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: Plasmapheresis is the treatment of choice for which of the following conditions?

Goodpasture's syndrome. **Explanation:** **Goodpasture’s Syndrome (Anti-GBM Disease)** is the correct answer because its pathogenesis involves circulating pathogenic autoantibodies directed against the alpha-3 chain of Type IV collagen in the glomerular and alveolar basement membranes [1]. **Plasmapheresis** is the treatment of choice because it directly and rapidly removes these circulating anti-GBM antibodies from the plasma, preventing further tissue damage [1]. It is typically combined with corticosteroids and cyclophosphamide to suppress further antibody production [1]. **Analysis of Incorrect Options:** * **Henoch-Schönlein Purpura (IgA Vasculitis):** This is usually a self-limiting condition, especially in children. Treatment is primarily supportive; steroids are used for severe abdominal or renal involvement, but plasmapheresis is not standard therapy. * **Wegener's Granulomatosis (GPA):** The mainstay of treatment is induction with corticosteroids and immunosuppressants (Cyclophosphamide or Rituximab). While plasmapheresis may be considered in severe cases with rapidly progressive glomerulonephritis (RPGN) or pulmonary hemorrhage, it is not the primary "treatment of choice." * **Acute Renal Transplant Rejection:** Cellular rejection is treated with high-dose steroids or anti-thymocyte globulin. Plasmapheresis is reserved only for antibody-mediated rejection (AMR), not all acute rejections. **High-Yield Clinical Pearls for NEET-PG:** * **Goodpasture’s Triad:** Glomerulonephritis (hematuria), Pulmonary hemorrhage (hemoptysis), and Anti-GBM antibodies. * **Immunofluorescence Pattern:** Characterized by **linear** IgG deposits along the glomerular basement membrane [1]. * **Other Indications for Plasmapheresis:** TTP (Treatment of choice), Guillain-Barré Syndrome, Myasthenia Gravis (crisis), and Hyperviscosity syndrome.

Q: Which of the following is a common cause of chronic liver disease?

Hepatitis C. The correct answer is **Hepatitis C**. The primary medical concept here is the **rate of chronicity**. Hepatitis C Virus (HCV) is notorious for its high propensity to cause persistent infection; approximately **75%–85%** of individuals infected with HCV fail to clear the virus and progress to chronic hepatitis [1]. Over decades, this chronic inflammation leads to cirrhosis and hepatocellular carcinoma (HCC), making it a leading cause of chronic liver disease (CLD) and liver transplantation worldwide [1]. **Analysis of Incorrect Options:** * **Hepatitis A and E:** These are transmitted via the **fecal-oral route** and typically cause acute, self-limiting hepatitis [2]. They **do not** cause chronic liver disease. (Exception: Hepatitis E can cause chronicity in severely immunocompromised individuals/transplant recipients, but this is not the "common" presentation). * **Hepatitis B:** While HBV is a major cause of CLD globally, its rate of chronicity in adults is relatively low (** HBV in neonates (90%) > HBV in adults (<5%) [3]. * **Screening:** Anti-HCV antibody is the initial screening test; **HCV RNA (PCR)** is the gold standard for confirming active infection [1]. * **Treatment:** Unlike HBV, which is usually managed with long-term suppression, HCV is now considered **curable** with Direct-Acting Antivirals (DAAs) like Sofosbuvir. * **Hepatitis D:** Requires the presence of HBsAg to replicate; it can significantly accelerate the progression of CLD in HBV-infected patients.

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: Exanthemas are caused by all of the following EXCEPT:

