Infectious Diseases Practice Questions

Q: A child presents with fever and unconsciousness for 1 day and pallor with no focal neurological deficit. What is the most probable diagnosis?

Cerebral malaria. ### Explanation The correct diagnosis is **Cerebral Malaria**. The clinical triad of **fever**, **altered sensorium (unconsciousness)**, and **pallor** is the classic presentation of severe *Plasmodium falciparum* malaria in children. The presence of pallor is a crucial diagnostic clue, indicating significant hemolysis or bone marrow suppression, which is characteristic of malaria but uncommon in isolated CNS infections. The absence of focal neurological deficits further supports this, as cerebral malaria typically presents with symmetrical encephalopathy. **Why other options are incorrect:** * **Viral Encephalitis:** While it presents with fever and altered sensorium, it is rarely associated with significant **pallor**. It often presents with more acute behavioral changes or seizures. * **Pyomeningitis (Acute Bacterial Meningitis):** This usually presents with high-grade fever, signs of meningeal irritation (Kernig’s/Brudzinski’s sign), and a bulging fontanelle in infants. Pallor is not a hallmark feature. * **Tubercular Meningitis (TBM):** TBM typically follows a **subacute/chronic course** (weeks, not 1 day). It often presents with cranial nerve palsies (focal deficits) and a prodromal phase of weight loss and low-grade fever. **Clinical Pearls for NEET-PG:** * **Definition:** Cerebral malaria is defined as unarousable coma (Glasgow Coma Scale 1 hour after a seizure, with *P. falciparum* parasitemia, after excluding other causes. * **Hypoglycemia:** Always check blood glucose in these patients, as it is a common complication of both severe malaria and quinine therapy. * **Drug of Choice:** According to current WHO and NVBDCP guidelines, **Intravenous Artesunate** is the treatment of choice for severe/cerebral malaria, regardless of the trimester of pregnancy or age. * **Retinopathy:** Funduscopic examination showing "malarial retinopathy" (whitening, vessel changes) is highly specific for cerebral malaria.

Q: What is the most common complication of measles?

Otitis media. **Explanation:** Measles (Rubeola) is a highly contagious viral infection characterized by high fever, cough, coryza, conjunctivitis (the 3 Cs), and the pathognomonic Koplik spots. While the virus itself causes significant morbidity, its complications are frequent. **Why Otitis Media is the correct answer:** **Otitis media** is statistically the **most common complication** of measles, occurring in approximately 7–10% of cases. It occurs due to the virus causing inflammation of the respiratory mucosa and secondary bacterial invasion, leading to middle ear infection. For NEET-PG, it is crucial to distinguish between the "most common" and "most fatal" complication. **Analysis of Incorrect Options:** * **Orchitis (A):** This is a classic complication of **Mumps**, not Measles. It typically occurs in post-pubertal males. * **Pneumonia (B):** This is the **most common cause of death** (most fatal complication) associated with measles in children. It can be primary viral (Hecht’s giant cell pneumonia) or secondary bacterial. * **Seizures (D):** While febrile seizures can occur due to high fever in measles, they are not as frequent as otitis media. **High-Yield Clinical Pearls for NEET-PG:** * **Most common complication:** Otitis media. * **Most common cause of death:** Pneumonia. * **Most serious/delayed complication:** Subacute Sclerosing Panencephalitis (SSPE), occurring years after the initial infection. * **Vitamin A supplementation:** Essential in management as it reduces the severity of complications and mortality. * **Infectivity:** Maximum during the **pre-eruptive (prodromal) stage**. The patient is infectious from 4 days before to 4 days after the appearance of the rash.

Q: A 6-month-old child presents with recurrent seizures and poor development. The evaluation reveals hydrocephalus, impaired movement of the extremities, hypotonia, and retinal abnormalities. A computerized tomography (CT) scan demonstrates large ventricles and calcified lesions. Which of the following is the most likely diagnosis?

