Infectious Diseases Practice Questions

Q: What is the most common cause of pleural effusion in AIDS patients?

TB. ***TB*** - **Tuberculosis (TB)** is a common opportunistic infection in **AIDS patients**, and pleural effusion is a frequent manifestation, often an **exudative effusio**n [1]. - The high prevalence of TB in immunocompromised individuals due to **HIV** makes it the leading cause of pleural effusions in this population [1]. *Kaposi sarcoma* - While Kaposi sarcoma can affect the pleura and cause effusions, it is **less common** than TB as a cause of pleural effusion in AIDS patients. - Pleural effusions from Kaposi sarcoma are typically **serosanguinous** or **hemorrhagic**. *Pneumocystis Jiroveci* - **Pneumocystis pneumonia (PJP)** is a very common infection in AIDS patients but **rarely causes significant pleural effusions** [1]. - PCP primarily leads to **interstitial lung disease** rather than large effusions [1]. *Mycoplasma* - **Mycoplasma pneumoniae** can cause pneumonia and mild pleural effusions, but it's **not an opportunistic infection specifically linked to AIDS** and is less common than TB in this population. - The effusions associated with Mycoplasma are usually **small and transient**.

Q: Pea soup diarrhea is seen in -

Typhoid. ***Typhoid*** - **Pea soup diarrhea** is a classic symptom of **typhoid fever**, caused by *Salmonella Typhi* [1]. - This characteristic stool is a greenish-yellow watery diarrhea due to inflammation and ulceration of the Peyer's patches in the small intestine [1]. *Cholera* - Characterized by **rice-water stools**, which are profuse, watery, and often contain flecks of mucus, resembling water in which rice has been rinsed [2]. - This type of diarrhea is due to the potent **cholera toxin** causing massive fluid and electrolyte secretion [2]. *Yersinosis* - Causes diarrhea that can range from watery to bloody, often associated with severe **abdominal pain** mimicking appendicitis. - While it can cause enterocolitis, the stool consistency is not typically described as "pea soup" like in typhoid. *Hepatitis* - Hepatitis primarily affects the **liver** and typically does **not cause diarrhea** as a prominent symptom. - Common symptoms include jaundice, dark urine, and pale stools due to impaired bilirubin metabolism.

Q: What is the primary cause of Waterhouse-Friderichsen syndrome?

Adrenal hemorrhage after meningococcal infection. ***Adrenal hemorrhage after meningococcal infection*** - **Waterhouse-Friderichsen syndrome** is characterized by **massive, bilateral adrenal hemorrhage**, leading to acute adrenal insufficiency [1]. - It is most commonly associated with overwhelming **meningococcal sepsis**, particularly due to *Neisseria meningitidis* [1]. *Adrenal hemorrhage post malignancy* - While malignancies can cause adrenal hemorrhage, it is not the primary cause of **Waterhouse-Friderichsen syndrome**. - This syndrome is specifically linked to severe **bacterial sepsis**, not typically cancer-related adrenal bleeding [1]. *Congenital adrenal deficiency* - **Congenital adrenal hyperplasia (CAH)** involves genetic defects affecting cortisol synthesis, leading to chronic adrenal insufficiency. - It does not involve acute **adrenal hemorrhage** as seen in Waterhouse-Friderichsen syndrome. *Adrenal hemorrhage after corticosteroid withdrawal* - Abrupt withdrawal of corticosteroids can precipitate an **adrenal crisis** due to suppression of the hypothalamic-pituitary-adrenal (HPA) axis [2]. - However, it does not typically cause the characteristic **massive adrenal hemorrhage** seen in Waterhouse-Friderichsen syndrome [2].

Q: What is the most common cause of lobar consolidation?

Streptococcus. ***Streptococcus*** - **_Streptococcus pneumoniae_** is the **most common bacterial cause** of community-acquired pneumonia, frequently leading to lobar consolidation. [1] - It often presents with classic symptoms such as **sudden onset of fever**, productive cough with **rusty sputum**, and pleuritic chest pain. [1] *Mycoplasma* - **_Mycoplasma pneumoniae_** typically causes **"walking pneumonia"**, characterized by a more indolent course and often presents with **interstitial infiltrates** rather than dense lobar consolidation. - Though common, it is a less frequent cause of true lobar consolidation compared to _Streptococcus pneumoniae_. *Chlamydia* - **_Chlamydia pneumoniae_** causes atypical pneumonia, similar to _Mycoplasma_, presenting with less severe symptoms and **patchy infiltrates** or **interstitial patterns** rather than lobar consolidation. - It is a common cause of **atypical pneumonia** but not the leading cause of lobar consolidation. *Legionella* - **_Legionella pneumophila_** can cause severe pneumonia with consolidation, but it is **less common overall** than pneumococcal pneumonia. [1] - **Legionnaires' disease** is often associated with exposure to contaminated water sources and may present with **gastrointestinal and neurological symptoms** in addition to respiratory manifestations.

