Infectious Diseases Practice Questions

Q: A patient with dengue hemorrhagic fever presents with myalgia and spontaneous skin bleeds. Laboratory tests show thrombocytopenia and a raised hematocrit. What is the Dengue Hemorrhagic Fever grade of the disease in this patient?

Grade II. ### Explanation The classification of Dengue Hemorrhagic Fever (DHF) is based on the severity of clinical manifestations and hemodynamic stability. The hallmark of DHF is **plasma leakage** (evidenced here by raised hematocrit) along with thrombocytopenia and hemorrhagic tendencies [1]. **Why Grade II is correct:** According to the WHO classification, DHF is divided into four grades: * **Grade I:** Fever with non-specific constitutional symptoms; the only hemorrhagic manifestation is a **positive tourniquet test** and/or easy bruising [1]. * **Grade II:** All signs of Grade I plus **spontaneous bleeding** (e.g., skin bleeds like petechiae/ecchymosis, epistaxis, or gum bleeding). [1] Since this patient presents with spontaneous skin bleeds and evidence of plasma leakage (raised hematocrit), they are classified as **Grade II**. **Why other options are incorrect:** * **Grade I:** Incorrect because the patient has spontaneous bleeding, which exceeds the criteria for Grade I (where bleeding is only induced/provoked). * **Grade III:** Incorrect because Grade III represents **Dengue Shock Syndrome (DSS)**, characterized by circulatory failure (rapid/weak pulse, narrowing of pulse pressure <20 mmHg, or hypotension) [1]. This patient is currently hemodynamically stable. * **Grade IV:** Incorrect because Grade IV is **profound shock** with undetectable blood pressure or pulse. **High-Yield Clinical Pearls for NEET-PG:** * **Critical Phase:** Usually occurs during defervescence (days 3–7). This is when plasma leakage is most prominent [1]. * **Warning Signs:** Abdominal pain, persistent vomiting, mucosal bleed, lethargy, and sudden increase in hematocrit with a rapid decrease in platelet count. * **Fluid Management:** Isotonic crystalloids (like Normal Saline or Ringer's Lactate) are the gold standard for resuscitation in DHF. * **Hematocrit:** A rise of $\geq 20\%$ from the baseline is a definitive objective sign of plasma leakage.

Q: In AIDS, Kaposi sarcoma may respond to which of the following treatments?

Alpha interferon. **Explanation:** **1. Why Alpha Interferon is Correct:** Kaposi Sarcoma (KS) is a multicentric angioproliferative tumor caused by **Human Herpesvirus 8 (HHV-8)**, typically occurring in HIV patients with low CD4 counts [1], [2]. **Interferon-alpha (IFN-α)** is an FDA-approved systemic therapy for AIDS-related KS. It works through a triple mechanism: * **Antiviral:** Inhibits the replication of HHV-8. * **Antiproliferative:** Directly inhibits the growth of tumor cells. * **Immunomodulatory:** Enhances the host’s immune response against the tumor. It is most effective in patients with relatively preserved immune function (CD4 count >200 cells/µL) and no systemic symptoms. **2. Why Other Options are Incorrect:** * **Interleukin-2 (IL-2):** While IL-2 is used to boost T-cell counts in some research settings, it is not a standard or effective treatment for the vascular lesions of Kaposi Sarcoma. * **Azathioprine:** This is an immunosuppressant. Since KS is an opportunistic malignancy driven by immunosuppression, giving Azathioprine would worsen the underlying immunodeficiency and potentially accelerate the progression of the tumor [2]. **3. NEET-PG High-Yield Pearls:** * **First-line Management:** The most important initial step in treating AIDS-related KS is the initiation of **Highly Active Antiretroviral Therapy (HAART)**. Many lesions regress simply by restoring the CD4 count. * **Chemotherapy of Choice:** For advanced or symptomatic visceral KS, **Liposomal Doxorubicin** is the first-line systemic chemotherapy. * **Histology:** Look for "spindle-shaped cells" and "slit-like vascular spaces" containing extravasated RBCs. * **Classic Association:** KS is the most common neoplasm associated with HIV/AIDS [2].

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.

Question 1

An active intravenous drug abuser presents with a 5-day history of fever, a cough occasionally productive of blood, and pleuritic chest pain. Petechiae are present in his mouth and conjunctiva, and small linear hemorrhages are visible under his fingernails. Which of the following test results would MOST likely confirm the identity of the causative agent?

Accepted Answer

Blood culture of a coagulase-positive, catalase positive, gram-positive coccus

Answer

Antibodies to p24 capsid antigen

Answer

Antibodies to Trichinella spiralis antigen

Answer

Blood culture of a catalase-positive, novobiocin-sensitive, gram-positive coccus

Question 2

Which feature would most likely be found in a patient with lepromatous leprosy?

Accepted Answer

Macrophages with a foamy appearance in the dermis

Answer

Absence of bacteremia

Answer

A positive lepromin reaction

Answer

A high cell-mediated response against Mycobacterium leprae

Question 3

Which maturation stage of RBCs is infected by Plasmodium falciparum?

Accepted Answer

RBC of all ages

Answer

Reticulocyte stage only

Answer

Normoblast stage

Answer

Old RBC

Question 4

A resident doctor sustains a needle-stick injury with a suture needle used on an HIV-infected patient. The patient has been compliant with therapy for several years, recently changed medications due to altered appearance, and has a last CD4 count of 360 cells/mm³. What is the recommended post-exposure prophylaxis regimen for the resident doctor?

Accepted Answer

Zidovudine, Lamivudine, and Indinavir

Answer

Zidovudine and Lamivudine

Answer

Zidovudine, Lamivudine, and Stavudine

Answer

Zidovudine, Lamivudine, and Abacavir

Question 5

A patient with dengue hemorrhagic fever presents with myalgia and spontaneous skin bleeds. Laboratory tests show thrombocytopenia and a raised hematocrit. What is the Dengue Hemorrhagic Fever grade of the disease in this patient?

Accepted Answer

Grade II

Answer

Grade I

Answer

Grade III

Answer

Grade IV

Question 6

Which of the following statements is NOT TRUE regarding infective endocarditis caused by HACEK organisms?

Accepted Answer

The clinical course of HACEK endocarditis tends to be acute and fulminant.

Answer

Cultures of blood from patients with HACEK endocarditis may require up to 4 weeks to be positive.

Answer

Embolization is common and occurs in around 50% of cases of HACEK endocarditis.

Answer

Valvular vegetations are seen in up to 85% of patients.

Question 7

In AIDS, Kaposi sarcoma may respond to which of the following treatments?

Accepted Answer

Alpha interferon

Answer

Interleukin-2 infusion

Answer

Azathioprine

Answer

Any of the above

Question 8

Which of the following is a new oral drug used in the treatment of chronic Hepatitis C?

Accepted Answer

Ledipasvir

Answer

Interferon alpha

Answer

Oseltamivir

Answer

Lamivudine

Question 9

A patient with AIDS and a CD4 cell count of 100/µL presents with persistent fever and weight loss associated with invasive pulmonary disease due to Mycobacterium avium complex. What is the optimal management for this case?

Accepted Answer

Treat the patient with clarithromycin, ethambutol, and rifabutin.

Answer

Select an antibiotic regimen based on drug susceptibility testing of the cultured organism.

Answer

Initiate treatment with isoniazid and rifampicin.

Answer

Treat with trimethoprim-sulfamethoxazole.

Question 10

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

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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