Infectious Diseases Practice Questions

Q: A child presents with complaints of oliguria, abdominal distension, and diarrhea. On examination, there is deep jaundice. Hepatomegaly was present, measuring 4 cm below the costal margin. Conjugated bilirubin in blood was 38 mg/dL, and there were urine urobilinogen and bile pigments. Hemoglobin was 4 g/dL and serum creatinine was 3 mg/dL. Which of the following tests is of least importance to diagnose this case?

Serum ceruloplasmin. The clinical presentation describes a child with **acute fulminant illness** characterized by the triad of **severe jaundice (conjugated hyperbilirubinemia), acute kidney injury (oliguria, high creatinine), and severe anemia (Hb 4 g/dL).** ### Why Serum Ceruloplasmin is the Least Important **Serum ceruloplasmin** is the screening test for **Wilson Disease**. While Wilson disease can present with acute liver failure and Coombs-negative hemolytic anemia, it typically occurs in older children (rarely under 5 years) and is characterized by **unconjugated hyperbilirubinemia** (due to hemolysis) and low alkaline phosphatase. In this acute, febrile-sounding presentation with multi-organ involvement (renal + hepatic), Wilson disease is the least likely diagnosis compared to acute infections or hematologic crises. ### Evaluation of Other Options * **G6PD level & Reticulocyte count:** The patient has severe anemia (4 g/dL) and jaundice. A G6PD deficiency trigger (infection/drugs) can cause a **hemolytic crisis** leading to hemoglobinuric acute tubular necrosis (renal failure). Reticulocyte count is essential to confirm hemolysis. * **Leptospiral antibody level:** This is a high-yield diagnosis for this triad. **Weil’s Disease (Leptospirosis)** classically presents with fever, diarrhea, hepatorenal syndrome (jaundice + oliguria), and hemorrhage/anemia. ### NEET-PG High-Yield Pearls * **Weil’s Syndrome Triad:** Jaundice, Renal Failure, and Hemorrhage (Leptospirosis). * **Conjugated Hyperbilirubinemia (>20% of total):** Always pathological; suggests hepatocellular damage or biliary obstruction, not simple hemolysis. * **Wilson Disease Presentation:** Suspect in any child >5 years with unexplained liver disease or neurological symptoms. The gold standard for diagnosis is a **liver biopsy** for copper content, though ceruloplasmin is the initial screen.

Q: A child patient presents to the outpatient department with a history of black central arch rashes on their body. What is your diagnosis?

Meningococcemia. ### Explanation **Correct Option: A. Meningococcemia** The hallmark clinical sign of Meningococcemia (caused by *Neisseria meningitidis*) is a rapidly progressing petechial or purpuric rash. These lesions often undergo central necrosis due to **disseminated intravascular coagulation (DIC)** and perivascular inflammation, leading to a characteristic **"black central arch"** or "gunmetal grey" appearance. This represents skin infarction and is a medical emergency, often progressing to Waterhouse-Friderichsen syndrome (adrenal hemorrhage). **Why other options are incorrect:** * **B. Dengue Hemorrhagic Fever:** While it presents with petechiae and ecchymosis due to thrombocytopenia, the classic rash is described as **"islands of white in a sea of red"** (convalescent rash). It typically lacks the necrotic black centers seen in meningococcemia. * **C. Leptospirosis:** Presents with conjunctival suffusion (pathognomonic), calf tenderness, and jaundice (Weil’s disease). While a petechial rash can occur, it is not the defining feature. * **D. Scrub Typhus:** The characteristic skin finding is an **Eschar**—a painless ulcer with a black crust at the site of the chigger bite—rather than generalized black central arch rashes. **NEET-PG High-Yield Pearls:** * **DOC for Prophylaxis:** Rifampicin (Close contacts); Ceftriaxone is preferred for pregnant women. * **DOC for Treatment:** Ceftriaxone or Cefotaxime. * **Glass Test:** Petechiae and purpura in meningococcemia are **non-blanching** (do not disappear when pressed with a glass). * **Most common serogroup in India:** Historically Serogroup A, though W-135 and Y are emerging globally.

