Congenital Anomalies — MCQs
All the following drugs are teratogenic except?
Which of the following anti-epileptic drugs has the highest teratogenic potential?
Which of the following STDs causes fetal abnormality?
Congenital megacolon develops secondary to failure of which?
Which of the following tests on amniotic fluid is most useful in distinguishing between open neural tube defects and ventral wall defects in a fetus?
Which of the following methods is used for prenatal diagnosis of Down Syndrome?
Which malformation is associated with mutations in the HOX gene?
Congenital Rubella Syndrome includes all except
During embryological development, failure of the urorectal septum to completely separate the cloaca results in which of the following congenital anomalies?
Which of the following statements about Sprengel's deformity is false?
Congenital Anomalies Indian Medical PG Practice Questions and MCQs
Question 1: All the following drugs are teratogenic except?
- A. Alcohol
- B. Phenytoin
- C. Warfarin
- D. Metoclopramide (Correct Answer)
Explanation: ***Metoclopramide*** - **Metoclopramide** is an antiemetic and prokinetic agent generally considered **safe during pregnancy**. - It does **not** have established teratogenic effects and is often used to treat **nausea and vomiting** in pregnant women. *Alcohol* - **Alcohol** is a well-known teratogen, leading to **fetal alcohol syndrome** characterized by facial dysmorphia, growth restriction, and CNS abnormalities. - Even moderate consumption can have detrimental effects on fetal development, particularly brain development. *Phenytoin* - **Phenytoin** is an antiepileptic drug associated with **fetal hydantoin syndrome**, which includes craniofacial anomalies, mental deficits, and distal phalangeal hypoplasia. - It interferes with **folate metabolism** and can increase the risk of neural tube defects. *Warfarin* - **Warfarin** is an anticoagulant that can cause **fetal warfarin syndrome** when used during the first trimester, leading to chondrodysplasia punctata, nasal hypoplasia, and skeletal abnormalities. - Its mechanism involves interfering with **vitamin K-dependent coagulation factors**, affecting fetal bone and cartilage development.
Question 2: Which of the following anti-epileptic drugs has the highest teratogenic potential?
- A. Carbamazepine
- B. Phenytoin
- C. Valproate (Correct Answer)
- D. Lamotrigine
Explanation: ***Correct: Valproate*** - **Valproate has the highest teratogenic potential** among all anti-epileptic drugs, with a **10-20% risk of major congenital malformations** - **Neural tube defects** (spina bifida) occur in **1-2% of exposed pregnancies**, which is 10-20 times higher than the general population - Other significant risks include **cardiac malformations, craniofacial abnormalities**, and **neurodevelopmental disorders** (autism spectrum disorder, reduced IQ) - **Fetal valproate syndrome** is a recognized clinical entity - Current guidelines strongly recommend **avoiding valproate in women of childbearing potential** unless no alternatives exist *Incorrect: Carbamazepine* - Has teratogenic risks but significantly **lower than valproate** (2-5% risk of major malformations) - Associated with **neural tube defects** (0.5-1% risk, lower than valproate) - Considered a safer alternative when valproate must be avoided *Incorrect: Phenytoin* - Causes **fetal hydantoin syndrome** with characteristic features: craniofacial anomalies, nail/digital hypoplasia, growth restriction, and developmental delay - Teratogenic risk is **moderate** (approximately 5-10% risk of major malformations) - Risk is significant but **lower than valproate** *Incorrect: Lamotrigine* - Considered **one of the safest anti-epileptic drugs** during pregnancy - Low teratogenic risk with **major malformation rate of 2-3%** (close to baseline population risk) - Slight increased risk of **oral clefts** at higher doses - **Preferred choice** for women of childbearing potential requiring anti-epileptic therapy
Question 3: Which of the following STDs causes fetal abnormality?
