Metabolic Bone Diseases Practice Questions

Q: A 60-year-old male presents with a bony abnormality at the upper tibia associated with sensorineural hearing loss. Laboratory examination reveals elevated serum alkaline phosphatase levels (440 mU/L) with normal serum calcium and phosphate. A skeletal survey shows "ivory vertebrae" and "cotton wool spots" on skull X-ray. What is the most likely diagnosis?

Paget disease. **Explanation:** The clinical presentation and radiographic findings are classic for **Paget Disease of Bone (Osteitis Deformans)**. This condition is characterized by disordered bone remodeling where excessive osteoclastic resorption is followed by disorganized osteoblastic bone formation. **Why Paget Disease is correct:** 1. **Biochemical Markers:** The hallmark is an **isolated elevation of Serum Alkaline Phosphatase (ALP)** with normal calcium, phosphate, and PTH levels. 2. **Radiology:** "Cotton wool spots" in the skull represent mixed lytic and sclerotic patches. "Ivory vertebra" refers to a dense, radio-opaque vertebral body. 3. **Clinical Features:** Sensorineural hearing loss occurs due to the involvement of the petrous temporal bone or compression of the CN VIII in the internal auditory meatus. The tibia is a common site for bowing and enlargement. **Why other options are incorrect:** * **Fibrous Dysplasia:** Typically presents in younger patients with "ground-glass" appearance on X-ray and "shepherd’s crook" deformity of the femur. * **Osteosclerotic Metastasis:** While it can cause ivory vertebrae (commonly from prostate cancer), it would not explain the cotton wool skull or the specific pattern of hearing loss and tibial enlargement. * **Osteoporosis:** This is a "silent" disease characterized by decreased bone mass and normal lab values (including ALP), leading to fractures rather than bony enlargement or sclerosis. **NEET-PG High-Yield Pearls:** * **Most common site:** Pelvis > Femur > Skull > Tibia. * **Histology:** "Mosaic pattern" or "Jigsaw puzzle" appearance of lamellar bone with prominent cement lines. * **Treatment of choice:** Bisphosphonates (Zoledronic acid). * **Complication:** The most dreaded complication is **Osteosarcoma** (suspect if there is a sudden increase in pain or a new soft tissue mass).

Q: Paget's disease involves which of the following bones?

Pelvis, Vertebrae, Skull. **Explanation:** Paget’s Disease (Osteitis Deformans) is a chronic disorder characterized by excessive and disorganized bone remodeling. It primarily affects the **axial skeleton** and long bones. The disease progresses through three stages: osteolytic, mixed, and osteosclerotic. **Why Option B is Correct:** Paget’s disease has a predilection for the axial skeleton. The most common sites involved are: 1. **Pelvis** (most common site, ~70%) 2. **Vertebrae** (Lumbar spine) 3. **Skull** (leads to increasing hat size and "Cotton wool" appearance on X-ray) 4. **Femur and Tibia** (leads to "saber shin" deformity) **Why Other Options are Incorrect:** * **Options C and D:** These include the **phalanges**. Paget’s disease characteristically **spares the small bones** of the hands and feet. If small bone involvement is seen, it is extremely rare and usually occurs only in very advanced, polyostotic cases. **High-Yield Clinical Pearls for NEET-PG:** * **Biochemical Marker:** Isolated elevation of **Serum Alkaline Phosphatase (ALP)** with normal Calcium, Phosphate, and PTH levels. * **Radiological Signs:** * **Skull:** *Osteoporosis circumscripta* (early), *Cotton wool spots* (late). * **Spine:** *Picture frame vertebra* or *Ivory vertebra*. * **Pelvis:** *Brim sign* (thickening of the pelvic brim). * **Complications:** The most dreaded complication is **Osteosarcoma** (secondary), seen in <1% of patients. Other complications include high-output heart failure and deafness (due to CN VIII compression). * **Drug of Choice:** **Bisphosphonates** (Zoledronic acid is highly effective).

Q: Which type of osteogenesis imperfecta is characterized by blue sclera?

