Red flags in pediatric presentations US Medical PG Practice Questions and MCQs
Practice US Medical PG questions for Red flags in pediatric presentations. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Red flags in pediatric presentations US Medical PG Question 1: A new mother expresses her concerns because her 1-day-old newborn has been having feeding difficulties. The child vomits after every feeding and has had a continuous cough since shortly after birth. The mother denies any greenish coloration of the vomit and says that it is only composed of whitish milk that the baby just had. The child exhibits these coughing spells during the exam, at which time the physician notices the child’s skin becoming cyanotic. The mother states that the child was born vaginally with no complications, although her records show that she had polyhydramnios during her last ultrasound before the delivery. Which of the following is the most likely cause of the patient’s symptoms?
- A. Failure of recanalization of duodenum
- B. Obstruction due to failure of rotation of pancreatic tissue
- C. Hypertrophy of the pyloric sphincter
- D. Failure of neural crest cells to migrate into the myenteric plexus
- E. Defective formation of the esophagus with tracheoesophageal connection (Correct Answer)
Red flags in pediatric presentations Explanation: ***Defective formation of the esophagus with tracheoesophageal connection***
- The combination of **feeding difficulties**, vomiting of **undigested milk**, **continuous coughing**, and **cyanosis** during coughing spells in a newborn strongly suggests a **tracheoesophageal fistula (TEF)**, often with **esophageal atresia**.
- **Polyhydramnios** during pregnancy is a classic prenatal sign due to the fetal inability to swallow amniotic fluid.
*Failure of recanalization of duodenum*
- This condition, known as **duodenal atresia**, typically presents with **bilious vomiting** if the obstruction is distal to the ampulla of Vater, or non-bilious if proximal, but typically does not cause continuous coughing or cyanosis during feeds.
- While it causes vomiting, it primarily affects digestion and nutrient absorption, and **polyhydramnios** can also be present due to impaired fetal swallowing.
*Obstruction due to failure of rotation of pancreatic tissue*
- This describes **annular pancreas**, where pancreatic tissue encircles the duodenum, causing obstruction and **vomiting** (often bilious).
- Like duodenal atresia, it doesn't explain the characteristic **coughing and cyanosis** with feeds seen in this case.
*Hypertrophy of the pyloric sphincter*
- **Pyloric stenosis** typically presents later (2-8 weeks of age) with **projectile non-bilious vomiting**, and an **olive-shaped mass** may be palpable in the abdomen.
- It does not cause coughing or cyanosis that correlates directly with feeding in a 1-day-old.
*Failure of neural crest cells to migrate into the myenteric plexus*
- This describes **Hirschsprung disease**, which primarily affects the colon and presents with symptoms of **intestinal obstruction** (e.g., abdominal distension, failure to pass meconium, bilious vomiting if severe).
- It is not associated with feeding difficulties, coughing, or cyanosis in the manner described.
Red flags in pediatric presentations US Medical PG Question 2: A 15-year-old boy is brought to the Emergency department by ambulance from school. He started the day with some body aches and joint pain but then had several episodes of vomiting and started complaining of a terrible headache. The school nurse called for emergency services. The boy was born at 39 weeks gestation via spontaneous vaginal delivery. He is up to date on all vaccines and is meeting all developmental milestones. Past medical history is noncontributory. He is a good student and enjoys sports. At the hospital, his blood pressure is 120/80 mm Hg, heart rate is 105/min, respiratory rate is 21/min, and his temperature is 38.9°C (102.0°F). On physical exam, he appears drowsy with neck stiffness and sensitivity to light. Kernig’s sign is positive. An ophthalmic exam is performed followed by a lumbar puncture. An aliquot of cerebrospinal fluid is sent to microbiology. A gram stain shows gram-negative diplococci. A smear is prepared on blood agar and grows round, smooth, convex colonies with clearly defined edges. Which of the following would identify the described pathogen?
