Metabolic Bone Diseases Practice Questions

Q: Which of the following is NOT true about Osteogenesis imperfecta?

Impaired healing of fractures. **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 a quantitative or qualitative defect in **Type I Collagen**. **Why Option A is the Correct Answer:** Contrary to what might be expected in a disease with "fragile bones," **fracture healing in OI is generally normal** in terms of timing and callus formation. The defect lies in the structural integrity of the bone matrix (collagen), not in the cellular mechanisms of the healing cascade (osteoblasts and fibroblasts). In fact, some patients may even develop "Hyperplastic Callus" (especially in Type V OI), which can sometimes be mistaken for osteosarcoma. **Analysis of Incorrect Options:** * **B. Deafness:** This is a classic feature (Otosclerosis). Conductive or sensorineural hearing loss occurs due to the involvement of the auditory ossicles, which are also composed of bone. * **C. Laxity of joints:** Type I collagen is a major component of ligaments and tendons. Its defect leads to significant ligamentous laxity and joint hypermobility. * **D. Fragile bones:** This is the hallmark of the disease. The defective collagen matrix leads to decreased bone density and extreme cortical thinning, making bones highly susceptible to multiple fractures from minimal trauma. **NEET-PG High-Yield Pearls:** * **Blue Sclera:** The most iconic clinical sign, caused by the thinning of the scleral collagen allowing the underlying choroidal veins to show through. * **Dentinogenesis Imperfecta:** "Opalescent teeth" due to deficiency in dentin. * **Classification:** The **Sillence Classification** is used to grade severity (Type II is the most severe/lethal perinatally). * **Treatment:** **Bisphosphonates** (like Pamidronate) are the mainstay to increase bone mineral density and reduce pain. Surgical management often involves **Sillence (telescopic) nails**.

Q: Triradiate pelvis is typically seen in which of the following conditions?

Rickets. ### Explanation **Correct Answer: A. Rickets** **Mechanism:** Triradiate pelvis (also known as a "heart-shaped" or "beaked" pelvis) is a classic radiological feature of **Rickets** (in children) and **Osteomalacia** (in adults). The underlying pathology is a failure of mineralization of the bone matrix (osteoid), leading to soft, pliable bones. Under the physiological stress of weight-bearing and the upward thrust of the femoral heads, the softened acetabula are pushed inward (protrusio acetabuli), while the sacrum is pushed downward. This structural collapse results in the characteristic three-rayed or "triradiate" appearance of the pelvic inlet. **Analysis of Incorrect Options:** * **B. Chondrodystrophy (e.g., Achondroplasia):** Typically presents with a **"Champagne glass"** appearance of the pelvis, characterized by a broad, short ilium and a narrow greater sciatic notch. * **C. Osteoporosis:** Characterized by a decrease in total bone mass (both matrix and mineral). While it leads to fractures (especially of the neck of femur and vertebrae), it does not typically cause the plastic deformation required to form a triradiate pelvis. * **D. Hyperparathyroidism:** Leads to subperiosteal bone resorption and "Salt and Pepper" skull. While it can cause osteopenia, the specific triradiate deformity is not a hallmark feature. **High-Yield Clinical Pearls for NEET-PG:** * **Rickets Radiological Signs:** Cupping, fraying, and splaying of metaphyses (best seen at the lower end of the radius/ulna), and **Harrison’s sulcus**. * **Looser’s Zones (Pseudofractures):** Pathognomonic for Osteomalacia; these are radiolucent lines oriented perpendicular to the cortex. * **Protrusio Acetabuli:** Also seen in Rheumatoid Arthritis, Paget’s disease, and Marfan syndrome. * **Pelvic Shapes:** * *Triradiate:* Rickets/Osteomalacia. * *Champagne Glass:* Achondroplasia. * *Mickey Mouse Ear:* Down Syndrome (iliac wings).

Q: In which type of osteogenesis imperfecta do 90% of newborns die before 4 weeks of age?

