A 35-year-old patient with no significant past medical history arrives to the ED with abdominal cramps, nausea, and vomiting. He has had no recent travel or chemical exposures; however, three other members of his family also arrived concurrently to the ED with abdominal cramps, nausea, and vomiting. When asked about their recent activities, they recall that they had shared a lunch of leftover fried rice and soft boiled eggs about 5 hours earlier. The patients are otherwise afebrile and deny any history of diarrhea. Which of the following toxins is the most likely to have caused these symptoms?
Q202
A 4-year-old male is brought by his mother to the emergency room with dyspnea and fever. His mother reports a two-day history of progressive shortness of breath, malaise, and a fever with a maximum temperature of 101.6°F (38.7°C). The child has visited the emergency room three times over the past two years for pneumonia and otitis media. His family history is notable for sarcoidosis in his mother, diabetes in his father, and an early childhood death in his maternal uncle. His temperature is 101.2°F (38.4°C), blood pressure is 110/90 mmHg, pulse is 110/min, and respirations are 24/min. Physical examination reveals scant lymphoid tissue. A serological analysis reveals decreased levels of IgA, IgG, and IgM. This patient most likely has a defect in a protein that is active in which of the following cellular stages?
Q203
An 8-month-old boy is brought to his pediatrician by his parents with a 12-hour history of fever and coughing. He has also been experiencing intermittent diarrhea and skin abscesses since birth. Otherwise, he has been meeting developmental milestones as expected. Analysis of this patient's sputum reveals acute angle branching fungi, and culture shows gram-positive cocci in clusters. A flow cytometry reduction test was obtained that confirmed the diagnosis. Which of the following processes is most likely defective in this patient?
Q204
A 32 year-old African American man with a past medical history of sickle cell anemia presents to his primary care physician for a routine check-up. He has no complaints. His physician notes that he likely has an increased susceptibility to infections with certain organisms. Which of the following patient groups has a similar pattern of increased susceptibility?
Q205
A 7-year-old boy presents with difficult left eye-opening in the morning, eye discharge, and irritation. These symptoms developed gradually over the past week. He attends a primary school where recently an outbreak of tonsillitis took place. He had otitis media 2 weeks ago treated with ampicillin. At the presentation, the patient’s vital signs are within normal limits. Eye examination reveals bulbar conjunctival injection, mild eyelid edema, and a moderate mucopurulent discharge with crusts on the lower eyelid. There is no corneal or eyelid ulceration. No lymphadenopathy is noted. Which of the following investigations should be performed to establish a diagnosis before the treatment?
Q206
A family doctor in a rural area is treating a patient for dyspepsia. The patient had chronic heartburn and abdominal pain for the last 2 months and peptic ulcer disease due to a suspected H. pylori infection. For reasons relating to affordability and accessibility, the doctor decides to perform a diagnostic test in the office that is less invasive and more convenient. Which of the following is the most likely test used?
Q207
To protect against a potentially deadly infection, a 19-year-old female receives a vaccine containing capsular polysaccharide. This vaccine will stimulate her immune system to produce antibodies against which organism?
Q208
A 42-year-old woman presents to a medical office with complaints of fatigue, weight loss, and low-grade fever for 1 week. She noticed bleeding spots on her feet this morning. The past medical history is significant for a recent dental appointment. She is a non-smoker and does not drink alcohol. She does not currently take any medications. On examination, the vital signs include temperature 37.8°C (100.0°F), blood pressure 138/90 mm Hg, respirations 21/min, and pulse 87/min. Cardiac auscultation reveals a pansystolic murmur in the mitral area with radiation to the left axilla. Laboratory studies show hemoglobin levels of 17.2 g/dL, erythrocyte sedimentation rate (ESR) of 25 mm/h, and a white blood cell (WBC) count of 12,000 cells/mm3. An echocardiogram reveals valvular vegetations on the mitral valve with mild regurgitation. Blood samples are sent for bacterial culture. Empiric antibiotic therapy is initiated with ceftriaxone and vancomycin. The blood cultures most likely will yield the growth of which of the following organisms?
