Neonatal candidiasis — MCQs

10 questions

A neonate born at 33 weeks is transferred to the NICU after a complicated pregnancy and C-section. A week after being admitted, he developed a fever and became lethargic and minimally responsive to stimuli. A lumbar puncture is performed that reveals the following: Appearance Cloudy Protein 64 mg/dL Glucose 22 mg/dL Pressure 330 mm H20 Cells 295 cells/mm³ (> 90% PMN) A specimen is sent to microbiology and reveals gram-negative rods. Which of the following is the next appropriate step in management?

A 74-year-old man is admitted to the medical ward after he developed a fungal infection. He has aplastic anemia. The most recent absolute neutrophil count was 450/µL. An anti-fungal agent is administered that inhibits the fungal enzyme, (1→3)-β-D-glucan synthase, and thereby disrupts the integrity of the fungal cell wall. He responds well to the treatment. Although amphotericin B is more efficacious for his condition, it was not used because of the side effect profile. What was the most likely infection?

A 3-month-old male is brought to the emergency room by his mother who reports that the child has a fever. The child was born at 39 weeks of gestation and is at the 15th and 10th percentiles for height and weight, respectively. The child has a history of eczema. Physical examination reveals an erythematous fluctuant mass on the patient's inner thigh. His temperature is 101.1°F (38.4°C), blood pressure is 125/70 mmHg, pulse is 120/min, and respirations are 22/min. The mass is drained and the child is started on broad-spectrum antibiotics until the culture returns. The physician also orders a flow cytometry reduction of dihydrorhodamine, which is found to be abnormal. This patient is at increased risk of infections with which of the following organisms?

A 29-year-old woman, gravida 2, para 1, at 10 weeks' gestation comes to the physician for a prenatal visit. Over the past two weeks, she has felt nauseous in the morning and has had vulvar pruritus and dysuria that started 5 days ago. Her first child was delivered by lower segment transverse cesarean section because of macrosomia from gestational diabetes. Her gestational diabetes resolved after the child was born. She appears well. Ultrasound confirms fetal heart tones and an intrauterine pregnancy. Speculum exam shows a whitish chunky discharge. Her vaginal pH is 4.2. A wet mount is performed and microscopic examination is shown. Which of the following is the most appropriate treatment?

A 41-year-old HIV-positive male presents to the ER with a 4-day history of headaches and nuchal rigidity. A lumbar puncture shows an increase in CSF protein and a decrease in CSF glucose. When stained with India ink, light microscopy of the patient’s CSF reveals encapsulated yeast with narrow-based buds. Assuming a single pathogenic organism is responsible for this patient’s symptoms, which of the following diagnostic test results would also be expected in this patient?

A mother delivers in a rural area under the guidance of a skilled care attendant. Which of the following statements is incorrect regarding the care provided by the skilled care attendant at birth?

A 15-month-old boy is brought to the pediatrician’s office by his mother due to abnormal muscle tone and an inability to walk. He was able to control his head at 5 months of age, roll at 8 months of age, sit at 11 months of age, and develop hand preference at 13 months of age. On physical exam, he is observed to asymmetrically crawl. He has a velocity-dependent increase in tone and 3+ biceps and patellar reflexes. His startle, asymmetric tonic neck, and Babinski reflexes are present. Which of the following is the most common risk factor for developing this patient’s clinical presentation?

A 4-week-old male presents with his parents to the pediatrician for a well-child visit. The patient’s mother reports that the patient was eating well until about one week ago, when he began vomiting after breastfeeding. His mother has tried increasing the frequency of feeds and decreasing the amount of each feed, but the vomiting seems to be getting worse. The patient now vomits after every feed. His mother states the vomitus looks like breastmilk. The patient’s mother is exclusively breastfeeding and would prefer not to switch to formula but worries that the patient is not getting the nutrition he needs. Two weeks ago, the patient was in the 75th percentile for weight and 70th for height. He is now in the 60th percentile for weight and 68th percentile for height. On physical exam, the patient has dry mucous membranes. His abdomen is soft and non-distended. Which of the following is the best next step in management?

