A 3-year-old boy presents to the emergency department with a fever and a rash. This morning the patient was irritable and had a fever which gradually worsened throughout the day. He also developed a rash prior to presentation. He was previously healthy and is not currently taking any medications. His temperature is 102.0°F (38.9°C), blood pressure is 90/50 mmHg, pulse is 160/min, respirations are 17/min, and oxygen saturation is 98% on room air. Physical exam is notable for a scarlatiniform rash with flaccid blisters that rupture easily, covering more than 60% of the patient’s body surface. The lesions surround the mouth but do not affect the mucosa, and palpation of the rash is painful. Which of the following is the most likely diagnosis?
Q52
A 4-year-old boy is brought to a pediatrician with a history of repeated episodes of right-ear symptoms, including irritability, fever, ear pain, and pulling at the ear, for the last 2 years. Each episode has been treated with an appropriate antibiotic for the recommended duration of time as prescribed by the pediatrician. The boy had experienced 3 episodes during his 3rd year of life and 5 episodes during the last year; the last episode occurred 2 months ago. There is no history of recurrent rhinosinusitis or nasal obstruction. On physical examination, vital signs are stable. Otoscopic examination of the right ear reveals a white tympanic membrane with decreased mobility. There is no erythema or bulging of the tympanic membrane. Which of the following interventions is most likely to be considered for further management of this child?
Q53
A 13-month-old female infant is brought to the pediatrician by her stepfather for irritability. He states that his daughter was crying through the night last night, but she didn’t want to eat and was inconsolable. This morning, she felt warm. The father also notes that she had dark, strong smelling urine on the last diaper change. The patient’s temperature is 101°F (38.3°C), blood pressure is 100/72 mmHg, pulse is 128/min, and respirations are 31/min with an oxygen saturation of 98% on room air. A urinalysis is obtained by catheterization, with results shown below:
Urine:
Protein: Negative
Glucose: Negative
White blood cell (WBC) count: 25/hpf
Bacteria: Many
Leukocyte esterase: Positive
Nitrites: Positive
In addition to antibiotics, which of the following should be part of the management of this patient’s condition?
Q54
An 8-year-old male presents to his pediatrician for a follow-up appointment for persistent fatigue. His mother reports that the patient's teacher called her yesterday to tell her that her son has been sitting out of recess every day for the past week. The patient first developed symptoms of fatigue and weakness several years ago and has returned to the physician with similar episodes once or twice a year. These episodes seem to sometimes be triggered by viral illnesses, but others have no identifiable trigger. The patient has been on daily folate supplementation with some improvement and requires red blood cell transfusions several times a year. He has an allergy to sulfa drugs, and last month he was treated with amoxicillin for an ear infection. His paternal grandfather was recently diagnosed with multiple myeloma, but his parents deny any other family history of hematologic conditions. His temperature is 99.0°F (37.2°C), blood pressure is 103/76 mmHg, pulse is 95/min, and respirations are 14/min. On physical exam, the patient is tired-appearing with conjunctival pallor. Laboratory tests performed during this visit reveal the following:
Leukocyte count: 9,700/mm³
Hemoglobin: 8.4 g/dL
Hematocrit: 27%
Mean corpuscular volume: 97 µm³
Mean corpuscular hemoglobin concentration (MCHC): 40% Hb/cell
Platelet count: 338,000/mm³
Reticulocyte index (RI): 4.2%
What is the most appropriate next step in management?
Q55
A 4-year-old boy is brought to the physician for the evaluation of fatigue since he returned from visiting family in South Africa one week ago. The day after he returned, he had fever, chills, and diffuse joint pain for 3 days. His symptoms improved with acetaminophen. He was born at term and has been healthy. His immunizations are up-to-date. His temperature is 37.6°C (99.68°F), pulse is 100/min, and blood pressure is 100/60 mm Hg. Examination shows conjunctival pallor. The remainder of the examination shows no abnormalities. Laboratory studies show:
Hemoglobin 10.8 g/dL
Mean corpuscular volume 68 μm3
Red cell distribution width 14% (N = 13%–15%)
Hemoglobin A2 6% (N < 3.5%)
A peripheral smear shows microcytic, hypochromic erythrocytes, some of which have a darkly stained center and peripheral rim, separated by a pale ring. Which of the following is the most appropriate next step in the management of this patient?
