Congenital defects US Medical PG Practice Questions and MCQs
Practice US Medical PG questions for Congenital defects. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Congenital defects US Medical PG Question 1: A 1-year-old girl born to a 40-year-old woman is undergoing an examination by a pediatric resident in the hospital. The pregnancy was uneventful and there were no complications during the delivery. The physical examination reveals midface hypoplasia with a flat nasal bridge and upslanting palpebral fissures. She has a small mouth and chest auscultation reveals a blowing holosystolic murmur that is heard best along the sternal border. The family history is unremarkable. A karyotype analysis is ordered because the resident suspects a numerical chromosomal disorder. Which of the following phenomena leads to the infant’s condition?
- A. Meiotic non-disjunction (Correct Answer)
- B. Uniparental disomy
- C. Genomic imprinting
- D. Partial deletion
- E. Trinucleotide repeat
Congenital defects Explanation: ***Meiotic non-disjunction***
- The combination of **midface hypoplasia**, **upslanting palpebral fissures**, **flat nasal bridge**, and a **holosystolic murmur** (suggesting a **ventricular septal defect**) in an infant born to an older mother is highly characteristic of **Down syndrome (Trisomy 21)**.
- **Trisomy 21** is most commonly caused by **meiotic non-disjunction**, where homologous chromosomes fail to separate during meiosis I or sister chromatids fail to separate during meiosis II, resulting in a gamete with an extra chromosome 21.
*Uniparental disomy*
- **Uniparental disomy** occurs when an individual receives both copies of a chromosome from a single parent, rather than one from each parent.
- While it can lead to various genetic disorders, it does not typically cause **Trisomy 21** or the specific constellation of features described.
*Genomic imprinting*
- **Genomic imprinting** is an epigenetic phenomenon where certain genes are expressed in a parent-of-origin specific manner.
- While relevant to conditions like Prader-Willi or Angelman syndromes, it is not the mechanism responsible for **Trisomy 21**.
*Partial deletion*
- A **partial deletion** refers to the loss of a segment of a chromosome.
- While chromosomal deletions cause various syndromes (e.g., Cri-du-chat syndrome), they would result in a **monosomy or partial monosomy**, not the extra chromosome seen in Trisomy 21.
*Trinucleotide repeat*
- **Trinucleotide repeat disorders** involve an abnormal expansion of a three-nucleotide sequence within a gene, leading to conditions like Huntington's disease or fragile X syndrome.
- This mechanism is not associated with the etiology of **Down syndrome**.
Congenital defects US Medical PG Question 2: A 10-year-old boy comes for a post-operative clinic visit with his ENT surgeon three months after airway reconstruction surgery and placement of a tracheostomy tube. Since the surgery, he says that he has been able to breathe better and is now getting used to tracheostomy care and tracheostomy tube changes. In addition to this surgery, he has had over twenty surgeries to implant hearing aids, reconstruct his cheekbones, and support his jaw to enable him to swallow. He was born with these abnormalities and had difficult breathing, hearing, and eating throughout his childhood. Fortunately, he is now beginning to feel better and is able to attend public school where he is one of the best students in the class. Abnormal development of which of the following structures is most likely responsible for this patient's malformations?
- A. Second branchial cleft
- B. First branchial pouch
- C. Third and fourth branchial pouches
- D. First branchial arch (Correct Answer)
- E. Second branchial arch
Congenital defects Explanation: ***First branchial arch***
- The clinical presentation describes features consistent with **Treacher Collins syndrome** (TCS), also known as mandibulofacial dysostosis, which results from maldevelopment of **both the first and second branchial arches**.
- However, the **predominant and most characteristic features** arise from **first branchial arch** abnormalities: **mandibular hypoplasia** (requiring jaw support for swallowing), **malar/zygomatic hypoplasia** (reconstructed cheekbones), and **maxillary hypoplasia**.
- These first arch skeletal abnormalities cause the **airway obstruction** (requiring tracheostomy) and feeding difficulties.
- The first branchial arch gives rise to: **mandible, maxilla, zygomatic bone, incus, malleus, muscles of mastication, and CN V** (trigeminal nerve).
- While hearing issues may involve second arch structures (stapes), the **overwhelming majority** of this patient's clinical problems stem from first arch malformations.
*Second branchial cleft*
- The second branchial cleft typically forms the **cervical sinus**, which normally obliterates. Persistence can lead to **cervical cysts or fistulas**, presenting as neck masses.
