A 7-year-old boy is brought to the emergency department because of a 3-day history of generalized fatigue, myalgia, and fever. He has sickle cell disease. His current medications include hydroxyurea and folic acid. He appears ill. His temperature is 39.2°C (102.6°F), pulse is 103/min, and respirations are 28/min. Examination shows pale conjunctivae. The lungs are clear to auscultation. The abdomen is soft and nontender. Neurologic examination shows no focal findings, His hemoglobin concentration is 10.3 g/dL and leukocyte count is 14,100/mm3. Intravenous fluid is administered and blood cultures are obtained. Which of the following is the most appropriate next step in treatment?
Q32
A 7-year-old male is admitted to the hospital with his fourth episode of wheezing and dyspnea. His symptoms are exacerbated by mold and pollen. Which of the following is most likely to be observed in this patient?
Q33
A 2-month-old girl is admitted to the hospital because of a 1-day history of fever and difficulty breathing. She has also had nasal congestion for 2 days. She was born at 28 weeks' gestation and weighed 1105 g (2 lb 7 oz); she currently weighs 2118 g (4 lb 11 oz). Her neonatal course was complicated by respiratory distress syndrome. She required supplemental oxygen for 36 days following birth. She was diagnosed with bronchopulmonary dysplasia 3 weeks ago. The infant missed an appointment with the pediatrician 2 weeks ago. Her only medication is vitamin D drops. She appears lethargic. Her temperature is 38.6°C (101.4°F), pulse is 160/min, respirations are 55/min, and blood pressure is 80/45 mm Hg. Pulse oximetry on room air shows an oxygen saturation of 87%. Physical examination shows moderate subcostal retractions. Wheezing is heard on auscultation of the chest. Her hemoglobin concentration is 10.5 g/dL, leukocyte count is 13,000/mm3, and platelet count is 345,000/mm3. Mechanic ventilatory support is initiated. After 4 days in the pediatric intensive care unit, the patient dies. Administration of which of the following is most likely to have prevented this patient's outcome?
Q34
A 7-year-old boy presents to the pediatric emergency department for knee pain. The child fell while riding his skateboard yesterday. He claims that ever since then he has had swelling and knee pain that is severe. His parents state that he has trouble walking due to the pain. The child has a past medical history of seasonal allergies and asthma. His current medications include loratadine, albuterol, and fluticasone. His temperature is 99.5°F (37.5°C), blood pressure is 95/48 mmHg, pulse is 110/min, respirations are 17/min, and oxygen saturation is 98% on room air. On physical exam, you note a young boy laying on the stretcher in pain. Cardiopulmonary exam is within normal limits. Inspection of the patient's left knee reveals an erythematous knee that is tender and warm to the touch. Passive movement of the knee elicits pain. The patient refuses to walk so you are unable to assess his gait. Which of the following is the best initial step in management?
Q35
Multiple patients present to your office with hematuria following an outbreak of Group A Streptococcus. Biopsy reveals that all of the patients have the same disease, characterized by large, hypercellular glomeruli with neutrophil infiltration. Which patient has the best prognosis?
Q36
A 12-year-old African American boy is brought to the emergency room due to a severely painful penile erection for the past 5 hours. He was attending a class at his school when his penis became spontaneously tumescent. A complete blood count and a cavernous blood gas analysis showed the following:
Hemoglobin (Hb) 11.5 g/dL; 14.5 g/dL (-2SD 13.0 g/dL) for boys 12–18 years of age
Mean corpuscular volume (MCV) 95 fL; 80–96 fL
Platelet count 250,000/mm3
pO2 38 mm Hg
pCO2 65 mm Hg
pH 7.25
sO2 % 60%
HCO3- 10 mEq/L
A peripheral blood smear reveals RBCs with Howell-Jolly bodies. Rapid detumescence is achieved after aspiration of blood and administration of an adrenergic agonist and analgesia. Which of the following etiologies should be considered in this patient?