Type II. **Explanation:** **Osteogenesis Imperfecta (OI)** is a group of genetic disorders primarily caused by mutations in the **COL1A1 and COL1A2** genes, leading to defective synthesis of Type I collagen. * **Why Type II is the correct answer:** Type II OI is the **most severe and lethal form** (Perinatal Lethal Type). It is characterized by extreme bone fragility, multiple in-utero fractures, and a "crumpled" appearance of long bones on X-ray. Most newborns (90%) die within the first few weeks of life due to **pulmonary hypoplasia** and respiratory failure resulting from a small, deformed thoracic cage. **Analysis of Incorrect Options:** * **Type I:** This is the most common and **mildest form**. It presents with blue sclerae and increased fracture risk after birth, but life expectancy is generally normal. * **Type III:** Known as the **Progressive Deforming** type. While severe, it is not typically lethal in the neonatal period. Patients survive but suffer from significant skeletal deformities and short stature. * **Type IV:** This is a moderate form with normal sclerae. It is intermediate in severity between Type I and Type III. **High-Yield Clinical Pearls for NEET-PG:** * **Sillence Classification:** The standard system used to categorize OI (Types I-IV). * **Blue Sclera:** Most prominent in Type I due to the thinning of collagen allowing the underlying choroidal veins to show through. * **Dentinogenesis Imperfecta:** Often associated with OI (opalescent teeth). * **Radiology:** Look for "Wormian bones" in the skull and "popcorn calcifications" near the growth plates in later stages. * **Treatment:** Bisphosphonates (e.g., Pamidronate) are the mainstay to increase bone mineral density.

Q: Pseudofractures are seen in which of the following conditions?

Osteomalacia. ### Explanation **Correct Answer: C. Osteomalacia** **Understanding the Concept:** Pseudofractures, also known as **Looser’s zones** or **Milkman’s lines**, are the hallmark radiological feature of **Osteomalacia** (and its pediatric counterpart, Rickets). They are not true fractures but represent stress fractures that have healed with **unmineralized osteoid** (callus) rather than mature bone. On X-ray, they appear as thin, radiolucent lines oriented perpendicular to the bone cortex, often occurring symmetrically. Common sites include the axillary border of the scapula, inner cortex of the femoral neck, pubic rami, and ribs. **Analysis of Incorrect Options:** * **A. Osteoarthritis:** This is a degenerative joint disease characterized by joint space narrowing, osteophytes, and subchondral sclerosis, not metabolic defects in mineralization. * **B. Rickets:** While Rickets is the childhood version of osteomalacia, the classic radiological findings emphasized in exams are **cupping, splaying, and fraying** of the metaphysis. While pseudofractures *can* occur, they are the definitive diagnostic sign for adult **Osteomalacia**. * **D. Osteoporosis:** This involves a decrease in total bone mass (both matrix and mineral are lost), leading to **fragility fractures** (e.g., Colles, vertebral compression). The bone that remains is normally mineralized, so pseudofractures do not form. **High-Yield Clinical Pearls for NEET-PG:** * **Biochemical Triad of Osteomalacia:** Low/Normal Calcium, Low Phosphate, and **Elevated Alkaline Phosphatase (ALP)**. * **Looser’s Zones** are most commonly found at the **axillary border of the scapula** (most specific site). * **Vitamin D Deficiency** is the most common cause. * **Clinical Presentation:** Diffuse bone pain, tenderness, and a characteristic **waddling gait** due to proximal muscle weakness.

Q: Sclerosis of bone is seen in all conditions listed below except?

Hyperparathyroidism. ### Explanation The core concept behind this question is distinguishing between **osteosclerotic** (increased bone density) and **osteolytic** (decreased bone density) processes. **Why Hyperparathyroidism is the correct answer:** Hyperparathyroidism (HPT) is characterized by an excess of Parathyroid Hormone (PTH), which stimulates **osteoclastic activity**. This leads to generalized **bone resorption** (osteopenia/osteoporosis) rather than sclerosis. Classic radiological hallmarks include subperiosteal resorption (pathognomonic, best seen in radial aspect of middle phalanges), "Salt and Pepper" skull, and Brown tumors (Osteitis Fibrosa Cystica). **Analysis of Incorrect Options (Conditions showing Sclerosis):** * **Fluorosis:** Chronic fluoride toxicity stimulates osteoblasts, leading to increased bone formation and dense, chalky white bones (osteosclerosis), particularly in the axial skeleton. * **Osteopetrosis (Marble Bone Disease):** A genetic defect in osteoclast function prevents normal bone resorption. This results in excessively dense, brittle bones with a "bone-within-bone" appearance. * **Secondaries from Prostate:** Prostatic metastasis to the bone is classically **osteoblastic**, resulting in focal or diffuse areas of increased bone density (sclerotic lesions) on X-ray. **NEET-PG High-Yield Pearls:** * **Rugger Jersey Spine:** Seen in secondary hyperparathyroidism (Renal Osteodystrophy); it is a rare instance where HPT shows sclerosis (at the vertebral endplates). However, primary HPT is predominantly resorptive. * **Osteoblastic Metastases:** Remember the mnemonic **"Prostate, Breast (can be mixed), Lung (small cell), Carcinoid, and Lymphoma."** * **Looser’s Zones:** Characteristic of Osteomalacia (pseudofractures), not sclerosis. * **Erlenmeyer Flask Deformity:** Classic sign of Osteopetrosis.

