Congenital Skeletal Anomalies — MCQs
In which condition is the presence of an extra pair of ribs sometimes observed?
Clavicle is absent in which of the following conditions?
Wormian bones are seen in all except?
Which of the following terms is MOST appropriate for growth of bone?
Osteogenesis imperfecta is due to a defect in what?
Blue sclera is seen in all of the following conditions except:
Select the type of bone disease which is most likely to be associated with genetically determined disorder in the structure or processing of type I collagen (SELECT 1 DISEASE)
An intrauterine scan at the 13th week of pregnancy showed a fetus with multiple long bone fractures. What is commonly associated with this finding?
Retardation of skeletal maturity can be caused by all of the following except:
Bone age is advanced in which of the following conditions?
Congenital Skeletal Anomalies Indian Medical PG Practice Questions and MCQs
Question 1: In which condition is the presence of an extra pair of ribs sometimes observed?
- A. Down syndrome
- B. Turner syndrome (Correct Answer)
- C. Holt-Oram syndrome
- D. Fibrous dysplasia
- E. Klinefelter syndrome
Explanation: ***Turner syndrome*** - **Turner syndrome** (45,X) is often associated with skeletal abnormalities, including an extra pair of ribs (cervical ribs) in some cases. - Other common skeletal features include **short stature**, a **shield chest**, and **cubitus valgus**. *Down syndrome* - **Down syndrome** (trisomy 21) is characterized by specific facial features, intellectual disability, and congenital heart defects. - While it can manifest with various skeletal anomalies, an extra pair of ribs is not a characteristic feature. *Klinefelter syndrome* - **Klinefelter syndrome** (47,XXY) is characterized by hypogonadism, tall stature, gynecomastia, and learning difficulties. - Skeletal features may include long limbs and decreased bone density, but cervical ribs are not typically associated with this condition. *Holt-Oram syndrome* - **Holt-Oram syndrome** is a genetic disorder affecting heart and limb development, specifically the upper limbs (thumb abnormalities, phocomelia). - It does not typically involve the presence of an extra pair of ribs. *Fibrous dysplasia* - **Fibrous dysplasia** is a bone disorder where normal bone is replaced by fibrous tissue, leading to weakened bone and fractures. - It is a localized bone condition and does not involve the presence of supernumerary ribs.
Question 2: Clavicle is absent in which of the following conditions?
- A. Osteogenesis imperfecta
- B. Cleidocranial dysostosis (Correct Answer)
- C. Fibrous dysplasia
- D. Osteopetrosis
Explanation: ***Cleidocranial dysostosis*** [1] - Characterized by the **absence of clavicles**, leading to wide-set shoulders, which is a hallmark feature of this condition. - It is a genetic disorder due to mutations in the **RUNX2** gene [1], impacting bone development. *Osteogenesis imperfecta* - Known as "brittle bone disease," primarily affecting **collagen production**, leading to fragile bones. - Does not typically involve **clavicular absence**; clavicles are usually present, though they may be brittle. *Osteopetrosis* - A condition marked by **abnormal bone density** due to osteoclast dysfunction, leading to dense yet fragile bones. - The clavicles remain intact, although may show **thickening** rather than absence. *Fibrous dysplasia* - Characterized by **replacement of normal bone with fibrous tissue**, leading to bone deformities or fractures. - The clavicle is usually preserved, although it can be affected by **expansile lesions** in some cases. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Bones, Joints, and Soft Tissue Tumors, p. 1186.
Question 3: Wormian bones are seen in all except?
- A. Osteogenesis imperfecta
- B. Rickets
- C. Fibrous dysplasia (Correct Answer)
- D. Cretinism
Explanation: ***Fibrous dysplasia*** - **Fibrous dysplasia** is a bone disorder where normal bone is replaced by fibrous tissue and immature woven bone, but it is not typically associated with the development of **Wormian bones**. - Its manifestations are usually localized to specific bones and include pain, deformity, and fractures, rather than abnormalities in cranial suture ossification. *Osteogenesis imperfecta* - **Osteogenesis imperfecta** (OI), or brittle bone disease, is a genetic disorder characterized by **fragile bones** and often includes **Wormian bones** due to defective collagen synthesis. - The presence of multiple Wormian bones is a common radiographic finding in individuals with OI. *Rickets* - **Rickets** is caused by a deficiency in vitamin D, calcium, or phosphate, leading to impaired bone mineralization and **softening of bones**. - While rickets primarily affects long bones, severe and prolonged cases, particularly in children, can lead to widespread defects in bone ossification, including the appearance of **Wormian bones** in the skull. *Cretinism* - **Cretinism** (congenital hypothyroidism) leads to delayed skeletal maturation and abnormal bone development. - One of the skeletal anomalies seen in cretinism is the presence of **Wormian bones**, reflecting impaired ossification of the skull.
