Developmental Abnormalities — MCQs
Double bubble sign is seen in -
Tetralogy of Fallot (TOF) includes all of the following components except:
Seal like limbs i.e. phocomelia is a specific side effect of -
A 6-week-old baby is brought in by the mother with complaints of vomiting. An X-ray shows a single bubble appearance. What is the most likely diagnosis?
Which of the following is the MOST accurate test for detecting neural tube defects?
Which of the following is a characteristic feature of Down syndrome?
What is the time period for the embryonic period?
The labia majora develop from which embryological structure?
All of the following are neural tube defects except:
The diagrammatic representation of the karyotype of an individual indicates a specific genetic abnormality. What is the diagnosis?
Developmental Abnormalities Indian Medical PG Practice Questions and MCQs
Question 1: Double bubble sign is seen in -
- A. Duodenal atresia
- B. Annular pancreas
- C. Ladd's band
- D. All of the options (Correct Answer)
Explanation: ***All of the options*** - The **"double bubble sign"** on an X-ray indicates **duodenal obstruction**, which can be caused by intrinsic factors like **duodenal atresia** or extrinsic compressions such as an **annular pancreas** or **Ladd's bands** associated with malrotation. - While differing in etiology, all these conditions lead to fluid and air accumulation in the stomach and proximal duodenum, creating the characteristic two dilated loops. *Duodenal atresia* - This is an **intrinsic congenital obstruction** of the duodenum, preventing the passage of gastric and duodenal contents. - On imaging, it shows **two distinct air-filled bubbles** (one for the stomach, one for the proximal duodenum) separated by the pylorus. *Ladd's band* - **Ladd's bands** are peritoneal fibrous bands that can compress the duodenum in cases of **intestinal malrotation**, leading to extrinsic obstruction. - The resulting proximal duodenal dilation, along with gastric distension, presents as the **double bubble sign**. *Annular pancreas* - An **annular pancreas** is a congenital anomaly where pancreatic tissue completely encircles and obstructs the second part of the duodenum. - This extrinsic compression causes significant dilation of the stomach and proximal duodenum, mimicking the appearance of the **double bubble sign**.
Question 2: Tetralogy of Fallot (TOF) includes all of the following components except:
- A. VSD
- B. ASD (Correct Answer)
- C. Pulmonary stenosis
- D. RVH
Explanation: ***ASD*** - While an **atrial septal defect (ASD)** can be present in some complex congenital heart diseases, it is **not considered a primary component of Tetralogy of Fallot** [1]. - The four classic components of **TOF** are **ventricular septal defect (VSD)**, **pulmonary stenosis**, **overriding aorta**, and **right ventricular hypertrophy (RVH)** [1]. *VSD* - A **ventricular septal defect (VSD)** is a **mandatory component** of Tetralogy of Fallot, allowing for mixing of oxygenated and deoxygenated blood [1]. - It's typically a **large, subaortic defect** that enables the overriding aorta to receive blood from both ventricles [1]. *Pulmonary stenosis* - **Pulmonary stenosis** (obstruction of blood flow from the right ventricle to the pulmonary artery) is a **key component** determining the severity of Tetralogy of Fallot [1]. - The degree of **pulmonary stenosis** dictates the amount of right-to-left shunting and the clinical manifestation of **cyanosis** [1]. *RVH* - **Right ventricular hypertrophy (RVH)** develops as a compensatory mechanism due to the increased workload on the right ventricle from the **pulmonary stenosis** and the **VSD** [1]. - It is a **consequence** of the increased pressure required to eject blood past the stenotic pulmonary valve and into the systemic circulation through the VSD [1].