- A. Syphilis (Correct Answer)
- B. Herpes
- C. Gonorrhea
- D. Hepatitis B
Explanation: ***Syphilis*** - **Congenital syphilis**, resulting from maternal infection, can lead to severe fetal abnormalities such as **bone deformities**, **saddle nose**, **Hutchinson's teeth**, and **neurological problems**. - It can also cause stillbirth, prematurity, or hydrops fetalis, emphasizing the importance of early detection and treatment during pregnancy. *Herpes* - While **neonatal herpes** can be life-threatening and cause neurological damage, it is typically acquired during passage through the birth canal and does not cause **fetal abnormalities** during gestation. - Herpes simplex virus primarily causes localized lesions and systemic infection in the neonate, not developmental defects. *Gonorrhea* - Gonorrhea primarily causes **ophthalmia neonatorum** (conjunctivitis) in newborns through exposure during birth, which can lead to blindness if untreated. - It does not typically cause **fetal abnormalities** or congenital defects through transplacental transmission. *Hepatitis B* - Hepatitis B can be transmitted to the fetus during birth, leading to **chronic hepatitis B infection** in the infant. - Although it causes a chronic disease, it does not typically result in **fetal abnormalities** or congenital malformations.
Question 4: Congenital megacolon develops secondary to failure of which?
- A. Failure of enteric neurogenesis
- B. Failure of external anal sphincter relaxation
- C. Failure of migration of vagal neural crest cells to the gut (Correct Answer)
- D. Failure of the defecation reflex development
Explanation: ***Failure of migration of vagal neural crest cells to the gut*** - **Congenital megacolon**, also known as **Hirschsprung disease**, results from the **failure of neural crest cells** to migrate completely during embryonic development. - These neural crest cells usually form the **submucosal (Meissner's) and myenteric (Auerbach's) plexuses** in the colon, which are essential for normal bowel motility. *Failure of enteric neurogenesis* - While ultimately leading to a lack of enteric nerves, this option is less specific. The primary defect is a failure of **migration** of the precursor cells (neural crest cells), rather than a failure of the neurogenesis process itself once the cells are in place. - **Enteric neurogenesis** usually occurs from neural crest cells that have successfully migrated to the gut wall. *Failure of external anal sphincter relaxation* - This description typically refers to conditions like **anismus** or pelvic floor dyssynergia, which are acquired disorders of defecation, not a congenital malformation like megacolon. - **Hirschsprung disease** involves the internal anal sphincter (which is aganglionic), not primarily the external anal sphincter. *Failure of the defecation reflex development* - The **defecation reflex** relies on intact enteric nervous system and extrinsic nerves. Dysfunction of this reflex in Hirschsprung disease is a consequence of the underlying aganglionosis. - This option describes a symptom or consequence rather than the fundamental embryonic defect.
Question 5: Which of the following tests on amniotic fluid is most useful in distinguishing between open neural tube defects and ventral wall defects in a fetus?
- A. Carcinoembryonic antigen
- B. Alpha-fetoprotein
- C. Sphingomyelin
- D. Acetylcholinesterase (Correct Answer)
Explanation: ***Acetylcholinesterase*** - **Acetylcholinesterase (AChE)** is highly specific to neural tissue and its presence in amniotic fluid, combined with elevated AFP, is highly indicative of an **open neural tube defect (NTD)**. - While AFP is elevated in both NTDs and ventral wall defects, **AChE** helps differentiate by confirming neural tissue exposure. *Carcinoembryonic antigen* - **Carcinoembryonic antigen (CEA)** is a tumor marker primarily used in the diagnosis and monitoring of certain cancers, particularly colorectal cancer. - It has no established role in the prenatal diagnosis or differentiation of neural tube defects or ventral wall defects. *Sphingomyelin* - **Sphingomyelin** is a component of pulmonary surfactant and is measured to assess fetal lung maturity, usually in conjunction with lecithin as the **L/S ratio**. - This test is not used for the diagnosis or differentiation of structural birth defects like neural tube defects or ventral wall defects. *Alpha-fetoprotein* - **Alpha-fetoprotein (AFP)** is elevated in maternal serum and amniotic fluid in both **open neural tube defects** and **ventral wall defects** (e.g., gastroschisis, omphalocele). - While useful for screening, **AFP alone cannot distinguish** between these two conditions, as it is non-specific for the type of open defect.