Toxoplasmosis. ### Explanation The clinical presentation of hydrocephalus, intracranial calcifications, and retinal abnormalities (chorioretinitis) forms the classic **Sabin Triad**, which is pathognomonic for **Congenital Toxoplasmosis**. **1. Why Toxoplasmosis is Correct:** Congenital Toxoplasmosis is caused by the transplacental transmission of *Toxoplasma gondii*. The CT findings of **diffuse intracranial calcifications** (scattered throughout the parenchyma) and ventriculomegaly (obstructive hydrocephalus due to aqueductal stenosis) are hallmark features. The "poor development" and "impaired movement" reflect the neurological sequelae of the infection, while "retinal abnormalities" typically refer to chorioretinitis, the most common ocular manifestation. **2. Why the Other Options are Incorrect:** * **Tay-Sachs Disease:** While it presents with developmental regression and hypotonia, it is characterized by a **cherry-red spot** on the macula and **macrocephaly** (due to GM2 ganglioside accumulation), not hydrocephalus or calcifications. * **Congenital Hydrocephalus:** This is a structural finding, not a primary diagnosis. It does not explain the intracranial calcifications or retinal abnormalities. * **Kernicterus:** This results from severe unconjugated hyperbilirubinemia. While it causes hypotonia (early) and movement disorders (choreoathetosis), it does not present with intracranial calcifications or hydrocephalus. **3. NEET-PG High-Yield Pearls:** * **Calcification Pattern:** In Toxoplasmosis, calcifications are **diffuse/scattered**; in Congenital CMV, they are typically **periventricular**. * **Classic Triad (Sabin Triad):** Hydrocephalus, Intracranial calcifications, and Chorioretinitis. * **Treatment:** The standard regimen is **Pyrimethamine, Sulfadiazine, and Folinic acid** for one year. * **Source:** Usually acquired via oocysts in cat feces or undercooked meat.

Q: A mother has been infected with rubella during pregnancy. Which of the following fetal congenital malformations can occur?

Pulmonary Stenosis (PS). **Explanation:** Congenital Rubella Syndrome (CRS) is a classic TORCH infection that occurs due to transplacental transmission of the Rubella virus, primarily during the first trimester. The virus causes vasculitis and inhibits mitosis, leading to multi-organ defects. **Why Pulmonary Stenosis (PS) is the correct answer:** While **Patent Ductus Arteriosus (PDA)** is the most common cardiac lesion overall in CRS, **Peripheral Pulmonary Artery Stenosis (PPS)** is the most characteristic and specific structural malformation associated with the syndrome. In many standardized exams, if both are present, PS (specifically peripheral) is frequently tested as the hallmark lesion. The virus directly damages the vascular endothelium of the pulmonary arteries during organogenesis. **Analysis of Incorrect Options:** * **A & B (VSD and ASD):** While these are common congenital heart defects in the general population, they are not classically associated with Congenital Rubella Syndrome. * **D (Patent Ductus Arteriosus):** Although PDA is the **most frequent** cardiac defect in CRS, it is often considered a "functional" failure of closure. In the context of this specific question format, Pulmonary Stenosis is often prioritized as the definitive structural malformation. **NEET-PG High-Yield Pearls:** * **Gregg’s Triad:** The classic presentation of CRS includes **Cataracts** (salt and pepper retinopathy), **Sensorineural Hearing Loss** (most common finding), and **Cardiac defects** (PDA/PS). * **"Blueberry Muffin" Rash:** Represents extramedullary hematopoiesis. * **Timing:** Risk is highest (up to 80%) if maternal infection occurs within the first 12 weeks of gestation. * **Diagnosis:** Confirmed by Rubella-specific IgM in the newborn or persistent IgG titers beyond 6 months.

Q: Primary pneumococcal peritonitis in children is most commonly associated with which of the following conditions?