Question 3: Seal like limbs i.e. phocomelia is a specific side effect of -
- A. Doxorubicin
- B. Thalidomide (Correct Answer)
- C. Cyclophosphamide
- D. Terazosin
Explanation: ***Thalidomide*** - **Phocomelia**, characterized by severely shortened or absent limbs resembling those of a seal, is a classic and well-documented **teratogenic effect** of thalidomide. - This drug, when taken during early pregnancy (especially between weeks 4 and 8), disrupts limb bud development. *Doxorubicin* - **Doxorubicin** is an **anthracycline antibiotic** used in cancer chemotherapy, known for its significant **cardiotoxicity**, leading to dilated cardiomyopathy. - While it has various side effects, **phocomelia** is not a reported teratogenic effect of doxorubicin. *Cyclophosphamide* - **Cyclophosphamide** is an **alkylating agent** used in chemotherapy and immunosuppression, with notable side effects including **hemorrhagic cystitis** and **myelosuppression**. - Although it is a teratogen and can cause various fetal malformations, it is not specifically associated with **phocomelia**. *Terazosin* - **Terazosin** is an **alpha-1 blocker** primarily used to treat hypertension and benign prostatic hyperplasia (BPH). - Its main side effects include **orthostatic hypotension** and dizziness; it is not known to be teratogenic or associated with **phocomelia**.
Question 4: A 6-week-old baby is brought in by the mother with complaints of vomiting. An X-ray shows a single bubble appearance. What is the most likely diagnosis?
- A. Duodenal atresia
- B. Annular pancreas
- C. Congenital hypertrophic pyloric stenosis (CHPS) (Correct Answer)
- D. Jejunal atresia
- E. Malrotation with midgut volvulus
Explanation: ***Congenital hypertrophic pyloric stenosis (CHPS)*** - The **single bubble appearance** observed in the X-ray, along with vomiting in a 6-week-old, is characteristic of an obstruction at the gastric outlet due to **pyloric stenosis**. The "bubble" represents the dilated stomach. - Infants with CHPS typically present with **non-bilious projectile vomiting** around 3-6 weeks of age, often accompanied by good appetite. *Duodenal atresia* - This condition classically presents with a **"double bubble" sign** on X-ray, representing dilation of the stomach and the proximal duodenum. - Vomiting is usually **bilious** and occurs earlier, often from birth. *Annular pancreas* - Annular pancreas can cause duodenal obstruction, leading to a **"double bubble" sign** similar to duodenal atresia. - The presentation would also be earlier, typically with **bilious vomiting** from birth or shortly thereafter. *Jejunal atresia* - Jejunal atresia would result in **multiple dilated loops of small bowel** proximal to the obstruction with air-fluid levels, rather than a single bubble. - The vomiting would be **bilious** and abdominal distension would be more prominent. *Malrotation with midgut volvulus* - This presents with **bilious vomiting** and can occur at any age, though commonly in the first few weeks of life. - X-ray findings include a **"corkscrew" or "whirl" sign** on contrast studies, or a gasless abdomen if complete obstruction occurs. - Unlike the single bubble of pyloric stenosis, malrotation typically shows abnormal bowel gas patterns or a paucity of gas in the abdomen.
Question 5: Which of the following is the MOST accurate test for detecting neural tube defects?
- A. USG (Correct Answer)
- B. Placentography
- C. Chromosomal analysis
- D. Amniocentesis
Explanation: ***USG (Ultrasound)*** - **High-resolution ultrasound** is the **gold standard and most accurate imaging modality** for detecting **neural tube defects (NTDs)** due to its ability to directly visualize anatomical structures of the fetus. - **Diagnostic accuracy**: Detection rate >95% for anencephaly and 80-90% for open spina bifida with targeted anomaly scan at 18-20 weeks. - Can identify specific features such as **lemon sign** (frontal bone scalloping), **banana sign** (cerebellar compression), direct visualization of **spina bifida**, **anencephaly**, or **encephalocele**. - **Non-invasive, safe, and widely available**, making it the primary diagnostic tool in clinical practice. *Amniocentesis* - **Amniocentesis** measures **alpha-fetoprotein (AFP)** and **acetylcholinesterase (AChE)** in amniotic fluid, which are elevated in open NTDs. - While highly accurate as a **confirmatory test** (near 99% sensitivity with both markers), it is **invasive** with risk of miscarriage (0.1-0.3%). - Used primarily when ultrasound findings are **equivocal** or for **biochemical confirmation**, not as the first-line diagnostic test. - In modern practice, ultrasound has largely replaced amniocentesis for NTD diagnosis due to superior imaging technology. *Chromosomal analysis* - **Chromosomal analysis** (karyotyping) detects **chromosomal abnormalities** like trisomies (Down syndrome, Edwards syndrome). - NTDs are **structural malformations**, not chromosomal abnormalities, though some chromosomal disorders may have associated structural defects. - Does not directly diagnose NTDs. *Placentography* - **Placentography** is used to localize the **placenta** in cases of suspected **placenta previa** or for guiding invasive procedures. - Provides no information about **fetal anatomy** and is not used for detecting NTDs.