Q209
A 68-year-old man presents to the physician with fever, cough, weakness, night sweats, and poor appetite for the past 6 months. Medical records suggest that he has lost 7.5 kg (16.5 lb) of weight during this period. There is no history of breathlessness, nasal discharge, nasal obstruction, palpitations, chest pain, or symptoms related to digestion. He was released from prison 9 months ago after serving a 2-year sentence. His temperature is 38.1°C (100.6°F), pulse is 84/min, respirations are 16/min, and blood pressure is 122/80 mm Hg. Physical examination shows hepatomegaly and generalized lymphadenopathy, and auscultation of the chest reveals diffuse crackles throughout the lung fields bilaterally. On direct ophthalmoscopy, three discrete, yellow-colored, 0.5 mm to 1.0 mm lesions with indistinct borders are seen in the posterior pole. A chest X-ray is shown in the image. Tuberculin skin test with purified protein derivative is negative. What is the most likely diagnosis?
Q210
A 47-year-old alcoholic man presents to the office for a 72-hour history of intense right hemithorax pain. He also complains of fever, chills, and sweating that started 10 days ago, as well as persistent coughing with abundant malodorous sputum. Chest radiography shows a round consolidation with air-fluid levels in the middle third of the right hemithorax. Sputum samples for a direct exam, culture, and acid-fast bacilli (AFB) are sent. What is the correct diagnosis?
Bacteria US Medical PG Practice Questions and MCQs
Question 201: A 35-year-old patient with no significant past medical history arrives to the ED with abdominal cramps, nausea, and vomiting. He has had no recent travel or chemical exposures; however, three other members of his family also arrived concurrently to the ED with abdominal cramps, nausea, and vomiting. When asked about their recent activities, they recall that they had shared a lunch of leftover fried rice and soft boiled eggs about 5 hours earlier. The patients are otherwise afebrile and deny any history of diarrhea. Which of the following toxins is the most likely to have caused these symptoms?
A. Shiga toxin
B. Cereulide (Correct Answer)
C. Endotoxin
D. Exotoxin A
E. Toxin B
Explanation: ***Cereulide***
- The rapid onset (within 5 hours) of gastrointestinal symptoms (nausea, vomiting, abdominal cramps) after consuming **fried rice** and **boiled eggs** is characteristic of intoxication by **cereulide**.
- This preformed toxin is produced by *Bacillus cereus* in improperly stored starchy foods like rice, leading to emetic-type food poisoning.
*Shiga toxin*
- **Shiga toxin** is produced by *Shigella dysenteriae* and Shiga toxin-producing *E. coli* (STEC), typically causing **bloody diarrhea** and **hemolytic uremic syndrome (HUS)**, which are not present here.
- The incubation period for Shiga toxin-mediated illness is usually longer, ranging from 1 to 8 days, making a rapid onset of symptoms unlikely.
*Endotoxin*
- **Endotoxin** (lipopolysaccharide or LPS) is a component of the outer membrane of **Gram-negative bacteria** and causes systemic symptoms like fever, shock, and organ dysfunction when released during bacterial lysis.
- While it can cause some gastrointestinal effects, the rapid onset of isolated emetic symptoms in a food poisoning cluster is not typical for endotoxin as the primary cause.
*Exotoxin A*
- **Exotoxin A** is a virulence factor produced by *Pseudomonas aeruginosa* and is associated with severe infections in immunocompromised patients, not typically foodborne illness.
- Its mechanism of action involves inhibiting protein synthesis, leading to tissue damage in specific infections, not acute emetic food poisoning.
*Toxin B*
- **Toxin B** is produced by *Clostridioides difficile* and is a major cause of **antibiotic-associated colitis** and **pseudomembranous colitis**, characterized by diarrhea and abdominal pain.
