Fever of Unknown Origin — MCQs
A man with chills, fever, and headache is thought to have "atypical" pneumonia. History reveals that he raises chickens, and that approximately 2 weeks ago he lost a large number of them to an undiagnosed disease. Which of the following is the most likely diagnosis of this man's condition?
A patient presents with fever and a rim-enhancing lesion with an air-fluid level on brain CT. What is the most likely diagnosis?
All of the following statements about Giant cell arteritis are true except?
Most common single cause of pyrexia of unknown origin
Which of the following statements regarding classical Dengue fever is FALSE?
Undulant fever is caused by -
Fever of unknown origin in a farmer who raises goats would most likely be caused by which of the following organisms?
A 65-year-old patient presents with severe headache, temporal artery tenderness, and decreased pulse. What is the most likely diagnosis?
How many blood samples should be drawn in cases of fever of unknown origin to optimize detection of intermittent bacteremia?
A 40-year-old man underwent kidney transplantation. Two months after transplantation, he developed fever and features suggestive of bilateral diffuse interstitial pneumonia. Which of the following is the most likely etiologic agent?
Fever of Unknown Origin Indian Medical PG Practice Questions and MCQs
Question 1: A man with chills, fever, and headache is thought to have "atypical" pneumonia. History reveals that he raises chickens, and that approximately 2 weeks ago he lost a large number of them to an undiagnosed disease. Which of the following is the most likely diagnosis of this man's condition?
- A. Leptospirosis
- B. Relapsing fever
- C. Anthrax
- D. Ornithosis (Correct Answer)
Explanation: ***Ornithosis*** - The patient's symptoms of **chills, fever, headache, and atypical pneumonia**, combined with a history of **raising chickens** that recently died from an undiagnosed disease, are highly suggestive of ornithosis (also known as **psittacosis** or **parrot fever**). [2], [3] - This zoonotic infection is caused by **Chlamydophila psittaci** and is transmitted to humans through inhalation of contaminated aerosols from infected birds (poultry, parrots, pigeons). [2] *Leptospirosis* - **Leptospirosis** is typically associated with exposure to **contaminated water or soil** with animal urine, not direct contact with sick poultry. - While it can cause fever and headache, it often presents with **jaundice, renal failure, and hemorrhagic manifestations**, which are not mentioned here. *Relapsing fever* - **Relapsing fever** is characterized by **recurrent episodes of fever** separated by afebrile periods, caused by **Borrelia** species transmitted by lice or ticks. - The clinical presentation does not align with the typical course or epidemiological link to sick chickens. *Anthrax* - **Inhalational anthrax** can cause severe respiratory symptoms and fever but is primarily associated with exposure to **Bacillus anthracis spores**, often from infected livestock (cattle, sheep) or bioweapon exposure. [1] - The rapid death of a large number of chickens and the patient's "atypical pneumonia" do not fit the typical presentation or common transmission routes of anthrax. [1]
Question 2: A patient presents with fever and a rim-enhancing lesion with an air-fluid level on brain CT. What is the most likely diagnosis?
- A. Glioblastoma
- B. Metastasis
- C. Tuberculoma
- D. Brain abscess (Correct Answer)
Explanation: ***Brain abscess*** - The presence of **fever** points towards an infectious etiology, and a **rim-enhancing lesion with an air-fluid level** on CT is highly characteristic of a brain abscess. The air-fluid level suggests gas-forming organisms or communication with an air-containing structure like a paranasal sinus. - An abscess is a collection of pus, and the "rim-enhancement" indicates the inflammatory capsule surrounding the infection, while the **air-fluid level** is virtually pathognomonic for an abscess containing gas. *Glioblastoma* - While glioblastoma can be a **rim-enhancing lesion**, it is a primary brain tumor and typically does not present with **fever** or an **air-fluid level**. - It often shows **irregular, thick enhancement** and typically causes significant surrounding edema, but the key differentiating factors here are the fever and air-fluid level. *Metastasis* - Brain metastases often present as **multiple, rim-enhancing lesions**, but they are tumors and do not typically cause **fever** (unless very large with extensive necrosis) or exhibit **air-fluid levels**. - The clinical context (e.g., history of cancer) would be important for metastasis, but the **air-fluid level** strongly differentiates this case. *Tuberculoma* - A tuberculoma is a **granulomatous lesion** that can also show **rim enhancement**, especially with central caseous necrosis. However, it typically does not present with an **air-fluid level**. - While fever can be present in tuberculosis, the **air-fluid level** is the most discriminating feature pointing away from tuberculoma and towards an abscess.