Q56
A 6-year-old boy is brought to the pediatrician by his parents. He has been coughing extensively over the last 5 days, especially during the night. His mother is worried that he may have developed asthma, like his uncle, because he has been wheezing, too. The boy usually plays without supervision, and he likes to explore. He has choked a few times in the past. He was born at 38 weeks of gestation via a normal vaginal delivery. He has no known allergies. Considering the likely etiology, what is the best approach to manage the condition of this child?
Q57
A 7-year-old boy is brought to the physician with a 2-day history of fever, chills, malaise, and a sore throat. He has otherwise been healthy and development is normal for his age. He takes no medications. His immunizations are up-to-date. His temperature is 38.4°C (101.4°F), pulse is 84/min, respirations are 16/min, and blood pressure is 121/71 mm Hg. Pulse oximetry shows an oxygen saturation of 100% on room air. Examination shows discrete 1–2-mm papulovesicular lesions on the posterior oropharynx and general erythema of the tonsils bilaterally. Which of the following conditions is most likely associated with the cause of this patient's findings?
Q58
An 11-year-old girl presents to the emergency department with a 12-hour history of severe abdominal pain. She says that the pain started near the middle of her abdomen and moved to the right lower quadrant after about 10 hours. Several hours after the pain started she also started experiencing nausea and loss of appetite. On presentation, her temperature is 102.5°F (39.2°C), blood pressure is 115/74 mmHg, pulse is 102/min, and respirations are 21/min. Physical exam reveals rebound tenderness in the right lower quadrant. Raising the patient's right leg with the knee flexed significantly increases the pain. Which of the following is the most common cause of this patient's symptoms in children?
Q59
A previously healthy 5-year-old boy is brought to the physician because of a 2-day history of itchy rash and swelling on his left lower leg. His mother says the boy complained of an insect bite while playing outdoors 3 days before the onset of the lesion. His immunizations are up-to-date. He is at the 50th percentile for height and the 85th percentile for weight. He has no known allergies. His temperature is 38.5°C (101.3°F), pulse is 120/min, and blood pressure is 95/60 mm Hg. The lower left leg is swollen and tender with erythema that has sharply defined borders. There is also a narrow red line with a raised border that extends from the lower leg to the groin. The remainder of the examination shows no abnormalities. Which of the following is the most likely cause of these findings?
Q60
A 9-year-old boy is brought to the emergency department by his mother. She says that he started having “a cold” yesterday, with cough and runny nose. This morning, he was complaining of discomfort with urination. His mother became extremely concerned when he passed bright-red urine with an apparent blood clot. The boy is otherwise healthy. Which of the following is the most likely underlying cause?
Infectious Disease US Medical PG Practice Questions and MCQs
Question 51: A 3-year-old boy presents to the emergency department with a fever and a rash. This morning the patient was irritable and had a fever which gradually worsened throughout the day. He also developed a rash prior to presentation. He was previously healthy and is not currently taking any medications. His temperature is 102.0°F (38.9°C), blood pressure is 90/50 mmHg, pulse is 160/min, respirations are 17/min, and oxygen saturation is 98% on room air. Physical exam is notable for a scarlatiniform rash with flaccid blisters that rupture easily, covering more than 60% of the patient’s body surface. The lesions surround the mouth but do not affect the mucosa, and palpation of the rash is painful. Which of the following is the most likely diagnosis?
A. Staphylococcal scalded skin syndrome (Correct Answer)
B. Toxic epidermal necrolysis
C. Toxic shock syndrome
D. Urticaria
E. Stevens Johnson syndrome
Explanation: ***Staphylococcal scalded skin syndrome***
- The presentation of a **fever**, **irritability**, and a **scarlatiniform rash with flaccid blisters** that rupture easily, especially with painful lesions and perioral involvement without mucosal lesions, is highly characteristic of **Staphylococcal scalded skin syndrome (SSSS)**.
- SSSS is caused by **exfoliative toxins** produced by *Staphylococcus aureus*, which target **desmoglein-1** in the skin, leading to widespread superficial blistering and epidermal sloughing.
*Toxic epidermal necrolysis*
- **Toxic epidermal necrolysis (TEN)** is a severe mucocutaneous reaction often triggered by **medications**, characterized by widespread **epidermal detachment (>30% BSA)** and **mucosal involvement**.
- TEN typically presents with full-thickness epidermal necrosis and severe systemic symptoms, often after drug exposure, which is not noted in this previously healthy, non-medicated child.