Cirrhosis. **Explanation:** **Primary Peritonitis** (also known as Spontaneous Bacterial Peritonitis or SBP) is an infection of the peritoneal fluid without an evident intra-abdominal source of perforation. **Why Cirrhosis is the Correct Answer:** In children, the most common underlying condition predisposing to primary peritonitis is **Nephrotic Syndrome**, followed closely by **Cirrhosis** (chronic liver disease). In patients with cirrhosis, the development of ascites provides a medium for bacterial growth. The underlying pathophysiology involves **impaired host defenses**, specifically decreased opsonic activity in the ascitic fluid and portosystemic shunting, which allows bacteria to bypass the hepatic reticuloendothelial system (Kupffer cells). While *Streptococcus pneumoniae* is the classic organism associated with primary peritonitis in Nephrotic Syndrome, it is also a major pathogen in cirrhotic patients, alongside Gram-negative organisms like *E. coli*. **Analysis of Incorrect Options:** * **B. Lymphoma:** While lymphoma causes immunosuppression, it is more commonly associated with opportunistic infections or secondary peritonitis due to bowel obstruction/perforation rather than primary pneumococcal peritonitis. * **C. Carcinoid tumors:** These are neuroendocrine tumors that do not typically predispose patients to spontaneous bacterial infections of the peritoneum. **NEET-PG High-Yield Pearls:** * **Most common organism overall:** *Streptococcus pneumoniae* is the most common cause of primary peritonitis in children (especially those with Nephrotic Syndrome). * **Clinical Presentation:** Sudden onset of fever, abdominal pain, and rebound tenderness in a child with pre-existing ascites. * **Diagnosis:** Established by paracentesis showing an **Absolute Neutrophil Count (ANC) >250 cells/mm³**. * **Treatment of choice:** Third-generation cephalosporins (e.g., Cefotaxime or Ceftriaxone).

Q: Which of the following statements about HIV in neonates is incorrect?

The transmission rate during pregnancy exceeds 90%.. **Explanation:** **1. Why Option C is the correct (incorrect statement):** The transmission rate of HIV from an untreated mother to her child is approximately **15% to 45%**, not >90%. With modern Prevention of Mother-to-Child Transmission (PMTCT) interventions—including Highly Active Antiretroviral Therapy (HAART), elective cesarean section, and avoidance of breastfeeding—this risk can be reduced to **less than 1–2%**. Therefore, the statement claiming a >90% transmission rate is factually incorrect. **2. Analysis of other options:** * **Option A:** Diagnosis in neonates is complex because maternal IgG antibodies cross the placenta and persist for up to 18 months. Therefore, standard ELISA/Western Blot cannot distinguish between infant infection and maternal antibodies. Diagnosis requires **HIV DNA or RNA PCR** (Nucleic Acid Testing). * **Option B:** Failure to thrive (FTT), persistent diarrhea, and recurrent infections (like oral candidiasis) are classic early clinical presentations of pediatric HIV. * **Option C:** Vertical transmission is the primary route of pediatric HIV, occurring in utero (transplacental), during delivery (birth canal), or postpartum (breastfeeding). **Clinical Pearls for NEET-PG:** * **Gold Standard Diagnosis:** HIV DNA PCR is the preferred test for infants <18 months. The first test is usually done within 4–6 weeks of birth. * **Prophylaxis:** All HIV-exposed infants should receive **Nevirapine** (or Zidovudine) prophylaxis immediately after birth for 6–12 weeks. * **Pneumocystis jirovecii (PJP) Prophylaxis:** Started at 6 weeks of age for all HIV-exposed infants until infection is ruled out. * **Breastfeeding:** In India (per NACO guidelines), exclusive breastfeeding is recommended for the first 6 months if replacement feeding is not "AFASS" (Affordable, Feasible, Acceptable, Sustainable, and Safe).

Q: Erythema infectiosum is seen in which of the following conditions?

