Metabolic Bone Diseases Practice Questions

Q: Looser's zone occurs in all of the following conditions except?

Hypoparathyroidism. **Explanation:** **Looser’s zones** (also known as pseudofractures, Milkman’s fractures, or Umbauzonen) are narrow radiolucent lines that represent cortical stress fractures replaced by unmineralized osteoid. They typically occur perpendicular to the bone cortex in weight-bearing areas (e.g., femoral neck, axillary border of the scapula, pubic rami). **Why Hypoparathyroidism is the correct answer:** Looser’s zones are a hallmark of conditions characterized by **excessive osteoid** or **increased bone turnover** where mineralization is defective. In **Hypoparathyroidism**, there is a deficiency of Parathyroid Hormone (PTH), leading to low bone turnover and increased bone density (osteosclerosis). Since there is no excess of unmineralized osteoid, Looser’s zones do not occur. **Analysis of incorrect options:** * **Osteomalacia:** This is the most common cause. Defective mineralization leads to the accumulation of soft osteoid at sites of mechanical stress. * **Paget’s disease:** Characterized by high bone turnover and disorganized remodeling. Pseudofractures can occur on the convex side of deformed long bones. * **Fibrous dysplasia:** A condition where normal bone is replaced by fibrous tissue and immature bone, creating structural weaknesses that predispose to pseudofractures. **NEET-PG High-Yield Pearls:** * **Common sites for Looser’s zones:** Axillary border of the scapula (most classic), neck of the femur, ribs, and pubic rami. * **Other conditions associated:** Rickets, Renal Osteodystrophy, and Osteogenesis Imperfecta. * **Radiological appearance:** Transverse lucent bands with sclerotic margins, often bilateral and symmetrical. * **Biochemical marker:** In Osteomalacia (the primary cause), expect **Low/Normal Calcium, Low Phosphate, and High Alkaline Phosphatase (ALP).**

Q: In osteoporosis, what is observed?

Decrease in absolute amount of bone mass. **Explanation:** **1. Why Option A is Correct:** Osteoporosis is defined as a metabolic bone disease characterized by a **decrease in the absolute amount of bone mass** (low bone mineral density). Crucially, while the quantity of bone is reduced, the **chemical composition** of the remaining bone matrix remains normal (normal mineralization). This distinguishes it from Osteomalacia, where the mineral-to-matrix ratio is decreased. **2. Analysis of Incorrect Options:** * **Option B:** Osteoporosis is significantly **more common in females**, particularly post-menopausal women, due to the cessation of the protective effect of estrogen on bone resorption. * **Option C:** Radiographs do **not** show normal bone density. However, they are insensitive for early diagnosis because osteopenia only becomes visible on X-ray after **30-50% of bone mass is lost**. The gold standard for diagnosis is the DEXA scan (T-score ≤ -2.5). * **Option D:** While Hormone Replacement Therapy (HRT) was historically used for prevention, it is **not the primary observation or definition** of the disease. Furthermore, due to risks of breast cancer and thromboembolism, Bisphosphonates (like Alendronate) are now the first-line pharmacological treatment. **High-Yield Clinical Pearls for NEET-PG:** * **Biochemical Profile:** In primary osteoporosis, Serum Calcium, Phosphate, and Alkaline Phosphatase are typically **Normal**. * **Most Common Fracture:** The most common site for an osteoporotic fracture is the **Vertebral body** (compression fracture), followed by the neck of the femur and Colles’ fracture. * **Ward’s Triangle:** An area of low bone density in the neck of the femur, which is one of the earliest signs of osteoporosis on X-ray. * **Singh’s Index:** Used to grade the severity of osteoporosis based on the disappearance of trabecular patterns in the proximal femur.

Q: Albers-Schonberg's disease is characterized by which of the following pathological conditions?