*Toxic shock syndrome*
- **Toxic shock syndrome (TSS)** is characterized by **fever**, **hypotension**, **diffuse erythematous rash**, and **multisystem organ dysfunction**.
- While a rash and fever are present, the hallmark **flaccid blistering** and **skin peeling** seen in SSSS is not typical for TSS; TSS rash is more often a blanching erythroderma.
*Urticaria*
- **Urticaria (hives)** presents as **pruritic, transient, raised erythematous wheals** that blanch with pressure.
- The rash in this patient is described as **scarlatiniform with flaccid blisters** and is painful, which is inconsistent with the typical appearance and symptoms of urticaria.
*Stevens Johnson syndrome*
- **Stevens-Johnson syndrome (SJS)** is a severe adverse drug reaction, similar to TEN but with less extensive skin involvement (**<10% BSA**), and is characterized by **erythematous macules**, **targetoid lesions**, and **mucosal involvement**.
- While blistering can occur, the widespread, painful, easily rupturing flaccid blisters without specific target lesions and prominent perioral involvement (without mucosal affection) point more strongly to SSSS over SJS.
Question 52: A 4-year-old boy is brought to a pediatrician with a history of repeated episodes of right-ear symptoms, including irritability, fever, ear pain, and pulling at the ear, for the last 2 years. Each episode has been treated with an appropriate antibiotic for the recommended duration of time as prescribed by the pediatrician. The boy had experienced 3 episodes during his 3rd year of life and 5 episodes during the last year; the last episode occurred 2 months ago. There is no history of recurrent rhinosinusitis or nasal obstruction. On physical examination, vital signs are stable. Otoscopic examination of the right ear reveals a white tympanic membrane with decreased mobility. There is no erythema or bulging of the tympanic membrane. Which of the following interventions is most likely to be considered for further management of this child?
A. Antibiotic prophylaxis with subtherapeutic dose of sulfonamide
B. Myringotomy without insertion of a tympanostomy tube
C. Myringotomy with insertion of a tympanostomy tube (Correct Answer)
D. Oral corticosteroids for 2 weeks
E. Adenoidectomy
Explanation: ***Myringotomy with insertion of a tympanostomy tube***
- This child has recurrent **acute otitis media (AOM)**, defined as three or more episodes in 6 months or four or more episodes in 12 months, with the last episode having occurred within the past 2 months. The physical exam finding of a **white tympanic membrane with decreased mobility** suggests **otitis media with effusion (OME)**, a common sequela of recurrent AOM. Insertion of tympanostomy tubes is indicated for recurrent AOM, especially when associated with OME, as it ventilates the middle ear and reduces recurrence.
- **Tympanostomy tube insertion** helps in draining middle ear fluid, equalizing pressure, and preventing further episodes of AOM and OME, thereby preserving **hearing** and preventing developmental delays.
*Antibiotic prophylaxis with subtherapeutic dose of sulfonamide*
- While antibiotic prophylaxis can be considered for recurrent AOM, it is less favored now due to concerns about **antibiotic resistance** and is generally reserved for situations where surgical intervention is not an option or as a bridge to surgery.
- The efficacy of prophylactic antibiotics is modest, and the current recommendation for this frequency of AOM tends towards **tympanostomy tube insertion**.
*Myringotomy without insertion of a tympanostomy tube*
- **Myringotomy** alone provides temporary relief by draining fluid, but the incision typically heals within days, leading to a recurrence of fluid accumulation and pressure issues.
- Without a tube, the benefits are short-lived, failing to address the underlying issue of ** Eustachian tube dysfunction** in the long term, which contributes to recurrent OME and AOM.
*Oral corticosteroids for 2 weeks*
- **Corticosteroids** are sometimes considered for OME to reduce inflammation, but their long-term efficacy in recurrent AOM with OME is limited and not a primary treatment option.
- Their use is generally reserved for specific cases and not recommended as a standalone treatment for recurrent AOM, especially given the established benefits of **tympanostomy tubes**.
*Adenoidectomy*
- **Adenoidectomy** is primarily considered for children with recurrent AOM only if they also have **nasal obstruction**, chronic rhinosinusitis, or evidence of adenoid hypertrophy contributing to Eustachian tube dysfunction, none of which are mentioned in this case.
