Infectious Diseases Practice Questions

Q: A 40-year-old with chronic hepatitis B develops fever, arthralgia, and palpable purpura. Most likely diagnosis?

Polyarteritis nodosa. ***Polyarteritis nodosa*** - The triad of **fever**, **arthralgia**, and **palpable purpura** in a patient with **chronic hepatitis B** is highly suggestive of polyarteritis nodosa [1]. - **Hepatitis B infection** is strongly associated with polyarteritis nodosa due to the formation of **immune complexes** that deposit in vessel walls, leading to inflammation and vasculitis [1]. *IgA vasculitis* - Typically presents with **palpable purpura**, arthralgia, and abdominal pain, often preceded by an **upper respiratory tract infection** [1]. - It is more common in **children** and is not typically linked to chronic hepatitis B infection [1]. *Wegener's granulomatosis* - Characterized by **granulomatous inflammation** of the upper and lower respiratory tracts, **glomerulonephritis**, and systemic vasculitis. - It is associated with **anti-neutrophil cytoplasmic antibodies (c-ANCA)**, which are not suggested by the clinical picture or hepatitis B status. *Cryoglobulinemia* - Often presents with **palpable purpura**, arthralgia, and neuropathy, and is strongly associated with **hepatitis C infection**. - While hepatitis B can rarely be a cause, hepatitis C is the dominant viral association with **mixed cryoglobulinemia**.

Q: A patient with advanced HIV presents with cryptococcal meningitis. Which CSF finding is most characteristic?

High opening pressure. ***High opening pressure*** - **Elevated intracranial pressure** is a hallmark of cryptococcal meningitis, often due to the **fungal burden** and associated inflammatory response, leading to impaired CSF outflow [1]. - This symptom is crucial for both diagnosis and management, as persistently high pressure can cause **neurological damage** and vision loss. *High protein* - While CSF protein can be mildly elevated in cryptococcal meningitis, it is **not the most characteristic finding** compared to the dramatic increase seen in bacterial meningitis [1]. - Protein levels typically increase with inflammation and breakdown of the **blood-brain barrier**, but less significantly than other findings in cryptococcal infection. *Low glucose* - **Low CSF glucose** (hypoglycorrhachia) is more typical of **bacterial meningitis** due to bacterial consumption of glucose. - In cryptococcal meningitis, glucose levels can be normal or mildly decreased, but **not as consistently low** as in bacterial infections. *Neutrophilic pleocytosis* - **Neutrophilic pleocytosis** (predominance of neutrophils) is a classic finding in **acute bacterial meningitis** [1]. - Cryptococcal meningitis typically presents with a **lymphocytic or mixed pleocytosis**, not neutrophilic, reflecting a more chronic or fungal inflammatory response.

Q: A patient develops sudden onset fever and confusion 2 days post-splenectomy. Most appropriate initial antibiotic?

Ceftriaxone. ***Ceftriaxone*** - Patients post-splenectomy are at high risk for **overwhelming post-splenectomy infection (OPSI)**, often caused by **encapsulated bacteria** like *Streptococcus pneumoniae* [2]. - **Ceftriaxone** provides broad coverage against common pathogens in OPSI, including both Gram-positive and Gram-negative bacteria, and can penetrate the CNS in cases of meningitis, which is crucial given the patient's confusion [1], [2]. *Azithromycin* - Primarily targets **atypical bacteria** (e.g., *Mycoplasma*, *Chlamydia*) and some Gram-positive organisms, but has limited efficacy against the most common encapsulated bacteria responsible for OPSI. - It is not a first-line antibiotic for severe, potentially life-threatening infections in asplenic patients. *Vancomycin* - Effective against **methicillin-resistant *Staphylococcus aureus* (MRSA)** and **multi-drug resistant *Streptococcus pneumoniae***, but does not cover Gram-negative organisms [2], [3]. - While important for resistant Gram-positives, it should typically be used in combination with another antibiotic (like a third-generation cephalosporin) in this critical setting, or reserved for cases where MRSA is suspected [3]. *Piperacillin-tazobactam* - Provides broad-spectrum coverage, including **Gram-positive, Gram-negative, and anaerobic bacteria**, making it suitable for many severe infections. - However, for suspected OPSI with a high risk of encapsulated bacteria like *Streptococcus pneumoniae* and potential meningitis, a third-generation cephalosporin like **ceftriaxone** is often preferred as initial monotherapy due to excellent penetration into the CSF and robust activity against these specific pathogens.

