Infectious Diseases Practice Questions

Q: What is the neutrophil count below which there is an increased risk of nosocomial invasive pulmonary aspergillosis?

Less than 1000-500 cells/microliter. **Explanation** **1. Why the Correct Answer is Right:** Invasive Pulmonary Aspergillosis (IPA) is an opportunistic infection caused by *Aspergillus* species. The primary host defense against *Aspergillus* spores (conidia) involves alveolar macrophages, while **neutrophils** are the critical defense against the germinating hyphae. The risk of invasive disease is directly proportional to the **severity and duration of neutropenia**. Clinically, the threshold for "significant neutropenia" begins below 1000 cells/µL, but the risk for invasive fungal infections increases exponentially when the Absolute Neutrophil Count (ANC) falls **below 500 cells/µL**, especially if this state persists for more than 10–14 days. This is why Option D is the standard clinical benchmark for high-risk susceptibility. **2. Why Incorrect Options are Wrong:** * **Options A, B, and C:** While these counts (4000, 3000, and 2000 cells/µL) are technically below the normal reference range for total leukocytes or high-normal for neutrophils, they do not constitute "severe neutropenia." At these levels, the body retains sufficient phagocytic capacity to prevent the angioinvasion characteristic of *Aspergillus*. **3. Clinical Pearls for NEET-PG:** * **Classic Radiology:** Look for the **"Halo Sign"** (early stage: ground-glass opacity surrounding a nodule) and the **"Air Crescent Sign"** (late stage: signifying convalescence/resolution). * **Diagnosis:** The **Galactomannan assay** (cell wall component) is a high-yield serum/BAL marker for invasive aspergillosis. * **Drug of Choice:** **Voriconazole** is the first-line treatment for Invasive Aspergillosis (replacing Amphotericin B). * **Risk Groups:** Most common in patients with hematological malignancies (Leukemia), post-HSCT (Hematopoietic Stem Cell Transplant), and those on prolonged high-dose corticosteroids.

Q: All of the following are true regarding progressive multifocal leukoencephalopathy except?

Cerebellar involvement is unknown.. **Explanation:** Progressive Multifocal Leukoencephalopathy (PML) is a demyelinating disease of the Central Nervous System caused by the reactivation of the **JC virus (John Cunningham virus)**, a polyomavirus [1]. **Why Option C is the correct answer (False statement):** The statement "Cerebellar involvement is unknown" is incorrect. While PML primarily affects the subcortical white matter of the cerebral hemispheres (parieto-occipital regions), it frequently involves the **cerebellum and brainstem**. In fact, ataxia and coordination deficits are common clinical presentations when the disease affects the cerebellar peduncles or the cerebellum itself. **Analysis of other options:** * **Option A (True):** JC virus is a ubiquitous virus that remains latent in the kidneys and lymphoid tissue of healthy individuals. PML is the **only clinically significant disease** caused by JC virus reactivation, occurring almost exclusively in the setting of profound cell-mediated immunodeficiency [1]. * **Option B (True):** PML is a classic opportunistic infection and an **AIDS-defining illness** [1]. It typically occurs as a late manifestation when CD4+ T-cell counts drop significantly, usually **below 100 cells/μL**. **High-Yield Clinical Pearls for NEET-PG:** * **Pathogenesis:** Selective destruction of **oligodendrocytes** (the myelin-producing cells of the CNS) [1]. * **MRI Findings:** Characterized by **multifocal, non-enhancing, T2/FLAIR hyperintense lesions** in the white matter without mass effect [1]. * **Diagnosis:** Gold standard is PCR for JC virus DNA in the **CSF**. Brain biopsy shows characteristic enlarged oligodendrocyte nuclei with viral inclusions. * **Drug Association:** Apart from HIV, PML is associated with **Natalizumab** (used in Multiple Sclerosis) and Rituximab.

Q: What is the drug of choice for Madura mycosis?

Itraconazole. **Explanation:** Madura mycosis, or **Mycetoma**, is a chronic granulomatous infection of the subcutaneous tissue characterized by a triad of localized swelling, underlying bone destruction, and the formation of sinus tracts that discharge grains [2]. It is classified into two types based on the causative agent: **Eumycetoma** (fungal) and **Actinomycetoma** (bacterial) [2]. 1. **Why Itraconazole is correct:** The term "Madura mycosis" specifically refers to **Eumycetoma** (caused by fungi like *Madurella mycetomatis*). For fungal mycetoma, medical management is challenging and often requires long-term antifungal therapy. **Itraconazole** is currently considered the drug of choice due to its superior efficacy and safety profile compared to older antifungals like Ketoconazole [2], [1]. 2. **Why other options are incorrect:** * **Dapsone & Amikacin:** These are components of the **Welsh Regime**, which is the gold standard treatment for **Actinomycetoma** (bacterial origin). They are ineffective against the fungal agents of Madura mycosis. * **Imipenem:** This is a broad-spectrum carbapenem antibiotic used for severe bacterial infections (including some Nocardia species in actinomycetoma) but has no role in treating fungal infections. **High-Yield Clinical Pearls for NEET-PG:** * **The "Dot-in-Circle" Sign:** A characteristic MRI finding in mycetoma where small grains appear as dark spots within high-intensity inflammatory circles. * **Grains:** The color of the discharged grains can hint at the etiology (e.g., **Black grains** are pathognomonic for Eumycetoma; **Yellow/White grains** are common in Actinomycetoma) [2]. * **Treatment Duration:** Eumycetoma often requires treatment for 6–12 months and may still necessitate surgical excision (debridement or amputation) due to poor drug penetration into the fibrotic lesion [2].