- While adenoidectomy can be beneficial, it's typically an adjunct to or considered after **tympanostomy tube placement** in specific situations, and not the initial primary intervention for this presentation.
Question 53: A 13-month-old female infant is brought to the pediatrician by her stepfather for irritability. He states that his daughter was crying through the night last night, but she didn’t want to eat and was inconsolable. This morning, she felt warm. The father also notes that she had dark, strong smelling urine on the last diaper change. The patient’s temperature is 101°F (38.3°C), blood pressure is 100/72 mmHg, pulse is 128/min, and respirations are 31/min with an oxygen saturation of 98% on room air. A urinalysis is obtained by catheterization, with results shown below:
Urine:
Protein: Negative
Glucose: Negative
White blood cell (WBC) count: 25/hpf
Bacteria: Many
Leukocyte esterase: Positive
Nitrites: Positive
In addition to antibiotics, which of the following should be part of the management of this patient’s condition?
A. Voiding cystourethrogram
B. Renal ultrasound (Correct Answer)
C. Prophylactic antibiotics
D. Repeat urine culture in 3 weeks
E. Hospitalization
Explanation: ***Renal ultrasound***
- A **renal ultrasound** is recommended for all infants and young children (age 2 months to 2 years) after their first febrile **urinary tract infection (UTI)**.
- This imaging is crucial to evaluate for any underlying **structural kidney abnormalities** or **urinary tract obstructions** that could predispose to recurrent UTIs.
*Voiding cystourethrogram*
- A **voiding cystourethrogram (VCUG)** is typically reserved for patients after an abnormal renal ultrasound or for those with **recurrent UTIs** to assess for **vesicoureteral reflux (VUR)**.
- Doing a VCUG after the first febrile UTI in every child is not typically recommended as initial management in the absence of other risk factors or ultrasound findings.
*Prophylactic antibiotics*
- **Prophylactic antibiotics** are generally indicated for children with recurrent UTIs or confirmed **vesicoureteral reflux (VUR)** to prevent future infections and renal damage.
- They are not routinely recommended after a first febrile UTI without further evaluation, such as identifying an underlying anatomical anomaly.
*Repeat urine culture in 3 weeks*
- A **repeat urine culture** is usually performed only if the initial UTI symptoms do not resolve with treatment or if there are concerns about treatment failure or **resistant organisms**.
- It's not a standard component of follow-up for an uncomplicated first febrile UTI in a child who responds well to antibiotics.
*Hospitalization*
- **Hospitalization** for intravenous antibiotics is considered for infants with a UTI who appear **toxic**, are unable to tolerate oral intake, or are very young (under 2-3 months of age).
- While this infant has a fever, she does not exhibit signs of severe illness or toxicity that would immediately warrant hospitalization solely based on the provided information.
Question 54: An 8-year-old male presents to his pediatrician for a follow-up appointment for persistent fatigue. His mother reports that the patient's teacher called her yesterday to tell her that her son has been sitting out of recess every day for the past week. The patient first developed symptoms of fatigue and weakness several years ago and has returned to the physician with similar episodes once or twice a year. These episodes seem to sometimes be triggered by viral illnesses, but others have no identifiable trigger. The patient has been on daily folate supplementation with some improvement and requires red blood cell transfusions several times a year. He has an allergy to sulfa drugs, and last month he was treated with amoxicillin for an ear infection. His paternal grandfather was recently diagnosed with multiple myeloma, but his parents deny any other family history of hematologic conditions. His temperature is 99.0°F (37.2°C), blood pressure is 103/76 mmHg, pulse is 95/min, and respirations are 14/min. On physical exam, the patient is tired-appearing with conjunctival pallor. Laboratory tests performed during this visit reveal the following:
Leukocyte count: 9,700/mm³
Hemoglobin: 8.4 g/dL
Hematocrit: 27%
Mean corpuscular volume: 97 µm³
Mean corpuscular hemoglobin concentration (MCHC): 40% Hb/cell
Platelet count: 338,000/mm³
Reticulocyte index (RI): 4.2%
What is the most appropriate next step in management?