Q: In which condition is Cepacia syndrome most commonly associated?

Cystic fibrosis. ***Cystic fibrosis*** - **Cepacia syndrome** is a severe and often fatal complication in patients with **cystic fibrosis** caused by infection with bacteria of the *Burkholderia cepacia complex*. - Patients with cystic fibrosis have impaired mucociliary clearance, making them highly susceptible to chronic bacterial infections, including those leading to Cepacia syndrome. *Sarcoidosis* - **Sarcoidosis** is a multisystem inflammatory disease characterized by the formation of **non-caseating granulomas**, primarily affecting the lungs and lymph nodes. - It is not associated with bacterial infections causing Cepacia syndrome. *Tuberculosis* - **Tuberculosis** is caused by *Mycobacterium tuberculosis* and primarily affects the lungs, leading to granuloma formation and tissue destruction. - While it is a chronic bacterial infection, it does not typically lead to or interact with the *Burkholderia cepacia complex* in the way seen in Cepacia syndrome. *Immotile cilia syndrome* - Also known as **primary ciliary dyskinesia**, this condition involves defective ciliary function leading to recurrent respiratory infections and other issues like situs inversus. - Although patients have recurrent respiratory infections, **Cepacia syndrome** is not a characteristic or commonly associated complication.

Q: Which of the following conditions is least commonly associated with Pneumocystis carinii in AIDS?

Otic polypoid mass. ***Otic polypoid mass*** - While *Pneumocystis jirovecii* (formerly *carinii*) can cause **extrapulmonary disease** in immunocompromised patients, an **otic polypoid mass** is an extremely rare and atypical presentation. - Extrapulmonary manifestations usually involve organs with rich vascular supply, but ear involvement in this form is not a characteristic feature. *Pneumonia* - **Pneumocystis pneumonia (PCP)** is the **most common opportunistic infection** and AIDS-defining illness caused by *Pneumocystis jirovecii* in individuals with AIDS [1]. - It typically manifests as **fever, cough, and dyspnea** with characteristic imaging findings [1]. *Ophthalmic choroid lesion* - **Choroid lesions** due to *Pneumocystis jirovecii* are a recognized, albeit less common, **extrapulmonary manifestation** in immunocompromised patients, particularly those with AIDS. - These lesions are usually **asymptomatic** and discovered incidentally on funduscopic examination. *Meningitis* - Although *Pneumocystis jirovecii* causing **meningitis** is rare, it has been reported in severely immunocompromised individuals with AIDS, often as part of disseminated disease. - Central nervous system involvement signifies **widespread dissemination** and advanced immunosuppression.

Q: What is the minimum induration measurement for a positive Tuberculin test?

>10mm. >10mm - A positive tuberculin skin test (TST) with an induration of **>10mm** is generally considered significant in the general population with no known risk factors for TB. - This cutoff helps identify individuals who have been infected with **Mycobacterium tuberculosis** and have developed a delayed-type hypersensitivity response. *>2mm* - An induration of **>2mm** is too small to be considered a positive TST result in any risk group. - Such a small reaction is typically interpreted as **negative** or non-specific. *>5mm* - An induration of **>5mm** is considered positive in specific high-risk groups, such as individuals with **HIV infection**, recent close contacts of TB cases, or those with **fibrotic changes** on chest X-ray consistent with prior TB. - It is not the general cutoff for a positive test in the broader population. *>7mm* - An induration of **>7mm** does not correspond to a standard interpretive cutoff for a positive TST in any established guideline. - It falls between the **>5mm** (high-risk) and **>10mm** (general population) criteria, making it an incorrect general threshold.

Q: Most common cause of death in diphtheria is due to

Toxic cardiomyopathy. ***Toxic cardiomyopathy*** - Diphtheria toxin primarily targets and damages the **myocardium**, leading to heart failure, arrhythmias, and ultimately death. - Myocardial damage can occur even in mild cases and is the most frequent cause of **fatality** in both treated and untreated diphtheria. *Airway obstruction* - While significant **pharyngeal and laryngeal pseudomembrane formation** can cause severe respiratory distress and obstruction, it is not the most common cause of death overall. - Prompt medical intervention, such as **tracheostomy** or antitoxin administration, can often alleviate acute airway issues. *Septic shock* - Diphtheria itself is a **toxin-mediated disease**, not typically characterized by overwhelming bacterial sepsis leading to septic shock as the primary cause of death. - While secondary infections can occur, direct **toxin-induced organ damage** is the main concern. *Descending polyneuropathy (rare)* - **Neurological complications**, such as polyneuropathy, can occur later in the course of diphtheria due to toxin effects. - However, these are generally less common and less immediately life-threatening than **cardiac complications**, and rarely the direct cause of death.