Q: Which of the following statements is FALSE regarding myositis ossificans progressiva?

Life longevity is typically normal.. **Explanation:** **Myositis Ossificans Progressiva (MOP)**, also known as **Fibrodysplasia Ossificans Progressiva (FOP)**, is a rare, autosomal dominant genetic disorder characterized by the progressive transformation of soft tissues (muscles, tendons, and ligaments) into heterotopic bone. **Why Option B is FALSE (The Correct Answer):** Life longevity is **not** normal. Most patients are severely disabled by their 20s and typically succumb to the disease by their 40s. The primary cause of death is **Thoracic Insufficiency Syndrome**, resulting from the ossification of intercostal muscles and the chest wall, leading to restricted lung expansion and respiratory failure. **Analysis of Other Options:** * **Option A (Pneumonia):** This is a common and often fatal complication. Due to the rigid chest wall and restricted ventilation, patients cannot clear secretions effectively, making them highly susceptible to recurrent pulmonary infections. * **Option C (Spine):** The disease characteristically follows a cranio-caudal and axial-to-appendicular pattern. The **spine, neck, and shoulders** are indeed the earliest and most common sites of involvement, leading to a "stone man" appearance. * **Option D (Onset < 6 years):** True. The condition typically manifests in early childhood, usually before the age of 6, often starting with painful soft tissue swellings (flare-ups). **Clinical Pearls for NEET-PG:** * **Hallmark Sign:** Congenital **short/malformed great toe** (hallux valgus/microdactyly) is the earliest diagnostic clue present at birth. * **Genetic Mutation:** Caused by a mutation in the **ACVR1 gene** (encoding the ALK2 receptor). * **Contraindication:** Avoid **intramuscular injections** and biopsies, as any local trauma can trigger a massive flare-up of heterotopic ossification.

Q: Regarding osteoporosis, all of the following statements are true except?

Raised alkaline phosphatase. **Explanation:** The correct answer is **A (Raised alkaline phosphatase)** because, in primary osteoporosis, biochemical markers including **Serum Calcium, Phosphorus, and Alkaline Phosphatase (ALP) typically remain within the normal range.** Osteoporosis is characterized by a decrease in bone mass (quantity) while the mineral-to-matrix ratio remains normal. Elevated ALP is instead a hallmark of conditions with high bone turnover or mineralization defects, such as Paget’s disease, Osteomalacia, or healing fractures. **Analysis of other options:** * **B. DEXA scan is helpful:** This is the **Gold Standard** for diagnosing osteoporosis. It measures Bone Mineral Density (BMD). A T-score of ≤ -2.5 SD is diagnostic of osteoporosis. * **C. Reduced bony matrix:** Osteoporosis is defined as a metabolic bone disease where there is a **quantitative reduction** in both the mineral and the organic osteoid matrix, leading to porous and brittle bones. * **D. Cod fish appearance on X-ray:** This refers to the biconcave appearance of vertebrae caused by the pressure of intervertebral discs on weakened, osteoporotic vertebral bodies. It is a classic radiological sign of the disease. **Clinical Pearls for NEET-PG:** * **Most common site of fracture:** Vertebral body (compression fracture), followed by the neck of the femur and Colles' fracture. * **Singh’s Index:** Used to grade osteoporosis based on the disappearance of trabecular patterns in the proximal femur. * **First-line treatment:** Bisphosphonates (e.g., Alendronate), which act by inhibiting osteoclast-mediated bone resorption. * **Ward’s Triangle:** An area of low bone density in the neck of the femur, often the first site to show changes in osteoporosis.

Q: Which of the following statements regarding osteogenesis imperfecta is false?

