A 18-year-old male presents to his primary care provider with his parents for a sports physical. He was last seen in clinic several months ago, when he was diagnosed with attention deficit hyperactivity disorder (ADHD). He was started on methylphenidate at that time, and the patient now reports improvement in his ability to concentrate in school and at home. He hopes to play baseball in college and has begun lifting weights daily in preparation for baseball season. The patient reports that he eats a healthy diet to fuel his exercise regimen. His parents have no concerns and are pleased with the recent improvement in his grades. On physical exam, the patient has tall stature with average muscle mass for his age. He has no dysmorphic features. His chest has a normal appearance other than mild gynecomastia. The patient has sparse facial hair and a moderate amount of coarse pubic hair that extends across the pubis and spares the medial thighs. His testes are small and firm. Due to the latter, laboratory testing is performed and reveals the following:
Follicle-stimulating hormone (FSH): 42 mIU/mL (Reference range: 4-25 mIU/mL)
Luteinizing hormone (LH): 38 mIU/mL (Reference range: 6-23 mIU/mL)
Which of the following is the most likely etiology of this patient’s presentation?
Q62
A 3-year-old girl is brought to her pediatrician with 2 days of fever and abdominal pain. She has also been crying and complaining of pain while urinating. She was born at term without incident and was previously healthy at regular checkups. On presentation, her temperature is 102.2°F (39°C), blood pressure is 137/85 mmHg, pulse is 122/min, and respirations are 24/min. Physical exam reveals a palpable, painless, abdominal mass that does not cross the midline. Which of the following additional findings would be associated with this patient's disorder?
Q63
A 4700-g (10.3-lb) male newborn is delivered at 37 weeks' gestation to a 30-year-old woman, gravida 2, para 1. Apgar scores are 7 and 8 at 1 and 5 minutes, respectively. The newborn appears pale. Temperature is 37°C (98.6°F), pulse is 180/min, and blood pressure is 90/60 mm Hg. Examination in the delivery room shows midfacial hypoplasia, infraorbital creases, and a large tongue. The right side of the body is larger than the left. Abdominal examination shows that the abdominal viscera protrudes through the abdominal wall at the umbilicus; the viscera are covered by the amniotic membrane and the peritoneum. The liver is palpated 2–3 cm below the right costal margin. Fingerstick blood glucose concentration is 60 mg/dL. Ultrasonography of the abdomen shows enlarged kidneys bilaterally. In addition to surgical closure of the abdominal wall, which of the following is the most appropriate next step in management?
Q64
A 6-week-old boy is brought for routine examination at his pediatrician’s office. The patient was born at 39 weeks to a 26-year-old G1P1 mother by normal vaginal delivery. External cephalic version was performed successfully at 37 weeks for breech presentation. Pregnancy was complicated by gestational diabetes that was well-controlled with insulin. The patient’s maternal grandmother has early onset osteoporosis. On physical examination, the left hip dislocates posteriorly with adduction and depression of a flexed femur. An ultrasound is obtained that reveals left acetabular dysplasia and a dislocated left femur. Which of the following is the next best step in management?
Q65
A 3-year-old boy is brought to the physician because of recurrent nosebleeds and fatigue for the past 2 months. He also frequently complains his head hurts. The patient has met all motoric milestones for his age but does not like to run because his legs start to hurt if he does. He is at the 40th percentile for both height and weight. His temperature is 37.0°C (98.6°F), pulse is 125/min, respirations are 32/min, and blood pressure in the right arm is 130/85 mm Hg. A grade 2/6 systolic murmur is heard in the left paravertebral region. Further evaluation of this patient is most likely to show which of the following findings?
Q66
A 5-year-old girl is brought to the emergency department after drinking a bottle of drain cleaner. It is unknown how much the child drank. She has a past medical history of Down syndrome and obesity. The patient's vitals are unremarkable. Physical exam is notable for a child in no acute distress. She is tolerating her oral secretions and interactive. Inspection of the oropharynx is unremarkable. Which of the following is appropriate management of this patient?
