Bone and Soft Tissue Pathology Practice Questions

Q: What is the basic pathology in myositis ossificans progressiva?

Muscle fibres. **Explanation:** **Myositis Ossificans Progressiva (MOP)**, also known as Fibrodysplasia Ossificans Progressiva (FOP), is a rare genetic disorder characterized by the progressive transformation of soft tissues—specifically **muscle fibers** and connective tissues—into heterotopic bone [1]. **Why Option A is correct:** The fundamental pathology involves the replacement of skeletal muscle fibers and associated fascia by well-formed lamellar bone. This occurs due to an autosomal dominant mutation in the **ACVR1 gene**, which encodes a bone morphogenetic protein (BMP) type I receptor. This mutation causes overactive BMP signaling, leading to the "metaplasia" of myogenic and connective tissue cells into osteoblasts. The process typically begins in early childhood, following a cranial-to-caudal pattern. **Why other options are incorrect:** * **B. Serum chemistry:** In MOP, serum levels of calcium, phosphorus, and alkaline phosphatase are typically **normal**. The pathology is structural and genetic, not a systemic metabolic or biochemical derangement. * **C. Body collagen:** While collagenous structures (fascia, tendons) are involved, the hallmark of the disease is the replacement of the **functional muscle unit** (fibers) with bone, leading to severe immobilization. "Body collagen" is too broad and non-specific. **High-Yield Clinical Pearls for NEET-PG:** * **Classic Triad:** Progressive ectopic ossification, congenital malformation of the **great toes** (microdactyly/hallux valgus), and short thumbs. * **Trigger Factors:** Minor trauma, intramuscular injections, or viral infections can trigger "flare-ups" leading to rapid ossification. * **Diagnosis:** Primarily clinical and radiological; biopsy is contraindicated as it can trigger new bone formation at the site. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Osteoarticular And Connective Tissue Disease, pp. 691-692.

Question 1

A 8-year-old boy presented with a three-month history of left eye swelling. Examination revealed proptosis of the left eye with preserved vision; the right eye is normal. A CT scan revealed an extraconal mass lesion, and a biopsy revealed embryonal rhabdomyosarcoma. The metastatic workup was normal. What is the standard line of treatment?

Accepted Answer

Chemotherapy and Radiation therapy

Answer

Chemotherapy only

Answer

Wide local excision

Answer

Enucleation

Question 2

Geographic lytic lesions in the vault of skull with beveled edges are seen with which of the following conditions?

Accepted Answer

Eosinophilic granuloma

Answer

Multiple myeloma

Answer

Hyperparathyroidism

Answer

Reticular cell carcinoma

Question 3

Pneumatosis intestinalis is diagnostic of?

Accepted Answer

Necrotizing enterocolitis

Answer

Ileal perforation

Answer

Meconium ileus

Answer

Colonic aganglionosis

Question 4

Which of the following statements is false?

Accepted Answer

B

Answer

A

Answer

C

Answer

D

Question 5

What is the most likely diagnosis for CD-99 positivity?

Accepted Answer

Ewing's sarcoma

Answer

SLL

Answer

Dermatofibroma protrubens

Answer

Malignant histiocytic fibroma

Question 6

Paget's disease commonly develops in which age group?

Accepted Answer

Fifth decade

Answer

First decade

Answer

Third decade

Answer

Seventh decade

Question 7

A strict vegetarian develops osteomalacia due to insufficient vitamin D intake. Which of the following changes characterizes osteomalacia in the bones?

Accepted Answer

Increased osteoid

Answer

Decreased osteoblasts

Answer

Increased osteoclast activity

Answer

Marrow fibrosis

Question 8

What is the basic pathology in myositis ossificans progressiva?

Accepted Answer

Muscle fibres

Answer

Serum chemistry

Answer

Body collagen

Answer

None of the above

Question 9

A 51-year-old man presents with right hip pain and diminished range of motion of the right hip for the past 3 months. Radiographs reveal a 10 x 13 cm mass involving the right ischium of the pelvis with irregular borders, extensive bony destruction, and scattered calcifications. The mass, resected grossly, has a bluish-white cut surface. Which of the following attributes is most likely to describe this mass?

Accepted Answer

Sometimes seen to arise in benign cartilaginous tumors

Answer

The most frequent primary tumor of bone

Answer

Usually seen in distal skeletal bones

Answer

More common in females

Question 10

Which fixative is used for bone histopathology?

Accepted Answer

10% formalin

Answer

Normal saline

Answer

Rectified spirit

Answer

Nothing

Bone and Soft Tissue Pathology — MCQs

Bone and Soft Tissue Pathology — MCQs

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