A 3-year-old boy is brought to the physician because of a 3-day history of a pruritic skin rash on his chest. His mother says that he has no history of dermatological problems. He was born at term and has been healthy except for recurrent episodes of otitis media. His immunizations are up-to-date. He appears pale. His temperature is 37°C (98.6°F), pulse is 110/min, respirations are 26/min, and blood pressure is 102/62 mm Hg. Examination shows vesicles and flaccid bullae with thin brown crusts on the chest. Lateral traction of the surrounding skin leads to sloughing. Examination of the oral mucosa shows no abnormalities. Complete blood count is within the reference range. Which of the following is the most likely diagnosis?

Q10

A 13-month-old girl is brought to the physician because of a pruritic rash for 2 days. The girl's mother says she noticed a few isolated skin lesions on her trunk two days ago that appear to be itching. The girl received her routine immunizations 18 days ago. Her mother has been giving her ibuprofen for her symptoms. The patient has no known sick contacts. She is at the 71st percentile for height and the 64th percentile for weight. She is in no acute distress. Her temperature is 38.1°C (100.6°F), pulse is 120/min, and respirations are 26/min. Examination shows a few maculopapular and pustular lesions distributed over the face and trunk. There are some excoriation marks and crusted lesions as well. Which of the following is the most likely explanation for these findings?

Neonatal candidiasis US Medical PG Practice Questions and MCQs

Question 1: A neonate born at 33 weeks is transferred to the NICU after a complicated pregnancy and C-section. A week after being admitted, he developed a fever and became lethargic and minimally responsive to stimuli. A lumbar puncture is performed that reveals the following: Appearance Cloudy Protein 64 mg/dL Glucose 22 mg/dL Pressure 330 mm H20 Cells 295 cells/mm³ (> 90% PMN) A specimen is sent to microbiology and reveals gram-negative rods. Which of the following is the next appropriate step in management?

A. MRI scan of the head
B. Start the patient on IV ceftriaxone
C. Provide supportive measures only
D. Start the patient on IV cefotaxime (Correct Answer)
E. Start the patient on oral rifampin

Explanation: ***Start the patient on IV cefotaxime*** - The cerebrospinal fluid (CSF) analysis with **cloudy appearance, elevated protein, low glucose, high pressure, and predominant PMNs**, coupled with **gram-negative rods** on microscopy, is highly suggestive of **bacterial meningitis** in a neonate. - **Cefotaxime** is a third-generation cephalosporin commonly used for neonatal meningitis caused by gram-negative organisms due to its excellent CSF penetration and broad-spectrum activity, particularly against common neonatal pathogens like *E. coli* which can present as gram-negative rods. *MRI scan of the head* - An MRI would be considered **after initiating appropriate antibiotic treatment** to assess for complications like abscess formation or ventriculitis, not as the immediate next step in an acute, life-threatening infection. - Delaying antibiotic treatment for imaging in acute bacterial meningitis can lead to increased morbidity and mortality. *Start the patient on IV ceftriaxone* - While ceftriaxone is a third-generation cephalosporin, it is **generally avoided in neonates** due to the risk of **biliary sludging** and **kernicterus**. - Ceftriaxone competes with bilirubin for albumin binding sites, which is particularly risky in neonates who are already prone to hyperbilirubinemia. *Provide supportive measures only* - Given the strong evidence of **bacterial meningitis**, providing only supportive measures without specific antibiotic treatment would be inadequate and would lead to rapid deterioration and potentially fatal outcomes. - Bacterial meningitis requires prompt and aggressive antimicrobial therapy. *Start the patient on oral rifampin* - **Rifampin is never used as monotherapy for bacterial meningitis** due to rapid resistance development and its primary role is in specific infections like tuberculosis or as part of combination therapy for certain resistant bacteria. - Oral administration is also not ideal for acutely ill neonates with meningitis needing rapid, high-concentration antibiotics in the CSF.

Question 2: A 74-year-old man is admitted to the medical ward after he developed a fungal infection. He has aplastic anemia. The most recent absolute neutrophil count was 450/µL. An anti-fungal agent is administered that inhibits the fungal enzyme, (1→3)-β-D-glucan synthase, and thereby disrupts the integrity of the fungal cell wall. He responds well to the treatment. Although amphotericin B is more efficacious for his condition, it was not used because of the side effect profile. What was the most likely infection?

