Infectious Diseases Practice Questions

Q: A 4-year-old child presented with fever for 6 days, generalized rash and cervical lymphadenopathy with strawberry tongue. What could be the diagnosis?

Kawasaki disease. ***Kawasaki disease*** * Kawasaki disease is a **vasculitis** affecting medium-sized arteries, predominantly in children. * **Persistent fever** for more than 5 days, **generalized rash**, **cervical lymphadenopathy**, and **strawberry tongue** are key diagnostic criteria. * The child's age (4 years) is also consistent with the typical presentation of Kawasaki disease. *Kimura disease* * Kimura disease is a **rare chronic inflammatory condition** primarily affecting the head and neck, characterized by subcutaneous nodules and enlarged lymph nodes. * It typically presents with **painless subcutaneous masses**, often in young adults of Asian descent, and does not commonly include a generalized rash or strawberry tongue. *Scarlet fever* * Scarlet fever is caused by **Group A Streptococcus** and typically presents with a **fine, sandpaper-like rash**, **strawberry tongue**, and fever. * While a strawberry tongue and rash are present, the rash of Kawasaki disease is more polymorphous, and cervical lymphadenopathy is often more pronounced and less generalized than in scarlet fever. *Rosai Dorfman disease* * Rosai-Dorfman disease, also known as **sinus histiocytosis with massive lymphadenopathy**, is characterized by striking, often **painless and massive lymph node enlargement**, predominantly in the cervical region. * Systemic symptoms like fever and rash can occur, but the classic presentation does not typically include a "strawberry tongue" or the specific constellation of symptoms seen in Kawasaki disease.

Q: The following age group is most severely affected by Rubella infection -

Unborn child. ***Unborn child*** - Rubella infection during pregnancy, especially in the **first trimester**, can lead to **Congenital Rubella Syndrome (CRS)**, causing severe birth defects. - CRS can manifest as **cardiac malformations**, **cataracts**, **deafness**, and neurological disorders, making it the most severely affected group. *Young girls* - While susceptible to rubella, young girls typically experience a **mild, self-limiting disease** with a rash, low-grade fever, and lymphadenopathy. - The risk of severe complications as seen in CRS is significantly lower in this age group compared to an unborn child. *Adolescent girls* - Rubella infection in adolescent girls is generally a **mild illness**, similar to young girls, characterized by a rash and mild constitutional symptoms. - The main concern for this group is if they become pregnant, as **maternal infection** then poses a severe risk to the fetus, not the adolescent herself. *Females aged 25 -- 35 Year* - In this age group, rubella infection is typically **mild and self-limiting**, similar to younger females. - The primary concern is if the woman is pregnant or becomes pregnant, as the **teratogenic effects** on the fetus are devastating, not the severity of the disease in the mother.

Q: Most common organism causing bacterial meningitis between 6 months and 2 years in vaccinated populations.

Pneumococcus. ***Pneumococcus*** - **Pneumococcus (Streptococcus pneumoniae)** is now the most common cause of bacterial meningitis in children aged 6 months to 2 years in countries with high vaccination rates for *H. influenzae type b (Hib)* and *N. meningitidis*. - The introduction of the **pneumococcal conjugate vaccine (PCV)** has significantly reduced the incidence of pneumococcal meningitis, but it still remains the leading cause among the remaining cases in this age group. *E. coli* - **E. coli meningitis** is primarily a concern in **neonates** (birth to 1 month of age), often acquired during passage through the birth canal. - Its incidence significantly decreases after the neonatal period, making it a much less common cause in children aged 6 months to 2 years. *H. influenzae* - Before routine vaccination, **Haemophilus influenzae type b (Hib)** was the leading cause of bacterial meningitis in children under 5 years old. - The widespread use of the **Hib vaccine** has drastically reduced its incidence, making it a rare cause in vaccinated populations. *N. meningitidis* - **Neisseria meningitidis** (meningococcus) is a significant cause of bacterial meningitis, especially in older children, adolescents, and young adults. - While it can occur in children aged 6 months to 2 years, widespread **meningococcal vaccination** in many regions has reduced its overall prevalence, making *Pneumococcus* a more frequent cause in this specific vaccinated age group.

Q: Which vaccine formulation is NOT recommended for use in adults?

DPT. ***DPT (Pediatric Formulation)*** - The **pediatric DPT vaccine** contains whole-cell pertussis antigen and higher doses of diphtheria toxoid, which cause significantly more **adverse reactions** (fever, local reactions) in adolescents and adults. - Adults should receive **Td (Tetanus-diphtheria)** or **Tdap (Tetanus-diphtheria-acellular pertussis)** instead, which contain: - Reduced diphtheria toxoid (lowercase 'd') - Acellular pertussis component (in Tdap) with fewer side effects - The pediatric formulation is **not recommended** (though not absolutely contraindicated) due to increased reactogenicity in older individuals. *Pneumococcal* - **Pneumococcal vaccines** (PCV13, PCV20, and PPSV23) are routinely recommended for adults, especially those over 65 years or with chronic medical conditions. - They protect against **_Streptococcus pneumoniae_**, preventing pneumonia, meningitis, and invasive pneumococcal disease. *Hepatitis A* - The **Hepatitis A vaccine** is recommended for adults at risk: travelers to endemic areas, individuals with chronic liver disease, MSM, healthcare workers, and food handlers. - Provides active immunity against **Hepatitis A virus**, preventing acute liver infection. *MMR* - The **MMR vaccine** (Measles, Mumps, Rubella) is given to adults without evidence of immunity, particularly healthcare workers, students, and international travelers. - This **live attenuated vaccine** is safe and effective in adults for preventing these highly contagious viral diseases.