Question 4: Which of the following terms is MOST appropriate for growth of bone?
- A. Increase in size (Enlargement)
- B. Hypertrophy
- C. Apposition (Correct Answer)
- D. Hyperplasia
Explanation: ***Apposition*** - **Appositional growth** refers to the increase in the **thickness** or diameter of a bone due to the addition of new bone matrix on the surface by **osteoblasts** [1]. - This process is crucial for the continuous remodeling and reshaping of bones throughout life [2]. *Increase in size (Enlargement)* - While bone *does* increase in size during growth, "enlargement" is a general term that doesn't specifically describe the cellular mechanism of how bone tissue itself grows. - It could refer to an increase in overall dimension without detailing the biological process. *Hypertrophy* - **Hypertrophy** is the increase in the **size of individual cells**, leading to an increase in the size of the tissue or organ [3]. - Bone growth primarily involves the deposition of new matrix and the proliferation of cells, not just the enlargement of existing bone cells. *Hyperplasia* - **Hyperplasia** is an increase in the number of cells in a tissue or organ [3]. - While cell proliferation (an increase in osteoblast numbers) is part of bone growth, the term "apposition" more accurately captures the process of adding new bone matrix to the surface, which is the primary mechanism for bone thickening and lengthening. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Bones, Joints, and Soft Tissue Tumors, pp. 1182-1184. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Osteoarticular And Connective Tissue Disease, pp. 662-663. [3] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 87-88.
Question 5: Osteogenesis imperfecta is due to a defect in what?
- A. Type II collagen
- B. Type IV collagen
- C. Type I collagen (Correct Answer)
- D. Type III collagen
Explanation: ***Collagen 1*** - Osteogenesis imperfecta is primarily caused by a defect in **type I collagen** [2], which is crucial for bone strength and structure. - This defect leads to **brittle bones**, resulting in frequent fractures and skeletal deformities . *Collagen 2* - Type II collagen is mainly found in **cartilage** and is critical for **hyaline cartilage formation**, not directly involved in bone integrity. - Defects in type II collagen are associated with conditions like **chondrodysplasia**, rather than osteogenesis imperfecta. *Collagen 4* - Type IV collagen is primarily found in **basement membranes** and plays a role in filtration and structural integrity of tissues. - While important for kidney and eye function, it is not related to the bone fragility seen in osteogenesis imperfecta. *Collagen 3* - Type III collagen is involved in the structure of **reticular fibers** and is crucial for skin and blood vessel integrity. - It is not the primary collagen affected in osteogenesis imperfecta, which is associated specifically with type I collagen defects. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Bones, Joints, and Soft Tissue Tumors, p. 1182. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Bones, Joints, and Soft Tissue Tumors, p. 1188.
Question 6: Blue sclera is seen in all of the following conditions except:
- A. Marfan's syndrome
- B. Osteogenesis imperfecta
- C. Keratoconus (Correct Answer)
- D. Rheumatoid arthritis
Explanation: ***Keratoconus*** - Keratoconus is a progressive eye disease in which the normally round cornea thins and begins to bulge into a cone-like shape, leading to **vision distortion**. - Blue sclera is **not a feature** of keratoconus. This is a **corneal condition** that does not affect the sclera. - Blue sclera, seen in the other conditions listed, occurs due to thinning of the sclera, making the underlying choroidal pigment visible. *Marfan's syndrome* - Patients with Marfan's syndrome can have blue sclera due to the **thinning of collagen** in the scleral tissue, allowing the underlying choroid to show through. - This connective tissue disorder affects multiple body systems, including the skeletal, cardiovascular, and ocular systems, with features like **arachnodactyly** and **aortic root dilation**. *Osteogenesis imperfecta* - Often referred to as **brittle bone disease**, osteogenesis imperfecta is characterized by defective **type I collagen synthesis**, which also affects the sclera. - The sclera becomes thin and translucent, revealing the underlying choroidal pigment, thus appearing **blue**. *Rheumatoid arthritis* - In rheumatoid arthritis, particularly with severe or long-standing disease, the sclera can become thinned due to **scleritis** or **scleromalacia perforans**. - This thinning can lead to a **blue discoloration** of the sclera, making the underlying choroid visible.
