Newborn screening programs US Medical PG Practice Questions and MCQs
Practice US Medical PG questions for Newborn screening programs. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Newborn screening programs US Medical PG Question 1: A 5-month-old boy is brought to the pediatrician by his parents, who began noticing that the infant was not able to hold his head upright when sitting or in a prone position. Upon examination, the infant has a musty odor, fair skin with patches of eczema, and blue eyes. The pediatrician orders laboratory tests and prescribes a special diet. Which of the following amino acids becomes essential and must be supplemented in this patient's condition?
- A. Thiamine
- B. Large neutral amino acids
- C. Arginine
- D. Phenylalanine-free amino acid formula
- E. Tyrosine (Correct Answer)
Newborn screening programs Explanation: ***Tyrosine***
- This patient presents with **phenylketonuria (PKU)**, characterized by the classic triad of developmental delay, musty odor (from phenylketones in urine), and hypopigmentation (fair skin, blue eyes, eczema).
- PKU is caused by **phenylalanine hydroxylase deficiency**, which prevents the conversion of phenylalanine to tyrosine.
- Because tyrosine cannot be synthesized from phenylalanine, **tyrosine becomes a conditionally essential amino acid** in PKU patients and must be supplemented in the diet.
- Treatment consists of a phenylalanine-restricted diet with **tyrosine supplementation** to ensure adequate protein synthesis and melanin production.
*Arginine*
- Arginine becomes conditionally essential in **urea cycle disorders**, where it helps drive nitrogen excretion.
- However, this patient's presentation (musty odor, hypopigmentation, eczema) is classic for PKU, not a urea cycle disorder.
- Urea cycle disorders typically present with hyperammonemia, vomiting, lethargy, and encephalopathy—not the findings described here.
*Phenylalanine-free amino acid formula*
- This is a **dietary intervention**, not an amino acid that becomes essential.
- While phenylalanine-free formulas are crucial in PKU management, the question specifically asks which amino acid becomes essential and must be supplemented.
- Phenylalanine itself is *restricted*, not supplemented.
*Thiamine*
- Thiamine (vitamin B1) is a **vitamin**, not an amino acid.
- It is a cofactor for enzymes in carbohydrate metabolism and is deficient in beriberi and Wernicke-Korsakoff syndrome.
- It is not relevant to PKU management.
*Large neutral amino acids*
- Large neutral amino acids (LNAAs) can be used as an **adjunctive therapy** in PKU to compete with phenylalanine for transport across the blood-brain barrier.
- However, they are not the amino acid that becomes conditionally essential due to the metabolic block.
- The primary nutritional requirement is **tyrosine supplementation** to replace what cannot be synthesized.
Newborn screening programs US Medical PG Question 2: A 6-month-old male presents to the emergency department with his parents after his three-year-old brother hit him on the arm with a toy truck. His parents are concerned that the minor trauma caused an unusual amount of bruising. The patient has otherwise been developing well and meeting all his milestones. His parents report that he sleeps throughout the night and has just started to experiment with solid food. The patient’s older brother is in good health, but the patient’s mother reports that some members of her family have an unknown blood disorder. On physical exam, the patient is agitated and difficult to soothe. He has 2-3 inches of ecchymoses and swelling on the lateral aspect of the left forearm. The patient has a neurological exam within normal limits and pale skin with blue irises. An ophthalmologic evaluation is deferred.
Which of the following is the best initial step?
- A. Genetic testing
- B. Complete blood count and coagulation panel (Correct Answer)
- C. Ensure the child's safety and alert the police
- D. Peripheral blood smear
- E. Hemoglobin electrophoresis
Newborn screening programs Explanation: ***Complete blood count and coagulation panel***
- The unusual amount of **bruising** after minor trauma, along with a family history of an unknown blood disorder, strongly suggests a potential **bleeding disorder**. A **CBC** and a **coagulation panel** (PT, aPTT, fibrinogen) are essential initial steps to evaluate for abnormalities in platelets, clotting factors, or other hematologic conditions.
