A 2-year-old boy is brought to the physician by his mother because of fever and left ear pain for the past 3 days. He has also been frequently rubbing his left ear since he woke up in the morning. He has a history of atopic dermatitis, and his mother is concerned that his symptoms may be caused by him itching at night. She says that he has not been having many flare-ups lately; the latest flare-up subsided in time for his second birthday party, which he celebrated at a swimming pool 1 week ago. Six months ago, he had an episode of urticaria following antibiotic treatment for pharyngitis. He takes no medications. His temperature is 38.5°C (101.3°F), pulse is 110/min, respirations are 25/min, and blood pressure is 90/50 mm Hg. Otoscopy shows an opaque, bulging tympanic membrane. Which of the following is the most appropriate next step in management?
Q152
A 7-year-old boy is brought to a new pediatrician to establish care. He presents with a history of extensive eczema, recurrent respiratory, skin, and gastrointestinal infections, and significant thrombocytopenia. 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. Given this classic grouping of clinical symptoms in a patient of this age, which of the following represents the most likely underlying medical condition?
Q153
A 2-year-old boy is brought to the physician by his parents for the evaluation of an unusual cough, a raspy voice, and noisy breathing for the last 2 days. During this time, the symptoms have always occurred in the late evening. The parents also report that prior to the onset of these symptoms, their son had a low-grade fever and a runny nose for 2 days. He attends daycare. His immunizations are up-to-date. His temperature is 37.8°C (100°F) and respirations are 33/min. Physical examination shows supraclavicular retractions. There is a high-pitched breath sound on inspiration. Which of the following is the most likely location of the abnormality?
Q154
A father brings in his 7-year-old twin sons because they have a diffuse rash. They have several papules, vesicles, pustules, and crusts on their scalps, torso, and limbs. The skin lesions are pruritic. Other than that, the boys appear to be well. The father reports that several children in school have a similar rash. The family recently returned from a beach vacation but have not traveled internationally. Both boys have stable vital signs within normal limits. What is the most common complication of the infection the boys appear to have?
Q155
An 8-month-old boy is brought to the emergency department by his mother. She is concerned that her son has had intermittent periods of severe abdominal pain over the past several days that has been associated with emesis and "currant jelly" stool. Of note, the family lives in a rural part of the state, requiring a 2 hour drive to the nearest hospital. He currently appears to be in significant pain and has vomited twice in the past hour. On physical examination, a sausage-shaped mass is noted on palpation of the right upper quadrant of the abdomen. Ultrasound of the abdomen was consistent with a diagnosis of intussusception. An air-contrast barium enema was performed, which confirmed the diagnosis and also successfully reduced the intussusception. Which of the following is the next best step in the management of this patient?
Q156
A 3-year-old girl is brought to the emergency department by her parents with sudden onset shortness of breath. They tell the emergency physician that their daughter was lying on the bed watching television when she suddenly began gasping for air. They observed a bowl of peanuts lying next to her when they grabbed her up and brought her to the emergency department. Her respirations are 25/min, the pulse is 100/min and the blood pressure is 90/65 mm Hg. The physical findings as of now are apparently normal. She is started on oxygen and is sent in for a chest X-ray. Based on her history and physical exam findings, the cause of her current symptoms would be seen on the X-ray at which of the following sites?
Q157
A previously healthy 9-year-old, Caucasian girl presents to your office with severe abdominal pain. Her mother also mentions that she has been urinating significantly less lately. History from the mother reveals that the girl suffers from acne vulgaris, mild scoliosis, and had a bout of diarrhea 3 days ago after a family barbecue. Lab work is done and is notable for a platelet count of 97,000 with a normal PT and PTT. The young girl appears dehydrated, yet her serum electrolyte levels are normal. What is the most likely etiology of this girl's urinary symptoms?