- A. Oxidase-positive and ferments glucose and maltose (Correct Answer)
- B. Oxidase-positive test and ferments glucose only
- C. Catalase-negative and oxidase-positive
- D. No growth on Thayer-Martin medium
- E. Growth in anaerobic conditions
Red flags in pediatric presentations Explanation: ***Oxidase-positive and ferments glucose and maltose***
- The patient's symptoms (fever, headache, neck stiffness, sensitivity to light, positive Kernig's sign) are classic for **meningitis**, and the CSF showing **gram-negative diplococci** points to *Neisseria meningitidis*.
- *Neisseria meningitidis* is identified by its positive **oxidase test** and its ability to ferment both **glucose and maltose**.
*Oxidase-positive test and ferments glucose only*
- This description corresponds to *Neisseria gonorrhoeae*, which primarily causes **gonorrhea** and occasionally meningitis due to disseminated infection but is less common in this age group and presentation.
- While *Neisseria gonorrhoeae* is also an **oxidase-positive gram-negative diplococcus**, it specifically ferments only *glucose*, not maltose.
*Catalase-negative and oxidase-positive*
- While *Neisseria meningitidis* is **oxidase-positive**, stating it is "catalase-negative" is incorrect; *Neisseria* species are actually **catalase-positive**.
- This option incorrectly describes a general metabolic property that would rule out *Neisseria meningitidis*.
*No growth on Thayer-Martin medium*
- Thayer-Martin medium is a **selective medium** specifically designed to isolate pathogenic *Neisseria species* by inhibiting the growth of commensal bacteria and fungi.
- Therefore, *Neisseria meningitidis* would **grow well** on Thayer-Martin medium, making "no growth" an incorrect identifier.
*Growth in anaerobic conditions*
- *Neisseria meningitidis* is an **obligate aerobe**, meaning it requires oxygen for growth.
- It would **not grow** in anaerobic conditions, making this statement false for identifying the described pathogen.
Red flags in pediatric presentations US Medical PG Question 3: A 2-year-old boy presents for a routine checkup. The patient’s mother says that he has been ‘under the weather’ for the past few days. She did not measure his temperature at home but states that he has felt warm. She denies any episodes of diarrhea or vomiting. No significant past medical history or current medications. The patient attends daycare. He is due for a hepatitis A vaccine. The patient was born at term with no prenatal or perinatal complications. The vital signs include: temperature 37.8°C (100.1°F), blood pressure 112/62 mm Hg, pulse 80/min, respiratory rate 18/min, and oxygen saturation 99% on room air. The patient is alert and responsive. The physical exam is unremarkable. Which of the following is the most appropriate next step in the management of this patient?
- A. Order a complete blood count
- B. Order liver function tests
- C. Strep rapid antigen detection test
- D. Administer the hepatitis A vaccine (Correct Answer)
- E. Delay the hepatitis A immunization until next visit
Red flags in pediatric presentations Explanation: ***Administer the hepatitis A vaccine***
- The patient has a **low-grade fever** (37.8°C), which is generally **not considered a contraindication** for vaccination, especially if the child is otherwise well and active.
- The patient's presentation of being "under the weather" with an unremarkable physical exam and stable vitals suggests a **mild illness**, allowing for routine vaccinations to proceed.
*Order a complete blood count*
- A **CBC is not indicated** at this time, as the patient displays only mild, non-specific symptoms and has a normal physical exam.
- This would be reserved for cases with more concerning signs of infection or systemic illness, such as persistent high fever, lethargy, or specific clinical findings.
*Order liver function tests*
- **Liver function tests are not warranted** as the patient has no symptoms or signs suggestive of liver disease (e.g., jaundice, right upper quadrant pain, dark urine).
- While the patient is due for a hepatitis A vaccine, there is no clinical evidence of active hepatitis or liver dysfunction requiring diagnostic workup.
*Strep rapid antigen detection test*
- The patient has **no symptoms consistent with streptococcal pharyngitis**, such as sore throat, tonsillar exudates, or cervical lymphadenopathy.
- Given the lack of specific symptoms, testing for strep throat would be inappropriate and potentially lead to unnecessary antibiotic use.
*Delay the hepatitis A immunization until next visit*
- Delaying vaccination is only recommended for **moderate to severe acute illnesses** with or without fever, or for certain contraindications.