- These tests can help narrow down the differential diagnosis between **platelet dysfunction**, **coagulopathies** (like hemophilia or von Willebrand disease), or other less common bleeding disorders, guiding further specific investigations.
- **Important consideration:** The presence of **blue sclera** (described as "blue irises") raises concern for **osteogenesis imperfecta (OI)**, a connective tissue disorder causing bone fragility. However, initial hematologic screening is still appropriate given the family history of blood disorder and presentation of excessive bruising. If coagulation studies are normal, imaging and further workup for OI would be indicated.
*Genetic testing*
- While a genetic component is plausible given the patient's family history and clinical presentation (blue sclera may suggest osteogenesis imperfecta), **genetic testing** is typically performed *after* initial laboratory workup has identified a specific type of bleeding or inherited disorder.
- Starting with genetic testing without basic hematologic parameters is not the most efficient or cost-effective initial diagnostic approach.
*Ensure the child's safety and alert the police*
- While child abuse should always be considered in cases of unexplained or excessive bruising, the presence of a **family history of a blood disorder** and the **blue sclera** (suggesting possible osteogenesis imperfecta) make **medical causes** more immediate concerns for initial investigation.
- Pursuing a medical workup first often clarifies whether abuse is the primary explanation, although child protective services should be notified if suspicion remains high after medical evaluation.
*Peripheral blood smear*
- A **peripheral blood smear** provides information on red blood cell morphology, platelet size and number, and white blood cell differential. While useful in assessing for some hematologic conditions, it is often performed *after* a CBC has indicated abnormalities or in conjunction with specialized testing.
- It would not be the *best initial step* as it doesn't directly assess clotting factor function, which is critical in evaluating significant bruising severity.
*Hemoglobin electrophoresis*
- **Hemoglobin electrophoresis** is used to diagnose **hemoglobinopathies** like sickle cell anemia or thalassemia.
- The patient's symptoms (easy bruising) are not characteristic of hemoglobinopathies, and while he has pale skin, this test would not be the initial step to investigate a bleeding disorder.
Newborn screening programs US Medical PG Question 3: A 35-year-old woman gravida 2, para 1, comes to the physician for her first prenatal visit. Pregnancy and delivery of her first child were uncomplicated. She is not sure about the date of her last menstrual period. Pelvic examination shows a uterus consistent in size with a 10-week gestation. An ultrasound examination confirms the gestational age and shows one fetus with no indication of multiple gestations. During counseling on pregnancy risks and possible screening and diagnostic tests, the patient states she would like to undergo screening for Down syndrome. She would prefer immediate and secure screening with a low risk to herself and the fetus. Which of the following is the most appropriate next step in management at this time?
- A. Nuchal translucency, pregnancy-associated plasma protein-A, human chorionic gonadotropin
- B. Maternal serum α-fetoprotein, human chorionic gonadotropin, unconjugated estriol, and inhibin A
- C. Chorionic villus sampling
- D. Amniocentesis
- E. Cell-free fetal DNA testing (Correct Answer)
Newborn screening programs Explanation: ***Cell-free fetal DNA testing***
- This is the most appropriate choice given the patient's desire for **immediate and secure screening with low risk** because it is a **non-invasive prenatal screening (NIPS)** method offering high sensitivity and specificity for Down syndrome, particularly in higher-risk pregnancies.
- It involves a simple maternal blood draw and can be performed as early as **10 weeks of gestation**, perfectly aligning with the patient's current gestational age and desire for early screening.
*Nuchal translucency, pregnancy-associated plasma protein-A, human chorionic gonadotropin*
- This combination represents the **first-trimester combined screen**, which is typically performed between 11 and 14 weeks of gestation. While suitable for early screening, **cell-free DNA testing offers higher detection rates and lower false-positive rates** for Down syndrome.
- The patient specifically asked for the most **secure and least risky** screening, and NIPS outperforms the combined screen in terms of diagnostic accuracy for aneuploidies.
