Infectious Diseases Practice Questions

Q: Tuberculosis lymphadenitis of the cervical lymph nodes is also called:

Scrofula. **Explanation:** **Tuberculous Lymphadenitis (Scrofula)** The correct answer is **Scrofula**. This term specifically refers to tuberculosis of the cervical lymph nodes. It is the most common form of extrapulmonary tuberculosis [1]. In adults, it is primarily caused by *Mycobacterium tuberculosis*, whereas in children, it can also be caused by atypical mycobacteria (e.g., *M. scrofulaceum*). Clinically, it presents as "cold abscesses"—painless, firm, or matted swellings that may eventually develop into discharging sinuses [1]. **Analysis of Incorrect Options:** * **A. Pott’s Disease:** This refers to tuberculosis of the **spine**, typically involving the intervertebral discs and adjacent vertebrae, often leading to kyphosis (gibbus deformity) [2]. * **B. Lupus Vulgaris:** This is a progressive form of **cutaneous (skin) tuberculosis** characterized by "apple-jelly" nodules on diascopy, most commonly occurring on the face and neck. * **C. Ghon’s Focus:** This is a **primary pulmonary lesion** consisting of a small area of granulomatous inflammation (usually subpleural) in the mid or lower lobes of the lung [3]. **High-Yield Clinical Pearls for NEET-PG:** * **Most common site:** The **jugulodigastric** node is the most frequently involved cervical node. * **Diagnosis:** Fine Needle Aspiration Cytology (FNAC) is the initial investigation of choice, showing caseating granulomas. * **Histopathology:** Characterized by Langhans giant cells and central caseous necrosis [3]. * **Paradoxical Upgrading Reaction:** During ATT, lymph nodes may temporarily enlarge or new ones may appear; this is an immune response, not treatment failure [1].

Q: In HIV infection, prophylaxis for Pneumocystis jiroveci pneumonia may be stopped if the CD4 count persists above 200 cells/mm for what duration?

3 months. **Explanation:** The primary goal of opportunistic infection (OI) prophylaxis in HIV patients is to prevent disease during periods of severe immunosuppression. For *Pneumocystis jiroveci* pneumonia (PCP), the risk of infection significantly decreases once the immune system recovers following the initiation of Highly Active Antiretroviral Therapy (HAART) [1]. **1. Why 3 months is correct:** According to standard clinical guidelines (CDC/WHO), PCP prophylaxis (usually with Trimethoprim-Sulfamethoxazole) can be safely discontinued if the **CD4+ T-cell count increases to >200 cells/mm³ for at least 3 consecutive months**. This duration is required to ensure that the immune recovery is stable and robust enough to handle potential exposure to the fungus without pharmacological support. **2. Why other options are incorrect:** * **1 and 2 months (Options A & B):** These durations are considered too short to confirm sustained immune reconstitution. Discontinuing prophylaxis prematurely increases the risk of "rebound" infections if the CD4 count fluctuates [2]. * **6 months (Option D):** While waiting 6 months is safe, it is not the minimum standard required. Guidelines aim to reduce pill burden and potential drug toxicities as soon as it is clinically safe to do so, which is established at the 3-month mark. **High-Yield Clinical Pearls for NEET-PG:** * **Indication for starting PCP prophylaxis:** CD4 count 200 cells/mm³ for >3 months. * **MAC Prophylaxis:** Discontinued when CD4 >100 cells/mm³ for >3 months.

Q: What is the most common fungal infection in febrile neutropenia?