A. Invasive aspergillosis
B. Mucormycosis
C. Histoplasmosis
D. Paracoccidioidomycosis
E. Candidemia (Correct Answer)

Explanation: ***Candidemia*** - The patient's **neutropenia** (absolute neutrophil count of 450/µL) due to aplastic anemia is a major risk factor for invasive candidiasis, including candidemia. - The antifungal agent's mechanism of action, targeting **(1→3)-β-D-glucan synthase**, is characteristic of **echinocandins**, which are first-line agents for candidemia, especially in critically ill or neutropenic patients, and often preferred over amphotericin B due to a better side effect profile. *Invasive aspergillosis* - While neutropenia is a significant risk factor for invasive aspergillosis, the primary antifungal drugs for this condition are typically **voriconazole** or **isavuconazole**, although echinocandins may be used as salvage therapy or in combination. - The description of the drug's mechanism specifically targeting **(1→3)-β-D-glucan synthase** does not make aspergillosis the *most likely* infection, as some Aspergillus species may have less β-D-glucan in their cell walls compared to *Candida*. *Mucormycosis* - This aggressive fungal infection is often seen in immunocompromised patients, particularly those with **diabetes** or profound neutropenia, but the primary treatment is usually **amphotericin B**. - Mucorales fungi typically **lack ergosterol** and their cell walls do not contain **(1→3)-β-D-glucan**, making echinocandins ineffective. *Histoplasmosis* - This is a dimorphic fungal infection endemic to certain geographic regions, primarily affecting the lungs and disseminating in immunocompromised individuals. - The drug of choice for severe or disseminated histoplasmosis is **amphotericin B**, followed by azoles; echinocandins are generally not active against *Histoplasma*. *Paracoccidioidomycosis* - This is a chronic systemic mycosis found in Latin America, primarily affecting the lungs, skin, and lymph nodes. - Treatment for severe forms typically involves **amphotericin B**, followed by sulfonamides or azoles for maintenance; echinocandins are not effective against *Paracoccidioides*.

Question 3: A 3-month-old male is brought to the emergency room by his mother who reports that the child has a fever. The child was born at 39 weeks of gestation and is at the 15th and 10th percentiles for height and weight, respectively. The child has a history of eczema. Physical examination reveals an erythematous fluctuant mass on the patient's inner thigh. His temperature is 101.1°F (38.4°C), blood pressure is 125/70 mmHg, pulse is 120/min, and respirations are 22/min. The mass is drained and the child is started on broad-spectrum antibiotics until the culture returns. The physician also orders a flow cytometry reduction of dihydrorhodamine, which is found to be abnormal. This patient is at increased risk of infections with which of the following organisms?

A. Giardia lamblia
B. Streptococcus viridans
C. Aspergillus fumigatus (Correct Answer)
D. Enterococcus faecalis
E. Streptococcus pyogenes

Explanation: ***Aspergillus fumigatus*** - The abnormal **dihydrorhodamine (DHR) flow cytometry** test indicates **chronic granulomatous disease (CGD)**, a defect in phagocyte function. - Patients with CGD are particularly susceptible to **catalase-positive organisms**, including *Aspergillus* species, *Staphylococcus aureus*, *Serratia marcescens*, *Burkholderia cepacia*, and *Nocardia* species. *Giardia lamblia* - *Giardia lamblia* is a **protozoan parasite** causing gastrointestinal infections, and susceptibility to it is primarily linked to **IgA deficiency**, not phagocyte dysfunction. - While patients with **immunodeficiencies** can have increased risk, CGD is not specifically associated with *Giardia* infections. *Streptococcus viridans* - *Streptococcus viridans* are **catalase-negative bacteria** and cause infections typically in patients with **valvular heart disease** or those undergoing dental procedures, and are not commonly associated with CGD. - CGD patients are more prone to infections by **catalase-positive organisms**, which this bacterium is not. *Enterococcus faecalis* - *Enterococcus faecalis* is a **catalase-negative bacterium** that primarily causes **urinary tract infections** and endocarditis, particularly in hospitalized patients. - While it can cause opportunistic infections, its catalase-negative status makes it less relevant to the specific phagocytic defect in CGD. *Streptococcus pyogenes* - *Streptococcus pyogenes* is a **catalase-negative bacterium** responsible for diseases like strep throat, scarlet fever, and necrotizing fasciitis. - Susceptibility to *S. pyogenes* is generally not increased in CGD patients due to its **catalase-negative nature**, which allows phagocytes to still effectively kill it.