Question 3: All of the following statements about Giant cell arteritis are true except?
- A. Involves large to small sized arteries (Correct Answer)
- B. Granulomatous inflammation
- C. Segmental nature of the involvement
- D. Can involve the aorta and its major branches
Explanation: ***Involves large to small sized arteries*** - Giant cell arteritis (GCA) predominantly affects **medium to large-sized arteries**, most commonly the branches of the **carotid artery**, such as the temporal arteries [1]. - While it can affect various arteries, it does not typically involve **small-sized arteries**, such as arterioles, directly as a primary site of inflammation. *Granulomatous inflammation* - GCA is characterized histologically by **granulomatous inflammation** within the arterial wall, which includes multinucleated **giant cells** and lymphocytes [2]. - This specific inflammatory pattern is a hallmark feature used in the diagnosis of GCA upon biopsy [2]. *Segmental nature of the involvement* - The arterial inflammation in GCA is often **segmental**, meaning that affected arteries may have inflamed and non-inflamed sections alternating along their length [2]. - This segmental involvement often necessitates **longer biopsies** (e.g., 2-3 cm for temporal artery biopsy) to increase the diagnostic yield. *Can involve the aorta and its major branches* - GCA can indeed affect the **aorta** (aortitis) and its major branches, leading to complications like **aneurysms** or **dissections**. - Involvement of these larger vessels can manifest as symptoms such as **claudication** in the limbs or asymptomatic aneurysms detectable on imaging [1]. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Osteoarticular And Connective Tissue Disease, pp. 688-689. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of Infancy and Childhood, pp. 516-517.
Question 4: Most common single cause of pyrexia of unknown origin
- A. Salmonella paratyphi
- B. Brucella
- C. Mycobacterium tuberculosis (Correct Answer)
- D. Salmonella typhi
Explanation: ***Mycobacterium tuberculosis*** - **Tuberculosis** (TB) is a common cause of **Pyrexia of Unknown Origin (PUO)** [2], especially in endemic areas, often presenting with fever, weight loss, and night sweats [3], [4]. - The fever in TB can be **intermittent** and **debilitating**, making diagnosis challenging without specific investigations like cultures or biopsies [1]. *Salmonella paratyphi* - This bacterium causes **paratyphoid fever**, which can present with prolonged fever similar to typhoid, but it is less common globally as a single cause of PUO compared to TB. - While it can manifest as a persistent fever, other characteristic symptoms like rash or gastrointestinal issues might be present, making it less "unknown" in some contexts. *Brucella* - **Brucellosis** (Malta fever) is characterized by **undulating fever**, arthralgia, and fatigue, but infections are often linked to exposure to infected animals or unpasteurized dairy products, limiting its prevalence as the *most common single* PUO cause. - Diagnosis requires specific serological tests or cultures, but its geographical distribution and transmission routes make it less globally pervasive than TB. *Salmonella typhi* - **Typhoid fever**, caused by *Salmonella typhi*, is a significant cause of prolonged fever, but its typical presentation often includes specific symptoms like **relative bradycardia**, **rose spots**, and gastrointestinal symptoms, which might lead to an earlier diagnosis than a true PUO. - While it can cause prolonged, high fever, global incidence and the often-distinctive clinical picture prevent it from typically being labeled as the *most common single* cause of PUO.
Question 5: Which of the following statements regarding classical Dengue fever is FALSE?