Q158
A 7-year-old boy is brought to the physician for the evaluation of sore throat for the past 2 days. During this period, he has had intermittent nausea and has vomited once. The patient has no cough, hoarseness, or rhinorrhea. He had similar symptoms at the age of 5 years that resolved spontaneously. He is otherwise healthy. His temperature is 37.9°C (100.2°F), pulse is 85/min, and blood pressure is 108/70 mm Hg. Head and neck examination shows an erythematous pharynx with grayish exudates overlying the palatine tonsils. There is no lymphadenopathy. Rapid antigen detection test for group A streptococci is negative. Which of the following is most appropriate next step in the management of this patient?
Q159
A previously healthy 2-year-old girl is brought to the physician by her mother after she noticed multiple painless, nonpruritic papules on her abdomen. The child attends daycare three times per week, and this past week one child was reported to have similar lesions. Her immunizations are up-to-date. Her brother had chickenpox one month ago. She is at the 50th percentile for height and the 60th percentile for weight. Vital signs are within normal limits. Examination shows several skin-colored, nontender, pearly papules with central umbilication on the abdomen and extremities. The remainder of the examination shows no abnormalities. Which of the following is the most likely diagnosis?
Q160
A 9-month-old boy is brought to the physician because of increased irritability, continual crying, and fever for 1 day. His mother has noticed that he refuses to lie down on his right side and keeps tugging at his right ear. One week ago, he had a runny nose that has since improved. He was born at term and has been otherwise healthy. He was exclusively breastfed until 2 months of age and is currently bottle-fed with some solid foods introduced. He has been attending a daycare center for the past 5 months. His temperature is 38.4°C (101.1°F) and pulse is 144/min. Otoscopic examination in this child is most likely to show which of the following?
Infectious Disease US Medical PG Practice Questions and MCQs
Question 151: A 2-year-old boy is brought to the physician by his mother because of fever and left ear pain for the past 3 days. He has also been frequently rubbing his left ear since he woke up in the morning. He has a history of atopic dermatitis, and his mother is concerned that his symptoms may be caused by him itching at night. She says that he has not been having many flare-ups lately; the latest flare-up subsided in time for his second birthday party, which he celebrated at a swimming pool 1 week ago. Six months ago, he had an episode of urticaria following antibiotic treatment for pharyngitis. He takes no medications. His temperature is 38.5°C (101.3°F), pulse is 110/min, respirations are 25/min, and blood pressure is 90/50 mm Hg. Otoscopy shows an opaque, bulging tympanic membrane. Which of the following is the most appropriate next step in management?
A. Tympanocentesis
B. Topical hydrocortisone and gentamicin eardrops
C. Otic ofloxacin therapy
D. Oral azithromycin (Correct Answer)
E. Tympanostomy tube placement
Explanation: ***Oral azithromycin***
- The patient presents with classic symptoms of **acute otitis media (AOM)**, including fever, ear pain, and an opaque, bulging tympanic membrane. Given his recent history of urticaria following antibiotic treatment for pharyngitis, **azithromycin** is an appropriate choice due to its effectiveness against common AOM pathogens and its use in patients with **penicillin allergies**.
- This patient is generally healthy, above 6 months of age, and not severely ill, making oral antibiotic therapy the standard and most appropriate first-line treatment.
*Tympanocentesis*
- This procedure involves puncturing the tympanic membrane to aspirate middle ear fluid for culture and relief of pressure, and is typically reserved for **severely ill children**, those with **immunocompromise**, or in cases of **treatment failure** on empiric antibiotics, which is not indicated here.
- It is an **invasive procedure** and not a first-line treatment for uncomplicated acute otitis media.
*Topical hydrocortisone and gentamicin eardrops*
- **Topical corticosteroids** are used to reduce inflammation in conditions like **otitis externa**, while **gentamicin** is an aminoglycoside antibiotic primarily used for topical infections.
- These eardrops are inappropriate for **acute otitis media (AOM)** because the infection is in the middle ear, behind an intact tympanic membrane, and thus topical medications cannot reach the site of infection.