Q: A 8-year-old boy presented with swelling on both sides of the face, below the ears, of 4 days duration. The swelling first started on the left side and then, 3 days later, appeared on the right side. Immunization to this disease can be achieved by which of the following vaccinations?

MMR. **Explanation:** The clinical presentation of bilateral facial swelling below the ears, starting on one side and progressing to the other, is a classic description of **Parotitis**, the hallmark of **Mumps**. Mumps is an acute viral infection caused by the *Rubulavirus* (Paramyxoviridae family). **Why MMR is correct:** The **MMR (Measles, Mumps, and Rubella)** vaccine is a live-attenuated vaccine that provides effective immunity against the Mumps virus. In the National Immunization Schedule (India) and IAP guidelines, it is typically administered in two doses (at 9 months as MR/MMR and 15 months as MMR). **Why other options are incorrect:** * **BCG (Bacillus Calmette-Guérin):** A live bacterial vaccine used to prevent severe forms of Tuberculosis (miliary and meningeal TB). * **Hepatitis B:** A subunit vaccine (HBsAg) used to prevent viral hepatitis caused by the Hepatitis B virus. * **Polio:** Administered as OPV (Sabin - live) or IPV (Salk - inactivated) to prevent poliomyelitis. **High-Yield Clinical Pearls for NEET-PG:** * **Most common complication in children:** Aseptic meningitis. * **Most common complication in post-pubertal males:** Epididymo-orchitis (usually unilateral; rarely leads to sterility). * **Other complications:** Pancreatitis (look for elevated serum amylase), Oophoritis, and Sensorineural hearing loss (usually unilateral). * **Infectivity:** Patients are most infectious from 2 days before to 5 days after the onset of parotid swelling. * **Diagnosis:** Primarily clinical; however, IgM antibodies or PCR can confirm the diagnosis.

Q: What is the approximate percentage of HIV transmission from an infected mother to her child?

20% – 30%. **Explanation:** The transmission of HIV from an infected mother to her child is known as **Vertical Transmission** or Mother-to-Child Transmission (MTCT). In the absence of any medical intervention (antiretroviral therapy, elective cesarean section, or avoidance of breastfeeding), the risk of transmission is approximately **20% to 30%**. **Breakdown of Transmission Timing:** * **In-utero (Transplacental):** ~5%–10% * **Intrapartum (During delivery):** ~10%–15% (Most common route) * **Postpartum (Breastfeeding):** ~5%–20% (Cumulative risk) **Analysis of Options:** * **Option A (20% – 30%):** Correct. This represents the standard global average for vertical transmission in non-interventional settings. * **Option B (10% – 20%):** Incorrect. This range is too low for a mother who is breastfeeding without treatment, though it may approximate the risk if breastfeeding is strictly avoided. * **Option C (70% – 80%):** Incorrect. HIV is not transmitted to every fetus; the placental barrier and maternal immune factors provide significant protection. * **Option D (100%):** Incorrect. Transmission is never guaranteed; even without treatment, the majority of infants born to HIV-positive mothers are born HIV-negative. **High-Yield Clinical Pearls for NEET-PG:** 1. **Prevention of Parent-to-Child Transmission (PPTCT):** With effective HAART (Highly Active Antiretroviral Therapy) and a suppressed maternal viral load, the risk can be reduced to **<1%–2%**. 2. **Most Common Route:** The **intrapartum period** (exposure to maternal blood and vaginal secretions) carries the highest risk. 3. **Diagnosis in Infants:** HIV DNA PCR (Nucleic Acid Test) is the gold standard for infants <18 months. Antibody tests (ELISA) are unreliable due to the persistence of maternal IgG antibodies. 4. **Prophylaxis:** In India, the NACP guidelines recommend **Nevirapine** syrup for the infant for at least 6 weeks.

Q: Raspberry tongue is seen in which of the following conditions?