Malaria. An **exanthema** is defined as a widespread skin rash that occurs as a symptom of a systemic disease, usually infectious in nature. **Why Malaria is the Correct Answer:** Malaria is a protozoal infection caused by *Plasmodium* species. Its clinical hallmark is the "malarial paroxysm" (chills, high fever, and sweating) and systemic features like splenomegaly and anemia. Crucially, **Malaria does not cause a skin rash (exanthema).** Any rash seen in a patient with malaria is likely due to a co-infection or a drug reaction [1]. **Why the other options are incorrect:** * **Typhoid (Enteric Fever):** Caused by *Salmonella typhi*, it classically presents with **"Rose Spots"**—faint, salmon-colored, blanching macules typically found on the chest and abdomen during the second week of illness [1]. * **Measles (Rubeola):** A viral infection characterized by a high-grade fever and a **maculopapular rash** that begins behind the ears and spreads cephalocaudally (downward) [1, 2]. It is also associated with Koplik spots [2]. * **Rubella (German Measles):** Presents with a similar but milder maculopapular rash compared to measles, often starting on the face and spreading rapidly [3]. It is famously associated with **Forchheimer spots** on the soft palate. **High-Yield Clinical Pearls for NEET-PG:** * **Rose Spots:** Pathognomonic for Typhoid; they are transient and often disappear within 2–5 days [1]. * **Koplik Spots:** Precede the Measles rash; located on the buccal mucosa opposite the lower molars [2]. * **Common Exanthematous Diseases:** Remember the "Classical Six" (Measles, Scarlet Fever, Rubella, Duke’s Disease, Erythema Infectiosum, and Roseola Infantum) [1]. * **Dengue:** Often presents with a "white islands in a sea of red" rash during the recovery phase [1].

Q: Hyperbaric oxygen is useful in which of the following conditions?

Gas gangrene. Explanation: Hyperbaric Oxygen Therapy (HBOT) involves breathing 100% oxygen at pressures greater than atmospheric pressure. It is a cornerstone adjunct treatment for Gas Gangrene (Clostridial Myonecrosis) [1]. Why Gas Gangrene is the correct answer: Gas gangrene is caused by Clostridium perfringens, an obligate anaerobe. HBOT works through two primary mechanisms: 1. Bactericidal/Bacteriostatic effect: High partial pressures of oxygen are directly toxic to anaerobic bacteria. 2. Inhibition of Alpha-toxin: HBOT halts the production of the alpha-toxin (lecithinase), which is the primary virulence factor responsible for tissue necrosis and systemic toxicity. This helps demarcate the wound and reduces the extent of surgical debridement required. Analysis of Incorrect Options: * Tetanus: While caused by an anaerobe (C. tetani), the pathology is driven by a fixed neurotoxin (tetanospasmin). HBOT does not neutralize the toxin or improve outcomes in clinical trials. * Frostbite: The primary treatment is rapid rewarming in water (37-39°C). While HBOT is occasionally studied for microvascular salvage, it is not a standard or first-line indication compared to gas gangrene. * Vincent’s Angina: Also known as "Trench Mouth" (necrotizing ulcerative gingivitis), it is treated with oral hygiene, saline rinses, and antibiotics (Metronidazole). HBOT is not indicated for this localized oral infection. Clinical Pearls for NEET-PG: * Absolute Contraindication for HBOT: Untreated tension pneumothorax. * Other High-Yield Indications: Carbon monoxide poisoning, Decompression sickness (The Bends), Air/Gas embolism, and refractory Chronic Osteomyelitis. * Most common side effect: Middle ear barotrauma (due to pressure changes).

Question 1

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 2

Plasmapheresis is the treatment of choice for which of the following conditions?

Accepted Answer

Goodpasture's syndrome

Answer

Henoch-Schönlein purpura

Answer

Wegener's granulomatosis

Answer

Acute renal transplant rejection

Question 3

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 4

Which of the following is a common cause of chronic liver disease?

Accepted Answer

Hepatitis C

Answer

Hepatitis B

Answer

Hepatitis A

Answer

Hepatitis E

Question 5

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 6

Exanthemas are caused by all of the following EXCEPT:

Accepted Answer

Malaria

Answer

Typhoid

Answer

Measles

Answer

Rubella

Question 7

A 25-year-old male student presents with a rash. He denies headache, fever, or myalgia. A slightly pruritic maculopapular rash is noted over the abdomen, trunk, palms of the hands, and soles of the feet. Inguinal, occipital, and cervical lymphadenopathy is also noted. Hypertrophic, flat, wart-like lesions are noted around the anal area. Laboratory studies show: Hct: 40%, Hgb: 14 g/dL, WBC: 13,000/mL with a differential of 50% segmented neutrophils and 50% lymphocytes. Which of the following is the most useful laboratory test in this patient?

Accepted Answer

Rapid Plasma Reagin (RPR) test

Answer

Human papillomavirus (HPV) serology

Answer

Nucleic acid amplification test for Chlamydia

Answer

Blood cultures

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

Hyperbaric oxygen is useful in which of the following conditions?

Accepted Answer

Gas gangrene

Answer

Tetanus

Answer

Frostbite

Answer

Vincent's angina

Question 10

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.

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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