Infection in Immunocompromised Hosts — MCQs

10 questions

WHO AIDS defining illnesses are all EXCEPT:

Meningitis in immunocompromised host is frequently caused by

A patient, who is a known case of HIV with a CD4 count of 200 cells/cu.mm, presents with 5 days of cough and high-grade fever without chills and rigors. There is no history of diarrhoea, vomiting, or nuchal rigidity. Chest x-ray is normal. What treatment will you give?

Decreased T cell immunity is a feature of what?

In which of the following conditions is post-exposure prophylaxis recommended and effective?

Increased susceptibility to N. meningitidis infections is associated with deficiency of which complement component:

Serious infections can occur when the absolute neutrophil count decreases to what level?

Which is a minor criterion for diagnosis of RF according to modified Jones criteria?

A 44-year-old female presented to OPD with complaints of pallor, fatigue, weakness, palpitations and dyspnea on exeion. Blood tests were conducted, which revealed, Anemia Thrombocytopenia Leukocytosis with neutropenia and increased blasts in the peripheral blood smear. Peripheral blood smear The patient was diagnosed with leukemia and she underwent allogenic stem cell transplantation for the same. After 24 days, she again presented with hypotension, tachycardia, and spO2 of 88% along with a new rash from which biopsy was taken and silver staining was done. Lab findings revealed severe Neutropenia. Which is the most likely organism causing the above skin condition: -

Q10

Which of the following can be prevented by transfusing irradiated RBCs?

Infection in Immunocompromised Hosts Indian Medical PG Practice Questions and MCQs

Question 1: WHO AIDS defining illnesses are all EXCEPT:

A. Persistent generalized lymphadenopathy (Correct Answer)
B. P. carinii pneumonia
C. CMV retinitis
D. Oropharyngeal candidiasis

Explanation: ***Persistent generalized lymphadenopathy*** - While associated with HIV infection, **persistent generalized lymphadenopathy** itself is not classified as an **AIDS-defining illness** by the WHO or CDC, but rather a common manifestation of chronic HIV infection (Stage 1 or 2) [1]. - AIDS-defining illnesses are typically severe opportunistic infections or cancers that occur when the immune system is severely compromised (CD4 count below 200 cells/µL). *P. carinii pneumonia* - **P. carinii pneumonia** (now known as **Pneumocystis jirovecii pneumonia** or **PJP**) is a classic and common **AIDS-defining opportunistic infection**. - Its presence indicates severe immunosuppression, often with CD4 counts below 200 cells/µL. *CMV retinitis* - **Cytomegalovirus (CMV) retinitis** is a severe opportunistic infection, particularly of the eye, that is recognized as an **AIDS-defining illness**. - It signifies profound immunodeficiency, typically with CD4 counts below 50 cells/µL. *Oropharyngeal candidiasis* - While common in HIV-infected individuals, **oropharyngeal candidiasis** (thrush) alone is generally not considered an **AIDS-defining illness** [1]. - It is classified as an HIV Stage 2 condition, indicating moderate immune compromise rather than severe, AIDS-defining immunosuppression [1].

Question 2: Meningitis in immunocompromised host is frequently caused by

A. Cryptococcus neoformans (Correct Answer)
B. Trichophyton rubrum
C. Epidermophyton flocculosum
D. Candida tropicalis

Explanation: ***Cryptococcus neoformans*** - This encapsulated yeast is **the most common cause of fungal meningitis** in **immunocompromised individuals**, particularly those with **HIV/AIDS** (CD4 count <100 cells/μL). - Infection occurs through **inhalation of spores** from pigeon droppings and soil, causing primary **pulmonary infection** before disseminating to the **CNS**. - Diagnosis: **India ink staining** shows encapsulated yeasts; **CSF cryptococcal antigen** is highly sensitive. - Classic clinical features include **subacute headache, fever, and altered mental status**. *Trichophyton rubrum* - This is a common **dermatophyte** causing **superficial fungal infections** of skin, hair, and nails (e.g., **tinea pedis**, **onychomycosis**). - It remains **confined to keratinized tissues** and does not cause invasive or systemic infections like meningitis, even in immunocompromised patients. *Epidermophyton flocculosum* - Another **dermatophyte** causing superficial infections, particularly **tinea cruris** (jock itch) and **tinea pedis**. - Like *Trichophyton rubrum*, it **cannot invade beyond the epidermis** and is not associated with deep-seated infections or meningitis. *Candida tropicalis* - While *Candida* species can cause invasive infections in immunocompromised patients, **meningitis due to *Candida tropicalis*** is **relatively rare** compared to *Cryptococcus neoformans*. - *Candida* meningitis typically occurs in **neonates, post-neurosurgical patients**, or following **candidemia**, rather than as a primary CNS infection in AIDS patients.