Q: Most common manifestation of HPV infection in children :

Common skin warts (verruca vulgaris). ***Common skin warts (verruca vulgaris)*** - **Verruca vulgaris**, or common skin warts, are the most frequent cutaneous manifestation of **human papillomavirus (HPV)** infection in children. - These warts are typically caused by **HPV types 2, 4, and 7** and are often found on the hands, fingers, and feet. - They account for the majority of HPV-related lesions in the pediatric population. *Condyloma acuminatum (genital warts)* - While **condyloma acuminatum** (genital warts) are caused by HPV (usually types 6 and 11), they are **much less common** in children compared to common skin warts. - In children, their presence may raise concerns about sexual abuse or vertical transmission from mother to child. - Common skin warts remain the predominant manifestation in the pediatric age group. *Sarcoma* - **Sarcomas** are malignant tumors of connective tissue and are not directly caused by HPV infection. - HPV is associated with **carcinomas** (epithelial cancers) like cervical, anal, and oropharyngeal cancers, but not sarcomas. *Osteoma* - An **osteoma** is a benign tumor composed of bone tissue, usually found on the skull or facial bones. - It is not associated with HPV infection and is typically a slow-growing, asymptomatic lesion.

Q: Oral Thrush develops in infants at

2-6 weeks. **2-6 weeks (Correct)** - **Oral thrush** commonly appears in infants between **2 to 6 weeks of age**, as their immune systems are still developing and they are exposed to *Candida albicans* during birth or from their environment. - This period aligns with the typical onset of symptoms like **white patches** on the tongue and buccal mucosa, which cannot be easily wiped away. - This is the **most common age** for initial presentation of oral thrush in otherwise healthy infants. *18 months (Incorrect)* - While toddlers can get **oral thrush**, it's less common for the initial development to occur as late as **18 months** in an otherwise healthy child. - By this age, the infant's immune system is generally more robust, making primary oral thrush less likely unless there are predisposing factors like antibiotic use or immunodeficiency. *6 days (Incorrect)* - **Oral thrush** can sometimes manifest in the first few days of life, particularly with **birth canal transmission** of *Candida*. - While possible, the classic full-blown presentation is more common at **2-6 weeks** when maternal antibody protection begins to wane. *10-12 weeks (Incorrect)* - Though still possible, **oral thrush** is less typical to first develop around **10-12 weeks** in healthy infants. - If it appears at this age, it might suggest ongoing exposure, recurrence, or other contributing factors rather than the most common timeframe for initial presentation.

Q: Which of the following methods is NOT recommended for the diagnosis of HIV infection in a 2-month-old child?

HIV ELISA. ***HIV ELISA*** - **HIV ELISA** (Enzyme-linked Immunosorbent Assay) detects **HIV antibodies**, which are maternally derived and can persist in newborns for up to 18 months, leading to **false positive** results. - Therefore, antibody-based tests are **not suitable** for diagnosing HIV infection in infants under 18 months of age. *Viral culture* - **HIV viral culture** can directly detect the presence of replication-competent virus in an infant's blood. - While sensitive, it is **expensive**, labor-intensive, and takes a long time (several weeks) to obtain results, making it less practical for routine diagnosis. *DNA-PCR* - **DNA PCR (Polymerase Chain Reaction)** directly detects **HIV proviral DNA** within infected cells, making it highly specific and sensitive for early infant diagnosis. - It is currently the **recommended method** for HIV diagnosis in infants and young children, especially in the first few months of life. *P24 antigen assay* - The **P24 antigen assay** detects the **core protein of the HIV virus**, indicating active viral replication. - It can be used for early diagnosis in infants but may be less sensitive than DNA PCR, particularly in the presence of maternal antibodies or during early infection.

Q: In children commonest organ involved in nocardiosis is

Lungs. ***Lungs*** - The **lungs** are the primary site of infection for **Nocardia** in both adults and children, as the pathogen is typically acquired via **inhalation**. - **Pulmonary nocardiosis** can manifest as pneumonia, nodules, or cavitary lesions, especially in immunocompromised individuals. *Brain* - While the **brain** can be involved in nocardiosis, leading to **abscesses**, it is usually a result of **hematogenous dissemination** from a primary pulmonary infection, making it a secondary rather than the commonest primary site. - **Cerebral nocardia** is a serious complication, but it does not represent the initial presentation in most cases. *Skin* - **Cutaneous nocardiosis** can occur through direct inoculation into the skin following trauma, but it is less common than pulmonary involvement in children. - Such infections may present as pustules, cellulitis, or subcutaneous abscesses, usually localized to the site of injury. *Renal* - **Renal involvement** in nocardiosis is rare and typically occurs via **hematogenous spread** from a primary site, often the lungs. - It can lead to **renal abscesses** but is not considered a common initial presentation or primary site of infection.

