Infectious Diseases Practice Questions

Q: A patient diagnosed to be HIV-positive was started on highly active antiretroviral therapy (HAART). Which of the following can be used to monitor treatment efficacy?

Viral load. ***Viral load*** - **Viral load** (HIV RNA copies per milliliter of plasma) is the most direct and sensitive measure of HAART efficacy, as it indicates the amount of actively replicating virus [1]. - A successful HAART regimen aims to reduce the **viral load** to undetectable levels, signaling effective suppression of viral replication [1]. *CD4+ T cell count* - While important for monitoring immune status and disease progression, **CD4+ T cell count** changes more slowly than viral load [1]. - An increase in **CD4+ T cell count** is a positive sign of immune reconstitution but is a lagging indicator of immediate treatment efficacy [1]. *p24 antigen* - **p24 antigen** is a core structural protein of HIV, primarily detectable early in acute infection and in advanced stages when viral replication is very high. - It is generally not used for routine monitoring of HAART efficacy in chronic HIV infection because its levels fluctuate and become undetectable as the immune system produces antibodies. *Viral serotype* - **Viral serotype** refers to the specific strain or subtype of HIV (e.g., HIV-1 vs. HIV-2, or different clades within HIV-1). - It is determined at diagnosis to understand the specific virus but does not change significantly during the course of treatment and is not used to monitor HAART efficacy.

Q: A 30-year-old male is found to be positive for HBsAg and HBeAg and is diagnosed with chronic hepatitis B. The patient's viral load is 2 × 10^5 IU/mL and ALT is elevated (2× upper limit of normal). What is the appropriate management in this patient?

Tenofovir. Tenofovir - This patient presents with chronic hepatitis B (HBsAg positive for >6 months), evidence of active viral replication (HBeAg positive, high viral load), and liver inflammation (elevated ALT). [3] This signifies chronic active hepatitis B, requiring treatment. [1] - Tenofovir is a highly potent nucleotide analog with a high barrier to resistance, making it a first-line treatment for chronic hepatitis B. *Lamivudine* - While an antiviral for HBV, lamivudine has a low genetic barrier to resistance, meaning resistance mutations can rapidly develop, reducing its long-term efficacy. - Due to the high risk of resistance, lamivudine is generally not recommended as a first-line monotherapy for treatment-naive patients with chronic hepatitis B, especially with a high viral load. *Pegylated interferon* - Pegylated interferon is an option for chronic hepatitis B, but it causes significant side effects (e.g., fatigue, depression, bone marrow suppression) and is usually administered by injection. [2] - Its efficacy in achieving sustained HBeAg seroconversion or HBsAg loss can be variable, and it is often reserved for patients who prefer a finite course of treatment and can tolerate the side effects, or for those without advanced liver disease. [2] *Combined pegylated interferon with lamivudine* - There is no significant evidence that combining pegylated interferon with lamivudine offers superior efficacy compared to monotherapy with a potent nucleos(t)ide analog like tenofovir or entecavir. - This combination would increase the side effect burden from interferon and still carry the risk of lamivudine resistance without substantial added benefit.

Q: A patient hailing from Delhi presents with fever, arthralgia, and extensive petechial rash for 3 days. Lab investigations revealed a hemoglobin of 9 g/ dL, a white blood cell count of 9000 cells/mm3, a platelet count of 20000 cells/mm3, and a prolonged bleeding time. The clotting time was normal. What is the most likely diagnosis?

Dengue. Dengue - The combination of **fever, arthralgia, extensive petechial rash**, and severe **thrombocytopenia** (platelet count 20,000/mm³) with **prolonged bleeding time** is highly characteristic of severe dengue infection, especially in an endemic area like Delhi [1]. - While leukocytosis (WBC 9000/mm³) is not typical for dengue (usually causes leukopenia), the other features strongly point to dengue hemorrhagic fever [1]. *Malaria* - Typically presents with **intermittent high fever**, chills, and sweats. While it can cause some thrombocytopenia and anemia, the **extensive petechial rash** is not a characteristic feature. - **Thrombocytopenia** in malaria is usually milder than observed here, and prolonged bleeding time is less common [2]. *Scrub typhus* - Caused by Orientia tsutsugamushi, it is characterized by **fever, headache, myalgia, and a characteristic eschar** (necrotic ulcer) at the bite site, which is not mentioned. - While it can cause rash and some thrombocytopenia, the **petechial rash** and such severe thrombocytopenia with prolonged bleeding time are less typical. *Typhoid* - Presents with **sustained high fever**, headache, bradycardia, and sometimes a **rose spot rash** (maculopapular), which is different from a petechial rash. - Typhoid typically causes **leukopenia** and can lead to gastrointestinal complications like intestinal bleeding, but severe thrombocytopenia and extensive petechiae are not common presenting features.

Q: A bronchial asthma patient on inhalational steroids presented with white patchy lesions on the tongue and buccal mucosa. What condition is likely to be present in this patient?