Q37
A 12-year-old boy is brought to the physician because of fever, malaise, and a painful, itchy rash on the right shoulder for 2 weeks. The patient's mother says the boy's condition has worsened over the past 4 days. He has a history of atopic dermatitis. He has lived with his mother at several public shelters since she separated from his physically abusive father 2 months ago. His immunizations are up-to-date. There is cervical lymphadenopathy. Laboratory studies show no abnormalities. A photograph of the rash is shown. Which of the following is the most likely diagnosis?
Q38
A 10-year-old girl is brought to the physician because of a severe, throbbing headache for 1 hour. The headache is located in the right frontotemporal region. It is her fifth such headache in the past 2 months. Her mother says that all the previous episodes started after soccer practice, following which the child would lock herself in her room, close the curtains, and sleep for a few hours. After waking up, the headache is either diminished or has stopped entirely. One month ago, the child was diagnosed with myopic vision and has been wearing glasses since. Her 4-year-old brother had herpetic gingivostomatitis 2 months ago. Her vital signs are within normal limits. Funduscopic examination is inconclusive because the child is uncooperative. The remainder of the examination shows no abnormalities. Which of the following is the most appropriate next step in management?
Q39
A 3-year-old girl is brought to the physician by her parents because of a barking cough, a raspy voice, and noisy breathing for the last 3 days. Five days ago, she had a low-grade fever and runny nose. She attends daycare. Her immunizations are up-to-date. Her temperature is 37.8°C (100°F) and respirations are 33/min. Physical examination shows supraclavicular retractions. There is a high-pitched sound present on inspiration. Examination of the throat shows erythema without exudates. Which of the following is the most likely location of the anatomic narrowing causing this patient's symptoms?
Q40
A 4-year-old boy is brought to the physician by his father because of a 3-day history of generalized rash. The rash is not pruritic. He has no cough. He has had a fever and a sore throat for 4 days. He was born at term and has been healthy except for an episode of tonsillitis 6 months ago treated with erythromycin. His immunizations are up-to-date. His temperature is 38.5°C (101.3°F). Examination shows cervical lymphadenopathy. The tongue is bright red. There is tonsillar erythema without any exudate. A photograph of the rash is shown. Which of the following is the most appropriate next step in management?
Infectious Disease US Medical PG Practice Questions and MCQs
Question 31: A 7-year-old boy is brought to the emergency department because of a 3-day history of generalized fatigue, myalgia, and fever. He has sickle cell disease. His current medications include hydroxyurea and folic acid. He appears ill. His temperature is 39.2°C (102.6°F), pulse is 103/min, and respirations are 28/min. Examination shows pale conjunctivae. The lungs are clear to auscultation. The abdomen is soft and nontender. Neurologic examination shows no focal findings, His hemoglobin concentration is 10.3 g/dL and leukocyte count is 14,100/mm3. Intravenous fluid is administered and blood cultures are obtained. Which of the following is the most appropriate next step in treatment?
A. Clindamycin
B. Prednisone
C. Vancomycin
D. Ceftriaxone (Correct Answer)
E. Levofloxacin
Explanation: ***Ceftriaxone***
- This patient presents with **fever** and **sickle cell disease**, placing him at high risk for bacterial infections, especially from **encapsulated organisms** like *Streptococcus pneumoniae* and *Haemophilus influenzae*. **Ceftriaxone** is a broad-spectrum third-generation cephalosporin that provides excellent coverage against these common pathogens.
- Due to the high risk of **sepsis** and rapid progression of infection in sickle cell patients, empiric, prompt administration of **intravenous antibiotics** is crucial, even before culture results are available.
*Clindamycin*
- **Clindamycin** is primarily effective against **anaerobic bacteria** and some gram-positive organisms, including methicillin-sensitive *Staphylococcus aureus* (MSSA).
- It does not provide adequate coverage against the most common and life-threatening pathogens in febrile sickle cell patients, such as encapsulated bacteria.