- A mild illness with low-grade fever, as in this case, is generally **not a reason to postpone** routine immunizations, as per CDC guidelines.
Red flags in pediatric presentations US Medical PG Question 4: A 26-year-old woman at 30 weeks 2 days of gestational age is brought into the emergency room following a seizure episode. Her medical records demonstrate poorly controlled gestational hypertension. Following administration of magnesium, she is taken to the operating room for emergency cesarean section. Her newborn daughter’s APGAR scores are 7 and 9 at 1 and 5 minutes, respectively. The newborn is subsequently taken to the NICU for further management and monitoring. Ten days following birth, the baby begins to refuse formula feedings and starts having several episodes of bloody diarrhea despite normal stool patterns previously. Her temperature is 102.2°F (39°C), blood pressure is 84/53 mmHg, pulse is 210/min, respirations are 53/min, and oxygen saturation is 96% on room air. A physical examination demonstrates a baby in mild respiratory distress and moderate abdominal distention. What do you expect to find in this patient?
- A. Positive blood cultures of group B streptococcus
- B. Gas within the walls of the small or large intestine on radiograph (Correct Answer)
- C. High levels of cow's milk-specific IgE
- D. Absence of ganglion cells on rectal biopsy
- E. Double bubble sign on abdominal radiograph
Red flags in pediatric presentations Explanation: ***Gas within the walls of the small or large intestine on radiograph***
- The clinical presentation of a **premature neonate** with **bloody diarrhea**, **abdominal distention**, feeding intolerance, and systemic signs like fever and tachycardia strongly points to **necrotizing enterocolitis (NEC)**.
- **Pneumatosis intestinalis** (gas within the bowel wall), recognized on an abdominal radiograph as bubbly or linear lucencies, is a hallmark diagnostic feature of NEC.
*Positive blood cultures of group B streptococcus*
- While **early-onset group B strep (GBS) sepsis** can manifest in neonates with fever and poor feeding, it typically presents within the first week of life and is less commonly associated with **bloody diarrhea** and **significant abdominal distention** as the primary symptoms, unlike NEC.
- The symptoms appear 10 days after birth, making **late-onset GBS sepsis** a possibility, but the specific gastrointestinal findings weigh more heavily towards NEC.
*High levels of cow's milk-specific IgE*
- This finding would suggest a **cow's milk protein allergy (CMPA)**, which can cause bloody stools and feeding issues.
- However, CMPA is an allergic reaction, usually without the severe systemic signs (fever, hypotension, tachycardia) and **abdominal distention** that accompany severe conditions like NEC.
*Absence of ganglion cells on rectal biopsy*
- This is the diagnostic finding for **Hirschsprung disease**, a congenital condition causing functional bowel obstruction.
- While Hirschsprung disease can present with abdominal distention and feeding difficulties, **bloody diarrhea** is not a typical hallmark, and the acute onset in a premature infant following a stressful birth is more consistent with NEC.
*Double bubble sign on abdominal radiograph*
- The **double bubble sign** on an abdominal radiograph is indicative of **duodenal atresia** or annular pancreas, causing a complete obstruction at the duodenum.
- This is a congenital anomaly that presents with bilious vomiting typically within the first 24-48 hours of life, not delayed onset bloody diarrhea and systemic illness like NEC.
Red flags in pediatric presentations US Medical PG Question 5: Four days after delivery, a 1400-g (3-lb 1-oz) newborn has a tonic seizure that lasts for 30 seconds. Over the past 24 hours, he has become increasingly lethargic. He was born at 31 weeks' gestation. Antenatal period was complicated by chorioamnionitis. Apgar scores were 4 and 5 at 1 and 5 minutes, respectively. He appears ill. His pulse is 130/min, respirations are 53/min and irregular, and blood pressure is 67/35 mm Hg. Examination shows a bulging anterior fontanelle. The pupils are equal and react sluggishly to light. Examination shows slow, conjugate back and forth movements of the eyes. Muscle tone is decreased in all extremities. The lungs are clear to auscultation. Which of the following is the most likely underlying cause?