Q: A patient with dengue fever develops warning signs. Which finding indicates severe disease requiring ICU care?

Hematocrit rise >20%. ***Hematocrit rise >20%*** * A significant rise in **hematocrit** (typically >20% from baseline or age/sex-adjusted average) indicates substantial **plasma leakage**, which is a critical sign of severe dengue and impending **shock** [1]. * This necessitates urgent fluid management and often **ICU admission** to prevent further clinical deterioration [1]. *Mild ascites* * While ascites is a sign of **plasma leakage**, mild ascites alone, without rapid accumulation or associated signs of shock, is considered a **dengue warning sign**, but doesn't immediately classify it as severe dengue requiring ICU. * It suggests potential for progression but doesn't, by itself, equate to the severe plasma leakage indicated by a sharp hematocrit rise. *Persistent vomiting* * **Persistent vomiting** is a **dengue warning sign** indicating potential for dehydration and fluid imbalance, but it does not directly signify severe plasma leakage or organ impairment requiring ICU care. * Fluid replacement can often be managed orally or intravenously in a ward setting. *Platelet count <20,000* * A **platelet count <20,000** is considered a **severe dengue criterion** due to the increased risk of severe bleeding [1]. * While it indicates severe disease and requires close monitoring, a **sudden large increase in hematocrit** is a more immediate indicator of life-threatening **plasma leakage and hypovolemic shock**, which often takes precedence for rapid ICU intervention [1].

Q: Patient: fever, joint pain, rash. Recent history of mosquito bite. Most likely diagnosis in urban area?

Chikungunya. ***Chikungunya*** - **Chikungunya** is a viral disease transmitted by mosquitoes that commonly presents with **fever**, severe **joint pain** (polyarthralgia), and a **rash**, fitting the patient's symptoms. - Its high prevalence in **urban areas** and recent history of **mosquito bites** make it a strong diagnostic consideration. *Dengue* - While Dengue also causes **fever** [1] and a **rash**, it is more typically associated with **severe muscle and bone pain** ("breakbone fever"), and **hemorrhagic manifestations** or shock, which are not mentioned. - **Joint pain** in dengue is usually less debilitating than in chikungunya. *Japanese Encephalitis* - This is a serious **neurological infection** characterized by **fever**, **headache**, seizures, and altered mental status, rather than prominent joint pain and rash. - It primarily affects the **brain** and is less likely to present with this specific symptom triad. *Malaria* - Malaria is characterized by **cyclic fevers**, chills, sweating, and fatigue, but typically **does not present with a rash** [1] or significant joint pain. - It is caused by a **parasite** transmitted by *Anopheles* mosquitoes, and its clinical picture differs from the described symptoms.

Q: 30-year male with recurrent sinopulmonary infections has low serum IgA. Most likely diagnosis?

Selective IgA deficiency. ***Selective IgA deficiency*** - This condition is characterized by **recurrent sinopulmonary infections** and **low serum IgA levels** while other immunoglobulin levels are typically normal [1]. - Due to IgA's role in mucosal immunity, its deficiency predisposes to infections of the respiratory and gastrointestinal tracts [1]. *X-linked agammaglobulinemia* - This disorder is marked by a severe deficiency of **all immunoglobulin classes** (IgG, IgA, IgM) due to a defect in **B-cell maturation** [1]. - Patients typically present with severe recurrent bacterial infections in **early infancy**, which is earlier than the age of presentation in this case (30-year-old male) [1]. *Hyper IgM syndrome* - This condition is characterized by **normal or elevated IgM levels** but **low IgG, IgA, and IgE levels**, resulting from a defect in **class switching**. - It often involves recurrent infections, but the specific pattern of immunoglobulin levels differs significantly from the description. *Common variable immunodeficiency* - This is a heterogeneous disorder characterized by **low levels of IgG** (and often IgA and/or IgM) leading to recurrent infections [1]. - Unlike selective IgA deficiency, CVID involves a broader defect in humoral immunity, with significant reductions in **IgG** in addition to IgA [1].