- A. Positive tourniquet test (Correct Answer)
- B. Low case fatality rate
- C. Self limiting disease
- D. Transmitted by Aedes aegypti
Explanation: **CRITICAL ISSUE:** This question as currently written is problematic because **all four statements are TRUE** about classical dengue fever, making it impossible to identify a FALSE statement. ***Analysis of Each Statement:*** **Positive tourniquet test** (Currently marked as answer) - This is actually a **TRUE statement** about classical dengue fever - The tourniquet test is **positive in classical dengue fever** and is used as a diagnostic criterion by WHO - A positive tourniquet test indicates capillary fragility and is seen in both classical dengue and DHF - **This should NOT be the answer** to a FALSE question **Low case fatality rate** - TRUE statement: Classical dengue fever has a very low case fatality rate (<1%) with proper supportive care - Mortality is primarily associated with severe dengue/DHF/DSS **Self limiting disease** - TRUE statement: Classical dengue is typically self-limiting, resolving within 7-10 days with symptomatic treatment - Characterized by fever, headache, retro-orbital pain, myalgia, and rash **Transmitted by Aedes aegypti** - TRUE statement: **Aedes aegypti** is the primary vector for dengue transmission - Also transmitted by Aedes albopictus in some regions - Day-biting mosquitoes found in urban/semi-urban areas **RECOMMENDATION:** This question needs revision as it currently has no correct answer. All options are true statements about classical dengue fever.
Question 6: Undulant fever is caused by -
- A. Bartonella
- B. Bordetella
- C. Brucella melitensis (Correct Answer)
- D. Borrelia recurrentis
Explanation: ***Brucella melitensis*** - **Brucellosis** is characterized by an **undulant fever**, meaning the fever waxes and wanes over days or weeks, giving it a wave-like pattern. - *Brucella melitensis* is one of the most common species causing human brucellosis, typically acquired through contact with infected animals or contaminated animal products like unpasteurized milk. *Bordetella* - *Bordetella pertussis* causes **whooping cough**, a severe respiratory infection characterized by paroxysmal cough followed by an inspiratory "whoop." - While it causes fever, it does not typically present with the classic undulant fever pattern seen in brucellosis. *Bartonella* - *Bartonella* species can cause various diseases, such as **cat scratch disease** (*Bartonella henselae*), trench fever (*Bartonella quintana*), and Carrion's disease (*Bartonella bacilliformis*). - These infections can present with fever but do not specifically cause an "undulant fever" pattern. *Borrelia recurrentis* - *Borrelia recurrentis* is a spirochete that causes **louse-borne relapsing fever**, characterized by recurrent episodes of high fever separated by afebrile periods. - While it causes episodic fever, the pattern is one of distinct relapses rather than the continuous, undulating pattern of brucellosis.
Question 7: Fever of unknown origin in a farmer who raises goats would most likely be caused by which of the following organisms?
- A. T. pallidum
- B. Histoplasma capsulatum
- C. Clostridium novyi
- D. Brucella melitensis (Correct Answer)
Explanation: ***Brucella melitensis*** - **Brucellosis** is a zoonotic infection commonly acquired through contact with infected animals or consumption of unpasteurized dairy products. - ***Brucella melitensis* is specifically associated with goats and sheep**, making it the most likely organism in this clinical scenario. - It classically presents as **fever of unknown origin (FUO)** due to its varied and non-specific clinical manifestations, including undulating fever, malaise, myalgia, arthralgia, and hepatosplenomegaly. *T. pallidum* - *Treponema pallidum* is the causative agent of **syphilis**, a sexually transmitted infection. - While syphilis can cause fever, its primary modes of transmission (sexual contact, vertical transmission) and clinical manifestations (e.g., chancres, rash, mucous patches) are distinct from the scenario described. - Not associated with occupational goat exposure. *Histoplasma capsulatum* - *Histoplasma capsulatum* causes **histoplasmosis**, a fungal infection associated with exposure to **bird or bat droppings**, particularly in endemic areas (e.g., Ohio and Mississippi River valleys). - Although it can cause disseminated disease and fever, the epidemiological context (exposure to goats, not birds/bats) makes it unlikely in this scenario. *Clostridium novyi* - *Clostridium novyi* is an anaerobic bacterium known to cause **gas gangrene** (clostridial myonecrosis) and occasionally **black disease** in livestock. - It is not typically associated with human fever of unknown origin in the context of occupational animal contact described. - More relevant to wound infections or animal disease rather than systemic FUO in farmers.
Question 8: A 65-year-old patient presents with severe headache, temporal artery tenderness, and decreased pulse. What is the most likely diagnosis?