Oral candidiasis. **Oral candidiasis** - **Inhaled corticosteroids** can suppress the local immune response in the oral cavity, creating an environment conducive to the overgrowth of *Candida albicans*. - The classic presentation includes **white patchy lesions** on the tongue and buccal mucosa, which can often be scraped off. *Oral lichen planus* - Characterized by **reticular (Wickham's striae)**, papular, or erosive lesions, which are often bilateral and symmetric [1]. - While it can present with white lesions, they are typically not easily scraped off and are not primarily associated with inhaled corticosteroid use [1]. *Aphthous ulcers* - These are typically **painful, solitary, or multiple ulcers** with a red halo and a yellowish-gray center [2]. - They are distinct from widespread white patchy lesions and are not directly caused by inhaled corticosteroid use [2]. *Oral leukoplakia* - Defined as a **white patch or plaque** on the oral mucosa that cannot be characterized clinically or pathologically as any other disease, and which is not removable by scraping. - It is often associated with tobacco use and alcohol consumption, and carries a risk of malignancy; it does not typically appear as a direct side effect of inhaled corticosteroids.

Q: In a patient presented with a fever and a positive filarial antigen test, what is the next appropriate method of management?

Detection of microfilariae in the blood smear. ***Detection of microfilariae in the blood smear*** - A positive **filarial antigen test** indicates the presence of adult worms, and the next step is to confirm active infection by identifying **microfilariae**. [1] - **Nocturnal blood samples** are crucial because microfilariae of *Wuchereria bancrofti* and *Brugia malayi* exhibit **nocturnal periodicity**, meaning they are most abundant in peripheral blood between 10 PM and 2 AM. [1] *Bone marrow biopsy* - This procedure is typically used to diagnose **hematological disorders**, such as leukemia or lymphoma, or investigate causes of unexplained fever, but it is not indicated for filariasis. - While filariasis can rarely lead to **eosinophilia**, a bone marrow biopsy is not a diagnostic tool for filarial infection itself. *DEC provocation test* - The **diethylcarbamazine (DEC) provocation test** is used to bring out microfilariae into the peripheral blood during the daytime for species that exhibit nocturnal periodicity. [1] - However, it carries a risk of severe adverse reactions due to rapid killing of microfilariae, especially in cases of heavy infection, and is generally avoided when antigen tests are positive. [1] *Ultrasound of the scrotum* - Scrotal ultrasound can detect the characteristic "filarial dance sign" (motile adult worms) in the **lymphatic vessels of the scrotum and epididymis**, confirming lymphatic filariasis. [2] - While useful for assessing advanced disease manifestations like **hydrocele**, it does not quantify microfilaremia or replace the need for microscopic confirmation of circulating microfilariae to guide treatment.

Q: A young male came to the hospital with a clean-cut wound without any bleeding. The patient received a full course of tetanus vaccination 10 years ago. What is the best management for this patient?

Single-dose tetanus toxoid. ***Single-dose tetanus toxoid*** - For a **clean-cut wound** in a patient who completed a **primary tetanus vaccination series** and received their last dose more than 5 years ago but less than 10 years ago, a **single booster dose** of tetanus toxoid is recommended. [1] - A booster ensures continued protection, as vaccine-induced immunity wanes over time, but the prior full course provides a robust anamnestic response with a single dose. *Human tetanus immunoglobulin and a full course of vaccine* - This regimen (tetanus immunoglobulin + vaccine) is typically reserved for patients with **unvaccinated status**, an **unknown vaccination history**, or a **severely contaminated wound** (e.g., rusty nail, soil contamination) who have not been fully vaccinated. - The patient had a **clean-cut wound** and completed a full course of vaccination 10 years ago, making immunoglobulin unnecessary and a full course of vaccine excessive. *Human tetanus immunoglobulin only* - Administering **tetanus immunoglobulin alone** is appropriate for immediate, passive immunity in situations where a patient is unvaccinated or has an unknown vaccination status and has a significant risk of tetanus from a contaminated wound. [2] - This patient has a clean wound and a history of full vaccination, so a booster is sufficient to stimulate active immunity. *No treatment required* - While the patient was fully vaccinated 10 years ago, the protection from tetanus vaccination can **wane over time**, especially after 5-10 years. - A **booster dose** is crucial to maintain adequate protection against tetanus, even for a clean wound, given the 10-year interval since the last dose.

Q: A male patient diagnosed with tuberculosis took complete treatment. Sputum examination was done after the completion of the intensive and the continuation phases. It was found to be negative. What is the status of the patient?