Scarlet fever. **Explanation:** **Scarlet Fever (Correct Answer):** Scarlet fever is caused by **Group A Streptococcus (Streptococcus pyogenes)** producing **Erythrogenic (Pyrogenic) toxins**. The "Raspberry tongue" is a classic clinical sign that evolves in stages. Initially, the tongue has a white coating with red, hypertrophied papillae projecting through it (**White Strawberry Tongue**). By day 4 or 5, the white coat desquamates, leaving a bright red, denuded surface with prominent papillae, known as the **Red Strawberry or Raspberry Tongue**. **Analysis of Incorrect Options:** * **Vitiligo:** This is an autoimmune skin disorder characterized by the loss of melanocytes, leading to depigmented white patches. It does not affect the tongue in this inflammatory manner. * **Vitamin B12 deficiency:** This typically causes a **"Beefy red tongue"** or Hunter’s glossitis, where the tongue appears smooth and shiny due to the atrophy of lingual papillae (atrophic glossitis), rather than the prominent papillae seen in Scarlet fever. * **Impetigo:** Also caused by *S. pyogenes* or *S. aureus*, this is a superficial skin infection characterized by "honey-colored crusts." It does not typically involve the tongue. **NEET-PG High-Yield Pearls:** * **Dick Test:** Historically used to determine susceptibility to Scarlet fever. * **Schultz-Charlton Reaction:** A diagnostic test where antitoxin injected into the skin causes blanching of the Scarlet fever rash. * **Pastia’s Lines:** Pink or red lines in skin creases (axilla/groin) seen in Scarlet fever. * **Differential Diagnosis:** Strawberry tongue is also a major diagnostic criterion for **Kawasaki Disease**.

Q: Congenital rubella causes all EXCEPT:

Hydrocephalus. **Explanation:** Congenital Rubella Syndrome (CRS) is caused by the transplacental transmission of the Rubella virus, typically during the first trimester. The classic clinical presentation is defined by **Gregg’s Triad**, which includes sensorineural deafness, eye anomalies, and congenital heart disease. **Why Hydrocephalus is the correct answer:** Hydrocephalus is **not** a feature of Congenital Rubella. Instead, the hallmark neurological finding in CRS is **Microcephaly** (small head size due to impaired brain growth). Hydrocephalus is more characteristically associated with **Congenital Toxoplasmosis** (part of the classic triad: hydrocephalus, chorioretinitis, and intracranial calcifications). **Analysis of Incorrect Options:** * **A. Deafness:** Sensorineural hearing loss is the **most common** manifestation of CRS, occurring in about 80% of affected infants. * **B. Cataract:** Ocular defects are common, with "pearlescent" nuclear cataracts and "salt-and-pepper" retinopathy being high-yield findings. * **C. Cardiac defects:** The most characteristic lesion is **Patent Ductus Arteriosus (PDA)**, followed by peripheral pulmonary artery stenosis. **High-Yield Clinical Pearls for NEET-PG:** * **Classic Triad:** Cataract, Deafness, and PDA. * **Skin manifestation:** "Blueberry muffin" rash (due to extramedullary hematopoiesis). * **Radiology:** "Celery stalking" appearance (longitudinal radiolucent striations in the metaphysis of long bones). * **Timing:** Risk is highest (up to 90%) if maternal infection occurs before 11 weeks of gestation. * **Diagnosis:** Detection of Rubella-specific IgM in the newborn or persistence of IgG titers beyond 6–12 months.

Q: Which of the following is NOT a complication of mumps?