Question 6: Which of the following methods is used for prenatal diagnosis of Down Syndrome?
- A. Karyotyping for chromosomal analysis (Correct Answer)
- B. Non-invasive prenatal testing (NIPT) for cell-free DNA analysis
- C. Triple test for biomarker screening
- D. Fetal ultrasonography for physical feature assessment
Explanation: ***Karyotyping for chromosomal analysis*** - **Karyotyping** is the gold standard definitive diagnostic method for Down syndrome (trisomy 21) as it directly visualizes and counts all chromosomes, identifying the presence of an extra copy of chromosome 21. - This cytogenetic method provides a clear genetic diagnosis with 100% accuracy, confirming the chromosomal abnormality responsible for Down syndrome. - Karyotyping can be performed on cells obtained via amniocentesis or chorionic villus sampling (CVS). *Triple test for biomarker screening* - The **triple test** measures biochemical markers (alpha-fetoprotein, unconjugated estriol, and hCG) to assess the risk of Down syndrome, but it is a **screening tool**, not a diagnostic method. - It has a detection rate of approximately 69% with a 5% false-positive rate. - Abnormal results require confirmatory diagnostic testing with karyotyping or other chromosomal analysis methods. *Fetal ultrasonography for physical feature assessment* - Fetal ultrasonography can detect **soft markers** such as increased nuchal translucency, absent/hypoplastic nasal bone, echogenic intracardiac focus, or structural anomalies that raise suspicion for Down syndrome. - However, ultrasound findings are **not diagnostic** on their own and have limited sensitivity and specificity. - Positive findings necessitate genetic testing like karyotyping for definitive diagnosis. *Non-invasive prenatal testing (NIPT) for cell-free DNA analysis* - **NIPT** analyzes cell-free fetal DNA in maternal blood and has high sensitivity (>99%) and specificity (>99%) for detecting trisomy 21. - Despite its excellent screening performance, NIPT is still classified as a **screening test**, not a diagnostic test. - Positive NIPT results require confirmation with diagnostic testing (karyotyping) before making clinical decisions regarding the pregnancy.
Question 7: Which malformation is associated with mutations in the HOX gene?
- A. Polysyndactyly (Correct Answer)
- B. Holoprosencephaly
- C. Mayer Rokitansky syndrome
- D. Gorlin syndrome
Explanation: ***Polysyndactyly*** - The **HOX gene** plays a critical role in limb development and is associated with the malformation of **polysyndactyly**, which is characterized by extra fingers or toes [1]. - This condition is due to the disruption of the normal **patterning** during limb formation, directly involving the action of HOX genes [1]. *Gorlin syndrome* - Gorlin syndrome is primarily caused by mutations in the **PTCH1 gene**, linked to **basal cell carcinoma** and other abnormalities. - It does not involve HOX gene mutations, hence is **not** related to limb malformations. *Holoprosencephaly* - Holoprosencephaly is a developmental condition often linked to **chromosomal anomalies** and abnormal embryonic development, **not specifically** HOX gene mutations. - It refers to the incomplete separation of the forebrain, distinct from the **limb malformations** associated with HOX genes. *Mayer Rokitansky syndrome* - Mayer-Rokitansky syndrome involves **agenesis** or **hypoplasia** of the uterus and upper two-thirds of the vagina, which is due to other genetic factors. - This condition is not related to the functions of the **HOX genes** in limb or skeletal development. **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 8: Congenital Rubella Syndrome includes all except
- A. SN deafness
- B. Cataract
- C. VSD
- D. Intracerebral hemorrhage (Correct Answer)
Explanation: ***Intracerebral hemorrhage*** - This is not a typical manifestation of **Congenital Rubella Syndrome** (CRS). Symptoms of CRS primarily include sensory, cardiac, and ocular defects, not bleeding into the brain. *SN deafness* - **Sensorineural (SN) deafness** is a very common and characteristic symptom of **Congenital Rubella Syndrome**, often bilateral, due to damage to the organ of Corti. - It is one of the classic triad of manifestations of CRS. *Cataract* - **Cataracts** (clouding of the lens) are a prominent ocular defect in CRS, often leading to significant vision impairment or blindness. - Ocular defects like cataracts and **microphthalmia** are part of the classic clinical picture. *VSD* - **Ventricular Septal Defect (VSD)** is a common cardiac anomaly seen in CRS, caused by rubella virus infection during heart development. - Other common cardiac defects include **Patent Ductus Arteriosus (PDA)** and **Pulmonary Artery Stenosis**.