*Prednisone*
- **Prednisone** is a corticosteroid used for its **anti-inflammatory** and immunosuppressive effects. It is not indicated for the initial management of fever and suspected bacterial infection.
- Administering corticosteroids in a patient with suspected infection without appropriate antibiotic coverage could worsen the infection.
*Vancomycin*
- **Vancomycin** is a powerful antibiotic primarily used to cover **multi-drug resistant gram-positive bacteria**, especially **MRSA** and drug-resistant *S. pneumoniae*.
- While it covers gram-positive organisms well, it does **not cover gram-negative bacteria** such as *H. influenzae* or *Salmonella* species, which are important pathogens in sickle cell patients. **Ceftriaxone** provides broader coverage including both gram-positive and gram-negative encapsulated organisms, making it the preferred empiric choice.
*Levofloxacin*
- **Levofloxacin** is a fluoroquinolone that provides broad-spectrum coverage, including against atypical organisms and some gram-negatives and gram-positives.
- However, **fluoroquinolones** are generally avoided in children due to potential adverse effects on cartilage development, and it is not the first-line empiric choice for severe bacterial infections in this age group, especially when **cephalosporins** are highly effective and safer.
Question 32: A 7-year-old male is admitted to the hospital with his fourth episode of wheezing and dyspnea. His symptoms are exacerbated by mold and pollen. Which of the following is most likely to be observed in this patient?
A. Normal FEV1/FVC
B. Normal FEV1
C. Abnormal chest radiograph
D. Ground glass opacities on chest CT
E. Sputum eosinophils (Correct Answer)
Explanation: ***Sputum eosinophils***
- The patient presents with recurrent wheezing, dyspnea, and exacerbations triggered by allergens (mold and pollen), which are classic signs of **asthma**.
- **Eosinophils** are key inflammatory cells in allergic asthma, and their presence in sputum is a common finding, especially during exacerbations.
*Normal FEV1/FVC*
- In asthma, there is **airway obstruction**, which typically leads to a **reduced FEV1/FVC ratio**, as FEV1 decreases proportionally more than FVC.
- A normal ratio would indicate the absence of obstructive lung disease, which contradicts the patient's symptoms.
*Normal FEV1*
- **Forced expiratory volume in 1 second (FEV1)** is typically decreased during an asthmatic exacerbation due to **bronchoconstriction** and airway narrowing.
- A normal FEV1 would be inconsistent with current breathing difficulties (wheezing and dyspnea) experienced by the patient.
*Abnormal chest radiograph*
- During an acute asthma exacerbation, a chest radiograph is often **normal** or may show signs of **hyperinflation** but generally does not show focal abnormalities.
- Significant abnormalities on chest X-ray might suggest complications like pneumonia or pneumothorax, which are not described here as the primary issue.
*Ground glass opacities on chest CT*
- **Ground glass opacities** on CT are characteristic of interstitial lung diseases or certain infections, like **pneumocystis pneumonia** or **viral pneumonia**.
- These are not typical findings in uncomplicated asthma and would suggest an alternative or coexisting pathology.
Question 33: A 2-month-old girl is admitted to the hospital because of a 1-day history of fever and difficulty breathing. She has also had nasal congestion for 2 days. She was born at 28 weeks' gestation and weighed 1105 g (2 lb 7 oz); she currently weighs 2118 g (4 lb 11 oz). Her neonatal course was complicated by respiratory distress syndrome. She required supplemental oxygen for 36 days following birth. She was diagnosed with bronchopulmonary dysplasia 3 weeks ago. The infant missed an appointment with the pediatrician 2 weeks ago. Her only medication is vitamin D drops. She appears lethargic. Her temperature is 38.6°C (101.4°F), pulse is 160/min, respirations are 55/min, and blood pressure is 80/45 mm Hg. Pulse oximetry on room air shows an oxygen saturation of 87%. Physical examination shows moderate subcostal retractions. Wheezing is heard on auscultation of the chest. Her hemoglobin concentration is 10.5 g/dL, leukocyte count is 13,000/mm3, and platelet count is 345,000/mm3. Mechanic ventilatory support is initiated. After 4 days in the pediatric intensive care unit, the patient dies. Administration of which of the following is most likely to have prevented this patient's outcome?