Osteopetrosis. **Explanation:** **Albers-Schönberg disease** is the eponym for the autosomal dominant (AD) form of **Osteopetrosis** (specifically Type II). It is a metabolic bone disorder characterized by a functional defect in **osteoclasts**, which fail to resorb bone. This leads to an imbalance where bone formation continues but remodeling is absent, resulting in excessively dense, "stone-like," but brittle bones. **Why the correct answer is right:** In Osteopetrosis, the failure of osteoclasts leads to the persistence of primary spongiosa. On imaging, this manifests as increased bone density (sclerosis) and the characteristic **"bone-within-a-bone"** appearance and **"sandwich vertebrae"** (Rugger-Jersey spine). **Why the incorrect options are wrong:** * **A. Osteomyelitis:** This is an infectious inflammation of the bone/bone marrow, usually bacterial (e.g., *S. aureus*). While osteopetrosis patients are prone to osteomyelitis (due to reduced vascularity), it is not the primary pathology. * **C. Condensing osteitis:** This is a localized reactive periapical bone sclerosis, usually associated with chronic dental pulp inflammation, not a systemic metabolic disease. * **D. Osteomalacia:** This is characterized by inadequate mineralization of the bone matrix (usually due to Vitamin D deficiency), leading to "soft" bones—the physiological opposite of the dense bones seen in Albers-Schönberg disease. **NEET-PG High-Yield Pearls:** * **Inheritance:** AD (Albers-Schönberg/Tarda) is milder; AR (Infantile/Malignant) is severe and presents with pancytopenia and hepatosplenomegaly due to marrow obliteration. * **Radiological Signs:** Erlenmeyer flask deformity (distal femur), Sandwich vertebrae, and "Space-alien" or "Mask-like" skull. * **Complications:** Pathological fractures (Chalk-stick fractures), cranial nerve palsies (due to foraminal narrowing), and secondary anemia.

Q: Osteoporosis is caused by all of the following, except?

Oestradiol. **Explanation:** **Concept:** Osteoporosis is characterized by a reduction in bone mass (low bone mineral density) due to an imbalance between bone resorption (osteoclasts) and bone formation (osteoblasts). **Why Oestradiol is the correct answer:** Oestradiol (Estrogen) is **bone-protective**. It inhibits bone resorption by inducing apoptosis of osteoclasts and suppressing pro-inflammatory cytokines (like IL-1, IL-6, and TNF-α) that stimulate osteoclastogenesis. A deficiency in oestradiol (as seen in menopause) is the primary cause of **Type I (Postmenopausal) Osteoporosis**. Therefore, oestradiol prevents rather than causes osteoporosis. **Why the other options are incorrect:** * **Corticosteroids:** These are the most common cause of drug-induced osteoporosis. They decrease osteoblast activity, reduce intestinal calcium absorption, and increase renal calcium excretion. * **Methotrexate:** This cytotoxic drug interferes with osteoblast proliferation and increases osteoclast activity, leading to "methotrexate osteopathy" at high or chronic doses. * **Chronic Heparin Therapy:** Long-term heparin use (usually >6 months) stimulates osteoclasts and inhibits osteoblasts, leading to decreased bone density. **High-Yield Clinical Pearls for NEET-PG:** * **Gold Standard Diagnosis:** DEXA Scan (Dual-energy X-ray Absorptiometry). Osteoporosis is defined as a **T-score ≤ -2.5**. * **Most common site of fracture:** Vertebral body (compression fracture), followed by the neck of the femur. * **Drug of Choice:** Bisphosphonates (e.g., Alendronate) are the first-line treatment. They act by inhibiting osteoclast-mediated bone resorption. * **Teriparatide:** A recombinant PTH analogue; it is the only **anabolic** agent (builds new bone) used in severe osteoporosis.

Q: Blue sclera is a characteristic feature of which condition?

Osteogenesis imperfecta. **Explanation:** **Osteogenesis Imperfecta (OI)**, also known as "Brittle Bone Disease," is the correct answer. It is a genetic disorder primarily caused by mutations in the **COL1A1 and COL1A2 genes**, leading to a defect in the synthesis of **Type I Collagen**. **Why Blue Sclera occurs:** The sclera is normally composed of Type I collagen. In OI, the collagen is either deficient or defective, causing the scleral coat to become abnormally thin. This thinness allows the underlying **choroidal veins** to show through, giving the eyes a characteristic blue or slate-gray appearance. **Analysis of Incorrect Options:** * **Osteopetrosis (Marble Bone Disease):** Characterized by defective osteoclast function leading to excessively dense, brittle bones. It does not involve collagen defects of the sclera. * **Cleidocranial Dysostosis:** A RUNX2 gene mutation affecting intramembranous ossification. Key features include absent/hypoplastic clavicles and delayed closure of fontanelles, but not blue sclera. * **Achondroplasia:** The most common cause of dwarfism, caused by a mutation in the **FGFR3 gene**. It affects endochondral ossification; scleral color is normal. **NEET-PG High-Yield Pearls:** * **Sillence Classification:** Used to grade OI (Type I is the most common and mildest; Type II is the most severe/lethal). * **Clinical Triad:** Blue sclera, fragile bones (multiple fractures), and early-onset otosclerosis (conductive hearing loss). * **Wormian Bones:** Often seen on skull X-rays in OI patients. * **Differential Diagnosis for Blue Sclera:** Apart from OI, it can be seen in Ehlers-Danlos Syndrome, Marfan Syndrome, and Pseudoxanthoma elasticum.