Question 3: A patient, who is a known case of HIV with a CD4 count of 200 cells/cu.mm, presents with 5 days of cough and high-grade fever without chills and rigors. There is no history of diarrhoea, vomiting, or nuchal rigidity. Chest x-ray is normal. What treatment will you give?

A. Co-trimoxazole + steroids
B. Co-trimoxazole only (Correct Answer)
C. Amoxicillin-clavulanic acid + Azithromycin
D. Antitubercular treatment

Explanation: ***Co-trimoxazole only*** - The patient has a CD4 count of 200 cells/cu.mm with cough and fever and a normal chest X-ray, all of which are highly suggestive of **Pneumocystis jirovecii pneumonia (PJP)**, even without classic infiltrates. Therefore, **co-trimoxazole** (trimethoprim-sulfamethoxazole) is the first-line treatment [1]. - In a patient with HIV and a CD4 count below 200, **PJP prophylaxis** with co-trimoxazole should also be considered [2], and its empirical treatment is indicated in this scenario. *Co-trimoxazole + steroids* - While co-trimoxazole is the correct treatment for PJP, **steroids** are typically reserved for patients with more severe disease, indicated by **hypoxia** (PaO2 < 70 mmHg or A-a gradient > 35 mmHg) or diffuse interstitial infiltrates on chest imaging, neither of which are described here [1]. - Adding steroids without clear indications could increase the risk of side effects in an immunocompromised patient. *Amoxicillin-clavulanic acid + Azithromycin* - This combination targets typical **bacterial community-acquired pneumonia**, which is less likely given the patient's HIV status, low CD4 count, and normal chest X-ray. - This regimen would not effectively treat **PJP**, which is the most probable diagnosis in this immunocompromised setting. *Antitubercular treatment* - While tuberculosis is common in HIV patients, the normal chest X-ray makes pulmonary tuberculosis less likely, especially without other classic symptoms like night sweats, weight loss, or hemoptysis. In patients with CD4 counts below 200, the clinical presentation of TB differences substantially from those without HIV [1]. - **Antitubercular treatment** would not address the immediate concern of possible PJP, which can rapidly progress if untreated.

Question 4: Decreased T cell immunity is a feature of what?

A. Hyper IgM syndrome
B. Severe congenital neutropenia
C. Chronic granulomatous disease
D. DiGeorge syndrome (Correct Answer)

Explanation: ***Digeorge syndrome*** - Characterized by **thymic hypoplasia**, leading to a significant reduction in **T cell production** and function. - Patients commonly present with **recurrent infections** and associated features like **hypoparathyroidism** and cardiac defects. *Hyper IgM syndrome* - Causes **defective antibody class switching**, resulting in elevated **IgM** levels and low levels of other immunoglobulins, but **T cell counts can be normal** [1]. - The main defect is in **B cell activation**, not T cell immunity, hence not relevant to decreased T cell immunity [1]. *Severe congenital neutropenia* - Primarily presents with **recurrent bacterial infections** due to low levels of **neutrophils**, rather than T cell dysfunction. - This condition does not directly affect T cell immunity but rather focuses on the **myeloid lineage's impairment** in white blood cells. *Chronic granulomatous disease* - Involves defective **respiratory burst in phagocytes**, leading to issues in engulfing certain types of bacteria, primarily affecting **neutrophil function**. - T cell immunity remains largely intact, as this disorder does not primarily involve T cell deficiency or dysfunction.

Question 5: In which of the following conditions is post-exposure prophylaxis recommended and effective?