It is caused by defects in type 1 collagen.. **Explanation:** The question asks for the **false** statement regarding Osteogenesis Imperfecta (OI). **Why Option A is the "False" Statement (The Correct Answer):** The statement "It is caused by defects in type 1 collagen" is actually a **true** statement. In the context of multiple-choice questions where you must identify the false option, if a statement is factually correct, it cannot be the answer unless there is a typographical error in the question's key or the phrasing of the options. *Note: In many standard medical exams, if all options are factually true, the question may be technically flawed. However, OI is fundamentally a disorder of **Type 1 Collagen** (COL1A1 and COL1A2 genes). If the option intended to say Type 2 or Type 3, it would be clearly false.* **Analysis of Other Options:** * **Option B (True):** Most cases of OI (Types I-IV) follow an **Autosomal Dominant** inheritance pattern. Rare types (Type V onwards) may show autosomal recessive patterns. * **Option C (True):** **Blue sclera** occurs due to thinning of the collagen, allowing the underlying choroidal veins to show through. **Deafness** (otosclerosis) is a common secondary feature due to middle ear ossicle involvement. * **Option D (True):** **Bisphosphonates** (like Pamidronate or Zoledronate) are the mainstay of medical management. They increase bone mineral density and reduce the frequency of fractures by inhibiting osteoclast activity. **NEET-PG High-Yield Pearls:** * **Sillence Classification:** The most common system used to classify OI (Types I to IV). * **Type II OI:** The most severe form; usually lethal in the perinatal period due to respiratory failure. * **Wormian Bones:** Small, irregular bones found in the sutures of the skull; a classic radiological sign of OI. * **Triad of OI:** Fragile bones, blue sclera, and early-onset deafness.

Question 1

Which of the following is NOT true about Osteogenesis imperfecta?

Accepted Answer

Impaired healing of fractures

Answer

Deafness

Answer

Laxity of joints

Answer

Fragile bones prone to fracture

Question 2

Triradiate pelvis is typically seen in which of the following conditions?

Accepted Answer

Rickets

Answer

Chondrodystrophy

Answer

Osteoporosis

Answer

Hyperparathyroidism

Question 3

In which type of osteogenesis imperfecta do 90% of newborns die before 4 weeks of age?

Accepted Answer

Type II

Answer

Type I

Answer

Type III

Answer

Type IV

Question 4

An 80-year-old man presents with slowly progressive enlargement of his head circumference, deformities of long bones and spine, and chronic pain of the affected skeletal segments. Laboratory studies show elevated serum alkaline phosphatase and high urine hydroxyproline. X-ray findings are consistent with Paget disease. Which of the following is the most likely pathogenetic mechanism of this condition?

Accepted Answer

Paramyxovirus infection of osteoclasts

Answer

Generalized reduction in bone mass

Answer

Genetic deficiency of carbonic anhydrase II

Answer

Monoclonal proliferation of plasma cells

Question 5

Pseudofractures are seen in which of the following conditions?

Accepted Answer

Osteomalacia

Answer

Osteoarthritis

Answer

Rickets

Answer

Osteoporosis

Question 6

A 28-year-old lady presented with nausea, vomiting and abdominal pain. X-Ray showed centrally located lytic lesions in metacarpals. What is the next line of management?

Accepted Answer

Parathyroid hormone and serum calcium levels measurement

Answer

Bone curettage with bone grafting

Answer

Extended curettage with phenol

Answer

Extended curettage with bone grafting

Question 7

Sclerosis of bone is seen in all conditions listed below except?

Accepted Answer

Hyperparathyroidism

Answer

Fluorosis

Answer

Osteopetrosis

Answer

Secondaries from prostate

Question 8

Which of the following statements is FALSE regarding myositis ossificans progressiva?

Accepted Answer

Life longevity is typically normal.

Answer

Pneumonia is a common complication.

Answer

The most common site involved is the spine.

Answer

Onset usually occurs before 6 years of age.

Question 9

Regarding osteoporosis, all of the following statements are true except?

Accepted Answer

Raised alkaline phosphatase

Answer

DEXA scan is helpful

Answer

Reduced bony matrix

Answer

Cod fish appearance on X-ray

Question 10

Which of the following statements regarding osteogenesis imperfecta is false?

Accepted Answer

It is caused by defects in type 1 collagen.

Answer

Predominantly autosomal-dominant inheritance is seen.

Answer

Blue sclerae and deafness may be associated.

Answer

Bisphosphonates are useful in the treatment.

Metabolic Bone Diseases — MCQs

Metabolic Bone Diseases — MCQs

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