Question 4: A 29-year-old woman, gravida 2, para 1, at 10 weeks' gestation comes to the physician for a prenatal visit. Over the past two weeks, she has felt nauseous in the morning and has had vulvar pruritus and dysuria that started 5 days ago. Her first child was delivered by lower segment transverse cesarean section because of macrosomia from gestational diabetes. Her gestational diabetes resolved after the child was born. She appears well. Ultrasound confirms fetal heart tones and an intrauterine pregnancy. Speculum exam shows a whitish chunky discharge. Her vaginal pH is 4.2. A wet mount is performed and microscopic examination is shown. Which of the following is the most appropriate treatment?

A. Topical nystatin
B. Oral fluconazole
C. Intravaginal clotrimazole (Correct Answer)
D. Oral metronidazole
E. Intravaginal treatment with lactobacillus

Explanation: ***Intravaginal clotrimazole*** - The patient's symptoms of **vulvar pruritus**, **dysuria**, **whitish chunky discharge**, a **vaginal pH of 4.2**, and microscopy consistent with **yeast buds and hyphae** are highly suggestive of **vulvovaginal candidiasis (VVC)**. - **Intravaginal azole antifungals** like clotrimazole are the **first-line treatment for VVC in pregnancy** due to their local action and minimal systemic absorption, making them safe for the fetus. *Topical nystatin* - While **nystatin** is an antifungal used for candidiasis, its **efficacy for vulvovaginal candidiasis is lower** compared to azoles. - **Topical nystatin** is generally **not the preferred first-line treatment** for VVC, especially when more effective alternatives like azoles are available. *Oral fluconazole* - **Oral fluconazole** is generally **avoided in the first trimester of pregnancy** due to potential risks of **teratogenicity**, including an increased risk of miscarriage and congenital malformations at higher doses, though lower single doses are considered by some to be low risk. - Given the patient is at **10 weeks' gestation**, topical treatment is preferred over oral options to minimize systemic exposure. *Oral metronidazole* - **Metronidazole** is an **antibiotic and antiprotozoal** medication primarily used to treat **bacterial vaginosis** or **trichomoniasis**, conditions that do not match the patient's presentation. - The patient's **vaginal pH of 4.2** and **chunky discharge** differentiate VVC from bacterial vaginosis (which typically has a pH >4.5 and thin, malodorous discharge) or trichomoniasis (often frothy discharge and high pH). *Intravaginal treatment with lactobacillus* - **Lactobacillus** is used to help restore the normal vaginal flora, often as an **adjunctive treatment** or for prophylaxis, particularly in cases of **recurrent bacterial vaginosis** or after antibiotic therapy. - It is **not a primary treatment for active fungal infections** like vulvovaginal candidiasis, as it does not directly eradicate the yeast.

Question 5: A 41-year-old HIV-positive male presents to the ER with a 4-day history of headaches and nuchal rigidity. A lumbar puncture shows an increase in CSF protein and a decrease in CSF glucose. When stained with India ink, light microscopy of the patient’s CSF reveals encapsulated yeast with narrow-based buds. Assuming a single pathogenic organism is responsible for this patient’s symptoms, which of the following diagnostic test results would also be expected in this patient?

A. Ring-enhancing lesions on CT imaging
B. Latex agglutination of CSF (Correct Answer)
C. Cotton-wool spots on funduscopic exam
D. Acid-fast oocysts in stool
E. Frontotemporal atrophy on MRI

Explanation: **Latex agglutination of CSF** - The presence of **encapsulated yeast with narrow-based buds** in the cerebrospinal fluid (CSF) on **India ink stain** is pathognomonic for **Cryptococcus neoformans**, the causative agent of **cryptococcal meningitis**. - **Latex agglutination** is a rapid and highly sensitive test that detects the **cryptococcal capsular polysaccharide antigen** in CSF, making it an expected diagnostic finding. *Ring-enhancing lesions on CT imaging* - **Ring-enhancing lesions** are typically associated with **Toxoplasma gondii encephalitis** (toxoplasmosis) in HIV-positive patients, which would also present with focal neurological deficits. - While cryptococcal meningitis can sometimes cause cryptococcomas that may enhance, these are less common and not the primary diagnostic feature. *Cotton-wool spots on funduscopic exam* - **Cotton-wool spots** are associated with **HIV retinopathy** or sometimes **cytomegalovirus (CMV) retinitis**, presenting as fluffy white lesions on the retina. - These findings are indicative of microinfarctions in the retinal nerve fiber layer due to various causes, but not directly linked to fungal meningitis. *Acid-fast oocysts in stool* - **Acid-fast oocysts in stool** are characteristic of infections such as **cryptosporidiosis** or **isosporiasis**, which cause chronic diarrhea in immunocompromised individuals. - These are gastrointestinal pathogens and would not directly lead to the neurological symptoms and CSF findings described in the patient. *Frontotemporal atrophy on MRI* - **Frontotemporal atrophy** is a feature of **neurocognitive disorders** such as **frontotemporal dementia** or **HIV-associated dementia (HAD)**, a chronic neurocognitive decline. - While HAD can occur in HIV-positive individuals, it does not explain the acute presentation of headaches, nuchal rigidity, and specific CSF findings suggestive of an acute infectious process like meningitis.