*Otic ofloxacin therapy*
- **Otic fluoroquinolone drops** like ofloxacin are primarily used for **otitis externa** or in cases of **perforated tympanic membranes** with otitis media, as they can directly reach the infection in the outer ear canal or middle ear.
- They are not indicated as a primary treatment for acute otitis media with an **intact, bulging tympanic membrane**, as the drops would not be able to reach the middle ear.
*Tympanostomy tube placement*
- This surgical procedure involves placing tubes through the tympanic membrane to **ventilate the middle ear** and prevent recurrent infections or persistent effusions.
- It is typically considered for **recurrent acute otitis media** (e.g., three episodes in 6 months or four in a year with at least one in the preceding 6 months) or **persistent otitis media with effusion** leading to hearing loss, neither of which is the case for this patient's first presentation.
Question 152: A 7-year-old boy is brought to a new pediatrician to establish care. He presents with a history of extensive eczema, recurrent respiratory, skin, and gastrointestinal infections, and significant thrombocytopenia. 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. Given this classic grouping of clinical symptoms in a patient of this age, which of the following represents the most likely underlying medical condition?
A. Hyper-IgE disease
B. Chediak-Higashi syndrome
C. Ataxia-telangiectasia
D. Severe combined immunodeficiency syndrome
E. Wiskott-Aldrich syndrome (Correct Answer)
Explanation: ***Wiskott-Aldrich syndrome***
- This syndrome is characterized by the classic triad of **eczema**, **thrombocytopenia** (often with small platelets), and **recurrent infections** (respiratory, skin, gastrointestinal).
- It is an X-linked recessive disorder affecting the immune system and platelet function.
*Hyper-IgE disease*
- This syndrome is characterized by extremely **high IgE levels**, **eczema**, **recurrent skin abscesses** (often staphylococcal), and often **skeletal abnormalities**; however, it does not typically include thrombocytopenia.
- While eczema and infections are present, the absence of thrombocytopenia makes it less likely than Wiskott-Aldrich syndrome.
*Chediak-Higashi syndrome*
- This is an immunodeficiency disorder characterized by **oculocutaneous albinism**, **recurrent pyogenic infections**, and **neuropathy**, none of which are described in the patient.
- While it involves recurrent infections, the specific features like albinism and neuropathy are crucial distinguishing factors that are absent here.
*Ataxia-telangiectasia*
- This condition is characterized by **ataxia** (neurological symptoms), **telangiectasias** (spider veins), and recurrent infections due to immunodeficiency.
- The patient's presentation does not include ataxia or telangiectasias, and he is meeting all developmental milestones, making this diagnosis less likely.
*Severe combined immunodeficiency syndrome*
- SCID presents as a severe, life-threatening immunodeficiency in infancy, with **failure to thrive**, **chronic diarrhea**, and **recurrent severe infections** (bacterial, viral, fungal, opportunistic).
- While it involves recurrent infections, it typically manifests much earlier and more severely, often without the specific triad of eczema and thrombocytopenia in the manner described.
Question 153: A 2-year-old boy is brought to the physician by his parents for the evaluation of an unusual cough, a raspy voice, and noisy breathing for the last 2 days. During this time, the symptoms have always occurred in the late evening. The parents also report that prior to the onset of these symptoms, their son had a low-grade fever and a runny nose for 2 days. He attends daycare. His immunizations are up-to-date. His temperature is 37.8°C (100°F) and respirations are 33/min. Physical examination shows supraclavicular retractions. There is a high-pitched breath sound on inspiration. Which of the following is the most likely location of the abnormality?
A. Epiglottis
B. Subglottic larynx (Correct Answer)
C. Supraglottic larynx
D. Bronchioles
E. Bronchi
Explanation: ***Subglottic larynx***
- The symptoms of **barking cough**, **raspy voice**, and **inspiratory stridor** (high-pitched breath sound on inspiration) are classic for **croup (laryngotracheobronchitis)**.