- The patient's presentation of acute onset nausea, vomiting, and abdominal cramps without diarrhea and no history of antibiotic use does not align with *C. difficile* infection.
Question 202: A 4-year-old male is brought by his mother to the emergency room with dyspnea and fever. His mother reports a two-day history of progressive shortness of breath, malaise, and a fever with a maximum temperature of 101.6°F (38.7°C). The child has visited the emergency room three times over the past two years for pneumonia and otitis media. His family history is notable for sarcoidosis in his mother, diabetes in his father, and an early childhood death in his maternal uncle. His temperature is 101.2°F (38.4°C), blood pressure is 110/90 mmHg, pulse is 110/min, and respirations are 24/min. Physical examination reveals scant lymphoid tissue. A serological analysis reveals decreased levels of IgA, IgG, and IgM. This patient most likely has a defect in a protein that is active in which of the following cellular stages?
A. Mature B-cell
B. Pro-B-cell
C. Immature B-cell
D. Pre-B-cell (Correct Answer)
E. Plasma cell
Explanation: ***Pre-B-cell***
- The patient's history of recurrent infections (pneumonia, otitis media), scant lymphoid tissue, and pan-hypogammaglobulinemia (decreased IgA, IgG, IgM) are classic findings of **X-linked agammaglobulinemia (XLA)**.
- XLA is caused by a defect in **Bruton's tyrosine kinase (BTK)**, which is crucial for B-cell maturation at the **pre-B-cell stage**, preventing them from developing into mature B lymphocytes and subsequently plasma cells.
*Mature B-cell*
- A defect at the mature B-cell stage would likely present with different patterns of immunoglobulin deficiencies, possibly affecting specific Ig classes or leading to lymphoproliferative disorders.
- In XLA, the arrest occurs earlier, preventing the formation of mature B cells altogether, hence the profound lack of all immunoglobulin classes.
*Pro-B-cell*
- Defects at the **pro-B-cell stage** would lead to an even more severe block in B-cell development, potentially preventing the formation of pre-B cells.
- While significant, the specific clinical picture and known genetic defects point more distinctly to an issue at or just before the pre-B cell stage.
*Immature B-cell*
- A block at the immature B-cell stage would allow for the presence of pre-B cells, but issues in developing tolerance or further maturation.
- The defining feature of XLA is the absence of mature B cells and immunoglobulins, which results from the failure of pre-B cells to develop into immature B cells.
*Plasma cell*
- Plasma cells are the final differentiated form of B cells responsible for antibody production.
- A defect solely at the plasma cell stage would imply normal B-cell development up to that point, which is inconsistent with the absence of all immunoglobulin classes and scant lymphoid tissue seen in XLA.
Question 203: An 8-month-old boy is brought to his pediatrician by his parents with a 12-hour history of fever and coughing. He has also been experiencing intermittent diarrhea and skin abscesses since birth. Otherwise, he has been meeting developmental milestones as expected. Analysis of this patient's sputum reveals acute angle branching fungi, and culture shows gram-positive cocci in clusters. A flow cytometry reduction test was obtained that confirmed the diagnosis. Which of the following processes is most likely defective in this patient?
A. Actin polymerization
B. Transforming oxygen into superoxide radicals (Correct Answer)
C. Transforming superoxide radicals into hydrogen peroxide
D. Leukocyte migration
E. Maturation of B-cells
Explanation: ***Transforming oxygen into superoxide radicals***
- The patient's history of **recurrent fungal and bacterial infections**, specifically with **Staphylococcus aureus** (gram-positive cocci in clusters leading to abscesses) and **Aspergillus** (acute angle branching fungi), is highly suggestive of **Chronic Granulomatous Disease (CGD)**.
- CGD is characterized by a defect in **NADPH oxidase**, which is responsible for converting **oxygen into superoxide radicals** during the **respiratory burst** in phagocytes, a critical step for killing ingested microbes. The flow cytometry reduction test (e.g., DHR test) confirms this diagnosis by showing reduced or absent superoxide production.
