Infectious Diseases Practice Questions

Q: What is the characteristic feature of early congenital syphilis?

Vesicular rash with bulla over palms and soles. **Explanation:** Congenital syphilis is divided into **Early** (presenting before 2 years of age) and **Late** (presenting after 2 years). **Why Option D is correct:** The characteristic skin lesion in early congenital syphilis is **Syphilitic Pemphigus**. This presents as a vesiculobullous or maculopapular rash that specifically involves the **palms and soles**. Unlike many other neonatal rashes, these bullae are highly infectious as they contain a high load of *Treponema pallidum*. Other early features include "snuffles" (persistent rhinitis), hepatosplenomegaly, and osteochondritis (Wimberger’s sign). **Analysis of Incorrect Options:** * **Option A (Microcephaly):** This is a classic feature of the **"TORCH"** group (especially CMV and Zika virus), but it is not a hallmark of congenital syphilis. * **Option B (Saddle nose):** This is a **Late** manifestation caused by the destruction of the nasal cartilage due to persistent inflammation (gummas). * **Option C (Interstitial keratitis with sabre shin):** These are features of **Late** congenital syphilis. Interstitial keratitis is part of the **Hutchinson’s Triad** (along with sensorineural deafness and Hutchinson teeth), while Sabre shin refers to the anterior bowing of the tibia. **Clinical Pearls for NEET-PG:** * **Hutchinson’s Triad:** Interstitial keratitis, 8th Nerve deafness, and notched incisors (Late Syphilis). * **Clutton’s joints:** Symmetrical painless swelling of the knees (Late Syphilis). * **Mulberry molars:** Poorly developed cusps of the first molars (Late Syphilis). * **Drug of Choice:** Parenteral **Penicillin G** remains the gold standard for treatment.

Q: What is the most common complication of rubella?

Polyarthritis. **Explanation:** **Rubella (German Measles)** is a viral infection caused by the Rubivirus (Togaviridae family). While generally a mild illness in children, it presents differently in adults, particularly females. **Why Polyarthritis is correct:** Arthralgia and **polyarthritis** are the most common complications of Rubella, occurring in up to 70% of adult females. It typically involves the small joints of the hands (PIP, MCP), wrists, and knees. The pathogenesis is thought to be immune-mediated (deposition of immune complexes) rather than direct viral invasion. It usually appears shortly after the rash and is self-limiting, resolving within a few weeks without permanent joint damage. **Why the other options are incorrect:** * **Encephalitis:** This is a rare but serious complication (1 in 6,000 cases). It is much less common than joint involvement. * **Orchitis:** This is a classic complication of **Mumps**, not Rubella. * **Thrombocytopenia:** Post-infectious thrombocytopenic purpura can occur (1 in 3,000 cases), but it is significantly rarer than polyarthritis. **NEET-PG High-Yield Pearls:** * **Incubation Period:** 14–21 days. * **Forchheimer Spots:** Small, red petechiae on the soft palate (seen in 20% of cases; not pathognomonic). * **Lymphadenopathy:** Post-auricular and sub-occipital lymphadenopathy is a hallmark clinical feature. * **Congenital Rubella Syndrome (CRS):** The most serious consequence if contracted during the first trimester. The classic triad includes **Cataract, Sensorineural deafness, and PDA (Patent Ductus Arteriosus).** * **Gregg’s Triad:** Another name for the CRS triad.

Q: What is the estimated risk of mother-to-child transmission of HIV?