- Croup is characterized by **inflammation and edema of the subglottic larynx**, which is the narrowest part of the pediatric airway, leading to obstruction.
*Epiglottis*
- **Epiglottitis** typically presents with a sudden onset of **high fever**, **dysphagia**, drooling, and a muffled voice, often without a preceding viral prodrome.
- Patients with epiglottitis usually appear severely ill and may adopt a **tripod position** to maximize airway opening, which is not described here.
*Supraglottic larynx*
- While inflammation can occur here, severe **supraglottic edema** leading to the described symptoms (especially the barking cough) is uncommon in typical croup.
- Conditions affecting the supraglottic area, such as **supraglottitis**, often cause a muffled voice and severe dysphagia, rather than a raspy voice and classic croupy cough.
*Bronchioles*
- Inflammation of the bronchioles typically causes **bronchiolitis**, characterized by **wheezing**, tachypnea, and increased work of breathing due to small airway obstruction.
- This condition does not typically present with a **barking cough** or **stridor**, which are indicative of upper airway obstruction.
*Bronchi*
- Inflammation of the bronchi (**bronchitis**) primarily causes a **cough** (often productive) and sometimes wheezing or rhonchi.
- It does not typically result in **stridor** or a **raspy voice**, as these symptoms arise from laryngeal or tracheal involvement.
Question 154: A father brings in his 7-year-old twin sons because they have a diffuse rash. They have several papules, vesicles, pustules, and crusts on their scalps, torso, and limbs. The skin lesions are pruritic. Other than that, the boys appear to be well. The father reports that several children in school have a similar rash. The family recently returned from a beach vacation but have not traveled internationally. Both boys have stable vital signs within normal limits. What is the most common complication of the infection the boys appear to have?
A. Encephalitis
B. Hepatitis
C. Bacterial superinfection of skin lesions (Correct Answer)
D. Cerebellar ataxia
E. Pneumonia
Explanation: ***Bacterial superinfection of skin lesions***
- The description of a **pruritic rash** with **papules, vesicles, pustules, and crusts** in various stages of healing, especially in young children with school exposure, is classic for **varicella (chickenpox)**.
- The most common complication of chickenpox is **secondary bacterial infection** of the skin lesions, often caused by *Staphylococcus aureus* or *Streptococcus pyogenes*, due to scratching compromising the skin barrier.
*Encephalitis*
- **Encephalitis** is a rare but severe neurological complication of varicella, occurring in less than 0.1% of cases.
- While possible, it is far less common than bacterial superinfection of the skin.
*Hepatitis*
- **Hepatitis** can occur with varicella, particularly in immunocompromised individuals or adults, but it is rare and not considered the most common complication in healthy children.
- The symptoms described do not suggest liver involvement.
*Cerebellar ataxia*
- **Cerebellar ataxia** is a known neurological complication of varicella, typically occurring acutely after the rash resolves.
- While it is a recognized complication, it is less common than bacterial skin infections and is usually self-limiting.
*Pneumonia*
- **Varicella pneumonia** is a serious complication, especially in adults, immunocompromised individuals, and neonates.
- In healthy children, however, it is much less common than bacterial superinfection of the skin lesions.
Question 155: An 8-month-old boy is brought to the emergency department by his mother. She is concerned that her son has had intermittent periods of severe abdominal pain over the past several days that has been associated with emesis and "currant jelly" stool. Of note, the family lives in a rural part of the state, requiring a 2 hour drive to the nearest hospital. He currently appears to be in significant pain and has vomited twice in the past hour. On physical examination, a sausage-shaped mass is noted on palpation of the right upper quadrant of the abdomen. Ultrasound of the abdomen was consistent with a diagnosis of intussusception. An air-contrast barium enema was performed, which confirmed the diagnosis and also successfully reduced the intussusception. Which of the following is the next best step in the management of this patient?