Question 6: A mother delivers in a rural area under the guidance of a skilled care attendant. Which of the following statements is incorrect regarding the care provided by the skilled care attendant at birth?

A. Start breastfeeding as early as possible
B. Cover the baby's head and body
C. Bathe the baby with warm water (Correct Answer)
D. Clear the eyes with a sterile swab
E. Dry the baby thoroughly and stimulate breathing

Explanation: ***Bathe the baby with warm water*** - **Delaying the first bath** for at least 6-24 hours after birth is recommended to prevent **hypothermia** and promote **skin-to-skin contact** for bonding and breastfeeding. - Early bathing can remove **vernix caseosa**, which provides natural antimicrobial protection and moisturization to the newborn's skin. *Start breastfeeding as early as possible* - **Early initiation of breastfeeding**, ideally within the first hour of birth, is crucial for both mother and baby. - It promotes **uterine contractions** to prevent **postpartum hemorrhage** and provides the newborn with **colostrum**, rich in antibodies. *Cover the baby's head and body* - Covering the newborn's head and body is essential to prevent **heat loss** and maintain a stable **body temperature**, immediately after birth. - Newborns are highly susceptible to **hypothermia** due to their large surface area to mass ratio and immature thermoregulation. *Clear the eyes with a sterile swab* - Clearing the newborn's eyes with a sterile swab is a standard part of immediate newborn care to remove any **mucus or blood** that might have entered during delivery. - This helps prevent **ophthalmia neonatorum**, especially if the mother has an infection like gonorrhea or chlamydia. *Dry the baby thoroughly and stimulate breathing* - **Drying the baby immediately** after birth is a critical first step in newborn resuscitation and care. - It helps prevent **hypothermia** and provides **tactile stimulation** to initiate breathing and crying, which is essential for transitioning from fetal to neonatal circulation.

Question 7: A 15-month-old boy is brought to the pediatrician’s office by his mother due to abnormal muscle tone and an inability to walk. He was able to control his head at 5 months of age, roll at 8 months of age, sit at 11 months of age, and develop hand preference at 13 months of age. On physical exam, he is observed to asymmetrically crawl. He has a velocity-dependent increase in tone and 3+ biceps and patellar reflexes. His startle, asymmetric tonic neck, and Babinski reflexes are present. Which of the following is the most common risk factor for developing this patient’s clinical presentation?

A. Intrauterine growth restriction
B. Prematurity (Correct Answer)
C. Perinatal hypoxic injury
D. Multiparity
E. Stroke

Explanation: ***Prematurity*** - **Cerebral palsy (CP)** is characterized by **delayed motor milestones**, **abnormal muscle tone (spasticity)**, **hyperreflexia**, and **persistent primitive reflexes** beyond the expected age. - **Prematurity** (especially birth before 32 weeks' gestation) is the **most common risk factor** for CP overall, accounting for approximately 40-50% of cases. - The developing brain of premature infants is particularly vulnerable to periventricular leukomalacia (PVL) and intraventricular hemorrhage (IVH), which can lead to various CP subtypes. - While this patient's **early hand preference** and **asymmetric crawling** suggest hemiplegic CP (often associated with stroke), the question asks for the most common risk factor **epidemiologically**, not the most likely cause in this specific case. *Intrauterine growth restriction* - While **IUGR** can be associated with developmental delays and is a risk factor for CP, it is less common than prematurity as the primary risk factor. - IUGR alone without complications (like prematurity or hypoxia) accounts for a smaller proportion of CP cases. *Perinatal hypoxic injury* - **Perinatal hypoxic-ischemic encephalopathy (HIE)** can cause CP, especially severe cases resulting in basal ganglia or watershed area damage. - However, with modern obstetric monitoring and intervention, severe perinatal hypoxia accounts for only ~10% of CP cases—less common than prematurity. *Multiparity* - **Multiparity** (having multiple previous births) is generally not considered a direct or common risk factor for cerebral palsy. - Any slight associations are typically due to confounding factors like increased risk of preterm birth in subsequent pregnancies, rather than multiparity itself. *Stroke* - **Perinatal stroke** can cause CP, typically presenting as **hemiplegic CP** with early hand preference and asymmetric motor findings—features seen in this patient. - While stroke is a significant cause of hemiplegic CP specifically, it accounts for a smaller proportion of overall CP cases compared to prematurity, which causes various CP subtypes and is more prevalent.