25%. **Explanation:** The risk of Mother-to-Child Transmission (MTCT) of HIV, in the **absence of any medical intervention** (antiretroviral therapy, elective cesarean section, or avoidance of breastfeeding), is estimated to be between **25% and 30%**. Transmission can occur during three distinct periods: 1. **In utero (Transplacental):** ~5–10% 2. **Intrapartum (During labor/delivery):** ~15% (This is the period of highest risk due to exposure to infected maternal blood and cervicovaginal secretions). 3. **Postpartum (Breastfeeding):** ~5–15%. **Analysis of Options:** * **Option A (25%):** This is the standard accepted figure for vertical transmission risk without intervention. With modern Highly Active Antiretroviral Therapy (HAART) and a suppressed viral load, this risk can be reduced to **less than 1%**. * **Options B, C, and D (50%, 60%, 75%):** These values significantly overestimate the biological efficiency of HIV transmission. Even without treatment, the majority of infants born to HIV-positive mothers do not contract the virus. **High-Yield Clinical Pearls for NEET-PG:** * **Most common route of pediatric HIV:** Vertical transmission (MTCT). * **Diagnosis in infants:** HIV DNA PCR is the gold standard (performed at birth, 6 weeks, 6 months). Antibody tests (ELISA) are unreliable until **18 months** due to the persistence of maternal IgG antibodies. * **Prophylaxis:** Nevirapine is typically administered to the newborn for 6 weeks. * **Breastfeeding:** In India, exclusive breastfeeding is recommended for the first 6 months if the mother is on ART, followed by complementary feeding. Mixed feeding should be strictly avoided as it increases the risk of transmission.

Q: A 2-month-old child born to an HIV-positive mother is under your care. Which of the following prophylactic therapies should be considered for this child?

Prophylaxis against Pneumocystis jiroveci pneumonia. **Explanation:** The correct answer is **B. Prophylaxis against Pneumocystis jiroveci pneumonia (PCP).** **Why it is correct:** *Pneumocystis jiroveci* pneumonia (PCP) is the most common opportunistic infection in HIV-infected infants, with a peak incidence between **2 and 6 months of age**. Because HIV-exposed infants are at high risk of rapid disease progression and severe respiratory failure from PCP, the WHO and National AIDS Control Organization (NACO) guidelines recommend starting **Cotrimoxazole (TMP-SMX) prophylaxis** for all HIV-exposed infants starting at **4–6 weeks of age**. This is continued until the infant is confirmed to be HIV-negative or, if positive, until they are clinically stable on ART with improved CD4 counts. **Why the other options are incorrect:** * **Option A:** Kaposi sarcoma is rare in the pediatric population and is not a routine screening requirement for infants. * **Option C:** While nutrition is important, Vitamin C supplementation is not a specific prophylactic therapy for HIV-exposed infants. * **Option D:** Oral Polio Vaccine (OPV) is a **live-attenuated vaccine**. In HIV-exposed or infected children, live vaccines are generally avoided if the child is severely symptomatic or immunocompromised. In many countries, Inactivated Polio Vaccine (IPV) is preferred to avoid the risk of vaccine-associated paralytic polio (VAPP). **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice for PCP Prophylaxis:** Cotrimoxazole (Trimethoprim-Sulfamethoxazole). * **Timing:** Start at 4–6 weeks of age in all HIV-exposed infants. * **Diagnosis in Infants:** HIV DNA PCR (at 6 weeks) is the gold standard for infants <18 months, as maternal IgG antibodies cross the placenta, making ELISA unreliable. * **Breastfeeding:** Exclusive breastfeeding for the first 6 months is recommended if the mother is on ART, followed by complementary feeding. Mixed feeding should be avoided.

Q: A 5-year-old boy presents to the emergency room after a dog bite on his right forearm. The laceration is small, irregular, and superficial, and bleeding has stopped. The child has a normal neuromuscular examination and intact perfusion. What is the most appropriate management for this injury?

Copious irrigation. **Explanation:** The primary goal in managing any animal bite is the prevention of infection (both bacterial and viral). **1. Why "Copious Irrigation" is correct:** The single most effective step in reducing the risk of infection following a dog bite is **copious irrigation** with normal saline or sterile water. This mechanical debridement flushes out saliva, debris, and pathogens (like *Pasteurella multocida*) from the wound. In the management of rabies-prone bites, immediate wound washing with soap and water for at least 15 minutes is the most critical initial step recommended by WHO and national guidelines. **2. Why other options are incorrect:** * **Option A:** While antimicrobial prophylaxis (Amoxicillin-Clavulanate) is often indicated for high-risk bites (cat bites, hand wounds, or immunocompromised patients), it is secondary to local wound care. * **Option B:** Tetanus prophylaxis is essential if the child is under-immunized, but "tetanus toxoid in the wound" is medically incorrect; vaccines are administered intramuscularly. * **Option C:** Rabies post-exposure prophylaxis (PEP) depends on the dog's vaccination status and the category of the bite. However, even if PEP is required, it never supersedes immediate local wound toilet. **Clinical Pearls for NEET-PG:** * **Organism:** *Pasteurella multocida* is the most common aerobic organism in dog/cat bites. *Capnocytophaga canimorsus* is a concern in splenectomized patients. * **Drug of Choice:** Amoxicillin-Clavulanate (covers anaerobes and *Pasteurella*). * **Suturing:** Dog bites on the extremities are generally left open (healing by secondary intention) to prevent abscess formation, unless they are on the face (for cosmesis). * **Rabies Categories:** Category I (touching/licking intact skin) needs no PEP; Category II (nibbling, minor scratches) needs vaccine; Category III (transdermal bites/licks on broken skin) needs vaccine + Rabies Immunoglobulin (RIG).

