates** (Zoledronic acid) are the drug of choice. * **Complications:** The most dreaded complication is **Osteosarcoma** (secondary), and the most common cause of death in extensive disease is high-output heart failure.

Question 1

Splaying and cupping of the metaphysis is seen in which condition?

Accepted Answer

Rickets

Answer

Scurvy

Answer

Paget's disease

Answer

Lead poisoning

Question 2

According to Sillence classification of osteogenesis imperfecta, which is the most common and mildest form?

Accepted Answer

Type 1

Answer

Type 2

Answer

Type 3

Answer

Type 4

Question 3

Osteoporosis is characterized by all the following except?

Accepted Answer

Decreased serum calcium, phosphorus, and alkaline phosphatase are seen

Answer

Decreased bone mineral density

Answer

Glucocorticoids can cause osteoporosis

Answer

Dorsolumbar spine is the most common site of osteoporotic fracture

Question 4

What is the most common site of osteoporosis?

Accepted Answer

Vertebrae

Answer

Humerus

Answer

Scapula

Answer

Flat bones

Question 5

Which of the following statements is WRONG regarding Hypophosphataemic Rickets?

Accepted Answer

Normal Alkaline Phosphatase (ALP)

Answer

Hypocalcemia

Answer

Elevated levels of Parathyroid Hormone

Answer

Intestinal malabsorption

Question 6

Which of the following conditions is NOT associated with "Umbau Zones"?

Accepted Answer

Osteomyelitis

Answer

Osteomalacia

Answer

Rickets

Answer

Osteogenesis imperfecta

Question 7

A 70-year-old woman with a history of vertebral crush fracture presents to the osteoporosis outpatient clinic. Which of the following investigations is most useful to assess the extent of her osteoporosis?

Accepted Answer

DEXA scan

Answer

Spinal x-rays

Answer

Full blood count, bone and liver biochemistry blood tests

Answer

Vitamin D levels

Question 8

Which of the following are features of Paget's disease?

Accepted Answer

All of the above.

Answer

Affecting the skull generally leads to a progressive increase in circumference of the head (osteoporosis circumscripta).

Answer

Jigsaw puzzle appearance of the bone.

Answer

Leontiasis ossea.

Question 9

What is the most likely diagnosis in a neonate with multiple, healed fractures of long bones?

Accepted Answer

Osteogenesis imperfecta

Answer

Osteomalacia

Answer

Osteopetrosis

Answer

Congenital rickets

Question 10

A 90-year-old male complains of hip and back pain. He has also developed headaches, hearing loss, and tinnitus. On physical exam, the skull appears enlarged with prominent superficial veins. There is marked kyphosis, and the bones of the leg appear deformed. Plasma alkaline phosphatase is elevated. A skull x-ray shows sharply demarcated lucencies in the frontal, parietal, and occipital bones. X-rays of the hip show thickening of the pelvic brim. What is the most likely diagnosis?

Accepted Answer

Paget's disease

Answer

Multiple myeloma

Answer

Hypercalcemia

Answer

Metastatic bone disease

Metabolic Bone Diseases — MCQs

Metabolic Bone Diseases — MCQs

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