*Maternal serum α-fetoprotein, human chorionic gonadotropin, unconjugated estriol, and inhibin A*
- This refers to the **quad screen**, which is typically performed in the **second trimester (15-20 weeks)**, making it too late for the patient's desire for immediate screening at 10 weeks gestational age.
- While a widely used screening tool, the quad screen has a **lower detection rate** for Down syndrome compared to cell-free DNA testing.
*Chorionic villus sampling*
- **Chorionic villus sampling (CVS)** is a **diagnostic, invasive procedure** that carries a small risk of miscarriage (approximately 1 in 455 or 0.22%) and is not a screening test.
- Although it can be performed earlier (typically between 10 and 13 weeks), the patient specifically requested a **low-risk screening** option, which CVS is not.
*Amniocentesis*
- **Amniocentesis** is also an **invasive diagnostic procedure** with a risk of miscarriage (approximately 1 in 900 or 0.11%) and is typically performed in the **second trimester (15-20 weeks)**.
- This option is unsuitable because the patient is at 10 weeks gestation and desires **immediate and low-risk screening**, not a diagnostic procedure with procedural risks a few weeks later.
Newborn screening programs US Medical PG Question 4: During the selection of subjects for a study on infantile vitamin deficiencies, a child is examined by the lead investigator. She is at the 75th percentile for head circumference and the 80th percentile for length and weight. She can lift her chest and shoulders up when in a prone position, but cannot roll over from a prone position. Her eyes follow objects past the midline. She coos and makes gurgling sounds. When the investigator strokes the sole of her foot, her big toe curls upward and there is fanning of her other toes. She makes a stepping motion when she is held upright and her feet are in contact with the examination table. Which of the following additional skills or behaviors would be expected in a healthy patient of this developmental age?
- A. Cries when separated from her mother
- B. Smiles at her mother (Correct Answer)
- C. Rolls over from her back
- D. Responds to calling of own name
- E. Reaches out for objects
Newborn screening programs Explanation: ***Smiles at her mother***
- The child exhibits developmental milestones consistent with a **2-month-old infant**, such as lifting her chest in a prone position, following objects past the midline, cooing, and gurgling. Social smiling typically emerges around **2 months of age**.
- Primitive reflexes like the **Babinski reflex** (big toe curling upward and fanning of other toes) and **stepping reflex** are normally present at this age, supporting the approximate age of 2 months.
*Cries when separated from her mother*
- This behavior suggests **separation anxiety**, which typically develops much later, usually around **8-9 months of age**.
- A 2-month-old infant does not yet have the cognitive understanding or object permanence needed to exhibit true separation anxiety.
*Rolls over from her back*
- Rolling over from the back to the stomach is usually achieved between **4 and 6 months of age**.
- The child in the vignette cannot even roll over from a prone position, indicating she is not yet at the age for rolling from her back.
*Responds to calling of own name*
- Responding to one's own name is a more advanced auditory and cognitive milestone, generally developing between **6 and 9 months of age**.
- At 2 months, infants respond to voices and sounds but do not associate specific words with themselves.
*Reaches out for objects*
- Purposeful reaching and grasping for objects (palmar grasp) typically develops around **4 to 6 months of age**.
- A 2-month-old infant may swat at objects reflexively but does not exhibit coordinated, intentional reaching.
Newborn screening programs US Medical PG Question 5: A 27-year-old G1P0 female presents for her first prenatal visit. She is in a monogamous relationship with her husband, and has had two lifetime sexual partners. She has never had a blood transfusion and has never used injection drugs. Screening for which of the following infections is most appropriate to recommend this patient?
- A. Syphilis and HIV
- B. Syphilis, HIV, and HBV (Correct Answer)
- C. Syphilis, HIV, HBV, and chlamydia
- D. Syphilis, HIV, and chlamydia
- E. No routine screening is recommended for this patient
Newborn screening programs Explanation: ***Syphilis, HIV, and HBV***
- The **American College of Obstetricians and Gynecologists (ACOG)** and the **Centers for Disease Control and Prevention (CDC)** recommend universal screening for syphilis, HIV, and hepatitis B virus (HBV) in all pregnant women at the first prenatal visit.