Q67
A 2-year-old girl presents to the emergency department with a 3-minute episode of a tonic-clonic seizure. The parents deny any previous history of seizure involving the patient or the family. Physical examination reveals an afebrile, well-groomed, and playful appearance, with normal vital signs. The patient carries a pink birthmark on the right side of her face extending from the forehead to the zygomatic arch. Which of the following findings is most likely on a head CT of this patient?
Q68
A 15-year-old boy is brought to the physician because of recurrent respiratory infections that cause him to miss several weeks of school each year. He also has bulky, foul-smelling stools that are difficult to flush. He has a good appetite and eats a variety of foods. His height and weight are below the 10th percentile. Physical examination shows multiple nasal polyps. There is mild wheezing over the lower lung fields. Further evaluation is most likely to show which of the following?
Q69
A 1-day-old infant in the general care nursery, born at full term by uncomplicated cesarean section delivery, is noted to have a murmur, but otherwise appears well. On examination, respiratory rate is 40/min and pulse oximetry is 96%. Precordium is normoactive. With auscultation, S1 is normal, S2 is single, and a 2/6 systolic ejection murmur is heard at the left upper sternal border. Echocardiography shows infundibular pulmonary stenosis, overriding aorta, ventricular septal defect and concentric right ventricular hypertrophy. Which of the following correlate with the presence or absence of cyanosis in this baby?
Q70
A 1-month-old girl presents to her pediatrician with her mother. The patient was born at 38 weeks gestation via Caesarian section for cervical incompetence. The patient’s mother has no complaints, although she notes that the child had a runny nose and cough for a few days last week. The patient’s mother endorses decreased appetite during the aforementioned illness which has now returned to baseline. The patient’s family history is significant for an older brother with glucose-6-phosphate dehydrogenase (G6PD) deficiency and a maternal uncle with cirrhosis secondary to chronic hepatitis B. On physical exam, the patient has scleral icterus and dark urine staining her diaper. Laboratory testing reveals the following:
Serum:
Na+: 137 mEq/L
Cl-: 102 mEq/L
K+: 4.2 mEq/L
HCO3-: 24 mEq/L
Urea nitrogen: 12 mg/dL
Glucose: 96 mg/dL
Creatinine: 0.36 mg/dL
Alkaline phosphatase: 146 U/L
Aspartate aminotransferase (AST): 86 U/L
Alanine aminotransferase (ALT): 76 U/L
Total bilirubin: 4.6 mg/dL
Direct bilirubin: 3.8 mg/dL
Which of the following is the most likely diagnosis?
Congenital defects US Medical PG Practice Questions and MCQs
Question 61: A 18-year-old male presents to his primary care provider with his parents for a sports physical. He was last seen in clinic several months ago, when he was diagnosed with attention deficit hyperactivity disorder (ADHD). He was started on methylphenidate at that time, and the patient now reports improvement in his ability to concentrate in school and at home. He hopes to play baseball in college and has begun lifting weights daily in preparation for baseball season. The patient reports that he eats a healthy diet to fuel his exercise regimen. His parents have no concerns and are pleased with the recent improvement in his grades. On physical exam, the patient has tall stature with average muscle mass for his age. He has no dysmorphic features. His chest has a normal appearance other than mild gynecomastia. The patient has sparse facial hair and a moderate amount of coarse pubic hair that extends across the pubis and spares the medial thighs. His testes are small and firm. Due to the latter, laboratory testing is performed and reveals the following:
Follicle-stimulating hormone (FSH): 42 mIU/mL (Reference range: 4-25 mIU/mL)
Luteinizing hormone (LH): 38 mIU/mL (Reference range: 6-23 mIU/mL)
Which of the following is the most likely etiology of this patient’s presentation?
A. CGG trinucleotide repeat disorder
B. Meiotic nondisjunction (Correct Answer)
C. CTG trinucleotide repeat disorder
D. Failure of neuronal migration
E. Anabolic steroid use
Explanation: ***Meiotic nondisjunction***
- This patient's presentation with **tall stature**, **gynecomastia**, **sparse facial hair**, and **small, firm testes** is highly characteristic of **Klinefelter syndrome (47, XXY)**.
- **Klinefelter syndrome** typically results from **meiotic nondisjunction**, leading to an extra X chromosome. The elevated **FSH** and **LH** indicate **primary hypogonadism**, common in this condition.