A. Ceftriaxone
B. Ribavirin
C. Palivizumab (Correct Answer)
D. Respiratory syncytial virus immune globulin
E. Postnatal glucocorticoid
Explanation: ***Palivizumab***
* This premature infant with a history of **bronchopulmonary dysplasia (BPD)** is at extremely high risk for severe **respiratory syncytial virus (RSV)** infection, which can be fatal.
* **Palivizumab** is a monoclonal antibody specifically designed to prevent severe RSV disease in high-risk infants, and its administration would have been crucial here.
*Ceftriaxone*
* **Ceftriaxone** is a broad-spectrum antibiotic used to treat bacterial infections, but the primary pathogen in this case is highly likely to be viral (RSV) given the symptoms and rapid deterioration despite supportive care.
* While bacterial superinfection is possible, **antibiotics** are not the primary preventative measure for the initial viral illness that led to this outcome.
*Ribavirin*
* **Ribavirin** is an antiviral medication used in some severe RSV cases, but it is typically reserved for hospitalized patients with severe disease, not for routine prophylaxis in high-risk infants.
* Its use is controversial, and it is not considered a primary preventative measure to achieve the outcome of preventing this patient's death.
*Respiratory syncytial virus immune globulin*
* **RSV immune globulin** (RespiGam) was an older prophylactic agent for RSV, but it has been largely replaced by **palivizumab** due to palivizumab's superior efficacy, easier administration (intramuscular vs. intravenous), and fewer side effects.
* While it aimed to provide passive immunity, it is not the current standard or most effective preventative intervention.
*Postnatal glucocorticoid*
* **Postnatal glucocorticoids** like dexamethasone are sometimes used in premature infants with BPD to reduce inflammation and dependence on ventilator support.
* However, administering glucocorticoids does not directly prevent severe RSV infection, which was the overwhelming cause of the patient's acute deterioration and death in this scenario.
Question 34: A 7-year-old boy presents to the pediatric emergency department for knee pain. The child fell while riding his skateboard yesterday. He claims that ever since then he has had swelling and knee pain that is severe. His parents state that he has trouble walking due to the pain. The child has a past medical history of seasonal allergies and asthma. His current medications include loratadine, albuterol, and fluticasone. His temperature is 99.5°F (37.5°C), blood pressure is 95/48 mmHg, pulse is 110/min, respirations are 17/min, and oxygen saturation is 98% on room air. On physical exam, you note a young boy laying on the stretcher in pain. Cardiopulmonary exam is within normal limits. Inspection of the patient's left knee reveals an erythematous knee that is tender and warm to the touch. Passive movement of the knee elicits pain. The patient refuses to walk so you are unable to assess his gait. Which of the following is the best initial step in management?
A. ESR, CRP, and CBC
B. Arthrocentesis (Correct Answer)
C. CT scan
D. Antibiotics
E. Supportive therapy and further physical exam
Explanation: ***Arthrocentesis***
- The patient presents with classic signs of **septic arthritis**, including acute onset of severe knee pain, warmth, erythema, tenderness, and refusal to bear weight, especially following a minor trauma which can sometimes be a precipitating factor or merely draw attention to existing infection.
- **Arthrocentesis** is the most crucial diagnostic and therapeutic step in suspected septic arthritis, as it allows for fluid analysis (cell count, Gram stain, culture) to identify the causative organism and guide targeted antibiotic therapy.
*ESR, CRP, and CBC*
- While these labs (erythrocyte sedimentation rate, C-reactive protein, and complete blood count) are important for assessing the degree of **inflammation** and **infection**, they are not the definitive initial step for diagnosing septic arthritis.