- Abnormalities of the second branchial cleft do not explain the extensive craniofacial malformations, hearing deficits, or airway compromise seen in this patient.
*First branchial pouch*
- The first branchial pouch gives rise to the **auditory (eustachian) tube** and the **tympanic cavity** (middle ear).
- While isolated first pouch defects could contribute to hearing problems, they would **not explain** the severe facial bone malformations (mandibular and malar hypoplasia), airway obstruction, or feeding difficulties.
- The pouch is distinct from the arch, which forms the skeletal and muscular structures.
*Third and fourth branchial pouches*
- The third branchial pouch contributes to the **inferior parathyroid glands** and the **thymus**. The fourth branchial pouch contributes to the **superior parathyroid glands** and the **ultimobranchial body** (parafollicular C cells of the thyroid).
- Abnormalities in these pouches, such as in **DiGeorge syndrome (22q11.2 deletion)**, lead to **T-cell immunodeficiency, hypocalcemia, and cardiac defects** but do not account for the craniofacial and hearing abnormalities described.
*Second branchial arch*
- The second branchial arch gives rise to the **stapes**, **styloid process**, **lesser horn and upper body of hyoid bone**, **stapedius muscle**, and **CN VII** (facial nerve).
- While Treacher Collins syndrome involves both first and second arch abnormalities, the **second arch contributions** are less prominent clinically.
- Second arch defects could contribute to **conductive hearing loss** (via stapes abnormalities) and **facial nerve issues**, but these are not the predominant features in this case.
- The critical skeletal malformations causing airway compromise, feeding difficulties, and facial dysmorphism are primarily **first arch** derivatives.
Congenital defects US Medical PG Question 3: A 25-year-old female comes to her obstetrician’s office for a prenatal visit. She has a transvaginal ultrasound that correlates with her last menstrual period and dates her pregnancy at 4 weeks. She has no complaints except some nausea during the morning that is improving. She comments that she has had some strange food cravings, but has no issues with eating a balanced diet. Her BMI is 23 kg/m^2 and she has gained 1 pound since the start of her pregnancy. She is curious about her pregnancy and asks the physician what her child is now able to do. Which of the following developments is expected of the fetus during this embryological phase?
- A. Formation of male genitalia
- B. Closure of the neural tube (Correct Answer)
- C. Movement of limbs
- D. Creation of the notochord
- E. Cardiac activity visible on ultrasound
Congenital defects Explanation: ***Closure of the neural tube***
- At **4 weeks gestation**, the **neural tube** is in the process of closing, forming the precursor for the brain and spinal cord, making this a critical developmental milestone.
- This period is vital for the prevention of neural tube defects like **spina bifida** and **anencephaly**.
*Formation of male genitalia*
- The differentiation of **external genitalia** (male or female) occurs much later, typically around weeks **9-12 of gestation**, much later than the 4-week mark discussed here.
- Prior to this, the genital ridges are bipotential and do not yet show sex-specific characteristics.
*Movement of limbs*
- While limb buds begin to appear around 4-5 weeks, coordinated **limb movements** are typically observed much later, around **10-12 weeks** of gestation, as muscular and neurological systems further develop.
- Early movements are typically subtle and reflex-like, rather than purposeful.
*Creation of the notochord*
- The **notochord** is formed during **gastrulation**, which occurs predominantly in the **third week of gestation**, prior to the 4-week mark.
- It serves as the primary axial support for the embryo and induces the formation of the neural tube.
*Cardiac activity visible on ultrasound*
- **Cardiac activity** typically becomes detectable on transvaginal ultrasound between **5 and 6 weeks gestation**, shortly after the 4-week mark.
- At 4 weeks, the heart tube may have started to form, but discernible beating is usually not yet evident.
Congenital defects US Medical PG Question 4: A 15-year-old female presents to her family physician for an annual school physical exam and check-up. She is accompanied by her mother to the visit and is present in the exam room. The patient has no complaints, and she does not have any past medical problems. She takes no medications. The patient reports that she remains active, exercising 5 times a week, and eats a healthy and varied diet. Which of the following would be the best way for the physician to obtain a more in-depth social history, including sexual history and use of alcohol, tobacco, or recreational drugs?
- A. Disallow the mother to be present in the examination room throughout the entirety of the visit
- B. Give the patient a social history questionnaire to fill out in the exam room
- C. Ask the mother to step outside into the hall for a portion of the visit (Correct Answer)
- D. Ask the patient the questions directly, with her mother still in the exam room
- E. Speak softly to the patient so that the mother does not hear and the patient is not embarrassed
Congenital defects Explanation: ***Ask the mother to step outside into the hall for a portion of the visit***
- This approach allows the physician to speak with the adolescent **privately and confidentially**, which is crucial for obtaining sensitive information such as sexual history, drug use, and mental health concerns.