Q: Patient with fever, photophobia, neck stiffness. CSF shows lymphocytic pleocytosis. Most likely virus?

Enterovirus. ***Enterovirus*** - **Enteroviruses** are the most common cause of **aseptic meningitis**, characterized by fever, photophobia, neck stiffness [2], and **lymphocytic pleocytosis** in the CSF. - They are transmitted via the **fecal-oral route** and are more prevalent in summer and fall [1]. *West Nile virus* - While West Nile virus can cause meningoencephalitis with lymphocytic pleocytosis, it is typically associated with **seasonal epidemics** and often presents with more severe neurological symptoms like **flaccid paralysis** or **encephalitis**. - Without specific exposure history or geographical context, it's a less common default answer for general aseptic meningitis. *HSV* - **Herpes simplex virus (HSV)** can cause meningitis or encephalitis, but HSV-1 often leads to severe focal encephalitis with specific neurological deficits [3] and may show **red blood cells** in the CSF. - HSV-2 is a common cause of recurrent aseptic meningitis (Mollaret's meningitis) but usually presents with **genital lesions**. *Mumps virus* - Prior to widespread vaccination, **mumps virus** was a significant cause of aseptic meningitis and orchitis. - However, in vaccinated populations, mumps meningitis is rare, and the presentation would typically include **parotitis** (swollen salivary glands), which is not mentioned here.

Q: HIV patient presents with chest X-ray showing bilateral reticulonodular infiltrates. CD4 count 80/µL. Most likely diagnosis?

Pneumocystis pneumonia. ***Pneumocystis pneumonia (PCP)*** - **Pneumocystis pneumonia** is a common opportunistic infection in HIV patients with a **CD4 count below 200 cells/L**, and a CD4 count of 80/L makes it highly likely [1]. - The classic chest X-ray finding for PCP is **bilateral interstitial or reticulonodular infiltrates**, which matches the patient's presentation [1]. *CMV infection* - While **cytomegalovirus (CMV) infection** can occur in advanced HIV disease, pulmonary involvement typically presents with **pneumonitis** or **pleural effusions** rather than exclusively reticulonodular infiltrates. - CMV pneumonitis often manifests with other organ involvement like **retinitis** or **colitis**, which are not mentioned here. *Cryptococcosis* - **Cryptococcus neoformans** primarily causes **meningitis** in HIV patients, though pulmonary cryptococcosis can occur. - Pulmonary involvement often presents as solitary or multiple **nodules** or **masses**, rather than diffuse reticulonodular infiltrates. *Tuberculosis* - **Tuberculosis (TB)** is common in HIV patients and can present with various radiographic patterns, including infiltrates, nodules, or cavitation [1]. - However, in advanced HIV (low CD4 count), **extrapulmonary TB** and atypical presentations are more common, and while pulmonary infiltrates occur, **PCP** is more classically associated with diffuse reticulonodular infiltrates in this specific CD4 range [1].

Q: Most common infection post solid organ transplantation

CMV. ***CMV*** - **Cytomegalovirus (CMV)** is the most common viral infection in solid organ transplant recipients, often reactivating in immunosuppressed patients [1]. - It can cause a wide range of clinical syndromes including **fever**, **leukopenia**, **hepatitis**, **pneumonitis**, and **gastroenteritis**, and is a significant cause of morbidity and mortality [1]. *EBV* - **Epstein-Barr virus (EBV)** is also common in transplant recipients but is most notably associated with **post-transplant lymphoproliferative disorder (PTLD)**, a serious complication [1]. - While present, it is not as frequently the cause of symptomatic infection as CMV in the immediate post-transplant period. *HSV* - **Herpes simplex virus (HSV)** infections can occur, manifesting as mucocutaneous lesions or, less commonly, severe systemic disease in transplant patients. - However, its incidence and severity are generally lower compared to CMV in the overall transplant population. *HPV* - **Human papillomavirus (HPV)** infections are typically associated with **warts** and increased risk of **malignancies** (e.g., anogenital cancers) in immunosuppressed individuals, including transplant recipients. - While important for long-term surveillance, HPV does not represent the most common acute infection post-transplant.