- A. Congenital hydrocephalus
- B. Germinal matrix hemorrhage (Correct Answer)
- C. Galactose-1-phosphate uridylyltransferase deficiency
- D. Phenylalanine hydroxylase deficiency
- E. Apoptosis of lower motor neurons
Red flags in pediatric presentations Explanation: ***Germinal matrix hemorrhage***
- This condition is most common in **premature infants** (born at 31 weeks' gestation) and is exacerbated by perinatal insults such as **chorioamnionitis** and **low Apgar scores**, leading to rupture of fragile germinal matrix vessels.
- The clinical presentation of a **tonic seizure**, increasing **lethargy**, **bulging fontanelle**, sluggish pupillary reflexes, and abnormal eye movements (slow conjugate back-and-forth movements) points towards increased **intracranial pressure** due to intraventricular hemorrhage.
- While GMH typically occurs within the first 72 hours of life, the **progressive symptoms over 24 hours** starting on day 3-4 with the acute presentation on day 4 is consistent with **evolving IVH with hydrocephalus**, which can manifest with delayed clinical deterioration as blood obstructs CSF flow.
- Among the given options, this is the **most likely diagnosis** given the prematurity, risk factors, and signs of increased ICP.
*Congenital hydrocephalus*
- While it can present with a **bulging fontanelle**, congenital hydrocephalus typically manifests with gradual progressive head enlargement rather than acute onset of seizures and rapid neurological decline.
- It would typically be identified antenatally or soon after birth due to progressive macrocephaly, and lacks the specific risk factors (prematurity, chorioamnionitis) that make hemorrhage more likely in this context.
*Galactose-1-phosphate uridylyltransferase deficiency*
- This enzyme deficiency causes **galactosemia**, a metabolic disorder presenting with **jaundice**, hepatomegaly, vomiting, and feeding difficulties, usually after the initiation of milk feeds.
- Seizures can occur in severe cases, but the primary symptoms are metabolic (hypoglycemia, liver dysfunction) and not typically linked to a bulging fontanelle or the specific perinatal risk factors (prematurity, chorioamnionitis) described.
*Phenylalanine hydroxylase deficiency*
- This deficiency leads to **phenylketonuria (PKU)**, a metabolic disorder that primarily causes neurological damage if untreated, typically presenting with developmental delay, intellectual disability, seizures, and microcephaly **later in infancy** (months, not days).
- It does not present acutely with bulging fontanelle and seizures in the first week of life, nor does it correlate with prematurity or chorioamnionitis as risk factors.
*Apoptosis of lower motor neurons*
- This is characteristic of conditions like **spinal muscular atrophy (SMA)**, which typically presents with progressive **muscle weakness**, **hypotonia**, and absent deep tendon reflexes without acute onset seizures.
- The neurological signs in this infant—**seizures**, **bulging fontanelle**, and **increased intracranial pressure**—are not features of lower motor neuron disease, which affects the anterior horn cells and peripheral motor function, not higher cortical or intracranial processes.
Red flags in pediatric presentations US Medical PG Question 6: A 5-week-old male infant is brought to the Emergency Department with the complaint of vomiting. His parents state he has been unable to keep normal feedings down for the past week and now has projectile non-bilious vomiting after each meal. He was given a short course of oral erythromycin at 4 days of life for suspected bacterial conjunctivitis. Physical examination is significant for sunken fontanelles and dry mucous membranes. A palpable, ball shaped mass is noted just to the right of the epigastrium. Which of the following conditions is most likely in this patient?
- A. Milk-protein allergy
- B. Gastroesophageal reflux
- C. Intussusception
- D. Midgut volvulus
- E. Hypertrophic pyloric stenosis (Correct Answer)
Red flags in pediatric presentations Explanation: ***Hypertrophic pyloric stenosis***
- The classic presentation includes **projectile non-bilious vomiting** in a 2-8 week old infant, a **palpable olive-shaped mass** in the epigastrium, and signs of **dehydration** (sunken fontanelles, dry mucous membranes).