Q: According to WHO staging, what stage is assigned to an HIV-infected child presenting with parotid enlargement?

Stage 2. **Explanation:** The WHO Clinical Staging of HIV in children is categorized based on clinical severity and the degree of immunosuppression. **Correct Option: B (Stage 2)** According to the WHO classification for children (<15 years), **Persistent Parotid Enlargement** is a characteristic feature of **Clinical Stage 2 (Mild Disease)**. This stage typically involves "mild" symptoms that are not life-threatening but indicate disease progression. Other common manifestations in Stage 2 include unexplained persistent hepatosplenomegaly, papular pruritic eruptions, extensive wart infections, and recurrent upper respiratory tract infections (e.g., sinusitis or otitis media). **Why other options are incorrect:** * **Stage 1:** This stage represents **Asymptomatic** infection. The only clinical finding allowed here is Persistent Generalized Lymphadenopathy (PGL). Parotid enlargement is considered a symptomatic progression beyond Stage 1. * **Stage 3:** This stage involves **Advanced** symptoms such as unexplained moderate malnutrition, persistent diarrhea, oral candidiasis, or pulmonary tuberculosis. * **Stage 4:** This stage represents **Severe (AIDS-defining)** illness, including conditions like Pneumocystis pneumonia (PCP), esophageal candidiasis, or HIV wasting syndrome. **Clinical Pearls for NEET-PG:** * **Parotid Enlargement:** In HIV-infected children, this is often due to **Lymphocytic Interstitial Pneumonitis (LIP)** or benign lymphoepithelial cysts. * **LIP vs. TB:** LIP is a Stage 3 condition, but isolated parotid enlargement remains Stage 2. * **Most Common Opportunistic Infection:** In children, it is often *Pneumocystis jirovecii* (Stage 4), which is why Co-trimoxazole prophylaxis is vital. * **Diagnosis:** For children 18 months, standard Antibody testing (ELISA) is used.

Q: What is the recommended dose of oseltamivir for chemoprophylaxis in an infant?

3 mg/kg once daily. **Explanation:** The correct answer is **A. 3 mg/kg once daily**. **Medical Concept:** Oseltamivir is a neuraminidase inhibitor used for both the treatment and chemoprophylaxis of Influenza A and B. In infants (aged 0–12 months), the dosing is weight-based rather than age-based due to the rapid physiological changes in renal clearance during the first year of life. For **chemoprophylaxis**, the standard recommendation is **3 mg/kg administered once daily** for 7–10 days following exposure. **Analysis of Options:** * **Option A (Correct):** 3 mg/kg once daily is the established prophylactic dose for infants to prevent the onset of symptoms after exposure. * **Option B, C, and D (Incorrect):** These options provide fixed doses (20 mg). While 30 mg, 45 mg, 60 mg, and 75 mg are standard fixed doses for older children and adults based on weight bands, infants require precise mg/kg dosing. Furthermore, "thrice a day" (Option D) is never a standard frequency for oseltamivir, which is typically dosed once daily (prophylaxis) or twice daily (treatment). **High-Yield Clinical Pearls for NEET-PG:** * **Treatment vs. Prophylaxis:** For infants, the **treatment** dose is 3 mg/kg **twice daily** for 5 days, whereas **prophylaxis** is **once daily**. * **Age Limit:** Oseltamivir is FDA-approved for treatment from birth and for prophylaxis from 3 months of age (though used off-label in younger infants during outbreaks). * **Mechanism of Action:** It inhibits the neuraminidase enzyme, preventing the release of new virions from infected host cells. * **Timing:** To be most effective, oseltamivir should be started within **48 hours** of symptom onset or exposure.