A. Keep patient NPO and initiate work-up to identify lead-point
B. Admit to hospital for 24 hour observation for complications and/or recurrence (Correct Answer)
C. Pursue urgent surgical reduction with resection of necrotic segments of bowel
D. Repeat barium enema q6 hrs to monitor for recurrence
E. Discharge to home with follow-up in 3 weeks in an outpatient pediatric gastroenterology clinic
Explanation: ***Admit to hospital for 24 hour observation for complications and/or recurrence***
- Following successful non-operative reduction of intussusception, there is a risk of **recurrence** (approximately 5-10%) and potential for **perforation** or other delayed complications, necessitating close hospital observation.
- The patient's presentation with significant pain and vomiting, coupled with the long travel time to the hospital, further supports the need for **hospital admission** to monitor for stability and potential early recurrence.
*Keep patient NPO and initiate work-up to identify lead-point*
- While keeping the patient NPO (nil per os) might be appropriate initially, a work-up for a **lead point** is generally performed if there are multiple recurrences or in older children, as most intussusceptions in infants are idiopathic.
- Doing this immediately without observation can delay identification of recurrence and prompt intervention.
*Pursue urgent surgical reduction with resection of necrotic segments of bowel*
- Surgical reduction is indicated if **non-operative reduction fails**, if there are signs of **perforation**, diffuse peritonitis, or if there is clinical evidence of **bowel necrosis**.
- Since the intussusception was successfully reduced by air-contrast enema and there are no signs of perforation or necrosis currently, urgent surgery is not the immediate next step.
*Repeat barium enema q6 hrs to monitor for recurrence*
- Repeated enemas carry risks such as **radiation exposure** and potential for perforation, and are not a standard monitoring strategy for recurrence.
- Clinical observation and physical examination are generally sufficient for monitoring during the initial 24-hour period.
*Discharge to home with follow-up in 3 weeks in an outpatient pediatric gastroenterology clinic*
- Discharging the patient home so soon after reduction is unsafe due to the significant risk of **early recurrence** (especially within the first 24-48 hours) or development of complications.
- A follow-up in 3 weeks is too delayed for immediate post-reduction concerns.
Question 156: A 3-year-old girl is brought to the emergency department by her parents with sudden onset shortness of breath. They tell the emergency physician that their daughter was lying on the bed watching television when she suddenly began gasping for air. They observed a bowl of peanuts lying next to her when they grabbed her up and brought her to the emergency department. Her respirations are 25/min, the pulse is 100/min and the blood pressure is 90/65 mm Hg. The physical findings as of now are apparently normal. She is started on oxygen and is sent in for a chest X-ray. Based on her history and physical exam findings, the cause of her current symptoms would be seen on the X-ray at which of the following sites?
A. The superior segment of the right lower lobe
B. The posterior segment of the right lower lobe (Correct Answer)
C. The lingula of the left upper lobe
D. The apical segment of the right upper lobe
E. The apical segment of the left upper lobe
Explanation: ***The posterior segment of the right lower lobe***
- This is the **most common site for foreign body aspiration in a supine or lying down position** due to gravity and anatomical orientation.
- The history explicitly states the child was **"lying on the bed watching television"** when aspiration occurred, making the **posterior segment of the right lower lobe** the most gravity-dependent and therefore most likely location.
- The **right main bronchus** is wider, shorter, and more vertical than the left, making the right lung the predominant site for aspiration, and in supine position, the posterior segment is most dependent [1, 2].
*The superior segment of the right lower lobe*
- The **superior segment of the right lower lobe** is the most common site for aspiration in **upright, standing, or semi-upright positions**, not in a supine position.
- Since the child was lying down (supine), gravity would direct the aspirated peanut to the **posterior segment** rather than the superior segment.
- This would be correct if the child had aspirated while sitting upright.