*Actin polymerization*
- Defects in actin polymerization are associated with disorders affecting **cytoskeletal function**, such as **Wiskott-Aldrich syndrome**, which presents with **thrombocytopenia**, **eczema**, and **recurrent infections**.
- While infections are part of the presentation, the specific pattern of **abscesses** and **fungal infections** with a positive flow cytometry reduction test for phagocyte function points away from a primary defect in actin dynamics.
*Transforming superoxide radicals into hydrogen peroxide*
- This process is catalyzed by **superoxide dismutase (SOD)**, which converts superoxide radicals into hydrogen peroxide and oxygen.
- In CGD, the primary defect is the **failure to generate superoxide radicals in the first place** due to NADPH oxidase deficiency, not a problem with their subsequent conversion. The flow cytometry reduction test specifically demonstrates the inability to produce superoxide, confirming this upstream defect.
*Leukocyte migration*
- **Leukocyte adhesion deficiencies (LADs)** involve impaired leukocyte migration due to defects in adhesion molecules like **integrins**.
- This would present with **delayed umbilical cord separation**, **recurrent bacterial infections without pus formation**, and **leukocytosis**, which are not the primary features described here.
*Maturation of B-cells*
- Defects in B-cell maturation lead to various forms of **primary immunodeficiency** characterized by **antibody deficiencies**, such as **X-linked agammaglobulinemia**.
- These conditions typically present with **recurrent bacterial infections** (especially encapsulated bacteria) but generally do not involve the characteristic **granulomatous inflammation** or vulnerability to specific opportunistic pathogens seen in CGD.
Question 204: A 32 year-old African American man with a past medical history of sickle cell anemia presents to his primary care physician for a routine check-up. He has no complaints. His physician notes that he likely has an increased susceptibility to infections with certain organisms. Which of the following patient groups has a similar pattern of increased susceptibility?
A. Hemophilia B
B. C5-9 complement deficiency
C. T-cell deficiency
D. Hemophilia A
E. C3 complement deficiency (Correct Answer)
Explanation: ***C3 complement deficiency***
- Patients with **sickle cell anemia** often experience **autosplenectomy** due to recurrent vaso-occlusive crises, leading to functional asplenia and impaired complement-mediated opsonization and clearance of encapsulated bacteria. A **C3 complement deficiency** directly impairs the entire complement cascade (both classical and alternative pathways), resulting in a similar defect in **opsonization** and clearance, particularly for **encapsulated bacteria**.
- Both conditions lead to an increased susceptibility to infections with encapsulated bacteria such as *Streptococcus pneumoniae*, *Haemophilus influenzae type b*, and *Neisseria meningitidis* due to the impaired ability to clear these pathogens from the bloodstream.
*Hemophilia B*
- This is an **X-linked recessive bleeding disorder** caused by a deficiency in coagulation factor IX.
- It results in **impaired clotting** and an increased risk of bleeding, not an increased susceptibility to specific infections.
*C5-9 complement deficiency*
- A deficiency in **C5-9 complement components** specifically impairs the formation of the **membrane attack complex (MAC)**.
- This primarily leads to an increased susceptibility to infections with **Neisseria species** (e.g., *N. meningitidis*, *N. gonorrhoeae*), as MAC is crucial for lysing these gram-negative bacteria. While C3 deficiency also increases susceptibility to *Neisseria*, C5-9 deficiency is more specifically and severely linked to this pathogen.
*T-cell deficiency*
- **T-cell deficiencies** (e.g., DiGeorge syndrome, HIV/AIDS) lead to impaired **cell-mediated immunity**.
- This results in increased susceptibility to **intracellular pathogens**, **viruses**, **fungi**, and **opportunistic infections** (e.g., *Pneumocystis jirovecii*, *Candida*, CMV), which is distinct from the encapsulated bacterial infections seen in sickle cell anemia.