- Adolescents are more likely to disclose personal information when their parents are not present, fostering trust and ensuring **comprehensive history-taking** vital for their well-being.
*Disallow the mother to be present in the examination room throughout the entirety of the visit*
- This is an **overly restrictive** approach that might create tension or distrust between the physician, patient, and parent, especially at the start of the visit.
- While privacy is essential for sensitive topics, parental presence can be valuable for discussing general health, family history, and **treatment plans**, especially for younger adolescents.
*Give the patient a social history questionnaire to fill out in the exam room*
- While questionnaires can be useful for gathering basic information, they often **lack the nuance** of a direct conversation and may not prompt the patient to elaborate on sensitive issues.
- Furthermore, having the mother present while the patient fills out a questionnaire on sensitive topics still **compromises confidentiality** and may lead to incomplete or dishonest answers.
*Ask the patient the questions directly, with her mother still in the exam room*
- Asking sensitive questions with a parent present is **unlikely to yield truthful and complete answers**, as adolescents may feel embarrassed, judged, or fear parental disapproval.
- This approach compromises the **confidentiality** that is fundamental to building trust with adolescent patients.
*Speak softly to the patient so that the mother does not hear and the patient is not embarrassed*
- Speaking softly is **unprofessional** and still does not guarantee privacy, as the mother might still overhear parts of the conversation.
- This method also **fails to establish true confidentiality**, which is central to building rapport and encouraging open communication with adolescent patients about sensitive topics.
Congenital defects US Medical PG Question 5: A 15-month-old boy is brought to the pediatrician for immunizations and assessment. His parents report that he is eating well and produces several wet diapers every day. He is occasionally fussy, but overall a happy and curious child. The boy was born at 39 weeks gestation via spontaneous vaginal delivery. On physical examination his vital signs are stable. His weight and height are above the 85th percentile for his age and sex. On chest auscultation, the pediatrician detects a loud harsh holosystolic murmur over the left lower sternal border. The first and second heart sounds are normal. An echocardiogram confirms the diagnosis of the muscular ventricular septal defect without pulmonary hypertension. Which of the following is the best management strategy for this patient?
- A. Surgical closure of the defect using cardiopulmonary bypass
- B. Reassurance of the parents and regular follow-up (Correct Answer)
- C. Oral digoxin and regular follow-up
- D. Antibiotic prophylaxis against infective endocarditis
- E. Transcatheter occlusion closure of the defect
Congenital defects Explanation: **Reassurance of the parents and regular follow-up**
- Most **small muscular VSDs (Ventricular Septal Defects)**, especially in asymptomatic children with normal growth and no signs of heart failure or pulmonary hypertension, **close spontaneously**.
- Given the patient's normal development, stable vital signs, good feeding, and lack of pulmonary hypertension, a conservative approach with **monitoring for spontaneous closure** is appropriate.
*Surgical closure of the defect using cardiopulmonary bypass*
- **Surgical VSD closure** is typically reserved for large defects causing **symptoms, growth failure, pulmonary hypertension**, or those that fail to close spontaneously.
- The patient in the scenario is asymptomatic and thriving, which does not warrant an invasive procedure at this time.
*Oral digoxin and regular follow-up*
- **Digoxin** is a medication used to improve **cardiac contractility** and manage symptoms of **heart failure**, which this patient does not exhibit.
- It would only be considered if there were signs of **congestive heart failure** due to a large VSD, which is not the case here.
*Antibiotic prophylaxis against infective endocarditis*
- Current guidelines from the American Heart Association (AHA) generally **do not recommend routine antibiotic prophylaxis** for VSDs unless there's a history of infective endocarditis or uncorrected cyanotic heart disease.
- The risk of **infective endocarditis** is very low in isolated VSDs and the potential side effects of prophylactic antibiotics outweigh the benefits.
*Transcatheter occlusion closure of the defect*
- **Transcatheter closure** is an option for certain types of VSDs, often **muscular VSDs**, but typically for those that are **larger, symptomatic**, and have not closed spontaneously.
- Similar to surgical closure, this invasive procedure is not indicated for an **asymptomatic, thriving child** with a muscular VSD that is likely to close on its own.
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