Infectious Diseases Practice Questions

Q: A diabetic patient presents with fungal infection of the sinuses and peri-orbital region with significant visual impairment. What is the best drug for treatment in this patient?

Amphotericin B. **Explanation:** The clinical presentation of a diabetic patient with fungal sinusitis, periorbital involvement, and visual impairment is classic for **Mucormycosis** (specifically Rhinocerebral Mucormycosis) [1]. This is a life-threatening, angioinvasive fungal infection that occurs most commonly in patients with uncontrolled diabetes mellitus (especially those in ketoacidosis) or immunosuppression [1]. **Why Amphotericin B is the correct answer:** **Liposomal Amphotericin B** is the drug of choice for Mucormycosis [1]. It works by binding to ergosterol in the fungal cell membrane, creating pores that lead to cell death. Because Mucormycosis is rapidly progressive and carries a high mortality rate, aggressive intravenous antifungal therapy combined with surgical debridement is mandatory [1]. **Why the other options are incorrect:** * **Itraconazole & Ketoconazole:** These are azole antifungals. While they are effective against some fungi (like *Candida* or *Histoplasma*), they have **no activity** against the *Mucorales* order (the causative agents of Mucormycosis). * **Broad-spectrum antibiotics:** These target bacteria, not fungi. While they may be used to treat secondary bacterial infections, they are ineffective against the primary fungal pathology and may even worsen the condition by altering normal flora. **High-Yield Clinical Pearls for NEET-PG:** * **Risk Factor:** Diabetic Ketoacidosis (DKA) is the strongest risk factor because the fungi thrive in acidic, iron-rich environments [1]. * **Diagnosis:** Look for **broad, non-septate hyphae with right-angle (90°) branching** on KOH mount or biopsy. * **Clinical Sign:** A **black eschar** on the palate or nasal turbinates is a pathognomonic finding. * **Alternative Drug:** **Isavuconazole** or **Posaconazole** can be used as step-down therapy or in patients intolerant to Amphotericin B.

Q: All the following are characteristics of AIDS when CD4 cell count drops below 100 cells, EXCEPT:

Persistent generalized lymphadenopathy. The progression of HIV/AIDS is characterized by a predictable decline in CD4+ T-cell counts, which correlates with the onset of specific opportunistic infections and malignancies [1]. **Why Option B is the Correct Answer:** **Persistent Generalized Lymphadenopathy (PGL)** is defined as enlarged lymph nodes (>1 cm) in two or more extra-inguinal sites for more than three months. Crucially, PGL is a feature of the **early clinical stage** of HIV infection (WHO Stage 1 or 2), typically occurring when the CD4 count is still relatively preserved (**>500 cells/mm³**) [2]. As the disease progresses to advanced AIDS (CD4 <200), the architecture of the lymph nodes often collapses (lymphocyte depletion), and PGL may actually resolve. **Why the other options are incorrect:** * **CNS Toxoplasmosis (D):** This is the most common cause of space-occupying lesions in AIDS patients [3]. It typically occurs when the CD4 count drops below **100 cells/mm³** [1]. * **Cryptococcal Meningitis (C):** This fungal infection is a major cause of morbidity in AIDS. It is rarely seen unless the CD4 count is **<100 cells/mm³** (often <50). * **Non-Hodgkin Lymphoma (A):** High-grade B-cell lymphomas (like Burkitt’s or Primary CNS Lymphoma) are AIDS-defining illnesses that frequently occur at advanced stages of immunosuppression, typically when CD4 counts are **<100 cells/mm³** [3]. **High-Yield Clinical Pearls for NEET-PG:** * **CD4 <200:** *Pneumocystis jirovecii* pneumonia (PCP). * **CD4 <100:** Toxoplasmosis, Cryptococcosis, Cryptosporidiosis. * **CD4 <50:** *Mycobacterium avium* complex (MAC), CMV Retinitis, and Primary CNS Lymphoma. * **Prophylaxis:** Trimethoprim-Sulfamethoxazole (TMP-SMX) is started when CD4 <200 to prevent PCP and Toxoplasmosis [3].

Q: Reactivation tuberculosis is usually seen where?