*Hemophilia A*
- This is an **X-linked recessive bleeding disorder** caused by a deficiency in coagulation factor VIII.
- Similar to Hemophilia B, it primarily causes **bleeding abnormalities** due to dysfunctional secondary hemostasis, not a heightened susceptibility to infections.
Question 205: A 7-year-old boy presents with difficult left eye-opening in the morning, eye discharge, and irritation. These symptoms developed gradually over the past week. He attends a primary school where recently an outbreak of tonsillitis took place. He had otitis media 2 weeks ago treated with ampicillin. At the presentation, the patient’s vital signs are within normal limits. Eye examination reveals bulbar conjunctival injection, mild eyelid edema, and a moderate mucopurulent discharge with crusts on the lower eyelid. There is no corneal or eyelid ulceration. No lymphadenopathy is noted. Which of the following investigations should be performed to establish a diagnosis before the treatment?
A. Scrapings with Gram staining
B. Rapid viral test
C. Polymerase chain reaction
D. Bacterial culture of the discharge
E. No investigations are required in this case (Correct Answer)
Explanation: ***No investigations are required in this case***
- This presentation is highly suggestive of **bacterial conjunctivitis**, characterized by **mucopurulent discharge**, **eyelid edema**, and **crusting**, especially in a child. The history of a recent tonsillitis outbreak and otitis media, while not directly causative for the conjunctivitis, indicates an environment where bacterial infections are circulating.
- In cases of typical acute bacterial conjunctivitis, especially in children, treatment (usually topical antibiotics) is often initiated empirically without prior microbiologic investigation, as the diagnosis is clear clinically and waiting for results can delay appropriate care.
*Scrapings with Gram staining*
- While Gram staining can identify bacteria, it is generally **not necessary for routine acute bacterial conjunctivitis** given the typical clinical picture. Empirical treatment is usually sufficient.
- It might be considered in cases of **severe, recurrent, or atypical conjunctivitis**, or if initial treatment fails, to guide antibiotic selection.
*Rapid viral test*
- The symptoms, particularly the **mucopurulent discharge** and **crusting**, are more indicative of a bacterial rather than a viral infection. Viral conjunctivitis typically presents with a watery discharge.
- A rapid viral test would likely be **negative** and is not indicated given the clinical presentation predominantly suggesting bacterial etiology.
*Polymerase chain reaction*
- PCR is a highly sensitive test for identifying pathogens but is **overkill for a straightforward case of bacterial conjunctivitis**. It's generally reserved for specific, hard-to-diagnose infections or research.
- Its use would **delay treatment** and is not cost-effective for a condition that can be managed empirically.
*Bacterial culture of the discharge*
- Bacterial culture, like Gram staining, is typically **not required for initial management** of acute bacterial conjunctivitis, as the condition often resolves with empirical antibiotic treatment.
- It is usually reserved for cases that are **severe, chronic, non-responsive to initial therapy, or recurrent**, to determine antibiotic sensitivity.
Question 206: A family doctor in a rural area is treating a patient for dyspepsia. The patient had chronic heartburn and abdominal pain for the last 2 months and peptic ulcer disease due to a suspected H. pylori infection. For reasons relating to affordability and accessibility, the doctor decides to perform a diagnostic test in the office that is less invasive and more convenient. Which of the following is the most likely test used?
A. Steiner's stain
B. Culture of organisms from gastric specimen
C. Stool antigen test (Correct Answer)
D. Detection of the breakdown products of urea in biopsy
E. Serology (ELISA testing)
Explanation: ***Stool antigen test***
- This **non-invasive** and **cost-effective** test detects *H. pylori* antigens in stool, making it suitable for a rural setting with limited resources.
- It is highly sensitive and specific, useful for both initial diagnosis and confirming eradication after treatment.
*Steiner's stain*
- **Steiner's stain** (Steiner silver stain) is primarily used for histological visualization of *Legionella* species, and **not for** *H. pylori* detection in routine clinical practice.