Question 6: Which of the following is a characteristic feature of Down syndrome?
- A. Trisomy 18
- B. Robertsonian translocation involving chromosome 21
- C. Trisomy 21 (Correct Answer)
- D. Trisomy 13
Explanation: ***Trisomy 21*** - **Down syndrome** is the most common autosomal chromosome abnormality and is characterized by the presence of an extra copy of chromosome 21 [1, 2]. - This extra genetic material leads to the characteristic physical features, intellectual disability, and medical conditions associated with the syndrome [1, 2]. *Trisomy 18* - **Trisomy 18**, also known as **Edwards syndrome**, is a serious chromosomal disorder distinct from Down syndrome [2]. - It is characterized by severe developmental problems, including **heart defects**, **kidney malformations**, and **severe intellectual disability**, with generally a much shorter life expectancy [2, 3]. *Robertsonian translocation involving chromosome 21* - A **Robertsonian translocation** involving chromosome 21 is a cause of Down syndrome, but it is not the characteristic feature itself; rather, it is a specific **chromosomal rearrangement** that can lead to an extra copy of chromosome 21 material [1, 2]. - This specific type of translocation accounts for only a small percentage (2-3%) of all Down syndrome cases, while **Trisomy 21** (nondisjunction) is the most common cause [1, 2]. *Trisomy 13* - **Trisomy 13**, also known as **Patau syndrome**, is a distinct chromosomal disorder characterized by the presence of an extra copy of chromosome 13 [2]. - It is associated with severe birth defects, including **cleft lip/palate**, **polydactyly**, and severe neurological problems, and is usually fatal within the first year of life [2]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Genetic Disorders, pp. 170-171. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Genetic Disorders, pp. 171-172. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Genetic Disorders, pp. 168-169.
Question 7: What is the time period for the embryonic period?
- A. 9 weeks to birth
- B. 22 weeks intrauterine to 7 days after birth
- C. 3rd to 8th week of gestation (Correct Answer)
- D. 0-14 days of gestation
Explanation: 3rd to 8th week of gestation - The embryonic period begins at the start of the 3rd week (around day 15-16, after gastrulation begins) and concludes at the end of the 8th week of gestation [2]. - During this critical period, all major organs and body systems are formed in a process called organogenesis [2]. - This is the most critical period of development when the embryo is most susceptible to teratogens [1]. 9 weeks to birth - This time frame describes the fetal period, which follows the embryonic period (starting at week 9) [2]. - The fetal period is primarily characterized by the growth and maturation of tissues and organs formed during the embryonic stage [1]. 22 weeks intrauterine to 7 days after birth - This period describes the perinatal period, which is a medical classification related to outcomes around birth. - It encompasses conditions affecting the fetus from viability until the first week postpartum, not the embryonic developmental stage. 0-14 days of gestation - This initial period is often referred to as the pre-embryonic stage or the period of the zygote and blastocyst [3]. - It involves fertilization, cleavage, blastulation, and implantation, leading to the formation of the bilaminar embryonic disc and early gastrulation [3].
Question 8: The labia majora develop from which embryological structure?
