Infectious Diseases Practice Questions

Q: What is the recommended treatment for an infant born to a mother with active tuberculosis?

Isoniazid prophylaxis. **Explanation:** The management of a neonate born to a mother with active tuberculosis (TB) focuses on preventing the high risk of primary infection and progression to disseminated disease (like TB meningitis) in the infant. **Why Option A is Correct:** According to the **National Tuberculosis Elimination Program (NTEP)** and WHO guidelines, if a mother has active pulmonary TB, the neonate should be started on **Isoniazid (INH) prophylaxis** at a dose of **5 mg/kg/day for 6 months**. This is because the infant is considered a "high-risk contact." BCG vaccination should be deferred until the completion of the 6-month INH course. After 6 months, if the infant is asymptomatic and the Mantoux test/Chest X-ray is negative, INH is stopped and BCG is administered. **Why Other Options are Incorrect:** * **Option B:** Incorrect because neonates have immature cell-mediated immunity; exposure without prophylaxis leads to a very high rate of progression to active disease. * **Options C & D:** These represent "Treatment" rather than "Prophylaxis." Full multi-drug therapy is only indicated if the neonate shows clinical signs of **Congenital TB** or has a positive evaluation (e.g., abnormal Chest X-ray or positive gastric aspirate for AFB). **High-Yield Clinical Pearls for NEET-PG:** * **Breastfeeding:** It is **not contraindicated**. The mother should continue breastfeeding while wearing a mask and practicing cough hygiene. * **Congenital TB:** The most common site of the primary complex in congenital TB is the **Liver** (due to umbilical vein spread), whereas in post-natal TB, it is the **Lungs**. * **Separation:** The infant should **not** be separated from the mother unless she is too ill to care for the child or has MDR-TB. * **Pyridoxine:** Should be supplemented (1 mg/kg) along with INH to prevent peripheral neuropathy.

Q: Which of the following vasculitides is typically not seen in adults?

Kawasaki disease. **Explanation:** **Kawasaki Disease (KD)** is the correct answer because it is an acute, self-limiting systemic vasculitis that almost exclusively affects infants and young children (85% of cases occur under age 5). While rare adult-onset cases exist, it is classically defined as a pediatric condition. It is a medium-vessel vasculitis with a predilection for the coronary arteries. **Analysis of Options:** * **Takayasu Arteritis (A):** Known as "pulseless disease," this large-vessel vasculitis typically affects young women (usually between ages 15 and 40). It is a classic adult/adolescent diagnosis. * **Susac Syndrome (B):** A rare microangiopathy characterized by the clinical triad of encephalopathy, branch retinal artery occlusions, and sensorineural hearing loss. It primarily affects young adults (ages 20–40). * **Henoch-Schönlein Purpura (C):** While HSP is the most common vasculitis in children, it is frequently seen in adults as well. In adults, the disease often presents with a more severe clinical course and a higher risk of significant renal involvement compared to children. **High-Yield Clinical Pearls for NEET-PG:** * **Kawasaki Diagnostic Criteria (CRASH and Burn):** **C**onjunctivitis (bilateral, non-exudative), **R**ash (polymorphous), **A**denopathy (cervical, usually unilateral), **S**trawberry tongue (and oral mucosal changes), **H**ands/feet (edema/desquamation), and **Burn** (High-grade fever for ≥5 days). * **Complication:** Coronary artery aneurysms are the most feared complication; **Echocardiography** is the mandatory initial investigation. * **Treatment:** High-dose IVIG + Aspirin (Note: This is one of the few pediatric indications where Aspirin is used despite the risk of Reye’s syndrome).

Q: Cancrum oris is associated with all the following EXCEPT:

None of the above. **Explanation:** **Cancrum Oris**, also known as **Noma**, is a devastating gangrenous stomatitis that leads to the rapid destruction of orofacial tissues. It primarily affects children (ages 2–6) in developing countries who are severely immunocompromised. **Why "None of the above" is correct:** The question asks which of the listed factors is *not* associated with Cancrum Oris. However, all three options (A, B, and C) are classic hallmarks or predisposing factors of the disease. Since all are associated, "None of the above" is the correct choice. * **Option A (Malnutrition):** This is the most significant predisposing factor. Severe Protein-Energy Malnutrition (PEM) weakens the immune system, allowing opportunistic oral flora to become invasive. * **Option B (Inflammatory swelling):** The clinical progression of Noma begins with a small intra-oral ulcer, followed by rapid, painful, **edematous inflammatory swelling** of the cheek or lip, which quickly progresses to necrosis. * **Option C (Vitamin deficiency):** Deficiencies in Vitamin B-complex and Vitamin C are frequently documented in these patients, further compromising mucosal integrity and immune response. **High-Yield Clinical Pearls for NEET-PG:** * **Microbiology:** It is a polymicrobial infection, but the key organisms involved are ***Fusobacterium necrophorum*** and ***Prevotella intermedia***. * **Preceding Infections:** It often follows a debilitating viral illness, most commonly **Measles**, but also Herpes simplex or Scarlet fever. * **Pathogenesis:** It is characterized by **rapidly spreading gangrene** that does not respect anatomical boundaries (bone and soft tissue are both destroyed). * **Treatment:** Management involves high-dose antibiotics (Penicillin/Metronidazole), nutritional rehabilitation, and delayed reconstructive surgery.

