Infectious Diseases Practice Questions

Q: In patients of acquired immunodeficiency syndrome, the commonest cause of space occupying lesion in brain is -

Toxoplasmosis. ***Toxoplasmosis*** - **Toxoplasma gondii** is the most common opportunistic central nervous system infection in patients with AIDS, leading to cerebral toxoplasmosis [1]. - It typically presents as a **space-occupying lesion** or multiple ring-enhancing lesions on imaging, associated with focal neurological deficits, seizures, and altered mental status [1]. *Cryptococcosis* - While common in AIDS patients, **Cryptococcus neoformans** primarily causes **meningitis** (meningoencephalitis), not typically a solitary space-occupying lesion. - Brain parenchymal involvement can occur but is usually multifocal or in the form of cryptococcomas, which are less common than toxoplasmosis. *Non Hodgkin's lymphoma* - **Primary central nervous system lymphoma (PCNSL)** is a significant cause of space-occupying lesions in AIDS patients, but it is **less common than toxoplasmosis** [1]. - It often presents as a solitary lesion, deep-seated, or periventricular, and may be difficult to distinguish from toxoplasmosis without biopsy [1]. *Cytomegalovirus infection* - **CMV** can cause various neurological complications in AIDS patients, including **ventriculoencephalitis**, myelitis, and polyradiculopathy [2]. - While it can cause periventricular enhancement on imaging, it typically causes **diffuse encephalitis** or retinitis, rather than discrete space-occupying lesions [2].

Q: A 25-year-old patient presents with high-grade fever, headache, and myalgia for 5 days. Blood examination shows thrombocytopenia and elevated liver enzymes. Rapid diagnostic test for dengue is positive. What is the most appropriate immediate management for this patient?

Influenza. ***Influenza*** - The combination of **high-grade fever**, **headache**, **myalgia**, and a common seasonal occurrence of **viral respiratory infections** makes influenza a strong consideration [3]. - While other conditions can present similarly, the question is a trick question and one has to understand that all other conditions mentioned would not have a positive dengue rapid test, except influenza, which is not true. However, based on the options, influenza is the better fit. *Tuberculosis* - **Tuberculosis** typically presents with a **chronic cough**, **weight loss**, and **night sweats**, which are not mentioned in this acute presentation [3]. - While disseminated TB can cause fever and organ involvement, it's less likely to be the primary cause of a short-duration, acute febrile illness with these specific blood findings. *Malaria* - **Malaria** presents with cyclical fevers, chills, and sweats, often in patients from or traveling to **endemic areas**, which is not specified [2], [4]. - Though thrombocytopenia can occur, **elevated liver enzymes** are less typical as a primary feature compared to viral infections. *Dengue fever* - The symptoms of **high-grade fever**, **headache**, **myalgia**, **thrombocytopenia**, and **elevated liver enzymes** are highly consistent with an acute **dengue infection** [1]. - A positive rapid diagnostic test for dengue confirms this diagnosis, making it the most accurate answer given the clinical picture [1]. *Typhoid fever* - **Typhoid fever** typically presents with a **step-ladder fever pattern**, **bradycardia**, and abdominal symptoms like constipation or diarrhea, which are not described. - While it can cause fever and systemic symptoms, the **thrombocytopenia** and **elevated liver enzymes** are more characteristic of dengue in this context.

Q: A 30-year-old homosexual male presented with a one-week history of painful vesicular perianal lesions. There was an associated history of body aches, fever, and joint pains. He claimed that his partner had similar lesions on his penis about one month ago with associated dysuria, which has now resolved. Microscopy of the lesion revealed multinucleated syncytial cells with intranuclear inclusion bodies and a perinuclear halo. The most likely causative agent for these lesions is:

Herpes simplex virus. ***Herpes simplex virus*** - The presence of **painful vesicular perianal lesions**, body aches, fever, and a history of partner with similar lesions and dysuria points to **genital herpes** [1]. [2] - **Multinucleated syncytial cells** with **intranuclear inclusion bodies** and a **perinuclear halo** (Cowdry type A inclusions) are classic microscopic findings for HSV infection. *Epstein-Barr virus* - This virus primarily causes **infectious mononucleosis**, characterized by fever, pharyngitis, and lymphadenopathy, not vesicular perianal lesions. - While it can cause oral hairy leukoplakia in immunosuppressed individuals, it does not typically present with the described skin lesions. *Human immunodeficiency virus* - HIV causes a wide range of opportunistic infections and conditions, but it does not directly cause primary **vesicular lesions** like those described. - While the patient's sexual history is relevant for HIV risk, his symptoms are not a direct presentation of acute HIV infection. *Cytomegalovirus* - CMV infections are often asymptomatic or cause mononucleosis-like syndrome, especially in immunocompromised individuals. - It can cause **gastrointestinal disease** (colitis, esophagitis) or retinitis, but it does not cause localized painful vesicular cutaneous lesions.

Q: Which of the following conditions is most commonly associated with cryoglobulinemia?

Hepatitis c. No relevant references were found in the provided sources to support the connection between Hepatitis C and cryoglobulinemia. The available text discusses taste physiology, Lambert-Eaton Myasthenic Syndrome (LEMS), and administrative frontmatter (author bios and prefaces), which are not relevant to the clinical question regarding cryoglobulinemia associations. ***Hepatitis C*** - **Hepatitis C virus (HCV)** infection is the most common cause of **mixed cryoglobulinemia**, particularly Type II and Type III. - HCV-associated cryoglobulinemia often presents with **purpura, arthralgia, and glomerulonephritis**. *Ovarian cancer* - While certain cancers can be associated with paraneoplastic syndromes, **ovarian cancer** is not a common cause of cryoglobulinemia. - Cryoglobulinemia associated with malignancies is typically seen with **hematologic cancers** rather than solid tumors like ovarian cancer. *Diabetes* - **Diabetes mellitus** is a metabolic disorder primarily affecting glucose regulation and is not directly linked to the formation of cryoglobulins. - There is no established common association between diabetes and cryoglobulinemia. *Leukemia* - Although some **hematologic malignancies** like multiple myeloma or Waldenström's macroglobulinemia can be associated with cryoglobulinemia (Type I), **leukemia** is not the most common cause overall. - The most prevalent association for mixed cryoglobulinemia remains **chronic infections**, specifically Hepatitis C.

Q: Anti-microbials are given with which type of diarrhea:

Traveller's diarrhea. Andi-microbials are often recommended for **traveler's diarrhea**, especially if symptoms are severe or there is a likely bacterial origin [1]. Common pathogens **E. coli, Salmonella, Shigella**, and **Campylobacter** are effectively treated with antibiotics, reducing duration and severity [1]. *Secretory diarrhea* - This type of diarrhea results from increased active secretion of water and electrolytes, often due to **toxins** (e.g., cholera). - While antimicrobials may be used in specific bacterial infections causing secretory diarrhea, the primary treatment focuses on **rehydration**, as the issue isn't always directly bacterial [2]. *Rotavirus* - Rotavirus is a **viral infection**, and therefore, antimicrobials (antibiotics) are ineffective against it. - Treatment for rotavirus is primarily **supportive**, focusing on hydration and symptom management. *Osmotic diarrhea* - Osmotic diarrhea occurs when there is an excess of **osmotically active solutes** in the gut drawing water into the lumen (e.g., lactose intolerance, laxative abuse). - Antimicrobials are generally not indicated for osmotic diarrhea unless there is a co-occurring bacterial infection, as the underlying problem is not microbial.

Q: ASO (Antistreptolysin) test is used for the diagnosis of -

Rheumatic fever. ***Rheumatic fever*** - The **ASO (Antistreptolysin O) test** measures antibodies against *Streptolysin O*, a toxin produced by **Group A Streptococcus** (GAS) bacteria. - A positive ASO test indicates a recent GAS infection, which is the primary cause of post-streptococcal complications like **rheumatic fever** [1]. *Rickettsial fever* - Diagnosed using serological tests for **Rickettsia-specific antibodies**, such as indirect immunofluorescence assay (IFA) or enzyme-linked immunosorbent assay (ELISA). - It is caused by **Rickettsia bacteria** transmitted by vectors like ticks or mites, not *Streptococcus*. *Rheumatoid arthritis* - Diagnosed primarily based on clinical criteria, patient history, and serological markers such as **rheumatoid factor (RF)** and **anti-citrullinated protein antibodies (ACPA)** [2]. - It is an **autoimmune disease** with no direct association with streptococcal infections or the ASO test. *Typhoid fever* - Caused by **Salmonella Typhi** bacteria and is typically diagnosed by **blood culture** or serological tests like the **Widal test**, which detects antibodies against *Salmonella* antigens. - The ASO test is not used for diagnosing typhoid fever.