Candida. **Explanation:** In patients with febrile neutropenia, fungal infections typically emerge as secondary infections after 4–7 days of persistent fever despite broad-spectrum antibiotic therapy [1]. **Why Candida is the correct answer:** **Candida species** are the most common cause of fungal infections in neutropenic patients. The primary reason is the disruption of mucosal barriers (mucositis) caused by chemotherapy, which allows commensal *Candida* from the gastrointestinal or genitourinary tract to enter the bloodstream [1]. Among the species, *Candida albicans* remains the most frequent isolate, though non-albicans species (like *C. tropicalis*) are increasing in prevalence [1]. **Analysis of Incorrect Options:** * **Aspergillus fumigatus (Option D):** This is the most common **mould** (filamentous fungus) and the second most common fungal infection overall. It typically presents as Invasive Pulmonary Aspergillosis (IPA) and is more common in patients with prolonged, profound neutropenia (>10–15 days) [2]. * **Aspergillus niger (Option A):** While a member of the Aspergillus family, it is a less common cause of invasive disease compared to *A. fumigatus* and is more frequently associated with otomycosis. * **Mucormycosis (Option C):** This is an aggressive, angioinvasive infection seen in neutropenic patients and diabetics, but it is significantly rarer than both *Candida* and *Aspergillus*. **High-Yield Clinical Pearls for NEET-PG:** * **First-line Fungal Prophylaxis:** Fluconazole or Posaconazole (depending on the risk profile). * **Empiric Treatment:** If fever persists >4 days, start Echinocandins (e.g., Caspofungin) or Liposomal Amphotericin B [1]. * **Diagnostic Marker:** Beta-D-Glucan assay is used for *Candida* and *Aspergillus*, while Galactomannan is specific for *Aspergillus* [2]. * **Imaging:** The "Halo Sign" on CT chest is highly suggestive of early Invasive Aspergillosis [2].

Q: Subacute sclerosing panencephalitis is associated with which virus?

Measles. **Explanation:** **Subacute Sclerosing Panencephalitis (SSPE)**, also known as Dawson disease, is a rare, progressive, and fatal neurodegenerative condition caused by a **persistent, aberrant infection of the Measles virus** (Rubeola) [1]. 1. **Why Measles is Correct:** SSPE occurs due to a mutated measles virus that lacks the 'M' (matrix) protein, preventing the virus from budding. Instead, it spreads directly from cell to cell via syncytia formation, evading the immune system. It typically manifests 7–10 years after an initial measles infection, especially in children infected before the age of two [1]. 2. **Why Incorrect Options are Wrong:** * **Mumps:** Primarily causes parotitis and orchitis; its neurological complication is typically acute aseptic meningitis, not a chronic panencephalitis. * **Exanthema Subitum (Roseola Infantum):** Caused by HHV-6. While it can cause febrile seizures, it is not associated with SSPE. * **Erythema Infectiosum (Fifth Disease):** Caused by Parvovirus B19. It is associated with aplastic crisis and hydrops fetalis, not chronic CNS degeneration. **High-Yield Clinical Pearls for NEET-PG:** * **Clinical Stages:** Characterized by behavioral changes (Stage 1), **myoclonic jerks** (Stage 2), and eventual vegetative state/decorticate rigidity. * **EEG Finding:** Pathognomonic **periodic, high-voltage slow-wave complexes** (Radermecker complexes). * **CSF Analysis:** Shows significantly **elevated anti-measles antibody titers** (intrathecal synthesis) and oligoclonal bands [2]. * **Diagnosis:** Brain biopsy shows **Cowdry type A** intranuclear inclusion bodies in neurons and glial cells. * **Prevention:** The most effective strategy is universal vaccination with the **MMR vaccine** [1].

Q: Which of the following is NOT a manifestation of Giardiasis?

Gastrointestinal bleeding. **Explanation:** The correct answer is **D. Gastrointestinal bleeding**. *Giardia duodenalis* (also known as *G. lamblia*) is a flagellated protozoan that colonizes the upper small intestine (duodenum and jejunum). Unlike invasive pathogens like *Entamoeba histolytica* or *Shigella*, *Giardia* is **non-invasive**. It attaches to the intestinal villi via a ventral sucking disc, causing villous atrophy and malabsorption without penetrating the mucosa or causing ulceration. Therefore, it does **not** cause inflammatory diarrhea, mucosal friability, or gastrointestinal bleeding. **Analysis of Options:** * **Malaise (A):** This is a common constitutional symptom of chronic giardiasis, often accompanied by fatigue and weight loss due to nutrient malabsorption. * **Diarrhea (B):** This is the hallmark symptom. It typically begins as watery diarrhea but can transition into chronic, greasy stools. * **Steatorrhea (C):** *Giardia* interferes with the action of lipase and deconjugates bile salts, leading to fat malabsorption. This results in foul-smelling, bulky, frothy stools that float (steatorrhea). **High-Yield Clinical Pearls for NEET-PG:** * **Incubation Period:** 1–3 weeks (longer than bacterial/viral causes). * **Diagnosis:** Stool microscopy (cysts or pear-shaped trophozoites with "owl-eye" appearance). **String Test** (Entero-test) can be used if stool exams are negative. * **Drug of Choice:** Tinidazole (single dose) or Metronidazole. * **Association:** Common in patients with **IgA deficiency** (Common Variable Immunodeficiency). * **Key Distinction:** *Giardia* = Malabsorption/Non-bloody; *E. histolytica* = Invasive/Bloody (Dysentery).

