Opportunistic Infections — MCQs
Given the immunologic abnormalities of normal serum IgG, normal serum IgA, normal serum IgM, decreased T-cell function, and decreased parathyroid function, which clinical presentation is most likely?
A child presents with a fever and a rash. Urine examination showed cells with owl's eye appearance. What is the most likely diagnosis?
Which of the following conditions is least commonly associated with Pneumocystis carinii in AIDS?
After a renal transplant, what is the most common opportunistic infection?
A 10-year-old child had fever for 5 days, along with which he developed multiple fluid filled lesions on the lips as shown below. What is the probable underlying etiology for the skin lesions?
Prophylaxis with cotrimoxazole is recommended in all situations except for which of the following?
A known HIV patient on anti-retroviral therapy presented with diarrhea of six months duration. Stool microscopy showed 10-30 micrometer cysts, Kinyoun stain was positive. What is the most likely diagnosis?
An 18-month-old child presents with cellulitis of the leg and SpO2 of 88%. There is no prior history of hospitalization or illness. What is the most probable organism?
A patient presented with 70% burns, and a sample was collected from the burn site. The image shows Gram-negative rods, and the suspected organism is an obligate aerobe. What is the most likely causative microbe?
A child with a fever of 102°F and vesicles in the oral cavity is probably suffering from:
Opportunistic Infections Indian Medical PG Practice Questions and MCQs
Question 1: Given the immunologic abnormalities of normal serum IgG, normal serum IgA, normal serum IgM, decreased T-cell function, and decreased parathyroid function, which clinical presentation is most likely?
- A. A 1-year-old boy with severe eczema, recurrent middle-ear infections, lymphopenia, and thrombocytopenia
- B. A 9-year-old boy with an eczema-like rash and recurrent severe staphylococcal infections
- C. A 5-year-old boy who, after 3 months of age, developed recurrent otitis media, pneumonia, diarrhea, and sinusitis, often with simultaneous infections at two or more disparate sites
- D. A distinctive-appearing 8-month-old boy with an interrupted aortic arch, hypocalcemia, and cleft palate (Correct Answer)
Explanation: ***A distinctive-appearing 8-month-old boy with an interrupted aortic arch, hypocalcemia, and cleft palate*** - This presentation is highly suggestive of **DiGeorge syndrome**, characterized by **thymic hypoplasia** (leading to decreased T-cell function) and **parathyroid hypoplasia** (causing hypocalcemia). - **Cardiac defects** (like an interrupted aortic arch) and **facial anomalies** (including cleft palate) are also classic features of this disorder, which involves a deletion on chromosome 22q11.2. *A 1-year-old boy with severe eczema, recurrent middle-ear infections, lymphopenia, and thrombocytopenia* - This clinical picture describes **Wiskott-Aldrich syndrome**, an X-linked disorder characterized by the triad of eczema, thrombocytopenia (with small platelets), and immunodeficiency leading to recurrent infections. - While it involves immunodeficiency and lymphopenia, it does not typically present with decreased parathyroid function. *A 9-year-old boy with an eczema-like rash and recurrent severe staphylococcal infections* - This presentation is characteristic of **hyper-IgE syndrome** (Job's syndrome), an immunodeficiency characterized by extremely elevated IgE levels, recurrent staphylococcal skin infections, and eczema. - The immunologic abnormalities described in the stem (normal Ig levels, decreased T-cell function, decreased parathyroid function) do not match the key features of hyper-IgE syndrome. *A 5-year-old boy who, after 3 months of age, developed recurrent otitis media, pneumonia, diarrhea, and sinusitis, often with simultaneous infections at two or more disparate sites* - This description is consistent with **X-linked agammaglobulinemia (XLA)**, where B-cell maturation is blocked, leading to a profound deficiency of all immunoglobulin classes. - The stem mentions normal serum IgG, IgA, and IgM, which rules out XLA.
Question 2: A child presents with a fever and a rash. Urine examination showed cells with owl's eye appearance. What is the most likely diagnosis?