- These tests support the suspicion of infection but do not provide the specific bacterial diagnosis or immediate relief of joint pressure that arthrocentesis offers.
*CT scan*
- A CT scan is generally not the initial diagnostic modality for **acute septic arthritis** unless there is a concern for osteomyelitis or other bony involvement not clearly visible on plain radiographs or if aspiration is difficult.
- **Plain radiographs** are usually the first imaging study to rule out fracture or other bony pathology, but they cannot diagnose joint infection.
*Antibiotics*
- While antibiotics are essential for treating septic arthritis, initiating them **before
arthrocentesis** can **sterilize the joint fluid**, making culture results negative and hindering the identification of the specific pathogen.
- Empirical antibiotics should only begin *after* joint fluid has been aspirated for diagnostic purposes.
*Supportive therapy and further physical exam*
- Supportive therapy (e.g., pain control, immobilization) is important but **insufficient** as the sole initial management for suspected septic arthritis, which is a **medical emergency**.
- Delaying definitive diagnosis and treatment (arthrocentesis) can lead to **rapid joint destruction** and long-term morbidity, outweighing the benefit of further physical exam beyond initial assessment.
Question 35: Multiple patients present to your office with hematuria following an outbreak of Group A Streptococcus. Biopsy reveals that all of the patients have the same disease, characterized by large, hypercellular glomeruli with neutrophil infiltration. Which patient has the best prognosis?
A. 38-year-old man with sickle cell trait
B. 65-year-old nulliparous woman
C. 18-year-old man treated with corticosteroids
D. 50-year-old man with a history of strep infection
E. 8-year-old boy who undergoes no treatment (Correct Answer)
Explanation: **8-year-old boy who undergoes no treatment**
- **Post-streptococcal glomerulonephritis (PSGN)** has an excellent prognosis in children, with over 95% making a full recovery, regardless of treatment.
- Children are known to spontaneously resolve the condition, often without long-term renal complications.
- **Age is the single most important prognostic factor** in PSGN, and pediatric patients have significantly better outcomes than adults.
*38-year-old man with sickle cell trait*
- While sickle cell trait is generally asymptomatic, it is not a factor that improves the prognosis of PSGN.
- Adult patients typically have a worse prognosis for PSGN compared to children, with only ~50% achieving complete recovery and higher risk of developing chronic kidney disease.
*65-year-old nulliparous woman*
- **Older age** is a significant risk factor for worse prognosis in PSGN, with elderly patients having the highest likelihood of progressing to chronic renal failure.
- Gender and parity status do not directly influence the prognosis of PSGN.
*18-year-old man treated with corticosteroids*
- Corticosteroids are **not indicated** for the routine treatment of PSGN and do not improve its prognosis, as the disease is typically self-limiting.
- This patient's age (18 years old) places him at the transition between pediatric and adult outcomes, generally with a less favorable prognosis than younger children.
*50-year-old man with a history of strep infection*
- A history of strep infection is the **etiological cause** of PSGN but provides no prognostic advantage.
- Middle-aged and older adults have significantly worse outcomes in PSGN compared to children, with increased risk of progression to chronic kidney disease.
Question 36: A 12-year-old African American boy is brought to the emergency room due to a severely painful penile erection for the past 5 hours. He was attending a class at his school when his penis became spontaneously tumescent. A complete blood count and a cavernous blood gas analysis showed the following:
Hemoglobin (Hb) 11.5 g/dL; 14.5 g/dL (-2SD 13.0 g/dL) for boys 12–18 years of age
Mean corpuscular volume (MCV) 95 fL; 80–96 fL
Platelet count 250,000/mm3
pO2 38 mm Hg
pCO2 65 mm Hg
pH 7.25
sO2 % 60%
HCO3- 10 mEq/L
A peripheral blood smear reveals RBCs with Howell-Jolly bodies. Rapid detumescence is achieved after aspiration of blood and administration of an adrenergic agonist and analgesia. Which of the following etiologies should be considered in this patient?