Cured. ***Cured*** - A patient is declared **cured** if they have completed the full course of treatment and have achieved **two negative sputum smear results**, with one at the end of the intensive phase and another at the completion of the treatment [1]. - This indicates that the **infection has been eradicated**, and the patient is no longer infectious. *Treatment completed* - This status applies when a patient has **completed the full treatment course** but does not have documented sputum smear results that meet the criteria for "cured." - While treatment was completed, the **bacteriological status is not confirmed** in the same way as for a cured patient. *Lost to follow up* - This term describes a patient who was **enrolled in treatment but was interrupted** for a specific period (e.g., two consecutive months or more) and their outcome cannot be determined. - They **ceased to attend follow-up appointments** and their treatment completion or success is unknown. *Treatment failed* - This status is assigned when a patient remains **sputum smear-positive at the end of the intensive phase** or at the end of the treatment, or if they initially converted to negative but later became positive again [1]. - It signifies that the **treatment regimen was ineffective** in eradicating the infection.

Q: Punched out ulcers in the esophagus are most commonly associated with which of the following conditions?

CMV. ***Oesophagitis*** - Characterized by **punched-out ulcers** in the esophagus, often related to infectious causes. - Common in patients with **immunocompromised** states, where mucosal inflammation leads to these distinctive lesions [1]. *cmv* - Typically associated with **shallow ulcers** and **larger lesions**, not specifically "punched-out" ulcers. - CMV esophagitis usually presents with **linear ulcerations** and is less common in the absence of immune deficiency [1]. *candida* - Characterized by **white plaques** or pseudomembranes rather than **punched-out ulcers**. - Common in individuals with **oral thrush** and presents as **esophageal symptoms** such as dysphagia [1]. *herpes* - Often leads to **sharp, serpiginous ulcers** that are distinct from the punched-out variety. - Typically associated with **oral lesions** and presents with acute severe pain while swallowing [1]. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Alimentary System Disease, pp. 347-348.

Question 1

Which of the following statements about herpes zoster complications is incorrect?

Accepted Answer

Postherpetic neuralgia is the most common complication of herpes zoster

Answer

Chickenpox and herpes zoster are caused by the same virus (VZV)

Answer

Herpes zoster typically occurs in a dermatomal distribution

Answer

Chickenpox vaccination prevents both primary varicella and herpes zoster reactivation completely

Question 2

A patient diagnosed to be HIV-positive was started on highly active antiretroviral therapy (HAART). Which of the following can be used to monitor treatment efficacy?

Accepted Answer

Viral load

Answer

CD4+ T cell count

Answer

p24 antigen

Answer

Viral serotype

Question 3

A 30-year-old male is found to be positive for HBsAg and HBeAg and is diagnosed with chronic hepatitis B. The patient's viral load is 2 × 10^5 IU/mL and ALT is elevated (2× upper limit of normal). What is the appropriate management in this patient?

Accepted Answer

Tenofovir

Answer

Combined pegylated interferon with lamivudine

Answer

Pegylated interferon

Answer

Lamivudine

Question 4

A patient hailing from Delhi presents with fever, arthralgia, and extensive petechial rash for 3    days. Lab investigations revealed a hemoglobin of 9 g/ dL, a white blood cell count of 9000    cells/mm3, a platelet count of 20000 cells/mm3, and a prolonged bleeding time. The clotting    time was normal. What is the most likely diagnosis?

Accepted Answer

Dengue

Answer

Malaria

Answer

Scrub typhus

Answer

Typhoid

Question 5

A bronchial asthma patient on inhalational steroids presented with white patchy lesions on the tongue and buccal mucosa. What condition is likely to be present in this patient?

Accepted Answer

Oral candidiasis

Answer

Oral lichen planus

Answer

Aphthous ulcers

Answer

Oral leukoplakia

Question 6

A woman with recurrent diarrhea is prescribed a broad-spectrum antibiotic. Which of the following statements is not true regarding Clostridium difficile infection?

Accepted Answer

IgM assay is used to confirm the diagnosis of Clostridium difficile infection.

Answer

Pseudomembrane is a layer of inflammatory debris

Answer

Oral fidaxomicin is used for treatment

Answer

It is toxin mediated

Question 7

In a patient presented with a fever and a positive filarial antigen test, what is the next appropriate method of management?

Accepted Answer

Detection of microfilariae in the blood smear

Answer

Bone marrow biopsy

Answer

DEC provocation test

Answer

Ultrasound of the scrotum

Question 8

A young male came to the hospital with a clean-cut wound without any bleeding. The patient    received a full course of tetanus vaccination 10 years ago. What is the best management for    this patient?

Accepted Answer

Single-dose tetanus toxoid

Answer

Human tetanus immunoglobulin only

Answer

Human tetanus immunoglobulin and a full course of vaccine

Answer

No treatment required

Question 9

A male patient diagnosed with tuberculosis took complete treatment. Sputum examination was done after the completion of the intensive and the continuation phases. It was found to be negative. What is the status of the patient?

Accepted Answer

Cured

Answer

Treatment completed

Answer

Lost to follow up

Answer

Treatment failed

Question 10

Punched out ulcers in the esophagus are most commonly associated with which of the following conditions?

Accepted Answer

CMV

Answer

Reflux esophagitis

Answer

Herpes simplex virus (HSV)

Answer

Candida

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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