Infectious Diseases Practice Questions

Q: An 18-month-old baby with poor feeding and fever for 3 days presents with lower limb weakness. On examination, the baby is lethargic, has abnormal movement of the lower limbs, and the anterior fontanelle is bulging. What is the diagnosis?

Meningitis. **Explanation:** The clinical presentation of fever, poor feeding, and lethargy in an 18-month-old is highly suggestive of an acute infection. The presence of a **bulging anterior fontanelle** is a hallmark sign of increased intracranial pressure (ICP), which, in the context of fever, strongly points toward **Acute Bacterial Meningitis**. The "abnormal movement" and lower limb weakness are likely manifestations of meningeal irritation or focal neurological deficits resulting from inflammation or vasculitis associated with the infection. **Why other options are incorrect:** * **Intracranial Hemorrhage:** While it causes a bulging fontanelle and lethargy, it usually presents with a sudden onset, often following trauma or in the context of a bleeding diathesis (e.g., Vitamin K deficiency), and typically lacks a high-grade fever. * **Pseudotumor Cerebri (Idiopathic Intracranial Hypertension):** This condition presents with signs of raised ICP (headache, papilledema) but is rare in infants and is characteristically associated with a lack of fever and normal CSF composition. * **Cerebral Palsy:** This is a non-progressive permanent disorder of posture and movement resulting from an insult to the developing brain (often prenatal or perinatal). It does not present acutely with fever and a bulging fontanelle. **High-Yield Pearls for NEET-PG:** * **Most common organisms:** *Streptococcus pneumoniae* is the most common cause of bacterial meningitis in children >1 month of age. * **Clinical Signs:** In infants, classic signs like Kernig’s and Brudzinski’s are often absent. Look for non-specific signs: bulging fontanelle, high-pitched cry, and paradoxical irritability. * **Diagnosis:** Lumbar puncture is the gold standard (unless signs of herniation are present). * **Treatment:** Empiric therapy usually involves 3rd generation cephalosporins (Ceftriaxone/Cefotaxime) plus Vancomycin.

Q: The teeth abnormality shown in the image is seen in which of the following diseases?

Congenital Syphilis. ***Congenital Syphilis*** - The dental abnormalities shown are likely **Hutchinson's teeth** (notched, peg-shaped incisors) and **mulberry molars** (dome-shaped first molars), pathognomonic of congenital syphilis. - These findings are part of **Hutchinson's triad** which includes interstitial keratitis, eighth nerve deafness, and Hutchinson's teeth. *Cleidocranial dysostosis* - Dental abnormalities include **delayed tooth eruption**, **supernumerary teeth**, and **impacted permanent teeth**. - Associated with **absent or hypoplastic clavicles** and **delayed fontanelle closure**, not the specific tooth morphology seen in the image. *Congenital Rubella* - Dental manifestations are minimal and include **delayed tooth eruption** and **enamel defects**. - Primary features are **cataracts**, **cardiac defects**, and **sensorineural hearing loss**, not characteristic dental malformations. *Congenital hypothyroidism* - Causes **delayed tooth eruption** and **prolonged retention of deciduous teeth**. - Associated with **growth retardation** and **mental retardation**, but does not cause the specific morphological tooth changes shown.

Q: Hutchinson teeth are a characteristic feature of which condition?

Late congenital syphilis. **Explanation:** **Hutchinson teeth** are a classic dental abnormality characterized by widely spaced, peg-shaped permanent incisors with a central notch on the cutting edge. This occurs due to the direct invasion of the developing tooth germs by *Treponema pallidum*. 1. **Why B is correct:** Hutchinson teeth are a component of the **Hutchinson’s Triad**, which is diagnostic of **Late Congenital Syphilis** (manifesting after 2 years of age). The triad includes: * Hutchinson teeth (Incisors) * Interstitial keratitis (leading to blindness) * Eighth nerve deafness (Sensorineural hearing loss) 2. **Why other options are incorrect:** * **A. Early congenital syphilis:** Presents before 2 years of age with features like snuffles (rhinitis), skin rashes (pemphigus syphiliticus), and hepatosplenomegaly. Dental changes only appear when permanent teeth erupt later in life. * **C. Rickets:** Characterized by delayed eruption of teeth and enamel hypoplasia, but not the specific notched, peg-shaped morphology. * **D. Scurvy:** Primarily affects the gums (swollen, bleeding) and leads to loose teeth due to defective collagen synthesis, but does not cause Hutchinson teeth. **High-Yield Clinical Pearls for NEET-PG:** * **Mulberry Molars:** Another dental sign of late congenital syphilis involving the first lower molars, which have multiple tiny globules of enamel instead of cusps. * **Saber Shins:** Anterior bowing of the tibia seen in late syphilis. * **Clutton’s Joints:** Painless, symmetrical swelling of the knees (hydrarthrosis). * **Higouménakis sign:** Unilateral thickening of the inner third of the clavicle.