- This **routine screening** is crucial due to the potential for vertical transmission and severe adverse outcomes for the neonate if untreated.
*Syphilis and HIV*
- While screening for syphilis and HIV is essential, it is **incomplete** as it omits HBV, which is also universally recommended for antenatal screening.
- This option does not align with the standard comprehensive screening guidelines for pregnancy.
*Syphilis, HIV, HBV, and chlamydia*
- Although syphilis, HIV, and HBV screening are appropriate, adding **chlamydia** to the universal prenatal screening for *all* pregnant women in the first trimester is not standard practice unless specific risk factors are present or local prevalence is high.
- Chlamydia screening is typically recommended for pregnant women who are **25 years or younger** or those with **risk factors** for sexually transmitted infections (STIs).
*Syphilis, HIV, and chlamydia*
- This option incorrectly includes chlamydia as a universal screen for all pregnant women while **omitting HBV**, which is universally recommended.
- Missing HBV screening leaves a critical gap in prenatal care, as it can be transmitted vertically and cause severe neonatal disease.
*No routine screening is recommended for this patient*
- This statement is incorrect as **universal screening** for syphilis, HIV, and HBV is recommended for all pregnant women, regardless of reported risk factors or monogamous relationships.
- Maternal infection can still occur, and screening helps prevent severe outcomes for both mother and child through timely detection and intervention.
Newborn screening programs US Medical PG Question 6: A 36-year-old primigravida presents to her obstetrician for antenatal care. She is at 24 weeks of gestation and does not have any current complaint except for occasional leg cramps. She does not smoke or drink alcohol. Family history is irrelevant. Her temperature is 36.9°C (98.42°F), blood pressure is 100/60 mm Hg, and pulse of 95/minute. Her body mass index is 21 kg/m² (46 pounds/m²). Physical examination reveals a palpable uterus above the umbilicus with no other abnormalities. Which of the following screening tests is suitable for this patient?
- A. Fasting and random glucose testing for gestational diabetes mellitus
- B. HbA1C for gestational diabetes mellitus
- C. Oral glucose tolerance test for gestational diabetes mellitus (Correct Answer)
- D. Complete blood count for iron deficiency anemia
- E. Wet mount microscopy of vaginal secretions for bacterial vaginosis
Newborn screening programs Explanation: ***Oral glucose tolerance test for gestational diabetes mellitus***
- The **oral glucose tolerance test (OGTT)**, typically performed between **24 and 28 weeks of gestation**, is the gold standard for screening and diagnosing **gestational diabetes mellitus (GDM)**. This patient is at 24 weeks, making it the appropriate time for this screening.
- GDM, if undiagnosed and untreated, can lead to significant maternal and fetal complications, including **macrosomia**, **preeclampsia**, **neonatal hypoglycemia**, and **shoulder dystocia**.
*Fasting and random glucose testing for gestational diabetes mellitus*
- While **fasting** or **random glucose** values can indicate hyperglycemia, they are **not sensitive or specific enough** on their own to reliably screen for or diagnose GDM.
- A single elevated reading might prompt further testing, but it's not the primary or most suitable screening method.
*HbA1C for gestational diabetes mellitus*
- **HbA1c** reflects **average blood glucose levels over the past 2-3 months** and is primarily used for diagnosing and monitoring **pre-existing diabetes** or assessing glycemic control in non-pregnant individuals.
- Due to the **physiological changes in red blood cell turnover during pregnancy** and the acute onset nature of GDM, HbA1c is **not recommended** as a first-line screening tool for GDM.
*Complete blood count for iron deficiency anemia*
- While **complete blood count (CBC)** is a routine prenatal screening test to check for **anemia**, it is typically done earlier in pregnancy and again in the third trimester. There are no specific symptoms in this patient that strongly suggest immediate concern for anemia beyond routine.