Q: A 9-month-old child has been diagnosed with measles. What is the recommended dose of vitamin A administration?

1,00,000 IU. **Explanation:** Vitamin A is a critical micronutrient for maintaining epithelial integrity and immune function. In the context of **Measles**, Vitamin A levels drop rapidly, increasing the risk of severe complications like blindness (keratomalacia), pneumonia, and diarrhea. Therefore, the WHO and National Guidelines recommend immediate supplementation for all children diagnosed with measles. The dosage is strictly **age-dependent**: * **< 6 months:** 50,000 IU * **6 – 11 months:** 1,00,000 IU (Correct Answer) * **≥ 12 months:** 2,00,000 IU **Analysis of Options:** * **Option A (50,000 IU):** This is the therapeutic dose for infants younger than 6 months. * **Option B (1,00,000 IU):** Correct. Since the child is 9 months old, they fall into the 6–11 month bracket. * **Option C (1,50,000 IU):** This is not a standard recommended dose in the Vitamin A protocol. * **Option D (2,00,000 IU):** This is the dose for children aged 1 year and older. **High-Yield Clinical Pearls for NEET-PG:** 1. **Schedule:** For measles treatment, two doses are given: the first immediately upon diagnosis and the second the following day. A third dose is added 4 weeks later if clinical signs of Vitamin A deficiency (e.g., Bitot’s spots) are present. 2. **Prophylaxis vs. Treatment:** Do not confuse this with the **National Prophylactic Program**, where the first dose (1 lakh IU) is given at 9 months (with Measles-Rubella vaccine) and subsequent doses (2 lakh IU) are given every 6 months until age 5 (total 9 doses/17 lakh IU). 3. **Mechanism:** Vitamin A reduces measles mortality by approximately 50%.

Q: A child's CSF was examined and showed slightly raised or normal PMN cells, raised lymphocytes, absence of mycotic growth, normal or above normal protein value, and normal glucose level. What is the most probable diagnosis?

Viral meningitis. ### Explanation The clinical presentation of cerebrospinal fluid (CSF) analysis is a high-yield topic for NEET-PG. The diagnosis of **Viral Meningitis** (Aseptic Meningitis) is based on the following characteristic CSF findings: 1. **Glucose Level:** This is the most critical differentiator. In viral meningitis, glucose is **normal** (typically >2/3rd of blood glucose), whereas it is significantly decreased in bacterial, fungal, and tuberculous meningitis. 2. **Cellular Profile:** There is a predominance of **lymphocytes**. While PMNs (polymorphonuclear cells) may be slightly raised in the very early stages (first 24 hours), the shift to lymphocytosis is classic. 3. **Protein:** Protein levels are usually **normal or mildly elevated** (typically <100 mg/dL), unlike the marked elevations seen in other types. #### Why the other options are incorrect: * **Pyogenic Bacterial Meningitis:** Characterized by marked **neutrophilic pleocytosis**, significantly **low glucose** (<40 mg/dL), and very high protein levels. * **Tuberculous Meningitis (TBM):** While it shows lymphocytosis, the **glucose is always low** and the protein is characteristically very high (often causing a cobweb coagulum). * **Fungal Meningitis:** Similar to TBM, it presents with low glucose and elevated protein. The question also specifically mentions the **absence of mycotic growth**. #### NEET-PG High-Yield Pearls: * **Most common cause of Viral Meningitis:** Enteroviruses (Coxsackie and Echovirus). * **Normal CSF Glucose:** 40–70 mg/dL (or 60-70% of plasma glucose). * **Normal CSF Protein:** 15–45 mg/dL. * **Mnemonic for TBM:** "Low Sugar, High Protein, Lymphocytes" (The "T" in TBM stands for "Tiny sugar").

Q: Mumps is characterized by a triad of which of the following?