*The lingula of the left upper lobe*
- The **lingula** is an uncommon site for aspiration because the **left main bronchus** has a sharper angle and smaller diameter compared to the right bronchus [2].
- The anatomical differences make aspiration into the right lung significantly more common than the left lung [2].
- The lingula is not a gravity-dependent area in the supine position.
*The apical segment of the right upper lobe*
- The **apical segment of the right upper lobe** is associated with aspiration when the patient is in **Trendelenburg position** (head lower than feet) or in extreme head-down positions.
- The described scenario of lying flat on the bed does not favor aspiration into apical segments, which are non-gravity-dependent in supine position.
- This location would be contra-gravity in the supine position.
*The apical segment of the left upper lobe*
- Aspiration into the **left upper lobe** is less frequent than the right lung due to the sharper angle of the left main bronchus [2].
- The **apical segment** would require head-down positioning (Trendelenburg) that is not described in this clinical scenario.
- This is the least likely location given both the supine position and left-sided anatomy.
Question 157: A previously healthy 9-year-old, Caucasian girl presents to your office with severe abdominal pain. Her mother also mentions that she has been urinating significantly less lately. History from the mother reveals that the girl suffers from acne vulgaris, mild scoliosis, and had a bout of diarrhea 3 days ago after a family barbecue. Lab work is done and is notable for a platelet count of 97,000 with a normal PT and PTT. The young girl appears dehydrated, yet her serum electrolyte levels are normal. What is the most likely etiology of this girl's urinary symptoms?
A. Hypothalamic dysfunction
B. Shiga-like toxin production from EHEC (Correct Answer)
C. Shiga toxin production from Shigella
D. Surreptitious laxative use
E. Toxic shock syndrome
Explanation: ***Shiga-like toxin production from EHEC***
- The combination of recent **diarrhea** (suggesting a gastrointestinal infection), severe **abdominal pain**, decreased urination (pointing to **renal impairment**), and **thrombocytopenia** (platelet count of 97,000) in a previously healthy child strongly indicates **Hemolytic Uremic Syndrome (HUS)**.
- HUS is characterized by the classic triad: **microangiopathic hemolytic anemia** (which would show schistocytes on blood smear), **thrombocytopenia**, and **acute kidney injury**.
- **Enterohemorrhagic E. coli (EHEC)**, particularly serotype O157:H7, is the most common cause of HUS through its production of **Shiga-like toxins**.
- The history of a family barbecue strongly suggests contaminated food (typically undercooked ground beef) as the source.
*Hypothalamic dysfunction*
- Hypothalamic dysfunction might cause symptoms like **polyuria** (due to diabetes insipidus) or hormonal imbalances, but it does not explain the **diarrhea**, **abdominal pain**, and significant **thrombocytopenia**.
- It would not lead to an acute presentation of **renal failure** and platelet abnormalities as seen in this case.
*Shiga toxin production from Shigella*
- While *Shigella dysenteriae* also produces a **Shiga toxin** and can cause HUS, the question mentions a family barbecue, which is a classic setting for **EHEC** transmission from contaminated food (e.g., undercooked meat).
- *Shigella* infections typically present with more severe, **bloody diarrhea** and are less commonly associated with foodborne outbreaks from barbecues compared to EHEC.
*Surreptitious laxative use*
- This might cause diarrhea and dehydration, however, it would not explain the severe **abdominal pain**, significant **thrombocytopenia**, or the acute **renal injury** manifested by decreased urination.
- Electrolyte abnormalities are also more commonly associated with chronic laxative abuse, whereas this patient has normal electrolytes.
*Toxic shock syndrome*
- Toxic shock syndrome (TSS) presents with **fever**, **rash**, **hypotension**, and multi-organ involvement, but it is typically associated with *Staphylococcus aureus* or *Streptococcus pyogenes* infections.
- While it can cause renal failure and thrombocytopenia, the preceding **diarrhea** is less characteristic of TSS, and it usually lacks the specific triad of HUS (microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury).