- The question specifically asks for the "most suitable" screening test at this gestational age, and the **GDM screening** takes precedence given the timing.
*Wet mount microscopy of vaginal secretions for bacterial vaginosis*
- There are **no symptoms of vaginal infection** (e.g., unusual discharge, itching, odor) mentioned in the patient's presentation that would warrant immediate screening for **bacterial vaginosis (BV)** at this visit.
- While BV can be associated with adverse pregnancy outcomes, routine asymptomatic screening by wet mount is **not universally recommended** at 24 weeks gestation without other indications.
Newborn screening programs US Medical PG Question 7: A 3-year-old boy is brought to his pediatrician by his parents for a follow-up visit. Several concerning traits were observed at his last physical, 6 months ago. He had developmental delay, a delay in meeting gross and fine motor control benchmarks, and repetitive behaviors. At birth, he was noted to have flat feet, poor muscle tone, an elongated face with large, prominent ears, and enlarged testicles. He takes a chewable multivitamin every morning. There is one other member of the family, on the mother’s side, with a similar condition. Today, his blood pressure is 110/65 mm Hg, heart rate is 90/min, respiratory rate is 22/min, and temperature of 37.0°C (98.6°F). On physical exam, the boy repetitively rocks back and forth and has difficulty following commands. His heart has a mid-systolic click, followed by a late systolic murmur and his lungs are clear to auscultation bilaterally. Several vials of whole blood are collected for analysis. Which of the following studies should be conducted as part of the diagnostic screening protocol?
- A. Northern blot with RNA probes
- B. Two-dimensional gel electrophoresis
- C. Southern blot with DNA probes (Correct Answer)
- D. Western blot
- E. PCR followed by northern blot with RNA probes
Newborn screening programs Explanation: ***Southern blot with DNA probes***
- The patient's presentation with developmental delay, repetitive behaviors, flat feet, hypotonia, elongated face, prominent ears, and macroorchidism (*enlarged testicles*) is highly suggestive of **Fragile X syndrome**.
- **Fragile X syndrome** is caused by an abnormal expansion of a **CGG trinucleotide repeat** in the *FMR1* gene on the X chromosome, which leads to hypermethylation and silencing of the gene. **Southern blot analysis with DNA probes** is the gold standard for detecting these expansions, as it can measure the size of the *CGG* repeat and the methylation status of the gene.
*Northern blot with RNA probes*
- **Northern blot analysis** is used to detect and quantify specific **RNA molecules**.
- While the *FMR1* gene's mRNA expression is affected in Fragile X syndrome, northern blot is not the primary diagnostic test for detecting the underlying **DNA repeat expansion** and methylation.
*Two-dimensional gel electrophoresis*
- **Two-dimensional gel electrophoresis** is a technique used to separate **proteins** based on their **isoelectric point** and then by **molecular weight**.
- This method is used for proteomic studies and is not relevant for diagnosing a genetic disorder caused by a DNA repeat expansion.
*Western blot*
- **Western blot analysis** is used to detect specific **proteins** in a sample.
- In Fragile X syndrome, the *FMR1* gene product, **FMRP (Fragile X Mental Retardation Protein)**, is absent or reduced, which could be theoretically detected by Western blot. However, the definitive diagnosis relies on identifying the genetic mutation (CGG expansion and methylation) in the DNA, for which Southern blot is superior.
*PCR followed by northern blot with RNA probes*
- **PCR (Polymerase Chain Reaction)** is used to amplify specific **DNA sequences**. While *PCR* can detect smaller *CGG* expansions, it often fails to accurately size the full mutations found in Fragile X syndrome due to the large repeat numbers.
- Combining *PCR* with **northern blot (RNA detection)** would still not be the primary diagnostic approach for the DNA-based *CGG* repeat expansion and methylation status, which is essential for diagnosing Fragile X.