Hepatitis. **Explanation:** Mumps is an acute viral illness caused by the **Rubulavirus** (Paramyxoviridae family), primarily characterized by painful swelling of the parotid glands. While the virus is systemic and can affect various glandular and neurological tissues, **Hepatitis (Option D)** is not a recognized or typical complication of mumps. Liver involvement is extremely rare, making it the correct answer for this "except" type question. **Analysis of Complications:** * **Orchitis (Option A):** This is the most common complication in post-pubertal males (occurring in up to 30-40% of cases). It is usually unilateral and can lead to testicular atrophy, though permanent infertility is rare. * **Oophoritis (Option B):** Occurring in about 5-7% of post-pubertal females, it presents with pelvic pain and tenderness but rarely affects fertility. * **Encephalitis (Option C):** Neurological involvement is common. While **aseptic meningitis** is the most frequent neurological complication, true encephalitis (direct brain parenchyma involvement) occurs in about 1 in 1,000 cases and is a significant cause of mumps-related morbidity. **High-Yield Clinical Pearls for NEET-PG:** * **Pancreatitis:** Mumps is a classic viral cause of acute pancreatitis. * **Deafness:** Mumps is a leading cause of **sudden onset sensorineural hearing loss** (usually unilateral) in children. * **Most common complication in children:** Aseptic meningitis. * **Most common complication in post-pubertal males:** Orchitis. * **Incubation Period:** 14–21 days. * **Infectivity:** Patients are most infectious from 2 days before to 5 days after the onset of parotitis.

Question 1

A 6-year-old child develops a sore throat with high-grade fever. On examination, there was tender bilateral cervical adenopathy. Considering the findings, which of the following complications or outcomes will NOT be prevented or reduced by the administration of antibiotics?

Accepted Answer

Acute Glomerulonephritis

Answer

Rheumatic fever

Answer

Transmission of infection to others

Answer

Peritonsillar abscess

Question 2

A child presents with complaints of oliguria, abdominal distension, and diarrhea. On examination, there is deep jaundice. Hepatomegaly was present, measuring 4 cm below the costal margin. Conjugated bilirubin in blood was 38 mg/dL, and there were urine urobilinogen and bile pigments. Hemoglobin was 4 g/dL and serum creatinine was 3 mg/dL. Which of the following tests is of least importance to diagnose this case?

Accepted Answer

Serum ceruloplasmin

Answer

G6PD level in blood

Answer

Reticulocyte count

Answer

Leptospiral antibody level

Question 3

A child patient presents to the outpatient department with a history of black central arch rashes on their body. What is your diagnosis?

Accepted Answer

Meningococcemia

Answer

Dengue hemorrhagic fever

Answer

Leptospirosis

Answer

Scrub typhus

Question 4

Which vaccine is contraindicated in an HIV-positive child?

Accepted Answer

Oral Polio Vaccine (OPV)

Answer

Measles, Mumps, and Rubella (MMR) vaccine

Answer

Rabies vaccine

Answer

Influenza vaccine

Question 5

A 8-year-old boy presented with swelling on both sides of the face, below the ears, of 4 days duration. The swelling first started on the left side and then, 3 days later, appeared on the right side. Immunization to this disease can be achieved by which of the following vaccinations?

Accepted Answer

MMR

Answer

BCG

Answer

Hepatitis B

Answer

Polio

Question 6

A lactating woman has sputum positive TB. The neonate is 3 months old. What is the recommended chemoprophylaxis?

Accepted Answer

INH 5mg/kg for 6 months

Answer

INH 3mg/kg for 3 months

Answer

INH 5mg/kg for 3 months

Answer

INH 3mg/kg for 6 months

Question 7

What is the approximate percentage of HIV transmission from an infected mother to her child?

Accepted Answer

20% – 30%

Answer

10% – 20%

Answer

70% – 80%

Answer

100%

Question 8

Raspberry tongue is seen in which of the following conditions?

Accepted Answer

Scarlet fever

Answer

Vitiligo

Answer

Vitamin B12 deficiency

Answer

Impetigo

Question 9

Congenital rubella causes all EXCEPT:

Accepted Answer

Hydrocephalus

Answer

Deafness

Answer

Cataract

Answer

Cardiac defects

Question 10

Which of the following is NOT a complication of mumps?

Accepted Answer

Hepatitis

Answer

Orchitis

Answer

Oophoritis

Answer

Encephalitis

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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