*CGG trinucleotide repeat disorder*
- This refers to **Fragile X syndrome**, characterized by **intellectual disability**, **macroorchidism**, and **distinct facial features**, none of which fully align with this patient's presentation beyond potential ADHD comorbidity.
- Fragile X syndrome is not directly associated with the specific hormonal profile (elevated FSH/LH with small, firm testes) and phenotypic presentation of Klinefelter syndrome.
*CTG trinucleotide repeat disorder*
- This points to **myotonic dystrophy**, which presents with **progressive muscle wasting**, **myotonia**, and other systemic features like cataracts and cardiac conduction defects.
- While hypogonadism can be a feature, the constellation of symptoms (tall stature, gynecomastia, small testes) and the hormonal profile are not typical for myotonic dystrophy.
*Failure of neuronal migration*
- This can lead to various **neurodevelopmental disorders** and **epilepsy**, but it is not directly linked to the specific constellation of primary hypogonadism, tall stature, and gynecomastia observed in this patient.
- There is no direct causal link between neuronal migration defects and the endocrine and phenotypic features described.
*Anabolic steroid use*
- While anabolic steroid use can cause **gynecomastia** and **testicular atrophy** due to suppression of endogenous testosterone, it would typically lead to **low FSH and LH levels** due to negative feedback, not the elevated levels seen in this patient.
- The patient's reported healthy diet and general presentation also do not strongly suggest steroid abuse.
Question 62: A 3-year-old girl is brought to her pediatrician with 2 days of fever and abdominal pain. She has also been crying and complaining of pain while urinating. She was born at term without incident and was previously healthy at regular checkups. On presentation, her temperature is 102.2°F (39°C), blood pressure is 137/85 mmHg, pulse is 122/min, and respirations are 24/min. Physical exam reveals a palpable, painless, abdominal mass that does not cross the midline. Which of the following additional findings would be associated with this patient's disorder?
A. Ash leaf spots
B. Opsoclonus myoclonus
C. Epstein-Barr virus
D. 11;22 chromosome translocation
E. Aniridia (Correct Answer)
Explanation: ***Aniridia***
- The clinical presentation of a **palpable, painless abdominal mass** that does not cross the midline, along with **hypertension** and symptoms suggesting a urinary tract infection (fever, dysuria, abdominal pain) in a 3-year-old girl, is highly indicative of **Wilms tumor (nephroblastoma)**.
- **Aniridia** (absence of the iris) is a congenital anomaly strongly associated with **Wilms tumor**, particularly as part of the **WAGR syndrome** (Wilms tumor, Aniridia, Genitourinary anomalies, and intellectual disability), caused by a deletion on chromosome 11 that includes the *WT1* gene.
*Ash leaf spots*
- **Ash leaf spots** are hypopigmented macules characteristic of **tuberous sclerosis complex**, a genetic disorder associated with hamartomas in various organs, including the brain, kidney, heart, and skin.
- While tuberous sclerosis can be associated with kidney lesions (e.g., angiomyolipomas), it does not typically present with a solitary renal mass like a Wilms tumor, nor are ash leaf spots directly linked to nephroblastoma.
*Opsoclonus myoclonus*
- **Opsoclonus-myoclonus syndrome (OMS)**, also known as **dancing eyes-dancing feet syndrome**, is a rare neurological disorder characterized by rapid, chaotic eye movements (opsoclonus) and involuntary muscle jerks (myoclonus).
- In children, OMS is most commonly a **paraneoplastic syndrome associated with neuroblastoma**, a tumor of the sympathetic nervous system, which typically presents with an abdominal mass that **often crosses the midline** and can present with systemic symptoms like pallor and periorbital ecchymoses, rather than the specific renal origin suggested by the lack of midline crossing.
*Epstein-Barr virus*
- The **Epstein-Barr virus (EBV)** is the causative agent of **infectious mononucleosis** and is implicated in various lymphoproliferative disorders and certain cancers, such as **Burkitt lymphoma** and nasopharyngeal carcinoma.
- While Burkitt lymphoma can present as an abdominal mass, EBV is not directly associated with Wilms tumor.