Q: Which of the following conditions does not present with a rash?

Q fever. ***Q fever*** - **Q fever** is typically characterized by **fever, headache, chills, and myalgia,** but a skin rash is generally absent. - The disease is caused by *Coxiella burnetii* and can lead to pneumonia or hepatitis, without cutaneous manifestations. *Scrub typhus* - **Scrub typhus** characteristically presents with a **maculopapular rash** that may become generalized [1]. - A distinguishing feature is the presence of an **eschar** at the site of the chigger bite [1]. *Epidemic typhus* - **Epidemic typhus** often involves a **macular or maculopapular rash** that begins on the trunk and spreads peripherally, typically sparing the face, palms, and soles [1]. - This rash usually appears 4-7 days after the onset of fever [1]. *Endemic typhus* - **Endemic (murine) typhus** is also associated with a **maculopapular rash**, which tends to be less extensive and less prominent than that seen in epidemic typhus [1]. - The rash typically starts on the trunk and spreads, usually after 4-5 days of fever [1].

Q: Which of the following symptoms is commonly associated with giardiasis?

Steatorrhea and flatulence. ***Steatorrhea and flatulence*** - **Giardiasis** is an intestinal infection caused by the parasite *Giardia lamblia*, leading to malabsorption and characteristic symptoms [1]. - The parasite attaches to the intestinal lining, interfering with fat absorption, which results in **steatorrhea** (fatty, foul-smelling stools) and increased gas production causing **flatulence** [1]. *Nausea and vomiting* - While **nausea** can occur in giardiasis, **vomiting** is less common as a primary or dominant symptom. - These symptoms are more characteristic of other gastrointestinal infections like **viral gastroenteritis**. *Abdominal pain* - **Abdominal pain** is a general symptom that can occur with many gastrointestinal issues, including giardiasis [1]. - However, it's not as specific or as clinically defining for giardiasis as **steatorrhea** and **flatulence**, which are direct consequences of the parasite's impact on fat absorption. *All of the options* - Although some patients with giardiasis may experience nausea and abdominal pain, **steatorrhea** and **flatulence** are the most direct and specific indicators of the malabsorption caused by *Giardia lamblia* [1]. - Choosing "all of the above" would imply that all listed symptoms are equally common and specific, which is not the case for giardiasis.

Question 1

What is the most common cause of pleural effusion in AIDS patients?

Accepted Answer

TB

Answer

Pneumocystis Jiroveci

Answer

Mycoplasma

Answer

Kaposi sarcoma

Question 2

Pea soup diarrhea is seen in -

Accepted Answer

Typhoid

Answer

Cholera

Answer

Yersinosis

Answer

Hepatitis

Question 3

What is the primary cause of Waterhouse-Friderichsen syndrome?

Accepted Answer

Adrenal hemorrhage after meningococcal infection

Answer

Adrenal hemorrhage post malignancy

Answer

Adrenal hemorrhage after corticosteroid withdrawal

Answer

Congenital adrenal deficiency

Question 4

What is the most common cause of lobar consolidation?

Accepted Answer

Streptococcus

Answer

Mycoplasma

Answer

Chlamydia

Answer

Legionella

Question 5

In which condition is Cepacia syndrome most commonly associated?

Accepted Answer

Cystic fibrosis

Answer

Immotile cilia syndrome

Answer

Sarcoidosis

Answer

Tuberculosis

Question 6

Which of the following conditions is least commonly associated with Pneumocystis carinii in AIDS?

Accepted Answer

Otic polypoid mass

Answer

Meningitis

Answer

Pneumonia

Answer

Ophthalmic choroid lesion

Question 7

What is the minimum induration measurement for a positive Tuberculin test?

Accepted Answer

>10mm

Answer

>5mm

Answer

>7mm

Answer

>2mm

Question 8

Most common cause of death in diphtheria is due to

Accepted Answer

Toxic cardiomyopathy

Answer

Airway obstruction

Answer

Septic shock

Answer

Descending polyneuropathy (rare)

Question 9

Which of the following conditions does not present with a rash?

Accepted Answer

Q fever

Answer

Scrub typhus

Answer

Epidemic typhus

Answer

Endemic typhus

Question 10

Which of the following symptoms is commonly associated with giardiasis?

Accepted Answer

Steatorrhea and flatulence

Answer

All of the options

Answer

Nausea and vomiting

Answer

Abdominal pain

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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