Q: Which of the following is not typically associated with hepatitis C infection?

Polyarteritis nodosa (PAN). The correct answer is **Polyarteritis nodosa (PAN)** because it is classically associated with **Hepatitis B virus (HBV)**, not Hepatitis C. Approximately 10–30% of PAN cases are linked to chronic HBV infection due to the deposition of immune complexes in small and medium-sized arteries. [1] **Analysis of Options:** * **Cryoglobulinemia (Option B):** This is the most common extrahepatic manifestation of Hepatitis C (HCV). Specifically, **Type II and III Mixed Cryoglobulinemia** occur because HCV triggers B-cell proliferation, leading to immune complexes that cause vasculitis, glomerulonephritis, and palpable purpura. [2] * **Porphyria cutanea tarda (Option C):** There is a strong epidemiological link between HCV and PCT. Chronic HCV infection can lead to an acquired deficiency of the enzyme *uroporphyrinogen decarboxylase*, resulting in skin fragility and blistering on sun-exposed areas. * **Lichen planus (Option D):** This mucocutaneous condition is frequently associated with HCV. Patients often present with the "6 Ps" (Planar, Purple, Polygonal, Pruritic, Papules, and Plaques) and Wickham striae. **NEET-PG High-Yield Pearls:** * **Hepatitis B associations:** Polyarteritis nodosa (PAN) and Membranous glomerulonephritis. [1] * **Hepatitis C associations:** Mixed Cryoglobulinemia, Porphyria Cutanea Tarda, Lichen Planus, and Membranoproliferative Glomerulonephritis (MPGN). [2] * **Key Distinction:** If a question mentions "Medium-vessel vasculitis + Hepatitis," think **HBV (PAN)**. If it mentions "Small-vessel vasculitis/Purpura + Hepatitis," think **HCV (Cryoglobulinemia)**.

Q: A patient presented with fever, jaundice, and neurological symptoms during the rainy season. What is the most probable diagnosis?

Leptospirosis. The clinical triad of **fever, jaundice, and neurological symptoms** (often presenting as aseptic meningitis) occurring during the **rainy season** is a classic presentation of **Leptospirosis** [1]. This zoonotic disease, caused by the spirochete *Leptospira interrogans*, is typically transmitted through water contaminated with the urine of infected rodents [1]. The severe form, known as **Weil’s Disease**, is characterized by the triad of jaundice, renal failure, and hemorrhage. **Why the other options are incorrect:** * **Dengue Fever:** While common in the rainy season, it typically presents with severe retro-orbital pain, arthralgia ("breakbone fever"), and a characteristic rash. While jaundice can occur in severe cases (Dengue Hemorrhagic Fever), neurological symptoms are less common than in Leptospirosis [1]. * **Brucellosis:** This is usually a chronic or subacute illness associated with unpasteurized dairy or livestock exposure. It presents with "undulant fever" and hepatosplenomegaly, but the acute seasonal/rainy association is absent. * **Lyme Disease:** Caused by *Borrelia burgdorferi*, it is transmitted by Ixodes ticks. While it can cause neurological symptoms (Bell’s palsy, meningitis), it does not typically present with jaundice or a rainy-season surge in the same epidemiological pattern as Leptospirosis. **High-Yield NEET-PG Pearls:** * **Gold Standard Diagnosis:** Microscopic Agglutination Test (MAT) [1]. * **Drug of Choice:** Doxycycline (mild cases) or IV Penicillin G (severe cases). * **Prophylaxis:** Doxycycline 200 mg once weekly for high-risk exposure. * **Pathognomonic Sign:** Conjunctival suffusion (redness without inflammatory exudate) is a highly specific clinical clue.

Q: Which of the following is NOT a clinical feature of Botulism?