A. Genetic testing for hereditary spherocytosis
B. Osmotic fragility test
C. Direct antiglobulin test (Coombs test)
D. Eosin-5-maleimide binding test
E. Peripheral blood smear review (Correct Answer)
Explanation: ***Correct: Peripheral blood smear review***
- The patient presents with **chronic hemolytic anemia** with recurrent episodes since early childhood, requiring transfusions and folate supplementation
- Key laboratory findings include **elevated MCHC (40%)** and **elevated reticulocyte index (4.2%)**, indicating active hemolysis with appropriate bone marrow response
- **Elevated MCHC >36%** is highly specific for **hereditary spherocytosis (HS)**, as spherocytes have decreased surface area-to-volume ratio
- The **peripheral blood smear** is the most appropriate next step to identify **spherocytes**, which would confirm the suspected diagnosis and guide further testing
- While 75% of HS cases show autosomal dominant inheritance, **25% are de novo mutations**, explaining the absence of family history
- A blood smear showing spherocytes would then prompt confirmatory testing (osmotic fragility or eosin-5-maleimide binding test)
*Incorrect: Direct antiglobulin test (Coombs test)*
- The DAT detects antibodies or complement on red blood cell surfaces, used to diagnose **autoimmune hemolytic anemia (AIHA)**
- While AIHA can cause spherocytes, the clinical presentation here (childhood onset, chronic course, elevated MCHC, no clear immune triggers) is more consistent with hereditary spherocytosis
- DAT would be reasonable to **rule out AIHA**, but the peripheral smear is the more fundamental first step in evaluating unexplained hemolytic anemia
- AIHA in children is often acute and associated with infections or autoimmune conditions, not chronic recurrent episodes over years
*Incorrect: Genetic testing for hereditary spherocytosis*
- While HS is likely given the elevated MCHC and clinical presentation, **genetic testing is not the initial next step**
- Diagnosis of HS is typically made by **peripheral smear** showing spherocytes, followed by confirmatory tests (osmotic fragility or eosin-5-maleimide)
- Genetic testing is reserved for atypical cases or when other tests are inconclusive
*Incorrect: Osmotic fragility test*
- This test diagnoses hereditary spherocytosis by demonstrating increased fragility of spherocytes in hypotonic solutions
- However, it is a **confirmatory test** performed after spherocytes are identified on peripheral smear
- The blood smear is the more appropriate initial step before proceeding to specialized confirmatory testing
*Incorrect: Eosin-5-maleimide binding test*
- This flow cytometry test is highly sensitive and specific for HS, detecting red cell membrane protein deficiencies
- Like osmotic fragility, it is a **confirmatory test** used after clinical suspicion is established
- The peripheral blood smear remains the initial diagnostic step to identify spherocytes and guide further workup
Question 55: A 4-year-old boy is brought to the physician for the evaluation of fatigue since he returned from visiting family in South Africa one week ago. The day after he returned, he had fever, chills, and diffuse joint pain for 3 days. His symptoms improved with acetaminophen. He was born at term and has been healthy. His immunizations are up-to-date. His temperature is 37.6°C (99.68°F), pulse is 100/min, and blood pressure is 100/60 mm Hg. Examination shows conjunctival pallor. The remainder of the examination shows no abnormalities. Laboratory studies show:
Hemoglobin 10.8 g/dL
Mean corpuscular volume 68 μm3
Red cell distribution width 14% (N = 13%–15%)
Hemoglobin A2 6% (N < 3.5%)
A peripheral smear shows microcytic, hypochromic erythrocytes, some of which have a darkly stained center and peripheral rim, separated by a pale ring. Which of the following is the most appropriate next step in the management of this patient?
A. Oral pyridoxine
B. Iron supplementation
C. Reassurance (Correct Answer)
D. Folic acid therapy
E. Oral succimer
Explanation: ***Reassurance***
- The patient's presentation with **microcytic anemia**, elevated **Hemoglobin A2 (6%)**, and **target cells** on peripheral smear is highly suggestive of **beta-thalassemia trait** (minor). This genetic condition is more common in individuals with Mediterranean, African, Middle Eastern, or South Asian ancestry.
- Beta-thalassemia trait is a **benign condition** that does not typically require specific medical intervention. The mild anemia does not usually cause significant symptoms or complications, and patients can live normal lives without treatment.
- The elevated HbA2 is the key diagnostic finding that distinguishes thalassemia trait from iron deficiency anemia.
*Oral pyridoxine*
- **Pyridoxine (Vitamin B6)** supplementation is indicated for **sideroblastic anemia**, which can also cause microcytic anemia.