Question 158: A 7-year-old boy is brought to the physician for the evaluation of sore throat for the past 2 days. During this period, he has had intermittent nausea and has vomited once. The patient has no cough, hoarseness, or rhinorrhea. He had similar symptoms at the age of 5 years that resolved spontaneously. He is otherwise healthy. His temperature is 37.9°C (100.2°F), pulse is 85/min, and blood pressure is 108/70 mm Hg. Head and neck examination shows an erythematous pharynx with grayish exudates overlying the palatine tonsils. There is no lymphadenopathy. Rapid antigen detection test for group A streptococci is negative. Which of the following is most appropriate next step in the management of this patient?
A. Reassurance and follow-up in two weeks
B. Obtain throat culture (Correct Answer)
C. Measurement of antistreptolysin O titer
D. Penicillin V therapy
E. Measurement of antiviral capsid antigen IgM antibody
Explanation: ***Obtain throat culture***
- A negative **rapid antigen detection test (RADT)** for Group A Streptococcus (GAS) does not rule out GAS infection, especially with the presence of **exudative pharyngitis** and history of previous spontaneous resolution of similar symptoms. A throat culture is a more sensitive test to confirm or rule out GAS.
- Given the patient's age (7 years old) and the clinical presentation (sore throat, fever, tonsillar exudates, no cough), there's a risk of **rheumatic fever** if GAS is not adequately treated. A throat culture is crucial for definitive diagnosis and to guide antibiotic therapy.
*Reassurance and follow-up in two weeks*
- This approach is inappropriate as it carries the risk of missing a **GAS infection**, which could lead to serious complications like acute **rheumatic fever** or acute **post-streptococcal glomerulonephritis**.
- Although the RADT was negative, the clinical picture is still highly suspicious for bacterial pharyngitis, making immediate follow-up and definitive diagnosis necessary.
*Measurement of antistreptolysin O titer*
- **Antistreptolysin O (ASO) titer** measures past exposure to GAS and is not useful for diagnosing acute infection. It typically peaks 3-6 weeks after the infection.
- For guiding acute management and antibiotic therapy, a real-time diagnostic test like a **throat culture** or RADT is required.
*Penicillin V therapy*
- Initiating antibiotic therapy empirically based on a negative RADT is not recommended. It could lead to **antibiotic overuse** if the infection is viral, or delay appropriate treatment if the RADT is a false negative.
- **Penicillin V** is the drug of choice for GAS pharyngitis, but it should only be prescribed once a definitive diagnosis is made, typically by a positive culture after a negative RADT.
*Measurement of antiviral capsid antigen IgM antibody*
- This antibody test is used to diagnose **Epstein-Barr virus (EBV)** infection (infectious mononucleosis), which can cause pharyngitis with exudates.
- While EBV is a possibility, a throat culture is a more direct and immediate next step to rule out **GAS**, which carries a higher risk of serious complications if untreated in this age group and clinical context.
Question 159: A previously healthy 2-year-old girl is brought to the physician by her mother after she noticed multiple painless, nonpruritic papules on her abdomen. The child attends daycare three times per week, and this past week one child was reported to have similar lesions. Her immunizations are up-to-date. Her brother had chickenpox one month ago. She is at the 50th percentile for height and the 60th percentile for weight. Vital signs are within normal limits. Examination shows several skin-colored, nontender, pearly papules with central umbilication on the abdomen and extremities. The remainder of the examination shows no abnormalities. Which of the following is the most likely diagnosis?
A. Cutaneous lichen planus
B. Verruca vulgaris
C. Chickenpox
D. Molluscum contagiosum (Correct Answer)
E. Insect bites
Explanation: ***Molluscum contagiosum***
- The presence of **painless, nonpruritic, skin-colored, pearly papules with central umbilication** is pathognomonic for molluscum contagiosum.