Q: A mother brings her 1-year-old daughter to the physician. She says that for the last 2 days her daughter has been fussy and crying more than usual. She also refuses formula. The patient has a fever of 39.4degC (102.9degF). Meningitis is suspected, and a lumbar puncture is performed. Analysis of the cerebrospinal fluid shows an opening pressure of 98 mm H2O, a leukocyte count of 1256/mm3, a protein level of 210 mg/dL, and a glucose level of 31 mg/dL.. The mother says that the patient has received no immunizations. Which of the following organisms is most likely responsible for this patient's illness?

Haemophilus influenzae. ***Haemophilus influenzae*** - *H. influenzae* type b (Hib) is the **most common cause of bacterial meningitis** in unvaccinated children aged 6 months to 5 years. - Before the introduction of the Hib vaccine, this organism was the **leading cause** of bacterial meningitis in this age group. - The CSF profile (high leukocyte count with **neutrophil predominance**, elevated protein >100 mg/dL, and low glucose <40 mg/dL) is classic for **bacterial meningitis**. - In an **unimmunized 1-year-old**, Hib remains the most likely pathogen. *Streptococcus pneumoniae* - *S. pneumoniae* is a common cause of bacterial meningitis across all age groups and is now the **most common cause in vaccinated populations** where Hib has been eliminated. - However, in an **unvaccinated child** of this age, *H. influenzae* type b is statistically more likely. - The CSF findings would be identical and cannot distinguish between these two organisms. *Group B Streptococcus* - **Group B Streptococcus** (*Streptococcus agalactiae*) primarily causes **early-onset neonatal meningitis** (first week of life) and **late-onset neonatal meningitis** (up to 3 months of age). - While late-late onset can occur beyond 3 months, it is uncommon at 1 year of age. - This organism is not a typical cause of meningitis in this age group. *Neisseria meningitidis* - *N. meningitidis* causes bacterial meningitis primarily in **older children, adolescents, and young adults**, often associated with outbreaks. - While possible in a 1-year-old, it is less common than Hib in unvaccinated children of this age. - Meningococcal meningitis is often associated with a **petechial or purpuric rash**, which is not mentioned in this case.

Question 1

A 4-year-old child presented with fever for 6 days, generalized rash and cervical lymphadenopathy with strawberry tongue. What could be the diagnosis?

Accepted Answer

Kawasaki disease

Answer

Kimura disease

Answer

Scarlet fever

Answer

Rosai-Dorfman disease

Question 2

The following age group is most severely affected by Rubella infection -

Accepted Answer

Unborn child

Answer

Young girls

Answer

Adolescent girls

Answer

Females aged 25-35 years

Question 3

Most common organism causing bacterial meningitis between 6 months and 2 years in vaccinated populations.

Accepted Answer

Pneumococcus

Answer

E. coli

Answer

H. influenzae

Answer

N. meningitidis

Question 4

Which vaccine formulation is NOT recommended for use in adults?

Accepted Answer

DPT

Answer

Pneumococcal

Answer

Hep A

Answer

MMR

Question 5

Most common manifestation of HPV infection in children :

Accepted Answer

Common skin warts (verruca vulgaris)

Answer

Condyloma acuminatum (genital warts)

Answer

Sarcoma

Answer

Osteoma

Question 6

Prophylaxis with Cotrimoxazole is recommended in the following situation EXCEPT:

Accepted Answer

Should be started only after the diagnosis of HIV is confirmed

Answer

All symptomatic HIV infected children > 5 years of age irrespective of CD4

Answer

All HIV infected infants less than 1 year age irrespective of symptoms or CD4 counts

Answer

All HIV exposed infants till HIV infection can be ruled out

Question 7

Oral Thrush develops in infants at

Accepted Answer

2-6 weeks

Answer

18 months

Answer

6 days

Answer

10-12 weeks

Question 8

Which of the following methods is NOT recommended for the diagnosis of HIV infection in a 2-month-old child?

Accepted Answer

HIV ELISA

Answer

Viral culture

Answer

DNA-PCR

Answer

P24 antigen assay

Question 9

In children commonest organ involved in nocardiosis is

Accepted Answer

Lungs

Answer

Brain

Answer

Skin

Answer

Renal

Question 10

A mother brings her 1-year-old daughter to the physician. She says that for the last 2 days her daughter has been fussy and crying more than usual. She also refuses formula. The patient has a fever of 39.4degC (102.9degF). Meningitis is suspected, and a lumbar puncture is performed. Analysis of the cerebrospinal fluid shows an opening pressure of 98 mm H2O, a leukocyte count of 1256/mm3, a protein level of 210 mg/dL, and a glucose level of 31 mg/dL.. The mother says that the patient has received no immunizations. Which of the following organisms is most likely responsible for this patient's illness?

Accepted Answer

Haemophilus influenzae

Answer

Group B Streptococcus

Answer

Neisseria meningitidis

Answer

Streptococcus pneumoniae

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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