Diarrhea. **Explanation:** Botulism is a severe paralytic illness caused by the neurotoxin produced by *Clostridium botulinum*. The toxin acts by irreversibly blocking the release of **Acetylcholine (ACh)** at the neuromuscular junction and autonomic synapses. **Why Diarrhea is the correct answer:** Botulism typically causes **constipation**, not diarrhea. Because the toxin inhibits the release of acetylcholine (the primary neurotransmitter for the parasympathetic nervous system), it leads to decreased gastrointestinal motility (paralytic ileus). While some patients with foodborne botulism may experience transient nausea or vomiting early on, the hallmark autonomic feature is constipation. **Why the other options are incorrect:** The clinical presentation of botulism is characterized by a **"Symmetric Descending Paralysis"** involving cranial nerves first: * **Ocular nerve paralysis & Blurring of vision:** These are classic early signs. The toxin affects the extraocular muscles and the ciliary body, leading to diplopia (double vision), ptosis, and fixed/dilated pupils (mydriasis). * **Dysarthria:** As the paralysis descends, it affects the bulbar muscles, leading to difficulty speaking (dysarthria) and swallowing (dysphagia). **NEET-PG High-Yield Pearls:** * **The "4 D’s" of Botulism:** Diplopia, Dysarthria, Dysphagia, and Dyspnea. * **Infant Botulism:** Associated with honey ingestion; presents as "Floppy Baby Syndrome." * **Wound Botulism:** Associated with black tar heroin use. * **Diagnosis:** Confirmed by demonstrating the toxin in serum, stool, or food via the **Mouse Bioassay** (Gold Standard). * **Treatment:** Equine Antitoxin (Heptavalent) and supportive care (mechanical ventilation if respiratory failure occurs).

Question 1

A 30-year-old person presents with fever and headache for 20 days. CSF values are: glucose 38 mg/dL, protein 60 mg/dL, and lymphocyte pleocytosis with 20 cells/mm³. What should be included in the initial investigations?

Accepted Answer

Herpes Simplex Virus (HSV) detection

Answer

Indian ink smear of CSF

Answer

Acid-Fast Bacilli (AFB) stain

Answer

Toxoplasmosis testing

Question 2

What is the neutrophil count below which there is an increased risk of nosocomial invasive pulmonary aspergillosis?

Accepted Answer

Less than 1000-500 cells/microliter

Answer

Less than 4000 cells/microliter

Answer

Less than 3000 cells/microliter

Answer

Less than 2000 cells/microliter

Question 3

All of the following are true regarding progressive multifocal leukoencephalopathy except?

Accepted Answer

Cerebellar involvement is unknown.

Answer

It is the only manifestation of JC virus infection.

Answer

It is a late manifestation of AIDS.

Answer

None of the above.

Question 4

Regarding hepatobiliary disease, which of the following statements is true?

Accepted Answer

Hepatitis B is the most common viral cause of cirrhosis worldwide.

Answer

Fewer than 5% of patients with chronic hepatitis C will develop cirrhosis.

Answer

In India, hepatitis B is transmitted primarily by the feco-oral route.

Answer

Hepatitis C is a more frequent cause for fulminant hepatitis than hepatitis B infection.

Question 5

What is the drug of choice for Madura mycosis?

Accepted Answer

Itraconazole

Answer

Imipenem

Answer

Dapsone

Answer

Amikacin

Question 6

Which of the following is not typically associated with hepatitis C infection?

Accepted Answer

Polyarteritis nodosa (PAN)

Answer

Cryoglobulinemia

Answer

Porphyria cutanea tarda

Answer

Lichen planus

Question 7

A 23-year-old female patient presents with a 2-month history of low-grade fever and moderate right-sided pleural effusion. Pleural fluid shows lymphocyte predominance with ADA levels of 120 IU/L. The patient is started on anti-tubercular therapy (WHO category 1). Two months later, the patient presents with progressive breathlessness, generalized body swelling, and raised JVP. Pleural fluid is now predominantly transudate. What is this patient likely to have developed?

Accepted Answer

Constrictive pericarditis

Answer

Hypoproteinemia

Answer

Drug-resistant TB

Answer

Collagen vascular disease

Question 8

A patient presented with fever, jaundice, and neurological symptoms during the rainy season. What is the most probable diagnosis?

Accepted Answer

Leptospirosis

Answer

Dengue fever

Answer

Brucellosis

Answer

Lyme disease

Question 9

A patient presents with fever of unknown origin (FUO). Empirical anti-tuberculosis treatment (ATT) was initiated, but the symptoms persisted after several weeks. How long should ATT be continued in the absence of a clinical response before discontinuation?

Accepted Answer

6 weeks

Answer

4 weeks

Answer

8 weeks

Answer

10 weeks

Question 10

Which of the following is NOT a clinical feature of Botulism?

Accepted Answer

Diarrhea

Answer

Dysarthria

Answer

Ocular nerve paralysis

Answer

Blurring of vision

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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