- The history of exposure in a daycare setting and a child with similar lesions further supports this diagnosis, as it is a **highly contagious viral infection**.
*Cutaneous lichen planus*
- Characterized by **pruritic, purple, polygonal papules and plaques** (the 6 P's), which are distinct from the described lesions.
- While it can affect children, the classic presentation does not match the **umbilicated, pearly appearance**.
*Verruca vulgaris*
- Commonly known as **warts**, these are typically **rough, hyperkeratotic papules** with an irregular surface, unlike the smooth, pearly lesions of molluscum.
- Warts are not typically described as having central umbilication.
*Chickenpox*
- Presents as a **pruritic rash** that progresses from macules to papules, then to **vesicles ("dewdrop on a rose petal")**, and finally crusts.
- The lesions in the question are described as painless, nonpruritic papules with central umbilication, which is inconsistent with active chickenpox. The child is also immunized and her brother had chickenpox one month ago, making a very recent infection less likely, and the lesions do not fit the description of chickenpox scars.
*Insect bites*
- Typically present as **pruritic, erythematous papules or wheals** that may have a central punctum.
- The lesions described are painless, nonpruritic, and pearly with central umbilication, which is not characteristic of typical insect bites.
Question 160: A 9-month-old boy is brought to the physician because of increased irritability, continual crying, and fever for 1 day. His mother has noticed that he refuses to lie down on his right side and keeps tugging at his right ear. One week ago, he had a runny nose that has since improved. He was born at term and has been otherwise healthy. He was exclusively breastfed until 2 months of age and is currently bottle-fed with some solid foods introduced. He has been attending a daycare center for the past 5 months. His temperature is 38.4°C (101.1°F) and pulse is 144/min. Otoscopic examination in this child is most likely to show which of the following?
A. Erythematous external auditory canal
B. Vesicles in the ear canal
C. Bulging erythematous tympanic membrane (Correct Answer)
D. Brown mass within the ear canal
E. Retracted opacified tympanic membrane
Explanation: ***Bulging erythematous tympanic membrane***
- The child's symptoms of **irritability**, **crying**, **fever**, **ear tugging**, and refusal to lie on one side, especially after a recent upper respiratory infection, are highly suggestive of **acute otitis media (AOM)**.
- In AOM, the **tympanic membrane (eardrum)** becomes inflamed, red (**erythematous**), and often **bulges** outwards due to the accumulation of fluid and pus in the middle ear.
*Erythematous external auditory canal*
- An **erythematous external auditory canal** is characteristic of **otitis externa** (swimmer's ear), which typically presents with pain upon manipulation of the tragus or pinna, and discharge, rather than the systemic symptoms like fever and irritability seen here.
- While some inflammation may extend to the external canal in AOM, the primary and most diagnostic finding for AOM is changes to the tympanic membrane itself.
*Vesicles in the ear canal*
- **Vesicles** in the ear canal or on the tympanic membrane, often accompanied by severe pain and possibly facial nerve palsy, are characteristic of **herpes zoster oticus** (Ramsay Hunt syndrome).
- This condition is caused by viral reactivation and does not fit the common presentation of fever, irritability, and ear tugging in an infant following a runny nose.
*Brown mass within the ear canal*
- A **brown mass** within the ear canal could indicate a cerumen impaction (earwax plug), a foreign body, or potentially a **cholesteatoma** (a benign skin growth that can erode bone).
- None of these conditions typically present with acute onset fever, irritability, and ear tugging in an infant, nor do they usually follow a recent upper respiratory infection.
*Retracted opacified tympanic membrane*
- A **retracted and opacified tympanic membrane** suggests changes in middle ear pressure, often seen in **eustachian tube dysfunction** or **otitis media with effusion (OME)**, where there is fluid but no acute infection.
- While OME can precede AOM, the presence of fever, acute irritability, and significant pain (implied by ear tugging and refusal to lie down) points strongly to an active, acute infection rather than just effusion or retraction.