Newborn screening programs US Medical PG Question 8: A group of gastroenterologists is concerned about low colonoscopy screening rates. They decide to implement a free patient navigation program to assist local residents and encourage them to obtain colonoscopies in accordance with U.S. Preventive Services Task Force (USPSTF) guidelines. Local residents were recruited at community centers. Participants attended monthly meetings with patient navigators and were regularly reminded that their adherence to screening guidelines was being evaluated. Colonoscopy screening rates were assessed via chart review, which showed that 90% of participants adhered to screening guidelines. Data collected via chart review for local residents recruited at community centers who did not participate in the free patient navigation system found that 34% of that population adhered to USPSTF guidelines. Which of the following has most likely contributed to the observed disparity in colonoscopy screening rates?
- A. Recall bias
- B. Confirmation bias
- C. Reporting bias
- D. Hawthorne effect (Correct Answer)
- E. Sampling bias
Newborn screening programs Explanation: ***Hawthorne effect***
- The **Hawthorne effect** is a type of reactivity in which individuals modify an aspect of their behavior in response to their awareness of being observed.
- In this study, participants were aware that their adherence to screening guidelines was being evaluated, likely leading to increased compliance simply due to this awareness rather than the efficacy of the patient navigation program alone.
*Recall bias*
- **Recall bias** occurs when participants disproportionately remember or inaccurately recall past events, often due to their current health status or beliefs.
- This bias is less likely here as colonoscopy screening rates were assessed via **chart review**, an objective measure, rather than participant self-report.
*Confirmation bias*
- **Confirmation bias** is the tendency to search for, interpret, favor, and recall information in a way that confirms one's preexisting beliefs or hypotheses.
- This bias typically affects the researchers or observers, not the participants' behavior in the observed manner, as the question focuses on the participants' increased screening rates.
*Reporting bias*
- **Reporting bias** refers to selective revealing or suppression of information during the reporting of research findings, and can occur when study participants selectively report symptoms or behaviors.
- While participants might selectively report, the data here was gathered through **chart review**, which is a more objective measure of actual behavior, making reporting bias less likely to explain the disparity in screening rates.
*Sampling bias*
- **Sampling bias** occurs when a sample is not representative of the population from which it is drawn, leading to skewed results.
- While there might be some sampling bias in who chose to participate in the free program, the observed disparity is specifically about behavior change in those *being observed*, pointing more strongly to the Hawthorne effect.
Newborn screening programs US Medical PG Question 9: A worried mother brings her 12-day-old son to the emergency room concerned that his body is turning "yellow". The patient was born at 39 weeks via spontaneous vaginal delivery without complications. The mother received adequate prenatal care and has been breastfeeding her son. The patient has had adequate urine and stool output. Physical exam demonstrates a comfortable, well nourished neonate with a jaundiced face and chest. The patient's indirect bilirubin was 4 mg/dL at 48 hours of life. Today, indirect bilirubin is 10 mg/dL, and total bilirubin is 11 mg/dL. All other laboratory values are within normal limits. What is the next best treatment in this scenario?
- A. Exchange transfusion
- B. Stop breastfeeding and switch to formula
- C. Phototherapy (Correct Answer)
- D. Reassure mother that jaundice will remit, advise her to continue breastfeeding
- E. Phenobarbital
Newborn screening programs Explanation: ***Phototherapy***
- The infant's bilirubin levels (total bilirubin 11 mg/dL, indirect bilirubin 10 mg/dL at 12 days old) are within the range that warrants **phototherapy** for a healthy term neonate to prevent **kernicterus**.
- Phototherapy helps convert unconjugated bilirubin into water-soluble isomers that can be excreted more easily.
*Exchange transfusion*
- **Exchange transfusion** is reserved for much higher bilirubin levels, typically above 20-25 mg/dL, or if there are signs of **acute bilirubin encephalopathy**.
- The current bilirubin levels do not meet the criteria for this invasive procedure.
*Phenobarbital*
- **Phenobarbital** induces hepatic enzymes, including UDP-glucuronosyltransferase, which aids bilirubin conjugation, but its effect is delayed and primarily used to prevent jaundice in specific high-risk situations (e.g., in infants of mothers with anti-Rh antibodies) or in treating **Crigler-Najjar syndrome**.