- However, sideroblastic anemia typically presents with **ring sideroblasts** in the bone marrow and does not have the characteristic elevated HbA2 seen in beta-thalassemia trait.
*Iron supplementation*
- **Iron deficiency anemia** is a common cause of microcytic hypochromic anemia, but it would present with **low ferritin** and **low or normal HbA2** (not elevated).
- In this case, iron supplementation would not be appropriate and could potentially be harmful due to the risk of **iron overload** in thalassemia syndromes, even in the trait form.
- The elevated HbA2 and normal RDW help distinguish thalassemia trait from iron deficiency.
*Folic acid therapy*
- **Folic acid** is primarily used in the management of **macrocytic anemias** or in conditions with high red blood cell turnover, such as **hemolytic anemias** or major thalassemia syndromes requiring chronic transfusions.
- It is not indicated for beta-thalassemia trait, which is a microcytic anemia with normal red blood cell turnover and no significant hemolysis.
*Oral succimer*
- **Succimer** is a chelating agent used to treat **lead poisoning**, which can cause microcytic anemia with basophilic stippling.
- There are no clinical or laboratory findings in this patient (e.g., **basophilic stippling**, developmental delays, neurological symptoms, abdominal pain) to suggest lead poisoning.
Question 56: A 6-year-old boy is brought to the pediatrician by his parents. He has been coughing extensively over the last 5 days, especially during the night. His mother is worried that he may have developed asthma, like his uncle, because he has been wheezing, too. The boy usually plays without supervision, and he likes to explore. He has choked a few times in the past. He was born at 38 weeks of gestation via a normal vaginal delivery. He has no known allergies. Considering the likely etiology, what is the best approach to manage the condition of this child?
A. Perform cricothyroidotomy
B. Encourage the use of a salbutamol inhaler
C. Perform bronchoscopy (Correct Answer)
D. Order a CT scan
E. Prescribe montelukast
Explanation: ***Perform bronchoscopy***
- The history of **choking episodes**, wheezing, and coughing in a 6-year-old child who "likes to explore" strongly suggests **foreign body aspiration**.
- **Bronchoscopy** is both diagnostic and therapeutic for removing an aspirated foreign body, which is the most appropriate initial management in this scenario.
*Perform cricothyroidotomy*
- **Cricothyroidotomy** is an emergency procedure used to establish an airway in cases of upper airway obstruction when intubation is impossible.
- While aspiration can cause airway obstruction, the presentation here (wheezing, coughing for days) is not immediately life-threatening and does not warrant this invasive emergency procedure as the primary management.
*Encourage the use of a salbutamol inhaler*
- **Salbutamol** (albuterol) is a short-acting beta-agonist used to relieve bronchospasm in conditions like asthma.
- While the child is wheezing, treating it as asthma without addressing the likely underlying foreign body aspiration delays appropriate diagnosis and treatment, and may not fully resolve symptoms caused by mechanical obstruction.
*Order a CT scan*
- A **CT scan** could potentially reveal a foreign body, but it exposes the child to radiation and is not the primary diagnostic or therapeutic tool for foreign body aspiration.
- Furthermore, it does not allow for removal of the foreign body, making bronchoscopy a more direct and efficient approach.
*Prescribe montelukast*
- **Montelukast** is a leukotriene receptor antagonist used for long-term control of asthma and allergic rhinitis.
- It would be ineffective in resolving symptoms caused by a foreign body aspiration and would delay the necessary intervention.
Question 57: A 7-year-old boy is brought to the physician with a 2-day history of fever, chills, malaise, and a sore throat. He has otherwise been healthy and development is normal for his age. He takes no medications. His immunizations are up-to-date. His temperature is 38.4°C (101.4°F), pulse is 84/min, respirations are 16/min, and blood pressure is 121/71 mm Hg. Pulse oximetry shows an oxygen saturation of 100% on room air. Examination shows discrete 1–2-mm papulovesicular lesions on the posterior oropharynx and general erythema of the tonsils bilaterally. Which of the following conditions is most likely associated with the cause of this patient's findings?
A. Rheumatic fever
B. Burkitt lymphoma
C. Infective endocarditis
D. Hand, foot, and mouth disease (Correct Answer)
E. Herpetic whitlow
Explanation: ***Hand, foot, and mouth disease***
- The patient's symptoms of **fever**, **sore throat**, and particularly the presence of **papulovesicular lesions on the posterior oropharynx** (also known as herpangina) are classic signs of **Coxsackievirus infection**, which typically causes hand, foot, and mouth disease.