Apical and posterior segments of upper lobes. **Explanation:** Reactivation (Secondary) Tuberculosis occurs in individuals previously sensitized to *Mycobacterium tuberculosis*. The classic site of involvement is the **apical and posterior segments of the upper lobes** (Option A) [1]. **Why Option A is correct:** * **High Oxygen Tension:** *M. tuberculosis* is a strict aerobe. The apices of the lungs have the highest ventilation-perfusion (V/Q) ratio, resulting in higher alveolar oxygen tension ($P_AO_2$), which favors the growth of the bacilli. * **Impaired Lymphatic Drainage:** Lower lymphatic flow in the upper lobes prevents the upper lobe apices from being cleared effectively of bacteria, allowing them to proliferate during reactivation. **Analysis of Incorrect Options:** * **Option B (Middle Lobe):** This is not a characteristic site for reactivation. However, "Middle Lobe Syndrome" (atelectasis) can occur due to extrinsic compression of the bronchus by tuberculous lymphadenopathy. * **Option C (Lower Lobe):** Primary TB typically involves the lower part of the upper lobe or the upper part of the lower lobe (Ghon focus) [1]. While reactivation can occasionally involve the superior segment of the lower lobe, the upper lobe apices remain the most frequent site. * **Option D (Pleural Space):** Involvement here leads to tuberculous pleurisy or empyema, which are complications or specific manifestations rather than the primary site of parenchymal reactivation. **High-Yield Clinical Pearls for NEET-PG:** * **Cavitation:** Unlike primary TB, secondary TB is characterized by **cavitation**, which leads to hematogenous spread or miliary TB. * **Ghon Complex:** Seen in Primary TB; consists of a parenchymal lesion + draining lymph node [1]. * **Ranke Complex:** A healed, calcified Ghon complex [1]. * **Simon’s Focus:** A nodular scar at the lung apex representing a healed primary infection; it is often the precursor site for reactivation.

Q: What is the most common ophthalmic lesion in AIDS?

Cotton wool spots. **Explanation:** **Cotton wool spots (CWS)** are the most common ophthalmic manifestation in patients with AIDS, occurring in approximately 25–50% of cases [1]. They are the hallmark of **HIV Microangiopathy**. * **Mechanism:** HIV causes immune complex deposition and direct endothelial damage in the retinal vasculature. This leads to precapillary arteriolar occlusion, resulting in focal ischemia of the nerve fiber layer. This ischemia causes axoplasmic stasis and the accumulation of "cytoid bodies," which appear clinically as fluffy, white, "cotton-like" lesions with indistinct margins. * **Clinical Significance:** Unlike CMV retinitis, CWS are non-infectious, asymptomatic, do not cause vision loss, and often resolve spontaneously. **Analysis of Incorrect Options:** * **Hard exudates (A):** These are lipid deposits resulting from chronic vascular leakage, typically seen in Diabetic Retinopathy or Hypertensive Retinopathy, not primarily in HIV. * **Angioid streaks (B):** These represent breaks in Bruch’s membrane. They are associated with systemic conditions like Pseudoxanthoma elasticum, Paget’s disease, and Sickle cell anemia (Mnemonic: **PEPSI**). * **Microaneurysms (D):** These are the earliest clinical sign of Diabetic Retinopathy, caused by pericyte loss and capillary wall weakening. **High-Yield Clinical Pearls for NEET-PG:** * **Most common opportunistic ocular infection in AIDS:** CMV Retinitis (characterized by "Pizza-pie" or "Crushed tomato and cheese" appearance). * **CMV Retinitis vs. CWS:** CMV retinitis follows a vascular pattern, involves full-thickness retinal necrosis, and causes permanent vision loss, whereas CWS are superficial and transient. * **CD4 Count Correlation:** CMV retinitis typically occurs when CD4 counts drop below **50 cells/mm³**, whereas HIV microangiopathy (CWS) can occur at higher counts [1].

Q: Which viral infections are associated with hemolysis?