*11;22 chromosome translocation*
- The **t(11;22)(q24;q12) translocation** is the characteristic cytogenetic abnormality found in **Ewing sarcoma**, a highly aggressive malignant tumor of bone and soft tissue.
- Ewing sarcoma can present as a soft tissue mass, but it is not a renal tumor and does not typically present with the specific clinical features of Wilms tumor such as severe hypertension or aniridia.
Question 63: A 4700-g (10.3-lb) male newborn is delivered at 37 weeks' gestation to a 30-year-old woman, gravida 2, para 1. Apgar scores are 7 and 8 at 1 and 5 minutes, respectively. The newborn appears pale. Temperature is 37°C (98.6°F), pulse is 180/min, and blood pressure is 90/60 mm Hg. Examination in the delivery room shows midfacial hypoplasia, infraorbital creases, and a large tongue. The right side of the body is larger than the left. Abdominal examination shows that the abdominal viscera protrudes through the abdominal wall at the umbilicus; the viscera are covered by the amniotic membrane and the peritoneum. The liver is palpated 2–3 cm below the right costal margin. Fingerstick blood glucose concentration is 60 mg/dL. Ultrasonography of the abdomen shows enlarged kidneys bilaterally. In addition to surgical closure of the abdominal wall, which of the following is the most appropriate next step in management?
A. Serum 17-hydroxyprogesterone measurement
B. Serum TSH measurement
C. Serum IGF-1 measurement
D. Cranial MRI
E. Serial abdominal ultrasonography (Correct Answer)
Explanation: ***Serial abdominal ultrasonography***
- The combination of **macrosomia**, **omphalocele**, **hemihyperplasia**, **visceromegaly** (large kidneys and liver), **macroglossia** (large tongue), and **facial anomalies** is highly suggestive of **Beckwith-Wiedemann Syndrome (BWS)**.
- Children with BWS have an increased risk of developing specific **embryonal tumors**, including **Wilms tumor** and **hepatoblastoma**, making regular abdominal ultrasonography crucial for early detection.
- **Current guidelines recommend abdominal ultrasound every 3 months until age 8** for tumor surveillance.
- Note: The mild hypoglycemia (60 mg/dL) should be monitored, as neonatal hypoglycemia is common in BWS, but tumor surveillance is the critical long-term management priority.
*Serum 17-hydroxyprogesterone measurement*
- This test is used to screen for **congenital adrenal hyperplasia (CAH)**.
- The clinical presentation does not suggest CAH, as there are no signs of **ambiguous genitalia** or **salt-wasting crisis**.
*Serum TSH measurement*
- **Thyroid-stimulating hormone (TSH)** is measured to screen for **congenital hypothyroidism**.
- While lethargy and feeding difficulties can occur in hypothyroidism, the described constellation of anomalies, especially macrosomia and omphalocele, is not characteristic of this condition.
*Serum IGF-1 measurement*
- **Insulin-like growth factor 1 (IGF-1)** levels are primarily evaluated in cases of suspected **growth hormone deficiency** or **excess (gigantism/acromegaly)**.
- While BWS involves overgrowth, the initial diagnostic and screening approach for associated tumor risk does not involve IGF-1 measurement.
*Cranial MRI*
- **Cranial MRI** is indicated for neurological symptoms or suspected brain anomalies.
- The patient's presentation does not include any neurological deficits or signs suggesting intracranial pathology as the primary concern.
Question 64: A 6-week-old boy is brought for routine examination at his pediatrician’s office. The patient was born at 39 weeks to a 26-year-old G1P1 mother by normal vaginal delivery. External cephalic version was performed successfully at 37 weeks for breech presentation. Pregnancy was complicated by gestational diabetes that was well-controlled with insulin. The patient’s maternal grandmother has early onset osteoporosis. On physical examination, the left hip dislocates posteriorly with adduction and depression of a flexed femur. An ultrasound is obtained that reveals left acetabular dysplasia and a dislocated left femur. Which of the following is the next best step in management?