Type 1. **Explanation:** **Osteogenesis Imperfecta (OI)**, also known as "Brittle Bone Disease," is a genetic disorder of Type 1 collagen synthesis. The classification is primarily based on the **Sillence Classification**. 1. **Why Type 1 is correct:** **Type 1 OI** is the most common and mildest form. It is characterized by a **quantitative defect** (decreased production) of structurally normal Type 1 collagen. The hallmark clinical feature is **persistent blue sclera** throughout life. The blue appearance occurs because the abnormally thin scleral collagen allows the underlying choroidal veins to show through. 2. **Why other options are incorrect:** * **Type 2:** This is the most severe, **perinatal lethal** form. It involves a qualitative defect in collagen leading to multiple in-utero fractures and death in the neonatal period. While sclerae may be blue, the primary clinical identifier is lethality. * **Type 3:** This is the **severely deforming** type. Patients have multiple fractures and significant limb/spine deformities. Sclerae may be blue at birth but usually **turn white** as the patient ages. * **Type 4:** This is a moderate form with normal (white) sclerae. It is distinguished from Type 1 primarily by the absence of blue sclera and more frequent fractures. **High-Yield Clinical Pearls for NEET-PG:** * **Inheritance:** Most cases (Types 1-4) are **Autosomal Dominant**. * **Associated Features:** Dentinogenesis imperfecta (opalescent teeth), otosclerosis (conductive hearing loss), and wormian bones on skull X-ray. * **Treatment:** **Bisphosphonates** (e.g., Pamidronate) are the medical mainstay to increase bone mineral density. * **Surgery:** "Sofield-Millar" procedure (multiple osteotomies and intramedullary nailing) is used for long bone deformities.

Q: All are features of osteogenesis imperfecta except?

Absent clavicle. **Explanation:** **Osteogenesis Imperfecta (OI)**, also known as **"Brittle Bone Disease,"** is a genetic disorder primarily caused by mutations in the **COL1A1 and COL1A2 genes**, leading to defective synthesis of **Type I Collagen**. Since Type I collagen is a major structural component of bone, skin, and sclera, its deficiency results in extreme bone fragility. **Why "Absent Clavicle" is the correct answer:** Absent or hypoplastic clavicles are a hallmark feature of **Cleidocranial Dysplasia**, not Osteogenesis Imperfecta. In Cleidocranial Dysplasia, patients can often approximate their shoulders in the midline due to the missing clavicles. In contrast, patients with OI have intact clavicles, though they are prone to fractures. **Analysis of other options:** * **A. Brittle bone disease:** This is the synonym for OI due to the characteristic susceptibility to multiple fractures from minimal trauma. * **B. Blue sclera:** This occurs because the thinning of the scleral collagen allows the underlying choroidal veins to show through. (Note: This is most common in Type I OI). * **C. Wormian bones:** These are accessory small bones found within the sutures of the skull. They are a classic radiological finding in OI (specifically more than 10 Wormian bones). **NEET-PG High-Yield Pearls:** * **Sillence Classification:** Used to categorize OI types (Type I is mildest/most common; Type II is perinatal lethal). * **Associated features:** Dentinogenesis imperfecta (translucent teeth), early-onset conductive hearing loss (otosclerosis), and ligamentous laxity. * **Differential for Wormian Bones:** Remember the mnemonic **"PORK CHOP"** (P-Pyknodysostosis, O-Osteogenesis Imperfecta, R-Rickets, K-Kinky Hair Syndrome, C-Cleidocranial Dysplasia, H-Hypothyroidism/Hypophosphatasia, O-One Down Syndrome, P-Pachydermoperiostosis).

Q: Osteoporosis may be seen in all of the following conditions EXCEPT:

Hypoparathyroidism. **Explanation:** **1. Why Hypoparathyroidism is the Correct Answer:** Osteoporosis is characterized by a decrease in bone mineral density (BMD) due to an imbalance between bone formation and resorption. In **Hypoparathyroidism**, there is a deficiency of Parathyroid Hormone (PTH). Since PTH is the primary driver of osteoclastic bone resorption, its absence leads to **increased bone mass** (osteosclerosis) rather than osteoporosis. The bone in hypoparathyroidism is typically denser, though it may be of poorer quality. **2. Analysis of Incorrect Options:** * **Hyperparathyroidism:** Excess PTH stimulates osteoclasts via the RANKL pathway, leading to significant bone resorption. This classically manifests as "brown tumors," osteitis fibrosa cystica, and generalized osteoporosis. * **Thyrotoxicosis:** High levels of thyroid hormones (T3/T4) increase the rate of bone turnover. The resorptive phase dominates over the formative phase, leading to a net loss of bone density. * **Heparin Administration:** Long-term heparin use (especially >6 months) is a well-known cause of secondary osteoporosis. It increases osteoclast activity and decreases osteoblast function, often seen in pregnant women on long-term anticoagulation. **3. NEET-PG High-Yield Pearls:** * **Drug-induced Osteoporosis:** Aside from Heparin, the most common cause is **Corticosteroids**. Others include Anticonvulsants (Phenytoin) and Proton Pump Inhibitors (PPIs). * **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. * **Biochemical Marker:** In primary osteoporosis, serum Calcium, Phosphate, and ALP levels are typically **normal**, unlike Osteomalacia or Hyperparathyroidism.