CMV. The correct answer is **CMV (Cytomegalovirus)**. **1. Why CMV is Correct:** Cytomegalovirus (CMV) is a well-documented cause of **Autoimmune Hemolytic Anemia (AIHA)**, typically mediated by warm-reactive IgG antibodies or, less commonly, cold agglutinins [1]. The underlying mechanism involves molecular mimicry or virus-induced alteration of red blood cell (RBC) surface antigens, leading to a loss of self-tolerance and subsequent destruction of RBCs by the splenic macrophages [1]. Hemolysis is a recognized complication in both immunocompetent patients (mononucleosis-like syndrome) and immunocompromised individuals [1]. **2. Analysis of Incorrect Options:** * **Hepatitis A, B, and C:** While these hepatotropic viruses primarily cause liver inflammation and can occasionally be associated with hematological issues (like aplastic anemia in rare cases of Hepatitis A or B, or cryoglobulinemia in Hepatitis C), they are **not** classically associated with direct hemolysis. Hepatitis A may rarely trigger hemolysis in patients with pre-existing G6PD deficiency due to oxidative stress, but CMV is the established primary viral cause of AIHA among the choices provided. **3. NEET-PG High-Yield Pearls:** * **Viral triggers for AIHA:** The two most common viral triggers are **EBV (Epstein-Barr Virus)** and **CMV** [1], [2]. * **EBV vs. CMV:** EBV is classically associated with **Cold Agglutinin Disease** (IgM mediated) [2], whereas CMV is more frequently associated with **Warm AIHA** (IgG mediated) [1]. * **Other infections:** *Mycoplasma pneumoniae* is the most common bacterial cause of cold-type hemolysis (anti-I antibodies) [2]. * **Clinical Hint:** If a patient presents with fever, lymphadenopathy, splenomegaly, and a sudden drop in hemoglobin with a positive Coombs test, suspect CMV or EBV [1].

Q: Most common central nervous system (CNS) manifestation of HIV infection is:

Dementia. The most common central nervous system (CNS) manifestation of HIV infection is **HIV-Associated Dementia (HAD)**, also known as AIDS Dementia Complex [1]. **1. Why Dementia is Correct:** HIV is a neurotropic virus that crosses the blood-brain barrier early in the course of infection, primarily via infected macrophages and monocytes (the "Trojan Horse" hypothesis). It resides in the microglial cells. HAD typically occurs in the late stages of the disease when CD4 counts drop below 200 cells/mm³. It is characterized by a subcortical dementia pattern involving cognitive decline, behavioral changes, and motor dysfunction (e.g., slowed movements). **2. Why Other Options are Incorrect:** * **Seizures:** While common in HIV patients, they are usually secondary to opportunistic infections (like Toxoplasmosis [1] or Cryptococcosis) or space-occupying lesions, rather than the primary effect of the virus itself. * **Focal Neurologic Deficits:** These are typically seen in secondary complications such as Progressive Multifocal Leukoencephalopathy (PML) or CNS Lymphoma [1], but they are not the most frequent overall manifestation. * **Stroke:** HIV patients have an increased risk of stroke due to chronic inflammation and vasculopathy, but it remains less common than cognitive impairment. **NEET-PG High-Yield Pearls:** * **Most common opportunistic infection of the CNS in HIV:** Cerebral Toxoplasmosis [1]. * **Most common fungal infection of the CNS in HIV:** Cryptococcal Meningitis. * **Most common cause of a space-occupying lesion in HIV:** Cerebral Toxoplasmosis (followed by Primary CNS Lymphoma) [1]. * **Imaging finding in HAD:** Diffuse cerebral atrophy with ventricular enlargement and symmetric white matter T2 hyperintensities on MRI.

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: What is true about amoebic liver abscess?