Fifth disease. **Explanation:** **Erythema infectiosum**, commonly known as **Fifth Disease**, is caused by **Parvovirus B19**. It is a mild febrile illness primarily affecting children. The characteristic clinical feature is a "slapped-cheek" appearance (confluent erythema on the malar area), followed by a symmetric, reticulate (lace-like) maculopapular rash on the trunk and extremities. **Analysis of Options:** * **Option B (Correct):** Erythema infectiosum is the medical term for Fifth Disease. It is named "Fifth" because it was the fifth in a historical classification of common childhood exanthems. * **Option A (Incorrect):** Rubella (German Measles) presents with a pinkish maculopapular rash that starts on the face and spreads cephalocaudally, often associated with post-auricular and suboccipital lymphadenopathy. * **Option C (Incorrect):** Scarlet fever is caused by Group A Streptococcus. It presents with a "sandpaper" rash, Pastia’s lines, and a "strawberry tongue," rather than the slapped-cheek rash. * **Option D (Incorrect):** Diphtheria is a bacterial infection characterized by a greyish pseudomembrane in the pharynx and bull-neck lymphadenopathy; it does not typically present with a viral exanthem. **High-Yield Clinical Pearls for NEET-PG:** 1. **Transmission:** Respiratory droplets; the patient is no longer contagious once the rash appears. 2. **Aplastic Crisis:** Parvovirus B19 infects erythrocyte precursors. In patients with high red cell turnover (e.g., Sickle Cell Anemia, Hereditary Spherocytosis), it can cause a life-threatening transient aplastic crisis. 3. **Pregnancy:** Infection during pregnancy can lead to **Hydrops Fetalis** due to severe fetal anemia. 4. **Adults:** Often presents with arthralgia or arthritis (small joints of hands/feet).

Q: A 60-year-old unvaccinated patient presents to the OPD with fever and red eyes. On examination, a specific type of rash is observed on the body. What is the most likely complication expected with this condition?

Myocarditis. ***Myocarditis*** - **Measles** (rubeola) commonly causes **myocarditis** as a serious cardiac complication, especially in adults and immunocompromised patients. - The clinical presentation of **fever**, **conjunctivitis** (red eyes), and **maculopapular rash** in an unvaccinated patient is classic for measles. *Nephritis* - **Nephritis** is not a recognized primary complication of **measles** (rubeola). - Kidney involvement is more commonly associated with other viral infections like **post-streptococcal glomerulonephritis**. *Pancreatitis* - **Pancreatitis** is a well-known complication of **mumps**, not measles. - Measles primarily affects the **respiratory system**, **skin**, and can cause **cardiac** and **neurological** complications. *Orchitis* - **Orchitis** is a classic complication of **mumps** infection, occurring in post-pubertal males. - This condition is characterized by the **3 C's** (cough, coryza, conjunctivitis) with **cephalocaudal rash progression**, not mumps symptoms.

Q: A child presents with seborrheic dermatitis, sinusitis, and chronically draining ears. On examination, the child has failure to thrive with hepatosplenomegaly and exophthalmos. What is the probable diagnosis?

Histiocytosis-X. **Explanation:** The clinical presentation described is a classic triad of **Langerhans Cell Histiocytosis (LCH)**, formerly known as **Histiocytosis-X**. **Why Histiocytosis-X is correct:** LCH is characterized by the abnormal proliferation of Langerhans cells. The case describes the **Hand-Schüller-Christian disease** variant, which typically presents with a triad of **exophthalmos, diabetes insipidus (due to pituitary involvement), and lytic bone lesions**. * **Skin:** Seborrheic dermatitis-like rash (often involving the scalp and diaper area) is a hallmark. * **Ears:** Chronic ear discharge (otitis media/externa) unresponsive to antibiotics is a high-yield sign. * **Systemic:** Hepatomegaly and failure to thrive indicate multisystem involvement (Letterer-Siwe disease spectrum). **Why other options are incorrect:** * **Wegener’s Granulomatosis:** While it causes sinusitis and ear issues, it typically presents with pulmonary nodules and glomerulonephritis (hematuria) in older patients, not seborrheic dermatitis or exophthalmos in children. * **Chronic Granulomatous Disease (CGD):** A defect in phagocytic NADPH oxidase leading to recurrent catalase-positive infections (abscesses, osteomyelitis). It does not cause exophthalmos or lytic bone lesions. * **Chediak-Higashi Syndrome:** Characterized by partial oculocutaneous albinism, giant granules in neutrophils, and recurrent pyogenic infections, not the specific triad seen here. **NEET-PG High-Yield Pearls:** 1. **Pathognomonic finding:** **Birbeck granules** (tennis-racket shaped) on electron microscopy. 2. **Immunohistochemistry:** Positive for **CD1a, S-100, and CD207 (Langerin)**. 3. **Bone Lesions:** "Punched-out" lytic lesions, especially in the skull. 4. **Ear Involvement:** Chronic draining ears in a child with a scalp rash should always trigger suspicion of LCH.