Q: Milkman's Fracture is a type of?

Pseudofracture. **Explanation:** **Milkman’s Fracture** is a classic example of a **Pseudofracture** (also known as **Looser’s zones** or Umbauzonen). These are not true traumatic fractures but are radiolucent lines representing stress fractures that have healed with unmineralized osteoid. 1. **Why Pseudofracture is correct:** In metabolic bone diseases like **Osteomalacia** (adults) or **Rickets** (children), there is defective mineralization of the bone matrix. Under physiological stress, small cortical cracks occur. Because the body cannot properly mineralize the repair tissue, these areas appear as thin, transverse lucent bands on X-rays, often symmetrical and perpendicular to the bone cortex. Common sites include the axillary border of the scapula, inner cortex of the femoral neck, ribs, and pubic rami. 2. **Why other options are incorrect:** * **Clavicular, Humeral, and Metacarpal fractures** typically refer to acute traumatic injuries or specific eponymous fractures (e.g., Smith’s, Colles’, or Boxer’s fracture). While these bones *can* develop pseudofractures, Milkman's syndrome specifically describes the clinical entity of multiple pseudofractures associated with osteomalacia. **High-Yield Clinical Pearls for NEET-PG:** * **Pathognomonic for:** Osteomalacia. * **Radiological appearance:** Transverse lucent lines with sclerotic margins, often bilateral and symmetrical. * **Common Sites:** Scapula (most common), ribs, pubic rami, and medial cortex of the femur. * **Biochemical markers:** Low Vitamin D, low Serum Calcium/Phosphate, and **Elevated Alkaline Phosphatase (ALP)**.

Question 1

A 60-year-old male presents with a bony abnormality at the upper tibia associated with sensorineural hearing loss. Laboratory examination reveals elevated serum alkaline phosphatase levels (440 mU/L) with normal serum calcium and phosphate. A skeletal survey shows "ivory vertebrae" and "cotton wool spots" on skull X-ray. What is the most likely diagnosis?

Accepted Answer

Paget disease

Answer

Fibrous dysplasia

Answer

Osteosclerotic metastasis

Answer

Osteoporosis

Question 2

Which of the following disorders is classified under defects in metabolic pathways?

Accepted Answer

Severe infantile osteopetrosis

Answer

Cherubism

Answer

Robinow syndrome

Answer

Pycnodysostosis

Question 3

Paget's disease involves which of the following bones?

Accepted Answer

Pelvis, Vertebrae, Skull

Answer

Pelvis, Vertebrae

Answer

Pelvis, Skull, Phalanges

Answer

Vertebrae, Skull, Phalanges

Question 4

24-hour estimation of urinary hydroxyproline levels is a good indicator for what in Paget's disease?

Accepted Answer

Extent and severity

Answer

Poor outcome

Answer

Diagnosis

Answer

Recurrence

Question 5

A 16-year-old male presents with extensive heterotropic ossification over the neck, back, and shoulders and decreased chest movements. He gives a history of progressive immobility since the age of 3 years. Which of the following statements about his affecting condition is not true?

Accepted Answer

They have a near normal life expectancy.

Answer

They are predisposed to pneumonia.

Answer

They have a short hallux.

Answer

Increased expression of BMP4 gene is seen.

Question 6

Which type of osteogenesis imperfecta is characterized by blue sclera?

Accepted Answer

Type 1

Answer

Type 2

Answer

Type 3

Answer

Type 4

Question 7

All are features of osteogenesis imperfecta except?

Accepted Answer

Absent clavicle

Answer

Known as brittle bone disease

Answer

Blue sclera

Answer

Wormian bones

Question 8

Osteoporosis may be seen in all of the following conditions EXCEPT:

Accepted Answer

Hypoparathyroidism

Answer

Hyperparathyroidism

Answer

Thyrotoxicosis

Answer

Heparin administration

Question 9

Paget's disease is associated with which of the following?

Accepted Answer

Increase in bone turnover

Answer

Decrease in bone mineralization

Answer

Increased bone resorption

Answer

Increased degradation of collagen

Question 10

Milkman's Fracture is a type of?

Accepted Answer

Pseudofracture

Answer

Clavicular fracture

Answer

Humeral fracture

Answer

Metacarpal fracture

Metabolic Bone Diseases — MCQs

Metabolic Bone Diseases — MCQs

On this page

Practice by Chapter

Want unlimited practice?