- It is not the immediate treatment for typical neonatal jaundice at these bilirubin levels.
*Stop breastfeeding and switch to formula*
- While **breast milk jaundice** can cause prolonged unconjugated hyperbilirubinemia, the infant's bilirubin levels are not dangerously high, and there is no indication to interrupt breastfeeding.
- Interruption is typically considered if bilirubin levels are very high and unresponsive to phototherapy, to differentiate from **breastfeeding jaundice** caused by inadequate intake.
*Reassure mother that jaundice will remit, advise her to continue breastfeeding*
- Although the infant is comfortable and well-nourished, a bilirubin level of 11 mg/dL at 12 days old in a term infant, especially with an indirect component of 10 mg/dL, is significant enough to warrant intervention like phototherapy to prevent potential complications.
- Simple reassurance without intervention would be inappropriate as it risks allowing bilirubin levels to rise further.
Newborn screening programs US Medical PG Question 10: A 10-year-old girl is admitted to the medical floor for a respiratory infection. The patient lives in a foster home and has been admitted many times. Since birth, the patient has had repeated episodes of pain/pressure over her frontal sinuses and a chronic cough that produces mucus. She was recently treated with amoxicillin for an infection. The patient is in the 25th percentile for height and weight which has been constant since birth. Her guardians state that the patient has normal bowel movements and has been gaining weight appropriately. The patient has a history of tricuspid stenosis. She also recently had magnetic resonance imaging (MRI) of her chest which demonstrated dilation of her airways. Her temperature is 99.5°F (37.5°C), blood pressure is 90/58 mmHg, pulse is 120/min, respirations are 18/min, and oxygen saturation is 94% on room air. Physical exam is notable for bruises along the patient's shins which the guardians state are from playing soccer. The rest of the exam is deferred because the patient starts crying. Which of the following findings is associated with this patient's most likely underlying diagnosis?
- A. Social withdrawal and avoidance of eye contact
- B. Hypocalcemia
- C. Repeat sinus infections secondary to seasonal allergies
- D. Diastolic murmur best heard along the right lower sternal border
- E. Increased chloride in the patient's sweat (Correct Answer)
Newborn screening programs Explanation: ***Increased chloride in the patient's sweat***
- The patient's history of recurrent respiratory infections, chronic productive cough, frontal sinus pain, and **bronchiectasis** (dilated airways on MRI) are highly suggestive of **cystic fibrosis**.
- **Elevated sweat chloride** is the hallmark diagnostic test for cystic fibrosis, reflecting defective chloride transport in exocrine glands.
*Social withdrawal and avoidance of eye contact*
- These are features associated with **autism spectrum disorder**, which is unrelated to the patient's respiratory and sinus symptoms.
- While possible as a co-occurring condition, it is not directly linked to the most likely **underlying diagnosis** described.
*Hypocalcemia*
- **Hypocalcemia** is typically associated with conditions like **hypoparathyroidism** or severe **vitamin D deficiency**.
- It is not a characteristic feature or direct complication of cystic fibrosis.
*Repeat sinus infections secondary to seasonal allergies*
- While seasonal allergies can cause sinus issues, the patient's history of **chronic, productive cough**, and **bronchiectasis** points to a more severe underlying condition like cystic fibrosis, not just allergies.
- Cystic fibrosis patients often have chronic sinusitis due to thick, inspissated mucus, not primarily due to allergens.
*Diastolic murmur best heard along the right lower sternal border*
- A diastolic murmur at the right lower sternal border might suggest **aortic regurgitation** or a specific type of **pulmonary regurgitation**, but it is not characteristic of the patient's known tricuspid stenosis.
- The patient has **tricuspid stenosis**, which typically causes a mid-diastolic murmur best heard at the left lower sternal border, often increasing with inspiration. This finding is unrelated to cystic fibrosis.
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