Q: Forcheimer sign is seen in which of the following conditions?

Rubella. **Explanation:** **Forchheimer sign** is a clinical finding characterized by small, reddish spots (petechiae) on the soft palate. It is seen in approximately 20% of patients with **Rubella** (German Measles). While it occurs during the prodromal phase or on the first day of the rash, it is not pathognomonic as it can occasionally be seen in other conditions. **Analysis of Options:** * **Rubella (Correct):** Forchheimer spots are a classic association. Rubella is also characterized by post-auricular and suboccipital lymphadenopathy and a rash that spreads cephalocaudally. * **Infectious Mononucleosis:** While palatal petechiae can occur in EBV infection, they are not referred to as Forchheimer spots. IM is better known for the triad of fever, pharyngitis, and lymphadenopathy. * **Scarlet Fever:** This is associated with **Pastia’s lines** (petechiae in skin folds) and a **Strawberry tongue** (white then red), caused by Group A Streptococcus. * **Rubeola (Measles):** The hallmark enanthem here is **Koplik spots** (bluish-white spots on an erythematous base opposite the lower molars), which are pathognomonic. **High-Yield Clinical Pearls for NEET-PG:** 1. **Koplik spots:** Measles (Rubeola). 2. **Forchheimer spots:** Rubella. 3. **Nagayama spots:** Roseola Infantum (HHV-6). 4. **Pastia’s lines/Strawberry tongue:** Scarlet Fever. 5. **Congenital Rubella Syndrome (CRS) Triad:** Cataract, Sensorineural hearing loss, and PDA (Patent Ductus Arteriosus).

Q: A rapid antigen test for meningitis organisms can be performed on which of the following specimens EXCEPT?

Throat swab. **Explanation:** Rapid Antigen Detection Tests (RADT), such as Latex Agglutination tests, are designed to detect soluble capsular polysaccharide antigens of common meningeal pathogens (e.g., *S. pneumoniae*, *N. meningitidis*, *H. influenzae* type b, and *G.BS*). These antigens are released into sterile body fluids during an active, systemic, or localized infection. **Why Throat Swab is the Correct Answer:** A throat swab is used to identify **colonization** or local respiratory infection. Many healthy individuals are asymptomatic carriers of *N. meningitidis* or *S. pneumoniae* in their nasopharynx. Detecting antigens in a throat swab does not differentiate between harmless colonization and invasive meningitis. Therefore, it is not a diagnostic specimen for meningitis. **Analysis of Other Options:** * **CSF:** This is the primary specimen. Antigen detection in CSF is highly specific and remains useful even if the patient has already received antibiotics (which may cause a negative culture). * **Urine:** Capsular antigens (especially from *H. influenzae* and *S. pneumoniae*) are excreted by the kidneys and concentrated in the urine, making it a non-invasive and effective sample for rapid testing. * **Blood:** During septicemia associated with meningitis, bacterial antigens are present in the serum and can be detected via RADT. **Clinical Pearls for NEET-PG:** * **Latex Agglutination:** The most common method used for rapid antigen detection in meningitis. * **Advantage:** It can detect antigens even when bacteria are non-viable (e.g., post-antibiotic therapy). * **Limitation:** A negative RADT does not rule out meningitis; **CSF Culture** remains the "Gold Standard" for diagnosis. * **Specific Pathogen:** For *Cryptococcus neoformans*, the CrAg (Cryptococcal Antigen) test in CSF is more sensitive than India Ink preparation.

Q: Koplik spots are seen in which of the following conditions?

Measles. **Explanation:** **Koplik spots** are the pathognomonic clinical sign of **Measles (Rubeola)**. They are small, irregular, bluish-white grains on an erythematous base (often described as "grains of salt on a red background") found on the buccal mucosa, typically opposite the lower second molars. They appear during the **prodromal stage**, approximately 48 hours before the characteristic maculopapular rash, and disappear as the rash breaks out. **Analysis of Options:** * **Mumps:** Characterized by painful swelling of the parotid glands (parotitis). It does not feature an enanthem like Koplik spots. * **Influenza:** A respiratory viral infection presenting with high fever, cough, and myalgia; it lacks specific oral mucosal findings. * **Rubella (German Measles):** While it presents with a rash, its characteristic oral finding is **Forchheimer spots** (small, red petechiae on the soft palate), which are not pathognomonic. **NEET-PG High-Yield Pearls:** * **Pathognomonic Sign:** Koplik spots = Measles. * **Timeline:** They appear in the prodromal phase and fade as the rash starts (which spreads in a cephalocaudal direction). * **Vitamin A:** Supplementation is crucial in measles management to reduce morbidity and mortality (especially ocular complications). * **Complications:** The most common complication is Otitis Media; the most common cause of death is Pneumonia; the most dreaded late complication is SSPE (Subacute Sclerosing Panencephalitis).