Epidemic parotitis, orchitis-oophoritis, pancreatitis.. **Explanation:** Mumps is an acute viral infection caused by the **Rubulavirus** (Paramyxoviridae family). It is characterized by its affinity for glandular and neurological tissues. The classic clinical triad of Mumps consists of **Epidemic parotitis, Orchitis/Oophoritis, and Pancreatitis**. 1. **Why Option A is correct:** The virus primarily replicates in the upper respiratory tract and then spreads hematogenously to target organs. * **Parotitis:** The most common manifestation (95% of symptomatic cases), usually bilateral. * **Orchitis/Oophoritis:** The most common extra-salivary site in post-pubertal males (orchitis is usually unilateral). * **Pancreatitis:** Presents as epigastric pain and vomiting; it is a classic component of the triad, though often mild. 2. **Why other options are incorrect:** * **Option B & C:** While **Meningoencephalitis** is the most common *neurological* complication of Mumps (often presenting as aseptic meningitis), it is not traditionally considered part of the "triad" of glandular involvement that defines the classic presentation in medical literature and competitive exams. **High-Yield Clinical Pearls for NEET-PG:** * **Incubation Period:** 14–21 days (Average 18 days). * **Infectivity:** Maximum 48 hours *before* the onset of parotitis. * **Diagnosis:** Primarily clinical; however, **Serum Amylase** is elevated in both parotitis and pancreatitis. * **Complications:** * Most common complication in children: **Aseptic meningitis**. * Most common cause of **acquired sensorineural deafness** in children (usually unilateral). * **Prevention:** Live attenuated vaccine (Jeryl Lynn strain) as part of the MMR vaccine.

Question 1

What is the characteristic feature of early congenital syphilis?

Accepted Answer

Vesicular rash with bulla over palms and soles

Answer

Microcephaly

Answer

Saddle nose

Answer

Interstitial keratitis with sabre skin

Question 2

What is the most common complication of rubella?

Accepted Answer

Polyarthritis

Answer

Encephalitis

Answer

Orchitis

Answer

Thrombocytopenia

Question 3

What is the estimated risk of mother-to-child transmission of HIV?

Accepted Answer

25%

Answer

50%

Answer

60%

Answer

75%

Question 4

A 2-month-old child born to an HIV-positive mother is under your care. Which of the following prophylactic therapies should be considered for this child?

Accepted Answer

Prophylaxis against Pneumocystis jiroveci pneumonia

Answer

Monthly evaluation for Kaposi sarcoma

Answer

Vitamin C supplementation

Answer

Oral polio virus vaccine

Question 5

A 5-year-old boy presents to the emergency room after a dog bite on his right forearm. The laceration is small, irregular, and superficial, and bleeding has stopped. The child has a normal neuromuscular examination and intact perfusion. What is the most appropriate management for this injury?

Accepted Answer

Copious irrigation

Answer

Irrigation and antimicrobial prophylaxis

Answer

Tetanus booster immunization and tetanus toxoid in the wound

Answer

Primary rabies vaccination for the child

Question 6

According to WHO staging, what stage is assigned to an HIV-infected child presenting with parotid enlargement?

Accepted Answer

Stage 2

Answer

Stage 1

Answer

Stage 3

Answer

Stage 4

Question 7

What is the recommended dose of oseltamivir for chemoprophylaxis in an infant?

Accepted Answer

3 mg/kg once daily

Answer

20 mg once a day

Answer

20 mg twice a day

Answer

20 mg thrice a day

Question 8

A 9-month-old child has been diagnosed with measles. What is the recommended dose of vitamin A administration?

Accepted Answer

1,00,000 IU

Answer

50,000 IU

Answer

1,50,000 IU

Answer

2,00,000 IU

Question 9

A child's CSF was examined and showed slightly raised or normal PMN cells, raised lymphocytes, absence of mycotic growth, normal or above normal protein value, and normal glucose level. What is the most probable diagnosis?

Accepted Answer

Viral meningitis

Answer

Pyogenic bacterial meningitis

Answer

Fungal meningitis

Answer

Tuberculous meningitis

Question 10

Mumps is characterized by a triad of which of the following?

Accepted Answer

Epidemic parotitis, orchitis-oophoritis, pancreatitis.

Answer

Orchitis-oophoritis, encephalitis, pancreatitis.

Answer

Epidemic parotitis, meningoencephalitis, pancreatitis.

Answer

None of the above.

Infectious Diseases — MCQs

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