- Exposure to **erythromycin** in early infancy is a recognized risk factor for developing pyloric stenosis due to its effect on gastrointestinal motility.
*Milk-protein allergy*
- Typically presents with symptoms like **bloody stools**, **diarrhea**, or **eczema**, rather than forceful projectile non-bilious vomiting.
- A palpable epigastric mass is not a feature of milk-protein allergy.
*Gastroesophageal reflux*
- While common in infants, GERD usually involves effortless spitting up or vomiting that is **not projectile** and generally **does not lead to significant dehydration** or a palpable mass.
- Symptoms tend to improve with age and positioning, unlike the progressive worsening seen here.
*Intussusception*
- Characterized by sudden onset of **crampy abdominal pain**, **currant jelly stools** (blood and mucus), and a sausage-shaped mass, usually in the right upper quadrant.
- The vomiting is typically **bilious** due to bowel obstruction, and it occurs later in presentation.
*Midgut volvulus*
- This is an acute surgical emergency presenting with sudden onset of **bilious vomiting** and signs of **intestinal obstruction**.
- It is associated with **malrotation** and can rapidly lead to bowel ischemia, which is a more severe and sudden presentation than described.
Red flags in pediatric presentations US Medical PG Question 7: Three days after delivery, a 1100-g (2-lb 7-oz) newborn has a tonic seizure that lasts for 25 seconds. She has become increasingly lethargic over the past 18 hours. She was born at 31 weeks' gestation. Antenatal period was complicated by chorioamnionitis. Apgar scores were 3 and 6 at 1 and 5 minutes, respectively. She appears ill. Her pulse is 123/min, respirations are 50/min and irregular, and blood pressure is 60/30 mm Hg. Examination shows a tense anterior fontanelle. The pupils are equal and react sluggishly to light. Examination shows slow, conjugate back and forth movements of the eyes. Muscle tone is decreased in all extremities. The lungs are clear to auscultation. Which of the following is the most likely diagnosis?
- A. Intraventricular hemorrhage (Correct Answer)
- B. Spinal muscular atrophy
- C. Galactosemia
- D. Congenital hydrocephalus
- E. Phenylketonuria
Red flags in pediatric presentations Explanation: ***Intraventricular hemorrhage***
- The combination of **prematurity** (31 weeks' gestation, 1100g), **tonic seizures**, increasing **lethargy**, tense **anterior fontanelle**, **sluggishly reactive pupils**, and **slow conjugate back-and-forth eye movements** (suggesting brainstem involvement from increased intracranial pressure) are classical signs of intraventricular hemorrhage (IVH) in a neonate.
- **IVH** is common in premature infants due to the fragility of germinal matrix vessels and can manifest acutely with neurological deterioration and increased intracranial pressure, typically within the first 72 hours of life.
- While maternal **chorioamnionitis** and low Apgar scores raise concern for neonatal sepsis/meningitis, the specific **ocular movement pattern** and acute neurological signs on day 3 are more characteristic of IVH in this extremely premature infant.
*Spinal muscular atrophy*
- This is a **neuromuscular genetic disorder** characterized by progressive muscle weakness and hypotonia due to anterior horn cell degeneration.
- It would typically present with **decreased muscle tone but without acute neurological signs** like seizures, tense fontanelle, or sluggish pupillary responses.
- Does not cause acute-onset seizures or rapidly progressing lethargy in the neonatal period.
*Galactosemia*
- This is a **metabolic disorder** that presents with symptoms such as **vomiting, jaundice, hepatomegaly**, and **sepsis-like symptoms** upon introduction of lactose-containing feeds (breast milk or regular formula), typically after several days of feeding.
- While it can cause lethargy and seizures, the acute neurological findings including **tense fontanelle** and **abnormal eye movements** in the immediate postnatal period of a premature infant more strongly suggest an anatomical/structural etiology like IVH.
*Congenital hydrocephalus*
- While **hydrocephalus** can cause a **tense fontanelle** and seizures, the **acute onset** of symptoms (day 3 of life with rapid deterioration over 18 hours following a specific tonic seizure) in an extremely premature infant strongly suggests an **acute hemorrhagic event** rather than congenital hydrocephalus.