Q: A 60-year-old female with a history of diabetes presents with nasal congestion, facial pain, and black necrotic patches on the palate. What is the most likely diagnosis?

Mucormycosis. ***Mucormycosis*** - The presence of **black necrotic patches on the palate** in a diabetic patient with sinusitis symptoms is highly characteristic of mucormycosis. - **Diabetes** is a significant risk factor for this aggressive fungal infection, which often presents with tissue necrosis. *Bacterial sinusitis* - While facial pain and nasal congestion are consistent with bacterial sinusitis, **black necrotic patches** are not a typical feature. - Bacterial sinusitis rarely causes deep tissue invasion and necrosis of this extent. *Rhinoscleroma* - This is a chronic granulomatous disease of the upper respiratory tract caused by *Klebsiella rhinoscleromatis*, primarily seen in specific endemic regions. - It presents with **progressive inflammatory masses** and **scarring**, not acute necrosis or black patches. *Granulomatosis with Polyangiitis (GPA)* - GPA can cause sinusitis, **nasal crusting**, and **cartilage destruction**, but typically presents with **granulomatous inflammation** and vasculitis, not primary necrotic patches on the palate. - It is often associated with **ANCA positivity** and systemic symptoms affecting the lungs and kidneys.

Question 1

A 40-year-old with chronic hepatitis B develops fever, arthralgia, and palpable purpura. Most likely diagnosis?

Accepted Answer

Polyarteritis nodosa

Answer

IgA vasculitis

Answer

Wegener's granulomatosis

Answer

Cryoglobulinemia

Question 2

A patient with advanced HIV presents with cryptococcal meningitis. Which CSF finding is most characteristic?

Accepted Answer

High opening pressure

Answer

High protein

Answer

Low glucose

Answer

Neutrophilic pleocytosis

Question 3

A patient develops sudden onset fever and confusion 2 days post-splenectomy. Most appropriate initial antibiotic?

Accepted Answer

Ceftriaxone

Answer

Azithromycin

Answer

Vancomycin

Answer

Piperacillin-tazobactam

Question 4

A patient with dengue fever develops warning signs. Which finding indicates severe disease requiring ICU care?

Accepted Answer

Hematocrit rise >20%

Answer

Mild ascites

Answer

Persistent vomiting

Answer

Platelet count <20,000

Question 5

Patient: fever, joint pain, rash. Recent history of mosquito bite. Most likely diagnosis in urban area?

Accepted Answer

Chikungunya

Answer

Dengue

Answer

Japanese Encephalitis

Answer

Malaria

Question 6

30-year male with recurrent sinopulmonary infections has low serum IgA. Most likely diagnosis?

Accepted Answer

Selective IgA deficiency

Answer

X-linked agammaglobulinemia

Answer

Hyper IgM syndrome

Answer

Common variable immunodeficiency

Question 7

Patient with fever, photophobia, neck stiffness. CSF shows lymphocytic pleocytosis. Most likely virus?

Accepted Answer

Enterovirus

Answer

West Nile virus

Answer

HSV

Answer

Mumps virus

Question 8

HIV patient presents with chest X-ray showing bilateral reticulonodular infiltrates. CD4 count 80/µL. Most likely diagnosis?

Accepted Answer

Pneumocystis pneumonia

Answer

CMV infection

Answer

Cryptococcosis

Answer

Tuberculosis

Question 9

Most common infection post solid organ transplantation

Accepted Answer

CMV

Answer

EBV

Answer

HSV

Answer

HPV

Question 10

A 60-year-old female with a history of diabetes presents with nasal congestion, facial pain, and black necrotic patches on the palate. What is the most likely diagnosis?

Accepted Answer

Mucormycosis

Answer

Bacterial sinusitis

Answer

Rhinoscleroma

Answer

Granulomatosis with Polyangiitis (GPA)

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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