Question 8: A 4-week-old male presents with his parents to the pediatrician for a well-child visit. The patient’s mother reports that the patient was eating well until about one week ago, when he began vomiting after breastfeeding. His mother has tried increasing the frequency of feeds and decreasing the amount of each feed, but the vomiting seems to be getting worse. The patient now vomits after every feed. His mother states the vomitus looks like breastmilk. The patient’s mother is exclusively breastfeeding and would prefer not to switch to formula but worries that the patient is not getting the nutrition he needs. Two weeks ago, the patient was in the 75th percentile for weight and 70th for height. He is now in the 60th percentile for weight and 68th percentile for height. On physical exam, the patient has dry mucous membranes. His abdomen is soft and non-distended. Which of the following is the best next step in management?

A. Abdominal radiograph
B. Trial of empiric proton pump inhibitor
C. Supplement breastfeeding with formula
D. Abdominal ultrasound (Correct Answer)
E. Trial of cow's milk-free diet

Explanation: ***Abdominal ultrasound*** - The history of **progressive non-bilious vomiting** after every feed, worsening over time, and **weight percentile drop** in a 4-week-old infant strongly suggests **pyloric stenosis**. The best next step for diagnosis is an abdominal ultrasound which can visualize the thickened pylorus (>3-4 mm muscle thickness, >14-16 mm channel length). - The physical exam finding of **dry mucous membranes** indicates dehydration, a common complication of recurrent vomiting. *Abdominal radiograph* - An abdominal radiograph is generally not the initial imaging of choice for diagnosing pyloric stenosis, as it is less sensitive and specific than ultrasound for visualizing soft tissue structures like the pylorus. - While it may show a **dilated stomach** or **absent gas in the distal bowel**, these findings are not diagnostic of pyloric stenosis and do not pinpoint the obstruction. *Trial of empiric proton pump inhibitor* - A proton pump inhibitor would be considered for **gastroesophageal reflux disease (GERD)**, but the **worsening pattern of vomiting after every feed** and **rapid weight loss** are atypical for simple GERD and point to a more serious mechanical obstruction. - Treating with a PPI would delay the proper diagnosis and treatment of pyloric stenosis, which requires surgical intervention (pyloromyotomy). *Supplement breastfeeding with formula* - While ensuring adequate nutrition is important, simply supplementing with formula will not resolve the underlying issue of **pyloric obstruction**, and the infant will likely continue to vomit and experience dehydration. - This approach would delay definitive diagnosis and treatment, potentially leading to further compromise of the infant's health. *Trial of cow's milk-free diet* - A cow's milk-free diet is indicated for suspected **cow's milk protein allergy (CMPA)**, which can present with vomiting, but typically also includes symptoms like **bloody stools**, **eczema**, or **colic**, which are not reported here. - The **progressive non-bilious vomiting after every feed** and rapid weight loss are more characteristic of a mechanical obstruction like pyloric stenosis than a dietary allergy.

Question 9: A 3-year-old boy is brought to the physician because of a 3-day history of a pruritic skin rash on his chest. His mother says that he has no history of dermatological problems. He was born at term and has been healthy except for recurrent episodes of otitis media. His immunizations are up-to-date. He appears pale. His temperature is 37°C (98.6°F), pulse is 110/min, respirations are 26/min, and blood pressure is 102/62 mm Hg. Examination shows vesicles and flaccid bullae with thin brown crusts on the chest. Lateral traction of the surrounding skin leads to sloughing. Examination of the oral mucosa shows no abnormalities. Complete blood count is within the reference range. Which of the following is the most likely diagnosis?