- Congenital hydrocephalus typically presents with **progressively enlarging head circumference** over time, rather than such acute neurological deterioration in the first 72 hours of life.
- IVH can lead to secondary post-hemorrhagic hydrocephalus, but the acute presentation favors primary IVH.
*Phenylketonuria*
- This is a **metabolic disorder** caused by phenylalanine hydroxylase deficiency that, if untreated, leads to **intellectual disability** and seizures.
- Symptoms typically manifest **several months after birth** (usually 3-6 months) as phenylalanine accumulates, and are not associated with acute neonatal neurological distress like tense fontanelle, abnormal eye movements, or acute lethargy in the first few days of life.
- Would not explain the acute deterioration on day 3 of life in this clinical context.
Red flags in pediatric presentations US Medical PG Question 8: A 55-year-old man presents to his primary care physician for trouble swallowing. The patient claims that he used to struggle when eating food if he did not chew it thoroughly, but now he occasionally struggles with liquids as well. He also complains of a retrosternal burning sensation whenever he eats. He also claims that he feels his throat burns when he lays down or goes to bed. Otherwise, the patient has no other complaints. The patient has a past medical history of obesity, diabetes, constipation, and anxiety. His current medications include insulin, metformin, and lisinopril. On review of systems, the patient endorses a 5 pound weight loss recently. The patient has a 22 pack-year smoking history and drinks alcohol with dinner. His temperature is 99.5°F (37.5°C), blood pressure is 177/98 mmHg, pulse is 90/min, respirations are 17/min, and oxygen saturation is 98% on room air. On physical exam, you note an overweight man in no current distress. Abdominal exam is within normal limits. Which of the following is the best next step in management?
- A. Endoscopy (Correct Answer)
- B. Omeprazole trial
- C. Manometry
- D. Barium swallow
- E. CT scan
Red flags in pediatric presentations Explanation: ***Endoscopy***
- The patient presents with **dysphagia to solids and liquids**, significant for **recent weight loss**, and a **history of smoking**, all of which are **alarm symptoms** necessitating an upper endoscopy to rule out malignancy.
- While he has **GERD symptoms** as well (retrosternal burning), the presence of alarm features mandates a direct investigation of the upper GI tract rather than empirical treatment.
*Omeprazole trial*
- An empirical trial of **PPIs** like omeprazole is appropriate for classic GERD symptoms without alarm features.
- However, **dysphagia to solids and liquids with associated weight loss**, especially in a patient with a significant **smoking history**, are alarm symptoms that require direct visualization via endoscopy, not just symptom management.
*Manometry*
- **Esophageal manometry** is used to evaluate the motility of the esophagus and diagnose conditions like achalasia or esophageal spasm.
- While the patient has dysphagia, **alarm symptoms (weight loss, smoking history)** raise concern for mechanical obstruction or malignancy, which should be investigated before motility disorders.
*Barium swallow*
- A **barium swallow** can identify structural abnormalities like strictures, masses, or webs, and also assess motility.
- However, in the context of alarm symptoms, a **barium swallow is less sensitive** for detecting subtle mucosal changes or early malignancy compared to endoscopy, and any positive findings would still prompt an endoscopy.
*CT scan*
- A **CT scan of the chest and abdomen** is useful for assessing extraluminal pathology, mediastinal involvement, or distant metastases.
- While it may eventually be part of staging if a malignancy is found, the **initial investigation for esophageal symptoms and alarm features** focuses on direct luminal visualization with endoscopy to identify the primary pathology.
Red flags in pediatric presentations US Medical PG Question 9: A 31-year-old man and his wife were referred to a genetic counselor. They are concerned about the chance that their children are likely to inherit certain conditions that run in their families. The wife's father and grandfather are both healthy, but her grandfather cannot see the color red. The husband is unaware if any member of his family has the same condition. The geneticist provides some details about genetic diseases and inheritance patterns, then orders lab tests to analyze the gene mutations carried by both partners. Which of the following are the correct terms regarding the genotype and phenotype of males affected by the condition described?