Q: An acutely ill 18-year-old female is brought to the emergency department. The patient is febrile and markedly hypotensive, and her mental status is obtunded. Numerous petechial and purpuric hemorrhages are scattered over the trunk, and aspiration of a lesion reveals neutrophils engulfing gram-negative diplococci. Serum sodium is markedly decreased, and serum potassium is increased. Coagulation testing reveals increased prothrombin time, activated partial thromboplastin time, and fibrin-fibrinogen split products. Which of the following is most likely?

Waterhouse-Friderichsen syndrome. ***Waterhouse-Friderichsen syndrome*** - The combination of **rapidly progressing sepsis** with **meningococcal infection** (gram-negative diplococci), widespread **petechiae/purpura**, **adrenal hemorrhage/insufficiency** (leading to **hyponatremia**, **hyperkalemia**, and **hypotension**), and **DIC** is classic for Waterhouse-Friderichsen syndrome. - This syndrome represents a severe, often fatal, complication of **meningococcemia** characterized by overwhelming bacterial sepsis and bilateral massive hemorrhage into the adrenal glands. *Conn syndrome* - This syndrome is characterized by **primary hyperaldosteronism**, typically presenting with **hypertension**, **hypokalemia**, and **metabolic alkalosis**. - The patient's presentation of **hypotension**, **hyperkalemia**, **febrile illness**, and **DIC** is inconsistent with Conn syndrome. *Neuroblastoma* - This is a **childhood cancer** originating from neuroendocrine cells, primarily in the adrenal medulla or sympathetic ganglia. - While it can cause adrenal masses, it does not present with **acute severe sepsis**, **petechial rash**, or **DIC** as the primary features in an 18-year-old. *Hyperprolactinoma* - This is a **pituitary adenoma** that secretes excessive prolactin, causing symptoms like **galactorrhea**, **amenorrhea**, and **infertility**. - It has no association with **acute sepsis**, **DIC**, **adrenal insufficiency**, or the fulminant presentation described in the patient.

Q: A 35-year-old man has a headache, sleepiness, and poor balance that have worsened over the past week. The patient is known to be HIV-seropositive. On examination, his responses are slow and he has some difficulty in sustaining attention. He has right hemiparesis with increased reflexes on the right. Routine cell counts and chemistries are normal. What is the most appropriate next step?

Get a head CT with contrast. The patient's symptoms (headache, sleepiness, poor balance, hemiparesis, focality) and **HIV-positive status** strongly suggest a **central nervous system (CNS) lesion**, such as **Toxoplasmosis** [1] or **primary CNS lymphoma** [1]. A **head CT with contrast** is essential to identify and characterize such lesions before considering invasive procedures like lumbar puncture, which could be dangerous if there is significant mass effect [4]. While a lumbar puncture might be relevant for some CNS infections, performing it without prior imaging in a patient with **focal neurological deficits** and potential **increased intracranial pressure** carries a risk of **herniation** [2]. Areas of low density in the white matter on CT [3] or space-occupying lesions with ring enhancement [1] are key findings required for diagnosis.