- A. Herpes simplex virus infection
- B. Toxoplasmosis caused by Toxoplasma gondii
- C. Cytomegalovirus (CMV) infection (Correct Answer)
- D. Infectious mononucleosis caused by Epstein-Barr virus
Explanation: ***Cytomegalovirus (CMV) infection*** - The presence of cells with an **owl's eye appearance** in urine sediment is a classic histological hallmark of **CMV infection**. - CMV can cause a variety of symptoms in children, including **fever and rash**, making this the most likely diagnosis. *Herpes simplex virus infection* - HSV causes characteristic **vesicular lesions** on mucocutaneous surfaces, often associated with fever. - While HSV can cause systemic illness, it does not typically present with **owl's eye inclusions** in urine cells. *Toxoplasmosis caused by Toxoplasma gondii* - **Toxoplasmosis** can cause fever and rash, especially in congenital infections or immunocompromised individuals. - However, it does not lead to **owl's eye inclusions** in urinary cells, which are pathognomonic for CMV. *Infectious mononucleosis caused by Epstein-Barr virus* - **Infectious mononucleosis** commonly presents with fever, fatigue, and lymphadenopathy, sometimes with a rash. - **Epstein-Barr virus (EBV)** infection does not produce cells with an **owl's eye appearance** in the urine; that is specific to CMV.
Question 3: Which of the following conditions is least commonly associated with Pneumocystis carinii in AIDS?
- A. Meningitis
- B. Otic polypoid mass (Correct Answer)
- C. Pneumonia
- D. Ophthalmic choroid lesion
Explanation: ***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.
Question 4: After a renal transplant, what is the most common opportunistic infection?
- A. Varicella Zoster Virus (VZV)
- B. Coxsackie Virus
- C. Epstein-Barr Virus (EBV)
- D. Cytomegalovirus (CMV) (Correct Answer)
Explanation: ***Cytomegalovirus (CMV)*** - **CMV** is the most common opportunistic infection after renal transplantation, particularly in the first 6 months due to immunosuppression [1]. - It can cause a range of clinical syndromes, including **fever**, **leukopenia**, **gastroenteritis**, **pneumonitis**, and **hepatitis**, and can also have indirect effects that increase the risk of graft rejection. *Varicella Zoster Virus (VZV)* - While VZV can cause opportunistic infections in transplant recipients (e.g., **shingles**), it is less common than CMV [1]. - VZV typically occurs later post-transplant and is characterized by a **vesicular rash** in a dermatomal distribution. *Coxsackie Virus* - **Coxsackie virus** infections are less frequently reported as significant opportunistic infections in renal transplant recipients compared to other viral pathogens. - They are generally associated with hand-foot-and-mouth disease, herpangina, or myocarditis, which are not the most common post-transplant complications. *Epstein-Barr Virus (EBV)* - **EBV** can cause post-transplant lymphoproliferative disorder (PTLD), which is a serious complication, but EBV infection itself is not the most common opportunistic infection overall [1]. - PTLD is more common in the first year after transplant and often presents with **lymphadenopathy**, **fever**, or **graft dysfunction**.
Question 5: A 10-year-old child had fever for 5 days, along with which he developed multiple fluid filled lesions on the lips as shown below. What is the probable underlying etiology for the skin lesions?
- A. Herpes simplex virus (Correct Answer)
- B. HIV
- C. Syphilis
- D. Cytomegalovirus
Explanation: **Herpes simplex virus** - The image shows **multiple small, fluid-filled vesicles** on the lips, consistent with **herpes labialis**, commonly caused by **Herpes Simplex Virus type 1 (HSV-1)**. - The presentation with **fever for 5 days** preceding or accompanying the lesions is typical, as fever can **trigger HSV reactivation** or be part of primary herpetic gingivostomatitis in children. *HIV* - HIV infection can lead to various oral manifestations, but **direct fever blisters (herpes labialis)** are not a primary feature of HIV itself; rather, recurrent HSV infections may be more severe or frequent in immunocompromised individuals. - The lesions in the image are classic for HSV and do not directly suggest the underlying etiology is HIV without other clinical findings. *Syphilis* - Oral lesions of syphilis, such as chancre (primary stage) or mucous patches (secondary stage), are typically **painless ulcers** or **whitish plaques**, not clusters of fluid-filled vesicles. - Syphilis is also less common in a 10-year-old child presenting solely with these oral lesions and fever. *Cytomegalovirus* - CMV can cause oral lesions, particularly in immunocompromised patients, but these are often **ulcerative** and not typically presenting as the vesicular "cold sore" appearance seen in the image. - CMV also causes a wider range of systemic symptoms and is less likely to present purely with fever and these specific lip lesions in an otherwise healthy child.
Question 6: Prophylaxis with cotrimoxazole is recommended in all situations except for which of the following?