A. Measles
B. Hepatitis B
C. Pertussis
D. Rabies (Correct Answer)

Explanation: ***Rabies*** - **Post-exposure prophylaxis (PEP) for rabies is the gold standard example of highly effective prophylaxis**, with near **100% efficacy** when administered correctly. - Consists of **thorough wound washing**, **rabies immunoglobulin (RIG)**, and **rabies vaccine** given according to the recommended schedule. - **Universally recommended** for all animal bite exposures where rabies cannot be ruled out, as untreated rabies is **uniformly fatal**. - PEP must be initiated as soon as possible after exposure but remains effective even if started several days after the bite. *Hepatitis B* - Hepatitis B PEP is also **highly effective (70-95%)** and well-established, using **HBIG and vaccine series**. - Recommended for occupational exposures, sexual contacts, and perinatal transmission. - While very effective, rabies PEP is considered the paradigm example due to its near-perfect efficacy and the invariably fatal outcome without treatment. *Measles* - Post-exposure prophylaxis with **MMR vaccine within 72 hours** or **immunoglobulin within 6 days** can be **moderately effective**. - Time-sensitivity limits effectiveness, and vaccine may not prevent disease if given too late after exposure. - Not as universally effective as rabies PEP. *Pertussis* - **Chemoprophylaxis with azithromycin** is recommended for close contacts of pertussis cases. - However, effectiveness is **limited** - primarily reduces transmission rather than reliably preventing disease in exposed individuals. - Not considered as definitively effective as rabies or hepatitis B PEP.

Question 6: Increased susceptibility to N. meningitidis infections is associated with deficiency of which complement component:

A. C1-C4 deficiency
B. C3 deficiency
C. C5-C9 deficiency (Correct Answer)
D. C2 deficiency

Explanation: ***C5-C9 deficiency*** - Deficiencies in **C5-C9 components** impair the formation of the **Membrane Attack Complex (MAC)**, which is crucial for lysing Gram-negative bacteria like **N. meningitidis**. - Patients with MAC deficiencies are at significantly higher risk for recurrent invasive **N. meningitidis** infections. *C1-C4 deficiency* - Deficiencies in **C1-C4 components** primarily affect the **classical complement pathway** and are associated with increased susceptibility to **bacterial infections** and **immune complex diseases** (e.g., SLE). - While these deficiencies compromise opsonization and inflammation, they are not specifically linked to recurrent **N. meningitidis** infections. *C3 deficiency* - **C3 deficiency** is a severe primary immunodeficiency leading to profound defects in complement activation via all pathways, affecting **opsonization** and the formation of the MAC. - This deficiency causes severe recurrent **pyogenic infections** due to encapsulated bacteria but is not as specifically or commonly linked to **N. meningitidis** as deficiencies in the terminal pathway. *C2 deficiency* - **C2 deficiency** is the most common complement deficiency and primarily impacts the **classical pathway**, leading to impaired opsonization and immune complex clearance. - It is often associated with recurrent infections (especially with encapsulated bacteria) and **lupus-like syndromes**, but not specifically increased susceptibility to **N. meningitidis** infections.

Question 7: Serious infections can occur when the absolute neutrophil count decreases to what level?

A. Less than 500/mL (Correct Answer)
B. Less than 1000/mL
C. Less than 1500/mL
D. Less than 800/mL

Explanation: **Less than 500/mL** - An **absolute neutrophil count (ANC)** below **500 cells/mm³** (or 0.5 x 10⁹/L) is defined as **severe neutropenia**. - At this level, the body's primary defense against **bacterial and fungal infections** is severely compromised, leading to a significantly increased risk of **serious and life-threatening infections**. *Less than 1000/mL* - An ANC between **500 and 1000 cells/mm³** is considered **moderate neutropenia**. - While reflecting a reduced immune response, the risk of serious infection is **lower** than with severe neutropenia, though still elevated compared to normal. *Less than 1500/mL* - An ANC below **1500 cells/mm³** (or 1.5 x 10⁹/L) is often considered the general threshold for **neutropenia**. - This level indicates a decreased number of neutrophils, but it generally does not carry the immediate and severe risk of infection seen with counts below 500/mL. *Less than 800/mL* - An ANC below **800 cells/mm³** falls within the range of **moderate neutropenia**. - While this level indicates some degree of immune compromise, it is not the critical threshold that defines the highest risk for severe, life-threatening infections, which is typically 500/mL.