The male to female ratio is greater than 10:1.. **Amoebic Liver Abscess (ALA)** is the most common extra-intestinal manifestation of infection by *Entamoeba histolytica*. [1] ### **Explanation of Options** * **Option A (Correct):** ALA shows a striking male preponderance, with a **male-to-female ratio often exceeding 10:1**. While intestinal amoebiasis affects both sexes equally, ALA is significantly more common in adult men. This is hypothesized to be due to the protective effect of menstrual blood loss (reducing iron availability for the parasite) and the hormonal influence on the immune response. * **Option B (Incorrect):** **Alcohol consumption** is a well-known predisposing factor for ALA. Chronic alcohol intake can impair the liver's Kupffer cell function and alter the local immune environment, making the liver more susceptible to abscess formation. * **Option C (Incorrect):** Unlike pyogenic liver abscesses, which are strongly associated with **Diabetes Mellitus**, ALA does not show a significant clinical correlation with diabetes. * **Option D (Incorrect):** *E. histolytica* is a protozoan, not a bacterium; it is **never isolated from blood cultures**. Diagnosis is typically made via serology (ELISA for antibodies) and imaging (USG/CT). ### **High-Yield Clinical Pearls for NEET-PG** * **Location:** Most commonly involves the **Right Lobe** of the liver (due to the bulk of portal blood flow). * **Aspirate:** Classically described as **"Anchovy sauce"** appearance (odorless, reddish-brown, consisting of liquefied hepatocytes). [1] * **Microscopy:** Trophozoites are rarely found in the pus (only in <15% of cases) because they reside in the abscess wall, not the necrotic center. * **Treatment of Choice:** **Metronidazole** (or Tinidazole) followed by a luminal amoebicide (e.g., Diloxanide furoate or Paromomycin) to eradicate the intestinal colonization.

Question 1

A diabetic patient presents with fungal infection of the sinuses and peri-orbital region with significant visual impairment. What is the best drug for treatment in this patient?

Accepted Answer

Amphotericin B

Answer

Itraconazole

Answer

Ketoconazole

Answer

Broad spectrum antibiotics

Question 2

All the following are characteristics of AIDS when CD4 cell count drops below 100 cells, EXCEPT:

Accepted Answer

Persistent generalized lymphadenopathy

Answer

Non-Hodgkin Lymphoma

Answer

Cryptococcal meningitis

Answer

CNS toxoplasmosis

Question 3

Reactivation tuberculosis is usually seen where?

Accepted Answer

Apical and posterior segments of upper lobes

Answer

Middle lobe

Answer

Lower lobe

Answer

Pleural space

Question 4

A 40-year-old paddy farmer presented with fever, chills, headache, and myalgias for 2 days. The patient also complained of acute onset of cough, shortness of breath, and a few episodes of hemoptysis. On examination, scleral icterus was present. There is a history of a minor lower limb injury while working in the fields, which were infested with rats. Lab findings revealed anemia, leukocytosis, deranged RFTs, prolonged PT and aPTT, increased serum bilirubin and alkaline phosphatase levels. Blood cultures, dark field microscopy, cultures, and MAT test were performed. Which electrolyte derangement will be most likely seen in the above condition?

Accepted Answer

Hypokalemia and hyponatremia

Answer

Hyperkalemia and hyponatremia

Answer

Hyperkalemia and hypernatremia

Answer

Hypokalemia and hypernatremia

Question 5

What is the most common ophthalmic lesion in AIDS?

Accepted Answer

Cotton wool spots

Answer

Hard exudates

Answer

Angioid streaks

Answer

Microaneurysms

Question 6

Which viral infections are associated with hemolysis?

Accepted Answer

CMV

Answer

Hepatitis B

Answer

Hepatitis C

Answer

Hepatitis A

Question 7

Most common central nervous system (CNS) manifestation of HIV infection is:

Accepted Answer

Dementia

Answer

Seizures

Answer

Focal neurologic deficits

Answer

Stroke

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 patient with AIDS presents with an acute episode of diarrhea. Stool examination reveals an oval structure, 8 to 9 micrometers in diameter, which is acid-fast and fluoresces blue under ultraviolet light. What is the drug of choice for this patient?

Accepted Answer

Trimethoprim-sulfamethoxazole

Answer

Nitazoxanide

Answer

Primaquine

Answer

Niclosamide

Question 10

What is true about amoebic liver abscess?

Accepted Answer

The male to female ratio is greater than 10:1.

Answer

It is not predisposed by alcohol consumption.

Answer

It is more common in patients with diabetes.

Answer

Entamoeba histolytica is isolated in more than 50% of cases from blood culture.

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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