- A. All symptomatic HIV infected children > 5 years of age irrespective of CD4 (Correct Answer)
- B. All HIV infected infants less than 1 year age irrespective of symptoms or CD4 counts
- C. All HIV exposed infants till HIV infection can be ruled out
- D. As secondary prophylaxis after initial treatment for Pneumocystis jirovecii pneumonia
Explanation: ***All symptomatic HIV infected children > 5 years of age irrespective of CD4*** - Cotrimoxazole prophylaxis is generally recommended for HIV-infected children with **CD4 counts below certain thresholds** or **specific clinical scenarios**, not just based on age and symptoms alone for those > 5 years. - The guidelines often focus on preventing **Pneumocystis jirovecii pneumonia (PJP)** and other opportunistic infections in pediatric HIV, with a nuanced approach to older children based on immune status. *All HIV exposed infants till HIV infection can be ruled out* - **Cotrimoxazole prophylaxis** is strongly recommended for **all HIV-exposed infants** from 4-6 weeks of age until HIV infection is definitively ruled out. - This prevents **P. jirovecii pneumonia**, which has a high mortality rate in this vulnerable population. *All HIV infected infants less than 1 year age irrespective of symptoms or CD4 counts* - **Cotrimoxazole prophylaxis** is indicated for **all HIV-infected infants younger than 1 year of age**, regardless of their clinical symptoms or CD4 counts. - This is due to their **immature immune system** and high risk of **opportunistic infections**, especially PJP. *As secondary prophylaxis after initial treatment for pneumocystis carini pneumonia* - **Cotrimoxazole** is the **standard drug** used for **secondary prophylaxis** following successful treatment of **Pneumocystis jirovecii pneumonia (PJP)**. - This prevents recurrence of PJP, which can be life-threatening in immunocompromised individuals.
Question 7: A known HIV patient on anti-retroviral therapy presented with diarrhea of six months duration. Stool microscopy showed 10-30 micrometer cysts, Kinyoun stain was positive. What is the most likely diagnosis?
- A. Balantidium coli
- B. Cryptosporidium
- C. Cystoisospora (Correct Answer)
- D. Strongyloides
Explanation: ***Cystoisospora*** - **Cystoisospora belli** is a common cause of chronic diarrhea in **HIV-infected patients** and presents with oocysts typically measuring **20-30 µm** (the described 10-30 micrometer range encompasses the typical size). - The **Kinyoun acid-fast stain** is characteristically positive for *Cystoisospora* oocysts, which is the key diagnostic feature supporting this diagnosis. - This organism is particularly important in **immunocompromised patients** on ART who present with chronic diarrhea. *Balantidium coli* - **Balantidium coli** is a large ciliate, and its cysts are significantly larger (typically **40-60 µm**) than those described in the patient's stool. - While it can cause diarrhea in immunocompromised individuals, it is **not acid-fast** and therefore would not be positive with the Kinyoun stain. *Cryptosporidium* - **Cryptosporidium** is another common cause of chronic diarrhea in HIV patients, and its oocysts are **acid-fast positive** with the Kinyoun stain. - However, **Cryptosporidium** oocysts are much smaller, typically **4-6 µm**, which is inconsistent with the 10-30 micrometer cysts observed in this case. *Strongyloides* - **Strongyloides stercoralis** is a nematode that can cause chronic diarrhea and hyperinfection in immunocompromised patients, but it primarily produces **larvae** (rhabditiform and filariform) in stool, not cysts. - Its diagnostic forms are **not acid-fast**, and its morphology in stool microscopy is distinctly different from the described cysts.
Question 8: An 18-month-old child presents with cellulitis of the leg and SpO2 of 88%. There is no prior history of hospitalization or illness. What is the most probable organism?