A. Hereditary spherocytosis
B. Glucose-6 phosphate dehydrogenase (G6PD) deficiency
C. Thalassemia
D. Sickle cell disease (SCD) (Correct Answer)
E. Thrombotic thrombocytopenic purpura (TTP)
Explanation: ***Sickle cell disease (SCD)***
- The painful **priapism** in an African American boy, along with **Howell-Jolly bodies** on peripheral smear and the **acidotic** cavernous blood gas, are classic indicators of a **sickle cell crisis**.
- The low pO2 and sO2% in the cavernous blood gas reflect **venous outflow obstruction** and local **hypoxia** due to sickling, while Howell-Jolly bodies indicate **functional asplenia**.
*Hereditary spherocytosis*
- This condition would typically present with **spherocytes** on a peripheral smear and evidence of **hemolytic anemia**, which are not described.
- While it can cause anemia, it is not directly associated with priapism as a primary manifestation.
*Glucose-6 phosphate dehydrogenase (G6PD) deficiency*
- G6PD deficiency causes **hemolytic anemia** triggered by certain drugs, foods, or infections, and characteristically presents with **Heinz bodies** and **bite cells** on blood smear.
- It is not typically associated with priapism or Howell-Jolly bodies.
*Thalassemia*
- Thalassemia involves **impaired global synthesis of alpha or beta globin chains**, leading to microcytic anemia, and often presents with target cells or basophilic stippling.
- Priapism can occur in severe forms, but the presence of Howell-Jolly bodies and the specific cavernous blood gas findings are more indicative of SCD.
*Thrombotic thrombocytopenic purpura (TTP)*
- TTP is characterized by a pentad of symptoms: **fever, neurologic symptoms, renal dysfunction, microangiopathic hemolytic anemia, and thrombocytopenia**.
- This patient's presentation does not align with the typical features of TTP; specifically, his platelet count is normal, and there's no mention of microangiopathic changes or neurologic signs.
Question 37: A 12-year-old boy is brought to the physician because of fever, malaise, and a painful, itchy rash on the right shoulder for 2 weeks. The patient's mother says the boy's condition has worsened over the past 4 days. He has a history of atopic dermatitis. He has lived with his mother at several public shelters since she separated from his physically abusive father 2 months ago. His immunizations are up-to-date. There is cervical lymphadenopathy. Laboratory studies show no abnormalities. A photograph of the rash is shown. Which of the following is the most likely diagnosis?
A. Bed bug bites
B. Shingles
C. Stevens-Johnson syndrome
D. Eczema herpeticum (Correct Answer)
E. Nonbullous impetigo
Explanation: ***Eczema herpeticum***
- This diagnosis is highly likely given the patient's history of **atopic dermatitis**, which predisposes to widespread viral infections like **herpes simplex virus (HSV)**.
- The rash presents as **painful, itchy vesicles and punched-out erosions** over the existing eczematous skin, accompanied by fever, malaise, and cervical lymphadenopathy.
*Bed bug bites*
- Bed bug bites typically appear as **pruritic, erythematous papules or wheals** arranged in a linear pattern ("breakfast, lunch, and dinner") and are not associated with fever, malaise, or lymphadenopathy.
- While living in public shelters could increase exposure, the disseminated vesicular and erosive nature of this rash is inconsistent with bed bug bites.
*Shingles*
- Shingles (herpes zoster) presents as a **unilateral, dermatomal vesicular rash**, which is not seen here as the rash is widespread and not confined to a single dermatome.
- Although caused by a herpesvirus, the distribution and appearance differ significantly from the presented image.
*Stevens-Johnson syndrome*
- Stevens-Johnson syndrome (SJS) is a severe mucocutaneous reaction characterized by **widespread epidermal necrosis, targetoid lesions, and mucositis**, often triggered by medications.