- A. Homozygote; reduced or incomplete penetrance
- B. Heterozygotes; reduced or incomplete penetrance
- C. Hemizygous; reduced or incomplete penetrance
- D. Heterozygotes; full penetrance
- E. Hemizygous; full penetrance (Correct Answer)
Red flags in pediatric presentations Explanation: ***Hemizygous; full penetrance***
- The condition described (**red color blindness**) is an **X-linked recessive** trait, meaning males have only one X chromosome and are thus **hemizygous** for genes on the X chromosome.
- **Full penetrance** in X-linked recessive traits means that if a male inherits the affected X chromosome, he will express the phenotype of the condition.
*Homozygote; reduced or incomplete penetrance*
- **Homozygous** refers to having two identical alleles for a particular gene, which is not applicable to an X-linked gene in males as they only have one X chromosome.
- **Reduced or incomplete penetrance** means that a person with the genotype may or may not express the phenotype, which is typically not the case for males with X-linked recessive color blindness.
*Heterozygotes; reduced or incomplete penetrance*
- **Heterozygous** means having two different alleles for a gene; this term is not applicable to males regarding X-linked genes.
- Males are **hemizygous** for X-linked genes, meaning they only have one allele, not two different ones.
*Hemizygous; reduced or incomplete penetrance*
- While males are indeed **hemizygous** for X-linked genes like color blindness, the penetrance for red-green color blindness in males is generally considered to be **full**, meaning if they carry the mutated gene, they will express the trait.
- **Reduced penetrance** would imply that some males with the genotype might not exhibit color blindness, which is rare for this condition.
*Heterozygotes; full penetrance*
- The term **heterozygous** applies to individuals with two different alleles for a gene, which is not the genetic state of males for X-linked genes.
- While penetrance is full, the term **heterozygotes** is incorrect for defining the male genotype in this context.
Red flags in pediatric presentations US Medical PG Question 10: A 47-year-old man presents to the clinic for an evaluation of intense itching of his right thigh region for the past few days. He states some ‘red bumps’ just began to form. The patient mentions that he was recently at a business conference in Miami. He has a past medical history of hypertension, diabetes type 2, and hyperlipidemia. He takes enalapril, metformin, and atorvastatin. He does not smoke or drink. His vitals are within normal limits today. On physical examination, a linear line with 3 red papules is present along the medial aspect of his right thigh. Additionally, there are small rows of bumps on his left leg and right forearm. Excoriations are also apparent in the same region. Which of the following is the most likely diagnosis?
- A. Scabies
- B. Bed bug bite (Correct Answer)
- C. Cutaneous larva migrans
- D. Flea bite
- E. Spider bite
Red flags in pediatric presentations Explanation: ***Bed bug bite***
- The presence of **linear lesions** (often described as "breakfast, lunch, and dinner") and **rows of bumps** on exposed skin, especially after recent travel, is highly characteristic of **bed bug bites**.
- **Intense itching** and **red papules** appearing a few days after exposure further support this diagnosis.
*Scabies*
- While scabies also causes intense itching and red papules, it typically presents with **serpiginous burrows** in characteristic locations such as the finger webs, wrists, and axillae.
- Scabies is also more often associated with generalized pruritus rather than localized linear lesions from recent exposure.
*Cutaneous larva migrans*
- This condition is caused by hookworm larvae and presents with a **highly pruritic, intensely erythematous, raised, serpiginous tract** that migrates over time.
- The described lesions are more consistent with bites in a linear pattern rather than a migratory burrow.
*Flea bite*
- Flea bites often appear as **small, red, itchy bumps** usually clustered around ankles or areas covered by tight clothing.
- While itchy, they typically do not form the distinct linear "breakfast, lunch, and dinner" pattern seen with bed bugs.
*Spider bite*
- Most spider bites present as a **single lesion**, often with a central puncture mark, and can range from mild local reactions to necrotic lesions, depending on the spider.
- Bites from multiple spiders or multiple bites in a linear pattern are highly unusual and do not fit the description of lesions in rows.
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