- It requires an **endoscopic biopsy**, making it more invasive and costly than the stool antigen test.
*Culture of organisms from gastric specimen*
- This method requires an **endoscopic biopsy** and specialized culture facilities, which may not be available in a rural doctor's office.
- It is more expensive and time-consuming, and primarily used when **antibiotic resistance** is suspected.
*Detection of the breakdown products of urea in biopsy*
- This refers to the **rapid urease test** (e.g., CLOtest), which is performed on a **gastric biopsy** obtained during endoscopy.
- While quick, it is an **invasive procedure** requiring endoscopy, which contradicts the patient's and doctor's preferences for a less invasive test.
*Serology (ELISA testing)*
- **Serology** detects antibodies to *H. pylori* but cannot differentiate between **active infection** and **past exposure**.
- Its utility in monitoring eradication is limited, and it's generally not recommended as the primary diagnostic test due to its inability to confirm active infection.
Question 207: To protect against a potentially deadly infection, a 19-year-old female receives a vaccine containing capsular polysaccharide. This vaccine will stimulate her immune system to produce antibodies against which organism?
A. Corynebacterium diphtheriae
B. Neisseria meningitidis (Correct Answer)
C. Streptococcus pneumoniae
D. Clostridium tetani
E. Haemophilus influenzae type b
Explanation: ***Neisseria meningitidis***
- The vaccine described, containing **capsular polysaccharide**, targets the **polysaccharide capsule** of *Neisseria meningitidis*, which is a key virulence factor.
- This bacterium causes **meningococcal meningitis**, a potentially deadly infection, especially in adolescents and young adults.
- The **meningococcal vaccine** is specifically recommended for adolescents and college students due to increased risk in this population.
*Corynebacterium diphtheriae*
- The vaccine against *C. diphtheriae* is a **toxoid vaccine**, meaning it contains an inactivated form of the **diphtheria toxin**, not capsular polysaccharide.
- This vaccine primarily protects against the effects of the **exotoxin**, which causes major symptoms like myocarditis and neuropathy.
*Streptococcus pneumoniae*
- While *S. pneumoniae* also has a **capsular polysaccharide vaccine** (PPSV23 and PCV13), it is primarily recommended for **young children, elderly adults, and immunocompromised patients**.
- A **19-year-old healthy female** would not routinely receive pneumococcal vaccine unless she had specific risk factors.
- The question context of a "potentially deadly infection" in this age group more specifically points to meningococcus.
*Clostridium tetani*
- The vaccine for *C. tetani* is a **tetanus toxoid vaccine**, similar to diphtheria, targeting the inactivated **tetanospasmin toxin** produced by the bacterium.
- This vaccine prevents the neurological symptoms of tetanus by neutralizing the toxin, not by targeting capsular polysaccharides.
*Haemophilus influenzae type b*
- While *H. influenzae* type b also has a **capsular polysaccharide-based vaccine** (conjugate vaccine), it is primarily given to **infants and young children** as part of routine childhood immunization.
- A 19-year-old would have already received this vaccine in childhood, and it is not routinely given to adolescents or adults.
- The age group and clinical context make meningococcus the more likely answer.
Question 208: A 42-year-old woman presents to a medical office with complaints of fatigue, weight loss, and low-grade fever for 1 week. She noticed bleeding spots on her feet this morning. The past medical history is significant for a recent dental appointment. She is a non-smoker and does not drink alcohol. She does not currently take any medications. On examination, the vital signs include temperature 37.8°C (100.0°F), blood pressure 138/90 mm Hg, respirations 21/min, and pulse 87/min. Cardiac auscultation reveals a pansystolic murmur in the mitral area with radiation to the left axilla. Laboratory studies show hemoglobin levels of 17.2 g/dL, erythrocyte sedimentation rate (ESR) of 25 mm/h, and a white blood cell (WBC) count of 12,000 cells/mm3. An echocardiogram reveals valvular vegetations on the mitral valve with mild regurgitation. Blood samples are sent for bacterial culture. Empiric antibiotic therapy is initiated with ceftriaxone and vancomycin. The blood cultures most likely will yield the growth of which of the following organisms?