A. Pavlik harness (Correct Answer)
B. Closed reduction and spica casting
C. Observation
D. Physiotherapy
E. Open reduction and femoral osteotomy
Explanation: ***Pavlik harness***
- A Pavlik harness is the **gold standard treatment** for **developmental dysplasia of the hip (DDH)** in infants younger than 6 months. It maintains the hips in a **flexed and abducted position**, promoting proper acetabular development and hip reduction.
- The patient's age (6 weeks), clear diagnosis of **acetabular dysplasia**, and a dislocated hip on ultrasound make the Pavlik harness the **most appropriate and least invasive initial treatment**.
*Closed reduction and spica casting*
- This treatment is typically reserved for children older than 6 months or those who **fail Pavlik harness treatment**.
- It involves a more aggressive reduction technique, often requiring **anesthesia**, and is followed by prolonged immobilization in a **spica cast**.
*Observation*
- **Observation is not appropriate** for a 6-week-old infant with a **diagnosed dislocated hip** and **acetabular dysplasia**.
- Untreated DDH can lead to **permanent hip instability**, pain, and early arthritis.
*Physiotherapy*
- While physiotherapy may play a role in rehabilitation after other interventions, it is **not sufficient as a primary treatment** for a dislocated hip in an infant.
- It cannot achieve or maintain the necessary **reduction and stabilization** required for proper hip development.
*Open reduction and femoral osteotomy*
- This is an **invasive surgical procedure** typically reserved for older children (older than 18-24 months) or in cases of **failed non-operative management** and closed reduction, especially in irreducible or severely dysplastic hips.
- It involves directly opening the joint to reduce the hip and may include reshaping bone (osteotomy) to improve hip stability. This is **premature** for a 6-week-old.
Question 65: A 3-year-old boy is brought to the physician because of recurrent nosebleeds and fatigue for the past 2 months. He also frequently complains his head hurts. The patient has met all motoric milestones for his age but does not like to run because his legs start to hurt if he does. He is at the 40th percentile for both height and weight. His temperature is 37.0°C (98.6°F), pulse is 125/min, respirations are 32/min, and blood pressure in the right arm is 130/85 mm Hg. A grade 2/6 systolic murmur is heard in the left paravertebral region. Further evaluation of this patient is most likely to show which of the following findings?
A. Inferior rib notching
B. Delayed pulse in lower extremities (Correct Answer)
C. Interarm difference in tissue oxygenation
D. Pulmonary valve stenosis
E. Left-axis deviation on ECG
Explanation: ***Delayed pulse in lower extremities***
- The patient's symptoms, including **recurrent nosebleeds**, **headaches**, **leg pain with activity**, **hypertension** (especially in the right arm), and a **systolic murmur in the left paravertebral region**, are highly suggestive of **coarctation of the aorta**.
- A key physical finding in coarctation of the aorta is a **delayed and diminished femoral pulse** compared to the radial pulse due to obstruction of blood flow to the lower body.
*Inferior rib notching*
- This finding is characteristic of **collateral circulation** developing around a coarctation in older children and adults, as the **intercostal arteries** become enlarged to supply blood to the lower body.
- While associated with coarctation, it is typically seen on **chest X-rays** in older patients and is less likely to be present or pronounced in a 3-year-old.
*Interarm difference in tissue oxygenation*
- While coarctation can cause an **interarm blood pressure difference**, it typically does not directly cause a significant interarm difference in **tissue oxygenation** unless severe unilateral subclavian artery involvement is present, which is not the primary mechanism.
- The primary oxygenation concern in coarctation is usually related to overall cardiac output or systemic effects rather than a localized interarm difference.
*Pulmonary valve stenosis*
- **Pulmonary valve stenosis** would typically present with a **systolic ejection murmur** heard best at the left upper sternal border, often radiating to the back.
- It does not explain the specific constellation of symptoms such as **hypertension in the upper extremities**, **leg pain with activity**, or differential pulses characteristic of coarctation of the aorta.
*Left-axis deviation on ECG*
- **Left-axis deviation** on an ECG is often associated with conditions causing **left ventricular hypertrophy** or conduction defects.
- While severe coarctation can lead to left ventricular hypertrophy, left-axis deviation is not a specific or direct diagnostic finding for coarctation and is less characteristic than the described physical exam findings.