- A. Giant cell arteritis (Correct Answer)
- B. Wegener's granulomatosis
- C. Microscopic polyangiitis
- D. Takayasu arteritis
Explanation: ***Giant cell arteritis*** - This presentation with **severe headache**, **temporal artery tenderness**, and a **decreased pulse** in a 65-year-old patient is highly classic for giant cell arteritis (GCA). GCA characteristically affects **medium and large arteries**, often the **temporal artery**. - **Decreased pulse** can indicate involvement of other large vessels, such as the subclavian artery, which can occur in GCA. Urgent diagnosis and treatment are crucial due to the risk of **permanent vision loss** [1]. *Wegener's granulomatosis* - This condition (**granulomatosis with polyangiitis**) is characterized by **upper and lower respiratory tract granulomatous inflammation**, **glomerulonephritis**, and small vessel vasculitis. - While it can manifest with systemic symptoms, **temporal artery tenderness** and a **decreased pulse** are not primary features of Wegener's. *Microscopic polyangiitis* - This is a **small vessel vasculitis** that primarily affects capillaries, venules, and arterioles. - It typically presents with **glomerulonephritis** and **pulmonary capillaritis**, but without granuloma formation, and does not involve the temporal arteries or lead to a decreased pulse in the manner described. *Takayasu arteritis* - Takayasu arteritis primarily affects the **aorta and its major branches**, leading to **claudication**, **pulse deficits** in the extremities, and often occurs in **younger women**. - While it can cause a decreased pulse, it is less likely to present with **temporal artery tenderness** and severe headache in a 65-year-old, as these symptoms are more characteristic of GCA.
Question 9: How many blood samples should be drawn in cases of fever of unknown origin to optimize detection of intermittent bacteremia?
- A. 2
- B. 3 (Correct Answer)
- C. 1
- D. 4
Explanation: ***3*** - Drawing **three separate blood samples** significantly increases the likelihood of detecting intermittent bacteremia, as bacteria may not always be present in high concentrations in the bloodstream. - This practice maximizes the diagnostic yield while minimizing the risk of false positives from contamination. *1* - A single blood sample has a **low sensitivity** for detecting intermittent bacteremia, as transient presence of bacteria might be missed. - Relying on one sample increases the chance of a **false negative**, delaying appropriate treatment. *2* - While two samples are better than one, they still may not be sufficient to reliably detect **intermittent bacteremia** which can fluctuate. - This quantity might be acceptable for some conditions but is suboptimal for robust exclusion of **bacteremia in FUO** [1]. *4* - While four samples might slightly increase sensitivity over three, the **incremental benefit** in diagnostic yield is often negligible. - This approach adds to the **patient discomfort** and increases resource utilization without substantial additional diagnostic value.
Question 10: A 40-year-old man underwent kidney transplantation. Two months after transplantation, he developed fever and features suggestive of bilateral diffuse interstitial pneumonia. Which of the following is the most likely etiologic agent?
- A. Varicella zoster virus
- B. Cytomegalovirus (Correct Answer)
- C. Herpes simplex virus
- D. Epstein-barr virus
Explanation: ***Cytomegalovirus*** - **CMV infection** is very common and a frequent opportunistic infection in **immunosuppressed solid organ transplant recipients**, especially within the first few months post-transplant [1]. - **CMV pneumonitis**, characterized by diffuse interstitial pneumonia and fever, is a classic presentation of CMV disease in this patient population [1]. *Varicella zoster virus* - While VZV can cause serious infections in immunosuppressed individuals, **pneumonia due to VZV** is typically part of a disseminated disease and less common than CMV pneumonitis in transplant recipients. - **Cutaneous vesicular lesions** would usually precede or accompany VZV pneumonia, which are not mentioned here. *Herpes simplex virus* - HSV can cause severe mucocutaneous infections in immunocompromised patients, but **HSV pneumonia** is rare and usually manifests as tracheobronchitis or a focal necrotizing pneumonia, not typically diffuse interstitial. - **Esophagitis or encephalitis** are more common serious manifestations of HSV in this population than primary pneumonitis. *Epstein-barr virus* - EBV is primarily associated with **post-transplant lymphoproliferative disorder (PTLD)** in transplant recipients, which can involve the lungs. - While PTLD can manifest with fever and pulmonary infiltrates, **diffuse interstitial pneumonia** solely due to primary EBV infection is less characteristic than for CMV.
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