A. Actinomyces israelii
B. Coxiella burnetii
C. Group B Streptococcus
D. Staphylococcus aureus
E. Streptococcus viridans (Correct Answer)
Explanation: ***Streptococcus viridans***
- The patient's recent **dental appointment**, the presence of an **oral organism**, and symptoms consistent with **subacute bacterial endocarditis** (fatigue, fever, weight loss, petechiae) strongly suggest *S. viridans* as the causative agent.
- *Streptococcus viridans* species are common inhabitants of the **oral flora** and are a leading cause of endocarditis following dental procedures, especially in individuals with pre-existing valvular abnormalities.
*Actinomyces israelii*
- While *Actinomyces israelii* is an oral commensal, it typically causes **actinomycosis**, a chronic, suppurative infection characterized by abscess formation and sinus tracts, often following dental procedures.
- It less commonly presents as acute or subacute endocarditis and would not typically cause the rapid progression of symptoms described.
*Coxiella burnetii*
- *Coxiella burnetii* causes **Q fever**, which can manifest as endocarditis, often associated with exposure to **farm animals** or their products.
- The patient's history lacks any such exposure, and the clinical presentation is more aligned with standard bacterial endocarditis from oral flora.
*Group B Streptococcus*
- **Group B Streptococcus** (*Streptococcus agalactiae*) is primarily known as a cause of **neonatal sepsis** and meningitis, and infections in immunocompromised adults or those with underlying conditions like diabetes.
- It is not typically associated with endocarditis following a dental procedure in an otherwise healthy adult.
*Staphylococcus aureus*
- **Staphylococcus aureus** can cause endocarditis, particularly in **intravenous drug users** or patients with prosthetic valves/indwelling lines, and often presents as a more **acute and aggressive disease**.
- While possible, the association with a recent dental procedure and the subacute course makes *Streptococcus viridans* a more likely culprit in this specific scenario.
Question 209: A 68-year-old man presents to the physician with fever, cough, weakness, night sweats, and poor appetite for the past 6 months. Medical records suggest that he has lost 7.5 kg (16.5 lb) of weight during this period. There is no history of breathlessness, nasal discharge, nasal obstruction, palpitations, chest pain, or symptoms related to digestion. He was released from prison 9 months ago after serving a 2-year sentence. His temperature is 38.1°C (100.6°F), pulse is 84/min, respirations are 16/min, and blood pressure is 122/80 mm Hg. Physical examination shows hepatomegaly and generalized lymphadenopathy, and auscultation of the chest reveals diffuse crackles throughout the lung fields bilaterally. On direct ophthalmoscopy, three discrete, yellow-colored, 0.5 mm to 1.0 mm lesions with indistinct borders are seen in the posterior pole. A chest X-ray is shown in the image. Tuberculin skin test with purified protein derivative is negative. What is the most likely diagnosis?
A. Bronchoalveolar carcinoma
B. Tuberculosis (Correct Answer)
C. Chronic histoplasmosis
D. Langerhans cell histiocytosis
E. Sarcoidosis
Explanation: ***Tuberculosis***
- The patient's history of **fever**, **cough**, **weakness**, **night sweats**, **weight loss**, and recent incarceration are highly suggestive of **tuberculosis (TB)**. His chest X-ray shows **miliary infiltrates**, indicative of **miliary tuberculosis**, and the presence of **choroidal tubercles** on ophthalmoscopy is pathognomonic for disseminated TB.
- While the **tuberculin skin test (TST)** is negative, this can occur in disseminated TB due to anergy, where the immune system is severely compromised and unable to mount a response. The **hepatomegaly** and **generalized lymphadenopathy** further support disseminated disease.