Question 66: A 5-year-old girl is brought to the emergency department after drinking a bottle of drain cleaner. It is unknown how much the child drank. She has a past medical history of Down syndrome and obesity. The patient's vitals are unremarkable. Physical exam is notable for a child in no acute distress. She is tolerating her oral secretions and interactive. Inspection of the oropharynx is unremarkable. Which of the following is appropriate management of this patient?
A. Dilute hydrochloric acid
B. Polyethylene glycol
C. Observation
D. Intubation
E. Endoscopy (Correct Answer)
Explanation: ***Endoscopy***
- Due to the **inherent danger of caustic ingestion**, regardless of initial symptoms, **esophagogastroduodenoscopy (EGD)** is the gold standard for assessing the extent and severity of injury to the upper gastrointestinal tract. This procedure is crucial within the first 12-24 hours to guide further management.
- While the patient is asymptomatic, **caustic injuries** can progress and develop into strictures or perforations even without immediate obvious symptoms, making direct visualization essential.
*Dilute hydrochloric acid*
- **Neutralizing alkalis with acids** (or vice-versa) is contraindicated as it can cause an **exothermic reaction**, leading to further thermal injury and worsening the damage.
- Chemical neutralization can also produce gas, which increases the **risk of esophageal perforation**.
*Polyethylene glycol*
- **Polyethylene glycol (PEG)** is an osmotic laxative used for **bowel preparation** or as a treatment for constipation but has no role in the management of caustic ingestion.
- It would not remove the caustic substance from the esophagus or stomach, nor would it mitigate the chemical damage.
*Observation*
- Despite being asymptomatic initially, **caustic ingestions** can lead to delayed and severe complications such as **stricture formation**, perforation, and mediastinitis.
- **Asymptomatic presentation** does not rule out significant internal injury, particularly because the full extent of the ingestion is unknown, making observation alone an unsafe approach.
*Intubation*
- While airway compromise is a potential complication of caustic ingestion, the patient is currently in no acute distress and is tolerating oral secretions, indicating a **patent airway**.
- **Prophylactic intubation** is not indicated at this stage unless there are signs of respiratory distress, stridor, or significant oropharyngeal edema.
Question 67: A 2-year-old girl presents to the emergency department with a 3-minute episode of a tonic-clonic seizure. The parents deny any previous history of seizure involving the patient or the family. Physical examination reveals an afebrile, well-groomed, and playful appearance, with normal vital signs. The patient carries a pink birthmark on the right side of her face extending from the forehead to the zygomatic arch. Which of the following findings is most likely on a head CT of this patient?
A. A non-enhancing hemispheric lesion
B. Subependymal giant cell astrocytoma
C. Intraparenchymal hemorrhage
D. Prominent intraparenchymal white matter calcification (Correct Answer)
E. Subependymal nodule
Explanation: ***Prominent intraparenchymal white matter calcification***
- The presentation of a **facial birthmark (port-wine stain)**, seizures, and the patient's age (2 years old) are highly characteristic of **Sturge-Weber syndrome**.
- **Intraparenchymal calcifications**, particularly in the gyri ("tram-track" calcifications), are a hallmark of Sturge-Weber syndrome seen on **CT scans**, reflecting underlying vascular malformations.
*A non-enhancing hemispheric lesion*
- This finding is too general and does not specifically point to Sturge-Weber syndrome.
- While Sturge-Weber involves brain abnormalities, the characteristic imaging finding is **calcification**, not just a non-enhancing lesion.
*Subependymal giant cell astrocytoma*
- This is a common finding in **Tuberous Sclerosis Complex**, another neurocutaneous disorder.
- Tuberous sclerosis typically presents with **ash-leaf spots**, facial angiofibromas, and other organ involvement, which are not described here.
*Intraparenchymal hemorrhage*
- While seizures can sometimes be caused by hemorrhage, the presence of a **port-wine stain** and the chronicity implied by a "birthmark" makes hemorrhage less likely to be the primary cause of the underlying syndrome.
- Hemorrhage would usually present with more acute and severe neurological deficits.
*Subependymal nodule*
- Similar to subependymal giant cell astrocytoma, **subependymal nodules** are characteristic of **Tuberous Sclerosis Complex**.