Q: Multidrug Resistance Tuberculosis (MDR-TB) should be considered in patients with which of the following findings?

All of the above. **Explanation:** Multidrug-resistant tuberculosis (MDR-TB) is defined as resistance to at least **Isoniazid (H) and Rifampicin (R)**. Identifying patients at high risk for MDR-TB is crucial for initiating appropriate second-line treatment and preventing further transmission. **Why "All of the Above" is correct:** * **Contact with a known case of MDR-TB (Option A):** This is the strongest epidemiological risk factor. Primary resistance occurs when a person is directly infected with a strain that is already resistant. * **Clinical deterioration (Option B):** If a patient’s symptoms (fever, cough, weight loss) worsen despite being on standard First-Line Treatment (FLT), it indicates that the drugs are likely ineffective against the infecting strain. * **Sputum smear positive at 5 months (Option C):** Under the National TB Elimination Program (NTEP) guidelines, a patient who remains sputum smear or culture positive at the end of 5 months or more of treatment is defined as a **"Treatment Failure."** Failure to convert to negative is a hallmark indicator of drug resistance [1]. **Clinical Pearls for NEET-PG:** * **Diagnosis:** The investigation of choice for rapid screening of MDR-TB is **CBNAAT (GeneXpert)**, which detects Rifampicin resistance (a surrogate marker for MDR-TB). * **Extensively Drug-Resistant TB (XDR-TB):** Defined as MDR-TB plus resistance to any **Fluoroquinolone** and at least one **Group A drug** (Bedaquiline or Linezolid) as per the updated WHO definition. * **Universal Drug Susceptibility Testing (UDST):** Current guidelines mandate that every diagnosed TB patient should be screened for drug resistance at the time of diagnosis.

Q: Which of the following is NOT a recognized infectious cause of eosinophilia?

Malaria. **Explanation:** The key to answering this question lies in understanding the host immune response to different types of pathogens. **Eosinophilia** is a hallmark of **helminthic (parasitic worm)** infections, particularly during the tissue-invasive phase of their life cycle [1]. **1. Why Malaria is the Correct Answer:** Malaria is caused by *Plasmodium* species, which are **protozoa**, not helminths. Protozoal infections (like Malaria, Amoebiasis, and Giardiasis) characteristically do **not** cause eosinophilia. Malaria typically presents with anemia, thrombocytopenia, and atypical lymphocytosis, but an elevated eosinophil count should prompt a search for a co-infection. **2. Why the other options are incorrect:** * **Ascaris lumbricoides:** Causes eosinophilia during the **Loeffler’s syndrome** phase, where larvae migrate through the lungs [1]. * **Filariasis:** Caused by *Wuchereria bancrofti*, it is a classic cause of tropical pulmonary eosinophilia (TPE), characterized by extreme elevations in eosinophil counts and IgE [2]. * **Strongyloidiasis:** This helminth can persist for decades in the host via autoinfection; it is a well-known cause of fluctuating or persistent eosinophilia [1]. **High-Yield Clinical Pearls for NEET-PG:** * **NAACP mnemonic** for causes of eosinophilia: **N**eoplasm, **A**llergy/Asthma, **A**ddison’s disease, **C**onnective tissue disorders, and **P**arasites (Helminths). * **Protozoa vs. Helminths:** Remember that protozoa (Malaria, Leishmaniasis, Trypanosomiasis) generally cause **leukopenia or normal counts**, whereas helminths (especially those with a tissue phase) cause **eosinophilia**. * **Exception:** Ectoparasites like Scabies can sometimes cause mild eosinophilia due to allergic sensitization.