*Bronchoalveolar carcinoma*
- Although it can present with **cough** and **weight loss**, **bronchoalveolar carcinoma** typically does not cause generalized lymphadenopathy or hepatomegaly unless it is widely metastatic, which would likely present with more severe respiratory compromise or other focal symptoms.
- The miliary pattern on chest X-ray and choroidal tubercles are not typical features of bronchoalveolar carcinoma, making it a less likely diagnosis.
*Chronic histoplasmosis*
- **Chronic histoplasmosis** can cause fever, cough, weight loss, and widespread pulmonary infiltrates, particularly in immunocompromised individuals or those with significant exposure (e.g., caves, bird/bat excrement).
- However, choroidal tubercles are rare in histoplasmosis, and the patient's history of incarceration (a risk factor for TB) makes histoplasmosis less probable in this context.
*Langerhans cell histiocytosis*
- **Langerhans cell histiocytosis** primarily affects young adults and often presents with respiratory symptoms, bone lesions, and sometimes skin involvement.
- The diffuse miliary pattern on chest X-ray and choroidal tubercles are not characteristic features of Langerhans cell histiocytosis, nor is generalized lymphadenopathy and hepatomegaly as initial presentation.
*Sarcoidosis*
- **Sarcoidosis** is characterized by non-caseating granulomas and can present with cough, fever, weight loss, and lymphadenopathy, especially hilar and mediastinal.
- While pulmonary infiltrates can occur, the miliary pattern characteristic of disseminated infection (as seen in TB) and choroidal tubercles, though sometimes seen in ocular sarcoidosis, are not the hallmark presentation for disseminated sarcoidosis in this manner.
Question 210: A 47-year-old alcoholic man presents to the office for a 72-hour history of intense right hemithorax pain. He also complains of fever, chills, and sweating that started 10 days ago, as well as persistent coughing with abundant malodorous sputum. Chest radiography shows a round consolidation with air-fluid levels in the middle third of the right hemithorax. Sputum samples for a direct exam, culture, and acid-fast bacilli (AFB) are sent. What is the correct diagnosis?
A. Bronchopulmonary sequestration
B. Bronchiectasis
C. Tuberculosis
D. Lung cancer
E. Lung abscess (Correct Answer)
Explanation: ***Lung abscess***
- The combination of **fever, chills, sweating, persistent coughing with malodorous sputum**, and a **round consolidation with air-fluid levels** on chest radiography in an alcoholic patient is highly indicative of a lung abscess.
- Alcoholism is a significant risk factor due to aspiration, leading to polymicrobial infections and subsequent tissue necrosis and cavitation.
*Bronchopulmonary sequestration*
- This is a rare congenital malformation where a portion of lung tissue is not connected to the tracheobronchial tree and receives its blood supply from the systemic circulation.
- It typically presents as a **mass lesion** on imaging, often without acute signs of infection like fever and malodorous sputum, unless it becomes secondarily infected.
*Bronchiectasis*
- Characterized by **irreversible dilation of the bronchi** resulting from chronic inflammation and infection, leading to chronic cough and sputum production.
- While it can cause chronic cough and sputum, the acute presentation with a distinct **round consolidation with air-fluid levels** points more specifically to an abscess.
*Tuberculosis*
- While tuberculosis can cause **fever, cough, and cavitary lesions** which might appear as air-fluid levels, the **malodorous sputum** is less typical, and the acute onset (72-hour intense pain after 10 days of symptoms) is more consistent with a pyogenic bacterial infection.
- Furthermore, a round consolidation with air-fluid levels without other classic features of TB (e.g., upper lobe predominance, Ghon complex) makes it less likely given the other findings.
*Lung cancer*
- Lung cancer can present as a **mass or consolidation** on imaging, and patients may experience cough, weight loss, and fatigue.
- However, the rapid onset of **fever, chills, malodorous sputum, and air-fluid levels** strongly suggests an infectious process with cavitation rather than an uncomplicated malignancy.