Question 7: Select the type of bone disease which is most likely to be associated with genetically determined disorder in the structure or processing of type I collagen (SELECT 1 DISEASE)
- A. Osteogenesis imperfecta (Correct Answer)
- B. Osteopetrosis
- C. Osteomalacia
- D. Osteitis fibrosa cystica
Explanation: ***Osteogenesis imperfecta*** - This condition is primarily caused by **genetic defects** in the production of **type I collagen**, leading to fragile bones. - Due to these defects, bones are prone to **fractures** with minimal trauma. *Osteopetrosis* - Characterized by abnormally **dense bones** due to a defect in **osteoclast function**, not collagen structure [1]. - This leads to bones that are brittle and prone to fracture, but the underlying cause is different from collagen abnormalities [1]. *Osteomalacia* - This refers to the **softening of bones** due to impaired **mineralization**, most commonly from **vitamin D deficiency** or phosphate imbalance. - It does not involve a primary defect in the genetic structure or processing of type I collagen. *Osteitis fibrosa cystica* - This is a bone lesion caused by **severe hyperparathyroidism**, leading to excessive bone resorption and replacement by fibrous tissue and cysts. - It is an endocrine disorder affecting **calcium metabolism**, not a primary collagenopathy. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Bones, Joints, and Soft Tissue Tumors, p. 1188.
Question 8: An intrauterine scan at the 13th week of pregnancy showed a fetus with multiple long bone fractures. What is commonly associated with this finding?
- A. Osteogenesis imperfecta (Correct Answer)
- B. Marfan syndrome
- C. Achondroplasia
- D. Cretinism
Explanation: ***Osteogenesis imperfecta*** - **Multiple long bone fractures** detected early in pregnancy are a classic presentation of **osteogenesis imperfecta (OI)**, a genetic disorder characterized by **bone fragility**. - OI is primarily caused by mutations in genes encoding **type I collagen**, leading to defective bone formation. *Achondroplasia* - This condition is a form of **dwarfism** characterized by disproportionately short limbs and a normal-sized trunk, resulting from a mutation in the **FGFR3 gene**. - While it affects bone growth, it typically does not cause **multiple fractures** prenatally. *Marfan syndrome* - This is a connective tissue disorder affecting the skeletal, ocular, and cardiovascular systems, characterized by **tall stature**, **long limbs and fingers**, and **aortic root dilation**. - It results from a mutation in the **fibrillin-1 gene** and is not primarily associated with prenatal long bone fractures. *Cretinism* - This is a historical term for **congenital hypothyroidism**, which results from severely deficient thyroid hormone production in a newborn. - It leads to developmental delays, growth retardation, and intellectual disability, but not to **multiple bone fractures**.
Question 9: Retardation of skeletal maturity can be caused by all of the following except:
- A. Protein energy malnutrition
- B. Congenital adrenal hyperplasia (Correct Answer)
- C. Hypothyroidism
- D. Chronic renal failure
Explanation: ***Congenital adrenal hyperplasia*** - This condition involves **excessive androgen production**, which can lead to **accelerated skeletal maturity** and premature epiphyseal fusion, rather than retardation. - The increased androgen levels **hasten bone age advancement**, leading to a shorter adult height. *Protein energy malnutrition* - **Severe nutritional deficiencies**, especially of protein and energy, impair growth hormone and IGF-1 axis, leading to **delayed bone growth** and skeletal maturation. - This directly impacts the ability of bones to grow and ossify properly. *Hypothyroidism* - Lack of **thyroid hormones** significantly affects bone development, leading to **delayed epiphyseal ossification** and skeletal maturation. - Thyroid hormones are crucial for normal bone growth and development. *Chronic renal failure* - **Chronic kidney disease** can cause **renal osteodystrophy**, which includes growth retardation and delayed bone age due to disturbances in calcium, phosphate, and vitamin D metabolism. - It also affects growth hormone sensitivity and IGF-1 production.
Question 10: Bone age is advanced in which of the following conditions?
- A. Congenital adrenal hyperplasia (Correct Answer)
- B. Hypothyroidism
- C. Hypopituitarism
- D. Constitutional delay in growth
Explanation: ***Congenital adrenal hyperplasia*** - In **congenital adrenal hyperplasia (CAH)**, the adrenal glands produce excessive androgens, leading to precocious puberty and **accelerated skeletal maturation**, thus advancing bone age. - The excess androgens cause early fusion of the **epiphyseal growth plates**, leading to a disproportionately taller stature in childhood but potentially shorter adult height. *Hypothyroidism* - **Hypothyroidism** causes delayed growth and development, including **delayed bone age**, due to insufficient thyroid hormone which is crucial for normal skeletal maturation. - Children with hypothyroidism typically have shorter stature for their chronological age and delayed ossification of epiphyses. *Hypopituitarism* - **Hypopituitarism**, especially growth hormone deficiency, leads to **delayed bone age** and significantly stunted growth because growth hormone is essential for normal skeletal development. - Insufficient growth hormone results in slower epiphyseal growth and delayed growth plate closure. *Constitutional delay in growth* - **Constitutional delay in growth and puberty** is characterized by a "late bloomer" pattern, where both linear growth and pubertal development are delayed, resulting in a **delayed bone age**. - These children typically have normal growth velocity for their bone age and will eventually reach a normal adult height, just later than their peers.
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