Q: Which is a common central nervous system (CNS) lesion in HIV?

All of the above. **Explanation:** In patients with HIV/AIDS, the central nervous system (CNS) is a frequent site of opportunistic infections and malignancies, particularly when the CD4 count drops below 200 cells/mm³. [1] 1. **Toxoplasma gondii:** This is the **most common** cause of focal CNS lesions in HIV patients. It typically presents with fever, headache, and focal neurological deficits. On MRI, it classically shows multiple "ring-enhancing lesions" with a predilection for the basal ganglia. [1] 2. **Primary CNS Lymphoma (PCNSL):** This is the second most common cause of focal CNS lesions. It is strongly associated with the **Epstein-Barr Virus (EBV)**. Radiologically, it often presents as a large, solitary, weakly enhancing lesion, making it the primary differential diagnosis for Toxoplasmosis. [1] 3. **Cryptococcus neoformans:** This is the **most common cause of fungal meningitis** in HIV. While it primarily presents as meningitis (diffuse involvement), it can also form "cryptococcomas" (solid lesions) or "soap-bubble" lesions in the basal ganglia. **Why "All of the above" is correct:** All three entities are hallmark opportunistic conditions in advanced HIV. While their clinical presentations differ slightly, they are all frequently encountered CNS pathologies in this patient population. **High-Yield Clinical Pearls for NEET-PG:** * **Most common CNS mass lesion:** Toxoplasmosis. * **Most common fungal CNS infection:** Cryptococcosis (Diagnosed via India Ink or CrAg test). * **Toxoplasmosis vs. Lymphoma:** If a patient fails to respond to anti-toxoplasma therapy (Pyrimethamine + Sulfadiazine) within 2 weeks, a brain biopsy is indicated to rule out Lymphoma. [1] * **Thallium-201 SPECT:** Positive (increased uptake) in Lymphoma, negative in Toxoplasmosis.

Question 1

Tuberculosis lymphadenitis of the cervical lymph nodes is also called:

Accepted Answer

Scrofula

Answer

Pott's disease

Answer

Lupus vulgaris

Answer

Ghon's focus

Question 2

In HIV infection, prophylaxis for Pneumocystis jiroveci pneumonia may be stopped if the CD4 count persists above 200 cells/mm

for what duration?

Accepted Answer

3 months

Answer

1 month

Answer

2 months

Answer

6 months

Question 3

What is the most common fungal infection in febrile neutropenia?

Accepted Answer

Candida

Answer

Aspergillus niger

Answer

Mucormycosis

Answer

Aspergillus fumigatus

Question 4

Subacute sclerosing panencephalitis is associated with which virus?

Accepted Answer

Measles

Answer

Mumps

Answer

Exanthema subitum

Answer

Erythema infectiosum

Question 5

Which of the following is NOT a manifestation of Giardiasis?

Accepted Answer

Gastrointestinal bleeding

Answer

Malaise

Answer

Diarrhea

Answer

Steatorrhea

Question 6

Multidrug Resistance Tuberculosis (MDR-TB) should be considered in patients with which of the following findings?

Accepted Answer

All of the above

Answer

Contact with a known case of MDR TB

Answer

Clinical deterioration

Answer

Sputum smear positive at 5 months of treatment

Question 7

In AIDS patients with a CD4 count >75 lymphocytes/mm
³, cotton wool spots on eye examination suggest infection by which of the following organisms?

Accepted Answer

Cytomegalovirus (CMV)

Answer

Toxoplasma gondii

Answer

Cryptococcus neoformans

Answer

Acanthamoeba

Question 8

Which of the following is NOT a recognized infectious cause of eosinophilia?

Accepted Answer

Malaria

Answer

Ascaris lumbricoides

Answer

Filariasis

Answer

Strongyloidiasis

Question 9

What is the treatment of choice for tropical splenomegaly?

Accepted Answer

Proguanil

Answer

Chloroquine for 6 months

Answer

Mefloquine for 3 months

Answer

Pyrimethamine + sulphadoxine for 1 month

Question 10

Which is a common central nervous system (CNS) lesion in HIV?

Accepted Answer

All of the above

Answer

Cryptococcus

Answer

Toxoplasma

Answer

Lymphoma

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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