Question 8: Which is a minor criterion for diagnosis of RF according to modified Jones criteria?

A. Past History of Rheumatic Fever
B. Fever (Correct Answer)
C. Subcutaneous nodules
D. ASO titre

Explanation: ***

Question 9: A 44-year-old female presented to OPD with complaints of pallor, fatigue, weakness, palpitations and dyspnea on exeion. Blood tests were conducted, which revealed, Anemia Thrombocytopenia Leukocytosis with neutropenia and increased blasts in the peripheral blood smear. Peripheral blood smear The patient was diagnosed with leukemia and she underwent allogenic stem cell transplantation for the same. After 24 days, she again presented with hypotension, tachycardia, and spO2 of 88% along with a new rash from which biopsy was taken and silver staining was done. Lab findings revealed severe Neutropenia. Which is the most likely organism causing the above skin condition: -

A. Neisseria meningitidis
B. Pseudomonas (Correct Answer)
C. Staphylococcus aureus
D. Vibrio vulnificus

Explanation: ***Pseudomonas*** - The clinical presentation of **neutropenia**, fever, and a rapidly progressive skin rash after stem cell transplantation is highly suggestive of **ecthyma gangrenosum**, a severe cutaneous infection typically caused by *Pseudomonas aeruginosa*. - **Silver staining** in a biopsy would highlight bacteria, and *Pseudomonas* is a common cause of severe infections in immunocompromised patients, especially those with **neutropenia**. *Neisseria meningitidis* - While *Neisseria meningitidis* can cause rash (e.g., **petechial or purpuric rash** in meningitis), it is less likely to present as a focal, rapidly necrotic skin lesion like ecthyma gangrenosum, especially in the context of profound neutropenia post-transplant without overt signs of meningococcal disease. - The rash associated with meningococcemia is typically due to **vasculitis and thrombosis**, not direct bacterial colonization leading to necrotic lesions in the same way *Pseudomonas* does. *Staphylococcus aureus* - *Staphylococcus aureus* can cause various skin infections, including **cellulitis, abscesses, or impetigo**, but ecthyma gangrenosum is not its typical presentation. - While *S. aureus* is a significant pathogen in immunocompromised patients, the constellation of severe neutropenia and a rapidly progressive, necrotic skin lesion characteristic of ecthyma gangrenosum points more strongly to *Pseudomonas*. *Vibrio vulnificus* - *Vibrio vulnificus* causes severe skin infections, particularly in individuals with **liver disease** or those exposed to **contaminated seawater** or raw seafood. - This patient's history of leukemia and stem cell transplantation, without mention of relevant exposures, makes *Vibrio vulnificus* a less likely pathogen in this scenario.

Question 10: Which of the following can be prevented by transfusing irradiated RBCs?

A. Graft versus host disease (Correct Answer)
B. HLA Alloimmunization
C. Transfusion Related Acute Lung Injury (TRALI)
D. Immunomodulation

Explanation: Graft versus host disease - **Irradiation** of red blood cell (RBC) products inactivates proliferating donor **T-lymphocytes**, which are responsible for mediating transfusion-associated **graft-versus-host disease (TA-GVHD)**. - TA-GVHD is a severe and often fatal complication where donor immune cells attack recipient tissues. *HLA Alloimmunization* - **HLA alloimmunization** is prevented by **leukoreduction**, which removes donor leukocytes expressing HLA antigens, not by irradiation. - Irradiation targets the proliferative capacity of T-lymphocytes, but does not remove the cells themselves or prevent the presentation of HLA antigens. *Transfusion Related Acute Lung Injury (TRALI)* - **TRALI** is primarily associated with **donor antibodies** (anti-HLA or anti-HNA) in plasma that react with recipient neutrophils, leading to lung injury. - It is prevented by selecting plasma donors who have not been pregnant or by using male-only plasma, not by irradiating RBCs. *Immunomodulation* - **Transfusion-related immunomodulation (TRIM)** is a broad effect associated with multiple blood components, including cytokines and biological response modifiers in the transfused products. - While leukoreduction may reduce some aspects of TRIM, irradiation is not specifically used to prevent or reduce this phenomenon.

Want unlimited practice?

Get full access to all questions, explanations, and performance tracking.

Start For Free