Question 9: During embryological development, failure of the urorectal septum to completely separate the cloaca results in which of the following congenital anomalies?
- A. Imperforate anus
- B. Cloacal exstrophy
- C. Rectovaginal fistula
- D. Persistent cloaca (Correct Answer)
Explanation: During embryological development, failure of the urorectal septum to completely separate the cloaca results in which of the following congenital anomalies? ***Persistent cloaca*** - This condition occurs when the **urorectal septum** fails to fully descend and partition the cloaca into the urogenital sinus anteriorly and the anorectal canal posteriorly [1]. - As a result, the rectum, vagina, and urinary tract all drain into a **single common channel**, leading to various functional and anatomical complications [1]. *Imperforate anus* - This anomaly involves the **absence or abnormal closure of the anal opening**, but it does not typically involve a shared channel with the urinary or reproductive tracts. - It arises from abnormal development of the **hindgut's caudal portion** or failure of the anal membrane to rupture. *Cloacal exstrophy* - This is a more complex and severe malformation characterized by the **exposure of the bladder, bowel, and sometimes genitalia** to the outside of the body. - While it involves cloacal derivatives, it's primarily a defect in the **closure of the ventral body wall** and does not directly result from incomplete septation in the same manner as a persistent cloaca. *Rectovaginal fistula* - This is an **abnormal connection between the rectum and the vagina**. While it involves a communication between two distinct structures, it is a localized defect. - It typically arises from **incomplete separation of the rectum and vagina**, which can be a consequence of less severe septation defects, but it is not the complete persistence of a single common channel like persistent cloaca.
Question 10: Which of the following statements about Sprengel's deformity is false?
- A. Associated with Diastematomyelia
- B. Associated with Dextrocardia (Correct Answer)
- C. High incidence with Klippel Feil syndrome
- D. Associated with Congenital scoliosis
Explanation: ***Associated with Dextrocardia*** - Sprengel's deformity, characterized by an **elevated and undescended scapula**, is not typically associated with **dextrocardia**. Dextrocardia is a congenital heart condition where the heart is pointed towards the right side of the chest. - The congenital abnormalities commonly linked with Sprengel's deformity are primarily musculoskeletal or neurological, not cardiac. *Associated with Diastematomyelia* - Sprengel's deformity can be associated with **diastematomyelia**, a congenital anomaly of the spinal cord where the cord is split longitudinally. - This association highlights the potential for multiple congenital malformations in patients with Sprengel's deformity. *High incidence with Klippel Feil syndrome* - Sprengel's deformity has a **high incidence** of co-occurrence with **Klippel-Feil syndrome**, a condition characterized by congenital fusion of cervical vertebrae. - Both conditions involve developmental abnormalities of the cervical spine and scapula, indicating a common developmental pathway disruption. *Associated with Congenital scoliosis* - **Congenital scoliosis**, a sideways curvature of the spine present at birth, is a known association with Sprengel's deformity. - This connection further emphasizes that Sprengel's deformity often presents as part of a broader spectrum of musculoskeletal and vertebral anomalies.
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