Q: A 12-year-old child presents with fever and cervical lymphadenopathy for the last 36 hours. Oral examination shows a grey membrane on the right tonsil. What is the primary treatment?

20,000-40,000 units IM equine-derived antitoxin. **Explanation:** The clinical presentation of fever, cervical lymphadenopathy ("bull neck" appearance), and a greyish adherent membrane on the tonsils is classic for **Faucial Diphtheria** caused by *Corynebacterium diphtheriae*. **Why Option B is Correct:** The primary and most urgent treatment for diphtheria is the administration of **Diphtheria Antitoxin (DAT)**. Since the exotoxin causes irreversible tissue damage and myocarditis, the antitoxin must be given immediately based on clinical suspicion without waiting for culture results. The dosage is determined by the site and severity of the disease: * **Tonsillar/Pharyngeal (limited):** 20,000–40,000 units. * **Nasopharyngeal:** 40,000–60,000 units. * **Severe/Late presentation (>48 hours) or Systemic:** 80,000–120,000 units. As this patient has localized tonsillar involvement and presented within 36 hours, 20,000–40,000 units is the appropriate dose. **Why Other Options are Incorrect:** * **Option A & D:** Antibiotics (Penicillin or Erythromycin) are **secondary** treatments. They serve to stop further toxin production and prevent the spread of the organism to others, but they do not neutralize the toxin already circulating in the body. * **Option C:** This higher dose is reserved for extensive disease, laryngeal involvement, or patients presenting late (usually >3 days of symptoms). **High-Yield Clinical Pearls for NEET-PG:** 1. **Schick Test:** Used to determine the immune status of an individual (not for diagnosis). 2. **Culture Media:** Löffler’s serum slope (rapid growth) and Potassium Tellurite agar (black colonies). 3. **Microscopy:** Albert stain shows metachromatic granules (Babes-Ernst granules) in a "Chinese letter" pattern. 4. **Most Common Complication:** Myocarditis (usually occurs in the 2nd week). 5. **Neurological Complication:** Palatal palsy is the most common early neurological sign.

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.

Question 1

A 4-month-old infant presents with failure to thrive, progressive muscular weakness, and poor head control. The mother states that she feeds the baby soy-based formula sweetened with honey. Which organism is most likely responsible for these symptoms?

Accepted Answer

Clostridium botulinum

Answer

Clostridium difficile

Answer

Clostridium perfringens

Answer

Clostridium tetani

Question 2

An 18-month-old baby with poor feeding and fever for 3 days presents with lower limb weakness. On examination, the baby is lethargic, has abnormal movement of the lower limbs, and the anterior fontanelle is bulging. What is the diagnosis?

Accepted Answer

Meningitis

Answer

Intracranial hemorrhage

Answer

Pseudotumor cerebri

Answer

Cerebral palsy

Question 3

The teeth abnormality shown in the image is seen in which of the following diseases?

Accepted Answer

Congenital Syphilis

Answer

Cleidocranial dysostosis

Answer

Congenital Rubella

Answer

Congenital hypothyroidism

Question 4

Which of the following is true about erythema infectiosum?

Accepted Answer

Defervescence occurs before the rash appears

Answer

Slapped cheek appearance is seen

Answer

It is caused by parvovirus

Answer

The rash appears on the head and neck

Question 5

Hutchinson teeth are a characteristic feature of which condition?

Accepted Answer

Late congenital syphilis

Answer

Early congenital spirochetal infection

Answer

Rickets

Answer

Scurvy

Question 6

A 12-year-old child presents with fever and cervical lymphadenopathy for the last 36 hours. Oral examination shows a grey membrane on the right tonsil. What is the primary treatment?

Accepted Answer

20,000-40,000 units IM equine-derived antitoxin

Answer

Penicillin IV for 10 days

Answer

80,000-120,000 units IM equine-derived antitoxin

Answer

Erythromycin for 2 weeks

Question 7

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 8

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 9

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 10

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

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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