- A. MRSA
- B. Streptococcus pyogenes
- C. Streptococcus pneumoniae (Correct Answer)
- D. All of the options
Explanation: ***Streptococcus pneumoniae*** - **Streptococcus pneumoniae** is the most probable organism given the clinical presentation of cellulitis with **hypoxia (SpO2 88%)** in a previously healthy 18-month-old child. - The key finding is the **low oxygen saturation**, which suggests **concurrent pneumonia or bacteremia** with respiratory involvement, not just isolated skin infection. - **Pneumococcal bacteremia** in young children commonly presents with distant site infections (including cellulitis) along with primary respiratory manifestations—explaining both the leg cellulitis and the desaturation. - This age group (18 months) is particularly susceptible to invasive pneumococcal disease, especially if not fully vaccinated or if vaccine coverage is incomplete. *Streptococcus pyogenes* - **Streptococcus pyogenes** (Group A Streptococcus) is indeed a common cause of **cellulitis** in children and can cause rapid local spread. - However, it typically does NOT cause significant **hypoxia** unless there is extensive tissue destruction (necrotizing fasciitis) or toxic shock syndrome, which would present with additional features like severe toxicity, shock, or multi-organ involvement. - The isolated finding of SpO2 88% with cellulitis is more consistent with a pathogen that commonly affects both skin and respiratory system simultaneously. *MRSA* - **MRSA (Methicillin-resistant Staphylococcus aureus)** is a significant cause of skin and soft tissue infections, particularly abscesses and furuncles. - While MRSA can cause severe cellulitis, the **hypoxia** would be unusual unless there is concurrent necrotizing pneumonia or sepsis with ARDS, which is less common in an otherwise healthy child with no prior hospitalization. - The absence of prior healthcare exposure makes community-acquired MRSA possible, but it doesn't explain the respiratory compromise as well as pneumococcus does. *All of the options* - While multiple organisms can cause pediatric cellulitis, the **specific clinical picture** with significant hypoxia points most strongly to **Streptococcus pneumoniae**. - The combination of cellulitis + respiratory compromise is characteristic of pneumococcal bacteremia in this age group, making it the MOST probable single organism.
Question 9: A patient presented with 70% burns, and a sample was collected from the burn site. The image shows Gram-negative rods, and the suspected organism is an obligate aerobe. What is the most likely causative microbe?
- A. Neisseria meningitidis (Meningococcus)
- B. Streptococcus pneumoniae (Pneumococcus)
- C. Pseudomonas aeruginosa (Correct Answer)
- D. Streptococcus pyogenes
Explanation: ***Pseudomonas aeruginosa*** - The image shows **Gram-negative rods**, and the patient has extensive **burns**, making *Pseudomonas aeruginosa* a highly likely causative agent due to its common association with burn wound infections. - *Pseudomonas aeruginosa* is an **obligate aerobe** and thrives in moist environments, making it a frequent colonizer of burn wounds, which are large, often moist surfaces. *Neisseria meningitidis (Meningococcus)* - *Neisseria meningitidis* is a **Gram-negative coccus**, typically appearing as diplococci, not rods, on Gram stain. - While it can cause severe infections, it is primarily associated with **meningitis** and **sepsis**, not typically burn wound infections. *Streptococcus pneumoniae (Pneumococcus)* - *Streptococcus pneumoniae* is a **Gram-positive coccus**, appearing as lancet-shaped diplococci or short chains, which contradicts the Gram-negative rod morphology seen in the image. - It is a common cause of **pneumonia** and **otitis media**, not primarily associated with burn wound infections. *Streptococcus pyogenes* - *Streptococcus pyogenes* is a **Gram-positive coccus** that grows in chains, which is inconsistent with the Gram-negative rod morphology. - Although it can cause skin infections like cellulitis and impetigo, it is not a typical cause of **burn wound infections** in the way *Pseudomonas aeruginosa* is.
Question 10: A child with a fever of 102°F and vesicles in the oral cavity is probably suffering from:
- A. Herpes simplex type-I
- B. Neutropenia
- C. Juvenile periodontitis
- D. Acute herpetic gingivostomatitis (Correct Answer)
Explanation: ***Acute herpetic gingivostomatitis*** - This condition is caused by **Herpes simplex virus (HSV-1)** and typically presents in young children with a **high fever**, malaise, and characteristic **vesicular lesions** in the oral cavity that quickly rupture to form painful ulcers. - The combination of **fever** and widespread **oral vesicles** strongly indicates acute herpetic gingivostomatitis. *Herpes simplex type-I* - While HSV-1 is the **etiologic agent** for acute herpetic gingivostomatitis, simply stating "Herpes simplex type-I" as the diagnosis is less specific than the clinical presentation. - HSV-1 can cause various oral conditions, but the described symptoms are best captured by the more specific diagnosis of **acute herpetic gingivostomatitis**. *Neutropenia* - **Neutropenia** is a reduction in neutrophils, which can lead to increased susceptibility to infections and oral ulcers, but it does not directly cause the characteristic **vesicular lesions** described. - The primary presentation would be recurrent severe infections, not necessarily acute fever with widespread oral vesicles. *Juvenile periodontitis* - **Juvenile periodontitis** (now often termed aggressive periodontitis) is a localized form of periodontal disease characterized by rapid **attachment loss** and **bone destruction** around permanent teeth in otherwise healthy adolescents. - It does not present with acute fever and vesicular lesions in the oral cavity.
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