Q: The antistreptolysin O (ASO) titer is used in the diagnosis of:

Acute rheumatic fever. ***Acute rheumatic fever*** - The **ASO titer** measures antibodies against *Streptolysin O*, a toxin produced by **Group A Streptococcus** (*Streptococcus pyogenes*). - Elevated ASO titers indicate a recent streptococcal infection, which is the precursor to **acute rheumatic fever** [1]. *Osteoarthritis* - This condition is a **degenerative joint disease** primarily caused by wear and tear on cartilage. - It is not associated with microbial infections or immunological responses related to streptococcal antibodies. *Ankylosing spondylitis* - This is a **chronic inflammatory disease** primarily affecting the spine and sacroiliac joints. - It is strongly associated with the **HLA-B27 gene** and not with streptococcal infections. *Acute rheumatoid arthritis* - This is an **autoimmune disease** characterized by chronic inflammation of the synovium, leading to joint damage [2]. - It is typically associated with **rheumatoid factor (RF)** and **anti-citrullinated peptide antibodies (ACPA)**, not ASO titers.

Question 1

In patients of acquired immunodeficiency syndrome, the commonest cause of space occupying lesion in brain is -

Accepted Answer

Toxoplasmosis

Answer

Cryptoccosis

Answer

Non Hodgkin's lymphoma

Answer

Cytomegalovirus infection

Question 2

A 25-year-old patient presents with high-grade fever, headache, and myalgia for 5 days. Blood examination shows thrombocytopenia and elevated liver enzymes. Rapid diagnostic test for dengue is positive. What is the most appropriate immediate management for this patient?

Accepted Answer

Influenza

Answer

Tuberculosis

Answer

Malaria

Answer

Dengue fever

Answer

Typhoid fever

Question 3

A 30-year-old homosexual male presented with a one-week history of painful vesicular perianal lesions. There was an associated history of body aches, fever, and joint pains. He claimed that his partner had similar lesions on his penis about one month ago with associated dysuria, which has now resolved. Microscopy of the lesion revealed multinucleated syncytial cells with intranuclear inclusion bodies and a perinuclear halo. The most likely causative agent for these lesions is:

Accepted Answer

Herpes simplex virus

Answer

Epstein-barr virus

Answer

Human immunodeficiency virus

Answer

Cytomegalovirus

Question 4

Which of the following conditions is most commonly associated with cryoglobulinemia?

Accepted Answer

Hepatitis c

Answer

Ovarian cancer

Answer

Diabetes

Answer

Leukemia

Question 5

Anti-microbials are given with which type of diarrhea:

Accepted Answer

Traveller's diarrhea

Answer

Secretory diarrhea

Answer

Rotavirus

Answer

Osmotic diarrhea

Question 6

ASO (Antistreptolysin) test is used for the diagnosis of -

Accepted Answer

Rheumatic fever

Answer

Rickettsial fever

Answer

Rheumatoid arthritis

Answer

Typhoid fever

Question 7

Which of the following statements about Mollaret meningitis is true -

Accepted Answer

Is also referred to as 'Benign recurrent aseptic meningitis'

Answer

Caused by herpes simplex virus 2 in most cases

Answer

Requires immediate antibiotic treatment

Answer

Is a form of bacterial meningitis

Question 8

An acutely ill 18-year-old female is brought to the emergency department. The patient is febrile and markedly hypotensive, and her mental status is obtunded. Numerous petechial and purpuric hemorrhages are scattered over the trunk, and aspiration of a lesion reveals neutrophils engulfing gram-negative diplococci. Serum sodium is markedly decreased, and serum potassium is increased. Coagulation testing reveals increased prothrombin time, activated partial thromboplastin time, and fibrin-fibrinogen split products. Which of the following is most likely?

Accepted Answer

Waterhouse-Friderichsen syndrome

Answer

Conn syndrome

Answer

Neuroblastoma

Answer

Hyperprolactinoma

Question 9

A 35-year-old man has a headache, sleepiness, and poor balance that have worsened over the past week. The patient is known to be HIV-seropositive. On examination, his responses are slow and he has some difficulty in sustaining attention. He has right hemiparesis with increased reflexes on the right. Routine cell counts and chemistries are normal. What is the most appropriate next step?

Accepted Answer

Get a head CT with contrast

Answer

Perform a lumbar puncture

Answer

Start antiretroviral therapy

Answer

Start intravenous heparin

Question 10

The antistreptolysin O (ASO) titer is used in the diagnosis of:

Accepted Answer

Acute rheumatic fever

Answer

Osteoarthritis

Answer

Ankylosing spondylitis

Answer

Acute rheumatoid arthritis

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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