- While the characteristic lesions on hands and feet are not mentioned, **herpangina alone** is a common presentation of Coxsackievirus, especially in children, and the oral lesions match the description.
*Rheumatic fever*
- This is a **delayed autoimmune complication** of Group A Streptococcus (GAS) pharyngitis and would typically present weeks after an untreated streptococcal infection, not with acute viral-like symptoms and vesicular lesions.
- Clinical manifestations include **arthritis**, **carditis**, **chorea**, and subcutaneous nodules, which are not described here.
*Burkitt lymphoma*
- This is a **highly aggressive B-cell non-Hodgkin lymphoma** and does not present with acute fever, sore throat, and vesicular oral lesions.
- It usually manifests as a rapidly growing mass, often in the **jaw or abdomen**, depending on the type (endemic vs. sporadic).
*Infective endocarditis*
- This is an infection of the **endocardial surface of the heart** and typically presents with a persistent fever, new or changing heart murmur, and systemic embolic phenomena.
- Oral lesions as described are not a primary feature, and the patient's acute presentation points away from this diagnosis.
*Herpetic whitlow*
- This is a **herpes simplex virus infection of the finger or toe**, characterized by painful, vesicular lesions typically on the digits.
- It does not present as a generalized febrile illness with **oropharyngeal papulovesicular lesions** as the primary complaint.
Question 58: An 11-year-old girl presents to the emergency department with a 12-hour history of severe abdominal pain. She says that the pain started near the middle of her abdomen and moved to the right lower quadrant after about 10 hours. Several hours after the pain started she also started experiencing nausea and loss of appetite. On presentation, her temperature is 102.5°F (39.2°C), blood pressure is 115/74 mmHg, pulse is 102/min, and respirations are 21/min. Physical exam reveals rebound tenderness in the right lower quadrant. Raising the patient's right leg with the knee flexed significantly increases the pain. Which of the following is the most common cause of this patient's symptoms in children?
A. Fecalith obstruction
B. Meckel diverticulum
C. Parasitic infection
D. Ingestion of indigestible object
E. Lymphoid hyperplasia (Correct Answer)
Explanation: ***Lymphoid hyperplasia***
- **Lymphoid tissue hyperplasia** in the appendix, often triggered by a viral infection of the gastrointestinal tract, is the **most common cause of appendicitis in children**.
- This enlargement obstructs the appendiceal lumen, leading to inflammation, bacterial overgrowth, and symptoms like **periumbilical pain migrating to the right lower quadrant**, fever, nausea, and signs of peritoneal irritation (e.g., rebound tenderness, positive psoas sign).
*Fecalith obstruction*
- While **fecaliths** are the most common cause of appendiceal obstruction in **adults**, they are less frequent in children compared to lymphoid hyperplasia.
- An obstruction by a fecalith can also lead to appendicitis, but it's not the primary mechanism in the pediatric population.
*Meckel diverticulum*
- A **Meckel diverticulum** is a congenital anomaly that can cause symptoms resembling appendicitis if it becomes inflamed, but it is a **less common cause** of acute abdominal pain than appendicitis itself.
- Inflammation of a Meckel diverticulum is known as Meckel's diverticulitis and would typically present in a similar fashion to appendicitis, but the incidence is lower.
*Parasitic infection*
- **Parasitic infections** can cause abdominal pain and other gastrointestinal symptoms, but they are a **rare cause of acute appendicitis**.
- While parasites like *Ascaris lumbricoides* can sometimes obstruct the appendix, it is not a common etiology for the presentation described.
*Ingestion of indigestible object*
- The **ingestion of indigestible objects** (e.g., foreign bodies) is a **very rare cause of acute appendicitis**.
- Though foreign bodies can theoretically lodge in the appendix and cause obstruction, it accounts for a minute percentage of appendicitis cases.
Question 59: A previously healthy 5-year-old boy is brought to the physician because of a 2-day history of itchy rash and swelling on his left lower leg. His mother says the boy complained of an insect bite while playing outdoors 3 days before the onset of the lesion. His immunizations are up-to-date. He is at the 50th percentile for height and the 85th percentile for weight. He has no known allergies. His temperature is 38.5°C (101.3°F), pulse is 120/min, and blood pressure is 95/60 mm Hg. The lower left leg is swollen and tender with erythema that has sharply defined borders. There is also a narrow red line with a raised border that extends from the lower leg to the groin. The remainder of the examination shows no abnormalities. Which of the following is the most likely cause of these findings?