Q: A child presents with a history of high fever for 4 days, followed by seizures. A rash develops on the trunk the day after the fever subsides. What is the most probable diagnosis?

Roseola infantum. ### Explanation **Correct Answer: A. Roseola Infantum (Exanthema Subitum)** The clinical presentation described is classic for **Roseola infantum**, caused by **Human Herpesvirus 6 (HHV-6)**. The hallmark of this disease is a high-grade fever (often >103°F) lasting 3–5 days in a child who otherwise appears relatively well. The most defining feature is that the **rash appears only after the fever subsides** (defervescence). Because the fever rises so rapidly, **febrile seizures** are a common complication, occurring in approximately 10–15% of cases. The rash is typically maculopapular, starting on the trunk and spreading to the neck and extremities. **Why other options are incorrect:** * **Measles (Rubeola):** The rash appears at the *peak* of the high fever, not after it subsides. It is preceded by the "3 Cs" (Cough, Coryza, Conjunctivitis) and Koplik spots. * **Rubella (German Measles):** Presents with a low-grade fever and prominent post-auricular or suboccipital lymphadenopathy. The rash and fever occur simultaneously. * **Varicella (Chickenpox):** Characterized by a pruritic, pleomorphic rash (vesicles, papules, and crusts in different stages) that appears while the patient is still febrile. **NEET-PG High-Yield Pearls:** * **Etiology:** HHV-6 (most common) and HHV-7. * **Nagayama Spots:** Erythematous papules on the soft palate and uvula (seen in some Roseola patients). * **Age Group:** Most common in infants aged 6 months to 2 years. * **Sequence:** High Fever → Fever drops (Defervescence) → Rash appears. This sequence is unique to Roseola.

Question 1

What is the recommended treatment for an infant born to a mother with active tuberculosis?

Accepted Answer

Isoniazid prophylaxis

Answer

No treatment required

Answer

Full treatment with Isoniazid, Rifampicin, and Ethambutol

Answer

Treatment with Isoniazid and Rifampicin

Question 2

A 5-year-old child presents with a febrile illness characterized by cough and a blotchy rash. The child has not received routine pediatric care. On examination, there is lymphadenopathy and an erythematous, maculopapular rash behind the ears and along the hairline, involving the neck and, to a lesser extent, the trunk. Examination of this patient's oropharynx would likely reveal which lesion?

Accepted Answer

Multiple small white spots on the buccal mucosa

Answer

Adherent thin, whitish patch on gingiva

Answer

Cold sores on the lips

Answer

Curdy white material overlying an erythematous base on the oral mucosa

Question 3

Which of the following vasculitides is typically not seen in adults?

Accepted Answer

Kawasaki disease

Answer

Takayasu arteritis

Answer

Susac syndrome

Answer

Henoch-Schönlein purpura

Question 4

Cancrum oris is associated with all the following EXCEPT:

Accepted Answer

None of the above

Answer

Malnutrition

Answer

Inflammatory swelling

Answer

Vitamin deficiency

Question 5

Forcheimer sign is seen in which of the following conditions?

Accepted Answer

Rubella

Answer

Infectious mononucleosis

Answer

Scarlet fever

Answer

Rubeola

Question 6

Which statement is true regarding the transmission of HIV to an infant from an infected mother?

Accepted Answer

Administer zidovudine during labor.

Answer

There is a 25% chance of vertical transmission.

Answer

Avoid breastfeeding.

Answer

Vaccinate the infant with OPV and MMR.

Question 7

A rapid antigen test for meningitis organisms can be performed on which of the following specimens EXCEPT?

Accepted Answer

Throat swab

Answer

Blood

Answer

Cerebrospinal fluid (CSF)

Answer

Urine

Question 8

Koplik spots are seen in which of the following conditions?

Accepted Answer

Measles

Answer

Mumps

Answer

Influenza

Answer

Rubella

Question 9

A child presents with a history of high fever for 4 days, followed by seizures. A rash develops on the trunk the day after the fever subsides. What is the most probable diagnosis?

Accepted Answer

Roseola infantum

Answer

Measles

Answer

Rubella

Answer

Varicella

Question 10

A 12.6-month-old baby was brought with difficulty in feeding. The child was found to be hypotonic with a weak gag. The child is on breast milk, and the mother also gives honey to the child during periods of excessive crying. What is the causative agent?

Accepted Answer

Toxin produced by gram positive anaerobic bacillus

Answer

Gram positive aerobic coccus

Answer

Gram positive anaerobic bacillus

Answer

Echovirus

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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