Q: An X-ray of the proximal femur in a patient presenting with hip pain shows a specific deformity. What is this deformity?

Shepherd crook deformity. ***Shepherd crook deformity*** - Classic **coxa vara** deformity of the proximal femur seen in **fibrous dysplasia**, where the femoral neck bends downward resembling a shepherd's crook. - Results from **mechanical stress** on weakened bone filled with fibrous tissue, causing progressive **varus angulation** of the femoral neck. *Blade of grass deformity* - Characteristic radiological appearance of the **tibia** in **Paget's disease**, showing widened cortex and trabecular pattern. - Involves **long bones** like tibia and fibula, not typically the proximal femur as described in this case. *Chicken wire appearance* - Pathognomonic feature of **vertebral hemangiomas** showing coarse vertical trabeculae on lateral radiographs. - Specifically affects **vertebral bodies**, not the proximal femur or hip region. *Corduroy appearance* - Another radiological sign of **vertebral hemangiomas** seen on **frontal radiographs** showing vertical striations. - Limited to **spinal vertebrae** and does not involve the femoral neck or hip joint area.

Question 1

Looser's zone occurs in all of the following conditions except?

Accepted Answer

Hypoparathyroidism

Answer

Osteomalacia

Answer

Paget's disease

Answer

Fibrous dysplasia

Question 2

In osteoporosis, what is observed?

Accepted Answer

Decrease in absolute amount of bone mass

Answer

More common in males

Answer

Radiographs show normal bone density

Answer

Hormonal replacement therapy

Question 3

Albers-Schonberg's disease is characterized by which of the following pathological conditions?

Accepted Answer

Osteopetrosis

Answer

Osteomyelitis

Answer

Condensing osteitis

Answer

Osteomalacia

Question 4

A 4-year-old child presents with blue sclera and a history of multiple fractures following minimal trauma. For the mentioned disorder, select the serum concentrations of calcium and phosphate with which it is most likely to be associated.

Accepted Answer

Normal phosphate, normal calcium

Answer

Low phosphate, normal calcium

Answer

Low phosphate, high calcium

Answer

Normal phosphate, low calcium

Question 5

Albright syndrome includes which of the following combinations of features?

Accepted Answer

Fibrous dysplasia, cafe au lait spots, and endocrinal abnormalities.

Answer

Fibrous dysplasia.

Answer

Fibrous dysplasia and cafe au lait spots.

Answer

None of the above.

Question 6

A 25-year-old female patient presented with anemia and seventh and eighth nerve palsy. Skull and spine X-rays revealed abnormalities consistent with a specific diagnosis. What is the diagnosis based on these findings?

Accepted Answer

Osteopetrosis

Answer

Paget's disease

Answer

Osteogenesis imperfecta

Answer

Osteomalacia

Question 7

What is true about Paget's disease?

Accepted Answer

Associated with hypercalcemia & hypophosphatemia

Answer

Common in young girls 10-16 years of age

Answer

Increased Alkaline Phosphatase (ALP)

Answer

More common in females, Associated with chondrosarcoma

Question 8

Osteoporosis is caused by all of the following, except?

Accepted Answer

Oestradiol

Answer

Corticosteroid

Answer

Methotrexate

Answer

Chronic heparin therapy

Question 9

Blue sclera is a characteristic feature of which condition?

Accepted Answer

Osteogenesis imperfecta

Answer

Osteopetrosis

Answer

Cleidocranial dysostosis

Answer

Achondroplasia

Question 10

An X-ray of the proximal femur in a patient presenting with hip pain shows a specific deformity. What is this deformity?

Accepted Answer

Shepherd crook deformity

Answer

Blade of grass deformity

Answer

Chicken wire appearance

Answer

Corduroy appearance

Metabolic Bone Diseases — MCQs

Metabolic Bone Diseases — MCQs

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