- The image does not show typical targetoid lesions or extensive skin detachment characteristic of SJS.
*Nonbullous impetigo*
- Nonbullous impetigo presents with **honey-colored crusted lesions** typically around the nose and mouth, often starting as small vesicles.
- While it can be itchy, the extensive, disseminated, and primarily vesicular/erosive nature of the rash, along with systemic symptoms like fever and malaise, is not typical for impetigo.
Question 38: A 10-year-old girl is brought to the physician because of a severe, throbbing headache for 1 hour. The headache is located in the right frontotemporal region. It is her fifth such headache in the past 2 months. Her mother says that all the previous episodes started after soccer practice, following which the child would lock herself in her room, close the curtains, and sleep for a few hours. After waking up, the headache is either diminished or has stopped entirely. One month ago, the child was diagnosed with myopic vision and has been wearing glasses since. Her 4-year-old brother had herpetic gingivostomatitis 2 months ago. Her vital signs are within normal limits. Funduscopic examination is inconclusive because the child is uncooperative. The remainder of the examination shows no abnormalities. Which of the following is the most appropriate next step in management?
A. MRI of the brain
B. Acyclovir therapy
C. Dihydroergotamine therapy
D. Neuro-optometric assessment
E. Acetaminophen therapy (Correct Answer)
Explanation: ***Acetaminophen therapy***
- This patient presents with symptoms highly suggestive of **migraine**, including a throbbing, unilateral headache, photophobia (wanting to close curtains), and improvement with sleep. **Acetaminophen** or NSAIDs are recommended as first-line abortive therapy for mild to moderate migraine attacks in children.
- Given the classic presentation and absence of **red-flag symptoms** (e.g., focal neurological deficits, altered mental status, papilledema), conservative management with an analgesic is the most appropriate initial step.
*MRI of the brain*
- An MRI is generally not indicated as the initial step for typical migraine presentations, especially when there are no **neurological deficits** or atypical features.
- While it can rule out structural abnormalities, the clinical picture strongly points towards a primary headache disorder, making imaging unnecessary at this stage.
*Acyclovir therapy*
- **Acyclovir** is an antiviral medication used to treat herpes virus infections. There is no indication of active herpes simplex virus (HSV) infection causing her headaches.
- The brother's **herpetic gingivostomatitis** 2 months prior is likely an unrelated past event and does not warrant antiviral therapy for the patient's current symptoms.
*Dihydroergotamine therapy*
- **Dihydroergotamine** is a potent vasoconstrictor used for acute migraine treatment, typically for severe attacks refractory to simpler analgesics. It is usually reserved for older adolescents and adults due to potential side effects like nausea and vomiting.
- It is not considered a first-line treatment for migraine in a 10-year-old girl, especially given the likelihood that milder medications would be effective.
*Neuro-optometric assessment*
- The patient was recently prescribed glasses for **myopia**, and while vision problems can cause headaches (**eyestrain headaches**), the characteristics here (throbbing, unilateral, photophobia, improvement with sleep) are more consistent with migraine.
- A specialized neuro-optometric assessment is not indicated as the initial step, as the current episode aligns well with migraine, and her existing vision correction addresses simple refractive error.
Question 39: A 3-year-old girl is brought to the physician by her parents because of a barking cough, a raspy voice, and noisy breathing for the last 3 days. Five days ago, she had a low-grade fever and runny nose. She attends daycare. Her immunizations are up-to-date. Her temperature is 37.8°C (100°F) and respirations are 33/min. Physical examination shows supraclavicular retractions. There is a high-pitched sound present on inspiration. Examination of the throat shows erythema without exudates. Which of the following is the most likely location of the anatomic narrowing causing this patient's symptoms?