Question 1

A child presents with fever and unconsciousness for 1 day and pallor with no focal neurological deficit. What is the most probable diagnosis?

Accepted Answer

Cerebral malaria

Answer

Viral encephalitis

Answer

Pyomeningitis

Answer

Tubercular meningitis

Question 2

What is the most common complication of measles?

Accepted Answer

Otitis media

Answer

Orchitis

Answer

Pneumonia

Answer

Seizures

Question 3

A 6-month-old child presents with recurrent seizures and poor development. The evaluation reveals hydrocephalus, impaired movement of the extremities, hypotonia, and retinal abnormalities. A computerized tomography (CT) scan demonstrates large ventricles and calcified lesions. Which of the following is the most likely diagnosis?

Accepted Answer

Toxoplasmosis

Answer

Tay-Sachs disease

Answer

Congenital hydrocephalus

Answer

Kernicterus

Question 4

A mother has been infected with rubella during pregnancy. Which of the following fetal congenital malformations can occur?

Accepted Answer

Pulmonary Stenosis (PS)

Answer

Ventricular Septal Defect (VSD)

Answer

Atrial Septal Defect (ASD)

Answer

Patent Ductus Arteriosus (PDA)

Question 5

Primary pneumococcal peritonitis in children is most commonly associated with which of the following conditions?

Accepted Answer

Cirrhosis

Answer

Lymphoma

Answer

Carcinoid tumors

Answer

None of the above

Question 6

Which of the following statements about HIV in neonates is incorrect?

Accepted Answer

The transmission rate during pregnancy exceeds 90%.

Answer

Diagnosis cannot be accurately made by current methods.

Answer

Failure to thrive may be a presenting sign.

Answer

Vertical transmission from mother to child can occur.

Question 7

Erythema infectiosum is seen in which of the following conditions?

Accepted Answer

Fifth disease

Answer

Rubella

Answer

Scarlet fever

Answer

Diphtheria

Question 8

A 60-year-old unvaccinated patient presents to the OPD with fever and red eyes. On examination, a specific type of rash is observed on the body. What is the most likely complication expected with this condition?

Accepted Answer

Myocarditis

Answer

Nephritis

Answer

Pancreatitis

Answer

Orchitis

Question 9

A child presents with seborrheic dermatitis, sinusitis, and chronically draining ears. On examination, the child has failure to thrive with hepatosplenomegaly and exophthalmos. What is the probable diagnosis?

Accepted Answer

Histiocytosis-X

Answer

Wegener's granulomatosis

Answer

Chronic granulomatous disease

Answer

Chediak-Higashi syndrome

Question 10

A 2-year-old female child was brought to a PHC with a history of cough and fever for 4 days and inability to drink for the last 12 hours. On examination, the child weighed 5 kg and had a respiratory rate of 45/minute with fever. How would this child be classified?

Accepted Answer

Very severe disease

Answer

Severe pneumonia

Answer

Pneumonia

Answer

No pneumonia

Infectious Diseases — MCQs

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