- A. Urogenital folds
- B. Labioscrotal swellings (Correct Answer)
- C. Müllerian ducts
- D. Genital tubercle
Explanation: ***Labioscrotal swellings*** - The **labia majora** develop from the **labioscrotal swellings**, which are paired bilateral structures that appear around week 9-10 of development [1]. - These swellings arise lateral to the urogenital folds and do not fuse in females, forming the labia majora. - In males, these same structures fuse in the midline to form the scrotum. - This is a key example of **sexual differentiation** in embryological development [1]. *Urogenital folds* - The urogenital folds form the **labia minora** in females, not the labia majora. - In males, these folds fuse to form the ventral aspect of the penis and enclose the penile urethra. *Genital tubercle* - The genital tubercle forms the **clitoris** in females and the **glans penis** in males. - It does not contribute to the formation of the labia majora. *Müllerian ducts* - The Müllerian (paramesonephric) ducts form the **upper vagina, uterus, and fallopian tubes** in females. - They are internal structures and do not contribute to external genitalia like the labia majora.
Question 9: All of the following are neural tube defects except:
- A. Holoprosencephaly (Correct Answer)
- B. Encephalocele
- C. Myelomeningocele
- D. Anencephaly
Explanation: ***Holoprosencephaly*** - This condition results from the **failure of the prosencephalon (forebrain)** to properly divide into two hemispheres, often leading to facial abnormalities. - It is considered a **forebrain malformation**, distinct from neural tube closure defects. *Encephalocele* - An encephalocele is a **neural tube defect** characterized by the protrusion of brain tissue and meninges through an opening in the skull. - It results from the **incomplete closure of the neural tube** during embryonic development. *Myelomeningocele* - Myelomeningocele is a severe form of **spina bifida**, a neural tube defect where the spinal cord and meninges protrude through an opening in the spine [2]. - This defect arises from the **failure of the neural tube to close completely** in the caudal region [1]. *Anencephaly* - Anencephaly is a lethal **neural tube defect** characterized by the absence of a major portion of the brain, skull, and scalp [3]. - It occurs due to the **failure of the cranial end of the neural tube to close** [3].
Question 10: The diagrammatic representation of the karyotype of an individual indicates a specific genetic abnormality. What is the diagnosis?
- A. Angelman syndrome
- B. Cri du Chat syndrome
- C. DiGeorge syndrome
- D. Prader-Willi syndrome (Correct Answer)
Explanation: ***Prader-Willi syndrome*** - The karyotype shows an abnormality on **chromosome 15**, which is consistent with Prader-Willi syndrome caused by **deletion of 15q11-q13** inherited from the **paternal** chromosome or **maternal uniparental disomy**. - While PWS deletions are typically **submicroscopic**, larger deletions can occasionally be visible on standard karyotyping, particularly when they represent **class I deletions** that are more extensive and involve additional chromosomal material beyond the typical PWS critical region. *Angelman syndrome* - Although Angelman syndrome also involves **chromosome 15q11-q13 deletion**, it results from **maternal** deletion or **paternal uniparental disomy**, and presents with distinctly different clinical features. - Clinical presentation includes **severe intellectual disability**, **ataxia**, **seizures**, **absent speech**, and **inappropriate laughter** (happy demeanor), which differs significantly from the PWS phenotype. *DiGeorge syndrome* - DiGeorge syndrome is caused by **deletion of chromosome 22q11.2**, not chromosome 15 as shown in the karyotype. - Clinical features include **cardiac defects** (conotruncal abnormalities), **thymic hypoplasia**, **parathyroid hypoplasia** (hypocalcemia), **cleft palate**, and characteristic facial features (CATCH-22 syndrome). *Cri du Chat syndrome* - This syndrome results from **deletion of chromosome 5p** (short arm of chromosome 5), not chromosome 15 as indicated in the karyotype. - Characteristic features include **high-pitched cry** resembling a cat's meow in infancy, **intellectual disability**, **microcephaly**, and **distinctive facial features**.
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