A. Streptococcus pyogenes infection (Correct Answer)
B. Sporothrix schenckii infection
C. Contact dermatitis
D. Staphylococcus aureus infection
E. Vasculitis
Explanation: ***Streptococcus pyogenes infection***
- The presentation of a rapidly spreading **erythema with sharply defined borders** and a **red streak (lymphangitis)** extending to the groin is characteristic of **cellulitis or erysipelas**, commonly caused by *Streptococcus pyogenes*.
- A **recent insect bite** or minor trauma provides a portal of entry for this bacterial infection, especially in active children.
*Sporothrix schenckii infection*
- This typically causes **sporotrichosis**, characterized by a **papule or nodule at the site of inoculation** (e.g., from thorns or sphagnum moss) that slowly ulcerates and can spread along lymphatic channels, forming secondary nodules.
- While it can cause lymphatic spread, the rapid onset, fever, and classic erysipelas-like appearance are less typical for *Sporothrix schenckii*.
*Contact dermatitis*
- This is an **inflammatory skin reaction** to an allergen or irritant, presenting with a pruritic rash, erythema, and sometimes vesicles or blisters, but it usually **lacks systemic symptoms** like fever and rarely presents with distinct **lymphangitic streaking**.
- The sharply defined, rapidly spreading erythema more strongly suggests an infectious process than an allergic reaction.
*Staphylococcus aureus infection*
- While *Staphylococcus aureus* is a common cause of skin infections, it typically presents as **folliculitis, furuncles, carbuncles, or abscesses**, often with **purulent drainage** and less commonly with the rapidly spreading, well-demarcated erythema characteristic of erysipelas caused by *Streptococcus pyogenes*.
- Although it can cause cellulitis, the strong lymphatic streaking and erysipelas-like appearance point more towards streptococcal involvement.
*Vasculitis*
- Vasculitis involves **inflammation of blood vessels** and can manifest with a variety of skin lesions, such as **purpura, livedo reticularis, or nodules**, but it **does not typically present with a red streaking pattern of lymphangitis** or the rapidly progressive, sharply bordered erythema seen in this case.
- Systemic vasculitis would also likely involve other organ systems.
Question 60: A 9-year-old boy is brought to the emergency department by his mother. She says that he started having “a cold” yesterday, with cough and runny nose. This morning, he was complaining of discomfort with urination. His mother became extremely concerned when he passed bright-red urine with an apparent blood clot. The boy is otherwise healthy. Which of the following is the most likely underlying cause?
A. BK virus infection
B. E. coli infection
C. CMV infection
D. Adenovirus infection (Correct Answer)
E. Toxin exposure
Explanation: ***Adenovirus infection***
- **Adenovirus** is a common cause of **hemorrhagic cystitis** in children, often following a mild upper respiratory tract infection.
- Symptoms like **dysuria**, **hematuria** with blood clots, and a preceding "cold" are classic presentations of adenovirus-induced cystitis.
*BK virus infection*
- **BK virus** is typically associated with **hemorrhagic cystitis** in **immunocompromised individuals**, particularly after bone marrow or kidney transplantation.
- The patient described is a healthy 9-year-old, making BK virus a less likely primary cause in this context.
*E. coli infection*
- **_E. coli_** is the most common cause of **urinary tract infections (UTIs)**, often presenting with dysuria, frequency, and urgency.
- While _E. coli_ can cause hematuria, the presence of **gross hematuria with blood clots** following a viral prodrome is more characteristic of viral hemorrhagic cystitis, especially due to adenovirus.
*CMV infection*
- **CMV (cytomegalovirus) infection** can cause various symptoms, but it is primarily known for causing serious disease in **immunocompromised individuals** or congenital infections.
- While CMV can rarely cause hemorrhagic cystitis, it is much less common than adenovirus in healthy children and not typically associated with the described acute presentation.
*Toxin exposure*
- **Toxin exposure**, such as certain chemicals or drugs (e.g., cyclophosphamide), can induce **hemorrhagic cystitis**.
- However, there is **no history of toxin exposure** in the clinical vignette, and the preceding "cold" symptoms strongly point towards an infectious cause.