- The clinical presentation with a facial port-wine stain points away from tuberous sclerosis and towards Sturge-Weber syndrome.
Question 68: A 15-year-old boy is brought to the physician because of recurrent respiratory infections that cause him to miss several weeks of school each year. He also has bulky, foul-smelling stools that are difficult to flush. He has a good appetite and eats a variety of foods. His height and weight are below the 10th percentile. Physical examination shows multiple nasal polyps. There is mild wheezing over the lower lung fields. Further evaluation is most likely to show which of the following?
A. Absence of the vas deferens (Correct Answer)
B. Apical impulse to the right of the sternum
C. Positive methacholine challenge test
D. Deficiency of immunoglobulin A
E. Antibodies to endomysium
Explanation: ***Absence of the vas deferens***
- The patient's symptoms (recurrent respiratory infections, bulky foul-smelling stools, failure to thrive, and nasal polyps) are highly suggestive of **cystic fibrosis**.
- Congenital bilateral absence of the **vas deferens** is a common **reproductive complication** in males with cystic fibrosis due to the abnormal development of the Wolffian ducts.
*Apical impulse to the right of the sternum*
- This finding suggests **dextrocardia**, which is a feature of **primary ciliary dyskinesia** (Kartagener's syndrome), not typically seen in cystic fibrosis.
- Although both conditions involve recurrent respiratory infections, **PCD** is characterized by immotile cilia and **situs inversus**, which is distinct from the pancreatic insufficiency and malabsorption seen in cystic fibrosis.
*Positive methacholine challenge test*
- A positive methacholine challenge test indicates **bronchial hyperresponsiveness**, which is characteristic of **asthma**.
- While some patients with cystic fibrosis may have reactive airway disease, asthma alone would not explain the **gastrointestinal symptoms** (bulky stools, failure to thrive) or **nasal polyps**.
*Deficiency of immunoglobulin A*
- **IgA deficiency** is the most common primary immunodeficiency and can lead to recurrent respiratory and gastrointestinal infections.
- However, IgA deficiency does not typically cause **malabsorption** with bulky, foul-smelling stools or **nasal polyps**, which are key features of cystic fibrosis.
*Antibodies to endomysium*
- Antibodies to endomysium are serological markers for **celiac disease**, an autoimmune disorder triggered by gluten consumption.
- While celiac disease causes malabsorption and failure to thrive, it does not typically lead to **recurrent respiratory infections** or **nasal polyps**.
Question 69: A 1-day-old infant in the general care nursery, born at full term by uncomplicated cesarean section delivery, is noted to have a murmur, but otherwise appears well. On examination, respiratory rate is 40/min and pulse oximetry is 96%. Precordium is normoactive. With auscultation, S1 is normal, S2 is single, and a 2/6 systolic ejection murmur is heard at the left upper sternal border. Echocardiography shows infundibular pulmonary stenosis, overriding aorta, ventricular septal defect and concentric right ventricular hypertrophy. Which of the following correlate with the presence or absence of cyanosis in this baby?
A. The degree of right ventricular outflow tract obstruction (Correct Answer)
B. The ratio of reduced hemoglobin to oxyhemoglobin
C. The concentration of hemoglobin
D. The size of ventricular septal defect
E. The concentration of pulmonary surfactant
Explanation: ***The degree of right ventricular outflow tract obstruction***
- The severity of **pulmonary stenosis** in **tetralogy of Fallot** dictates the amount of blood shunted from the right ventricle to the aorta via the **ventricular septal defect (VSD)**.
- A **less severe obstruction** allows more blood to flow to the lungs, leading to less right-to-left shunting and consequently **less cyanosis**.
*The ratio of reduced hemoglobin to oxyhemoglobin*
- While this ratio directly reflects the presence of cyanosis, it does not explain its *cause* in the context of the given congenital heart defect.
- The question asks what *correlates* with the presence or absence of cyanosis, implying a causal or pathophysiological link rather than a descriptive measure.