A. Bronchioles
B. Pharynx
C. Subglottic larynx (Correct Answer)
D. Distal trachea
E. Epiglottis
Explanation: ***Subglottic larynx***
- The patient's symptoms of **barking cough**, **raspy voice**, **stridor** (high-pitched inspiratory sound), and **supraclavicular retractions** are classic for **croup** (laryngotracheobronchitis), which is caused by inflammation and narrowing of the subglottic region of the larynx.
- The preceding low-grade fever and runny nose are typical of a viral upper respiratory infection, which commonly precedes croup.
*Bronchioles*
- Narrowing in the bronchioles typically causes **wheezing** (a high-pitched whistling sound on expiration) and **respiratory distress**, often seen in conditions like **bronchiolitis** or **asthma**.
- A barking cough and raspy voice are not characteristic symptoms of bronchiolar obstruction.
*Pharynx*
- Inflammation and narrowing of the pharynx primarily cause **sore throat**, **difficulty swallowing** (dysphagia), and sometimes **muffled voice**.
- It would not typically lead to a barking cough, stridor, or severe inspiratory distress.
*Distal trachea*
- While tracheal narrowing can cause stridor, the classic **barking cough** and **hoarseness** (raspy voice) are more specifically localized to the laryngeal area.
- Obstruction in the distal trachea would be less likely to affect voice quality as significantly as subglottic narrowing.
*Epiglottis*
- **Epiglottitis** presents as a rapidly progressive, life-threatening condition with **high fever**, **dysphagia**, **drooling**, and a **muffled "hot potato" voice**.
- The patient would typically appear toxic and prefer to sit in the **tripod position**, which is not described in this case, and her symptoms are less acute.
Question 40: A 4-year-old boy is brought to the physician by his father because of a 3-day history of generalized rash. The rash is not pruritic. He has no cough. He has had a fever and a sore throat for 4 days. He was born at term and has been healthy except for an episode of tonsillitis 6 months ago treated with erythromycin. His immunizations are up-to-date. His temperature is 38.5°C (101.3°F). Examination shows cervical lymphadenopathy. The tongue is bright red. There is tonsillar erythema without any exudate. A photograph of the rash is shown. Which of the following is the most appropriate next step in management?
A. Detection of antistreptolysin titer
B. Monospot test
C. Echocardiography
D. Rapid streptococcal antigen test (Correct Answer)
E. Measurement of C-reactive protein
Explanation: ***Rapid streptococcal antigen test***
- The patient presents with symptoms highly suggestive of **scarlet fever**, including fever, sore throat, cervical lymphadenopathy, and a bright red "strawberry" tongue, which are classic signs of **Group A Streptococcus (GAS)** infection.
- A **rapid streptococcal antigen test** is the most appropriate initial diagnostic step to confirm GAS infection, as it provides quick results to guide immediate antibiotic treatment and prevent complications like **acute rheumatic fever**.
*Detection of antistreptolysin titer*
- **Antistreptolysin O (ASO)** titers are used to confirm a recent or past GAS infection, particularly in cases of suspected **acute rheumatic fever** or **post-streptococcal glomerulonephritis**.
- This test is not suitable for acute diagnosis as titers rise slowly over weeks and would delay critical treatment for the current infection.
*Monospot test*
- The **Monospot test** is used to diagnose **infectious mononucleosis**, which is caused by the **Epstein-Barr virus**.
- While cervical lymphadenopathy and pharyngitis can occur in mononucleosis, the characteristic rash of scarlet fever and the bright red tongue are not typical features.
*Echocardiography*
- **Echocardiography** is performed to detect **cardiac complications**, such as valvular damage in **acute rheumatic fever**, which is a potential sequela of untreated GAS infection.
- It is not an initial diagnostic test but rather a follow-up investigation for complications, making it inappropriate as the first step in management.
*Elevated C-reactive protein*
- **C-reactive protein (CRP)** is a non-specific marker of **inflammation** and would likely be elevated in any significant infection, including scarlet fever.
- However, an elevated CRP does not specifically diagnose GAS infection or guide treatment.