A. Bullous pemphigoid
B. Dermatitis herpetiformis
C. Bullous impetigo (Correct Answer)
D. Pemphigus vulgaris
E. Stevens-Johnson syndrome

Explanation: ***Bullous impetigo*** - The presence of **flaccid bullae with thin brown crusts** and the positive **Nikolsky's sign** (sloughing with lateral traction), in the absence of mucosal involvement, are classic signs of bullous impetigo, a **Staphylococcus aureus** infection. - This condition is common in children and can present with localized lesions, as seen on the chest. *Bullous pemphigoid* - Typically presents with **tense bullae** in older adults, often with **urticarial plaques**, unlike the flaccid bullae and crusts seen here. - **Nikolsky's sign is negative** in bullous pemphigoid, which helps distinguish it from bullous impetigo and pemphigus conditions. *Dermatitis herpetiformis* - Characterized by intensely **pruritic papules and vesicles** found symmetrically on extensor surfaces, often associated with **celiac disease**. - The lesions are usually small and grouped, not flaccid bullae with positive Nikolsky's sign. *Pemphigus vulgaris* - Presents with **flaccid bullae** and a positive Nikolsky's sign, but characteristically also involves the **oral mucosa**, which is normal in this patient. - It usually affects older individuals and can be more widespread than the localized rash described. *Stevens-Johnson syndrome* - A severe mucocutaneous reaction typically characterized by **widespread epidermal necrosis**, **target lesions**, and often involves **mucous membranes** (oral, ocular, genital) extensively. - This patient's localized rash without mucosal involvement, target lesions, or systemic toxicity does not fit the criteria for SJS.

Question 10: A 13-month-old girl is brought to the physician because of a pruritic rash for 2 days. The girl's mother says she noticed a few isolated skin lesions on her trunk two days ago that appear to be itching. The girl received her routine immunizations 18 days ago. Her mother has been giving her ibuprofen for her symptoms. The patient has no known sick contacts. She is at the 71st percentile for height and the 64th percentile for weight. She is in no acute distress. Her temperature is 38.1°C (100.6°F), pulse is 120/min, and respirations are 26/min. Examination shows a few maculopapular and pustular lesions distributed over the face and trunk. There are some excoriation marks and crusted lesions as well. Which of the following is the most likely explanation for these findings?

A. Antigen contact with presensitized T-lymphocytes
B. Reactivation of virus dormant in dorsal root ganglion
C. Immune complex formation and deposition
D. Crosslinking of preformed IgE antibodies
E. Replication of the attenuated vaccine strain (Correct Answer)

Explanation: ***Replication of the attenuated vaccine strain*** - The presentation of a **pruritic rash with maculopapular and pustular lesions**, along with crusted lesions, describes the classic **polymorphic rash** of **varicella (chickenpox)**. - The timing of the rash, appearing **18 days after routine immunizations** (which commonly include the attenuated **MMRV vaccine** at 12-15 months), strongly suggests a vaccine-induced varicella rash due to the replication of the live attenuated virus. *Antigen contact with presensitized T-lymphocytes* - This mechanism describes a **Type IV hypersensitivity reaction** (delayed-type hypersensitivity), such as **contact dermatitis** or a **tuberculin skin test**. - While it can cause a rash, it typically presents differently (e.g., vesicles in contact dermatitis) and the timeline of 18 days post-vaccination is less consistent with a primary contact-mediated reaction causing widespread varicella-like lesions. *Reactivation of virus dormant in dorsal root ganglion* - This process describes the pathogenesis of **herpes zoster (shingles)**, which occurs due to the reactivation of the **latent varicella-zoster virus (VZV)** from the dorsal root ganglia. - Shingles typically presents with a **dermatomal rash** in older individuals or immunocompromised patients, not a widespread polymorphic rash in an otherwise healthy toddler. *Immune complex formation and deposition* - This mechanism describes a **Type III hypersensitivity reaction**, where antigen-antibody complexes deposit in tissues, leading to inflammation. - Conditions like **serum sickness**, **lupus**, or some forms of **vasculitis** are examples, which present with fever, arthralgia, and urticarial or purpuric rashes, differing from the described varicella-like lesions. *Crosslinking of preformed IgE antibodies* - This mechanism describes a **Type I hypersensitivity reaction**, commonly known as an **allergic reaction**. - It typically results in **urticaria (hives)**, angioedema, or anaphylaxis, which are acute reactions characterized by wheals and pruritus, rather than the polymorphic rash with pustules and crusts seen here.

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