*The concentration of hemoglobin*
- **Hemoglobin concentration** affects the *visibility* of cyanosis (e.g., polycythemia can make mild desaturation appear more cyanotic), but it doesn't primarily determine the *presence* or *absence* of shunt-related cyanosis itself.
- A patient can be significantly desaturated with a normal hemoglobin concentration, and the degree of desaturation is largely driven by the shunt.
*The size of ventricular septal defect*
- In tetralogy of Fallot, the **VSD is typically large and non-restrictive**, meaning its size itself doesn't limit blood flow between the ventricles.
- The **pulmonary stenosis** is the primary determinant of the shunt direction and magnitude, not the size of the VSD.
*The concentration of pulmonary surfactant*
- **Pulmonary surfactant** is crucial for maintaining alveolar stability and preventing atelectasis, thereby ensuring efficient gas exchange in the lungs.
- While important for overall respiratory function, it does not directly correlate with the degree of shunting and cyanosis in **tetralogy of Fallot**.
Question 70: A 1-month-old girl presents to her pediatrician with her mother. The patient was born at 38 weeks gestation via Caesarian section for cervical incompetence. The patient’s mother has no complaints, although she notes that the child had a runny nose and cough for a few days last week. The patient’s mother endorses decreased appetite during the aforementioned illness which has now returned to baseline. The patient’s family history is significant for an older brother with glucose-6-phosphate dehydrogenase (G6PD) deficiency and a maternal uncle with cirrhosis secondary to chronic hepatitis B. On physical exam, the patient has scleral icterus and dark urine staining her diaper. Laboratory testing reveals the following:
Serum:
Na+: 137 mEq/L
Cl-: 102 mEq/L
K+: 4.2 mEq/L
HCO3-: 24 mEq/L
Urea nitrogen: 12 mg/dL
Glucose: 96 mg/dL
Creatinine: 0.36 mg/dL
Alkaline phosphatase: 146 U/L
Aspartate aminotransferase (AST): 86 U/L
Alanine aminotransferase (ALT): 76 U/L
Total bilirubin: 4.6 mg/dL
Direct bilirubin: 3.8 mg/dL
Which of the following is the most likely diagnosis?
A. Increased production of bilirubin
B. Increased enterohepatic circulation of bilirubin
C. Decreased metabolism of bilirubin
D. Obstruction of the extrahepatic biliary tree (Correct Answer)
E. Obstruction of the intrahepatic biliary tree
Explanation: ***Obstruction of the extrahepatic biliary tree***
- The elevated **direct bilirubin** (3.8 mg/dL out of 4.6 mg/dL total) in a 1-month-old, along with **scleral icterus** and **dark urine**, is highly suggestive of **biliary atresia**, which is an extrahepatic biliary obstruction.
- While other forms of cholestasis can occur, this presentation with significant direct hyperbilirubinemia in a young infant points strongly towards a structural issue in the extrahepatic bile ducts.
*Increased production of bilirubin*
- This would primarily cause an elevation in **unconjugated (indirect) bilirubin**, as the liver would conjugate it efficiently.
- The patient's lab results show a predominant elevation in **direct (conjugated) bilirubin**, making overproduction less likely as the primary cause.
*Increased enterohepatic circulation of bilirubin*
- This typically occurs in **physiologic jaundice** of the newborn, characterized by increased **unconjugated bilirubin** returning to the liver, often exacerbated by poor feeding.
- The predominance of **direct bilirubin** in this case rules out increased enterohepatic circulation as the main etiology.
*Decreased metabolism of bilirubin*
- Conditions causing decreased bilirubin metabolism, such as **Crigler-Najjar syndrome** or **Gilbert's syndrome**, primarily affect the **conjugation process**, leading to elevated **unconjugated bilirubin**.
- This patient presents with predominantly **conjugated hyperbilirubinemia**, indicating that conjugation is occurring but excretion is impaired.
*Obstruction of the intrahepatic biliary tree*
- While intrahepatic cholestasis can cause conjugated hyperbilirubinemia, conditions like **Alagille syndrome** or progressive familial intrahepatic cholestasis typically lack the complete obstruction seen in biliary atresia.
- Biliary atresia is a more common and severe cause of **extrahepatic obstruction** presenting similarly to this case, often requiring surgical intervention.