Patterns of inflammatory response — MCQs

10 questions

A 22-year-old sexually active, otherwise healthy female presents to her primary care physician complaining of several days of dysuria, frequency, urgency, and suprapubic pain. She denies fever, flank pain, vaginal itching, or vaginal bleeding/discharge. Which organism is most likely responsible for this patient's symptoms?

A 62-year-old woman presents to the emergency department with a 2-hour history of sharp chest pain. She says that the pain is worse when she inhales and is relieved by sitting up and leaning forward. Her past medical history is significant for rheumatoid arthritis, myocardial infarction status post coronary artery bypass graft, and radiation for breast cancer 20 years ago. Physical exam reveals a rubbing sound upon cardiac auscultation as well as increased jugular venous distention on inspiration. Pericardiocentesis is performed revealing grossly bloody fluid. Which of the following is most specifically associated with this patient's presentation?

A 38-year-old woman presents with fever and acute onset chest pain for the past 12 hours. She describes the pain as severe, sharp and stabbing in character, and localized to the retrosternal area. She also says the pain is worse when she breathes deeply or coughs. Past medical history is significant for recently diagnosed systemic lupus erythematosus (SLE). Her vital signs include: blood pressure 110/75 mm Hg, pulse 95/min, and temperature 38.0°C (100.4°F). Physical examination is significant for a friction rub heard best at the lower left sternal border. Which of the following is the most likely diagnosis in this patient?

A 62-year-old man comes to the physician because of an oozing skin ulceration on his foot for 1 week. He has a history of type 2 diabetes mellitus and does not adhere to his medication regimen. Physical exam shows purulent discharge from an ulcer on the dorsum of his left foot. Pinprick sensation is decreased bilaterally to the level of the mid-tibia. A culture of the wound grows beta-hemolytic, coagulase-positive cocci in clusters. The causal organism most likely produces which of the following virulence factors?

A 45-year-old immigrant presents with unintentional weight loss, sleep hyperhidrosis, and a persistent cough. He says these symptoms have been present for quite some time. Upon imaging, many granulomas in the upper lobes are present. It is noted that these apical granulomas have centers of necrosis that appear cheese-like in appearance. Encircling the area of necrosis are large cells with cytoplasms pale in color. Of the following surface markers, which one is most closely associated with these cells?

A 30-year-old man comes to the physician because of an episode of bloody vomiting this morning and a 1-week history of burning upper abdominal pain. Two weeks ago, he sustained a head injury and was in a coma for 3 days. An endoscopy shows multiple, shallow hemorrhagic lesions predominantly in the gastric fundus and greater curvature. Biopsies show patchy loss of epithelium and an acute inflammatory infiltrate in the lamina propria that does not extend beyond the muscularis mucosa. Which of the following is the most likely diagnosis?

An 18-year-old man presents with bloody diarrhea and weight loss. He undergoes endoscopic biopsy which shows pseudopolyps. Biopsies taken during the endoscopy show inflammation only involving the mucosa and submucosa. He is diagnosed with an inflammatory bowel disease. Which of the following characteristics was most likely present?

A 34-year-old woman comes to the physician because of a 6-week history of fever and productive cough with blood-tinged sputum. She has also had a 4-kg (8.8-lb) weight loss during the same time period. Examination shows enlarged cervical lymph nodes. An x-ray of the chest shows a 2.5-cm pulmonary nodule in the right upper lobe. A biopsy specimen of the lung nodule shows caseating granulomas with surrounding multinucleated giant cells. Which of the following is the most likely underlying cause of this patient's pulmonary nodule?

A 60-year-old man comes to the office because of an 8-month history of cough, night sweats, shortness of breath, and fatigue. He has also had a 9-kg (19.8-lb) weight loss during this time. He appears pale. Abdominal examination shows hepatosplenomegaly. His leukocyte count is 80,000/mm3 and his leukocyte alkaline phosphatase level is increased. A peripheral blood smear shows > 82% neutrophils with band forms and immature and mature neutrophil precursors. An x-ray of the chest shows a 9-mm right hilar nodule. Which of the following is the most likely cause of this patient's laboratory findings?

Q10

A 32-year-old man who recently emigrated from Somalia comes to the physician because of a 4-week history of fever, cough, and chest pain. He has had a 5-kg (11-lb) weight loss over the last 3 months despite no changes in appetite. His temperature is 38.1°C (100.6°F). Physical examination shows enlarged cervical lymph nodes. The lungs are clear to auscultation. The results of an interferon-γ release assay are positive. An x-ray of the chest shows bilateral mediastinal lymphadenopathy. A transbronchial needle aspiration biopsy of a mediastinal lymph node is performed; a photomicrograph of the specimen is shown. The structure indicated by the arrow is most likely comprised of which of the following types of cells?

Patterns of inflammatory response US Medical PG Practice Questions and MCQs

Question 1: A 22-year-old sexually active, otherwise healthy female presents to her primary care physician complaining of several days of dysuria, frequency, urgency, and suprapubic pain. She denies fever, flank pain, vaginal itching, or vaginal bleeding/discharge. Which organism is most likely responsible for this patient's symptoms?

A. Escherichia coli (Correct Answer)
B. Chlamydia trachomatis
C. Proteus mirabilis
D. Staphylococcus saprophyticus
E. Klebsiella pneumoniae

Explanation: ***Escherichia coli*** - **_E. coli_** is the most common cause of **uncomplicated urinary tract infections (UTIs)**, accounting for 75-95% of cases. - The patient's symptoms of **dysuria, frequency, urgency**, and **suprapubic pain** are classic for cystitis, a common manifestation of _E. coli_ infection. *Chlamydia trachomatis* - While _Chlamydia_ can cause **urethritis** with dysuria, it is often associated with vaginal discharge/bleeding and is primarily a sexually transmitted infection. - The absence of **vaginal symptoms** makes it less likely to be the primary cause of these specific urinary symptoms in this scenario. *Proteus mirabilis* - **_Proteus mirabilis_** is a common cause of UTIs, particularly those associated with **struvite stones** due to its urease activity. - While it can cause similar symptoms, it is less common than _E. coli_ in uncomplicated cystitis and often seen in complicated UTIs or those with a history of recurrent infections. *Staphylococcus saprophyticus* - _Staphylococcus saprophyticus_ is a common cause of UTIs in sexually active young women, but it is typically the **second most common** after _E. coli_. - While a possibility, **_E. coli_ remains the most likely** given its high prevalence in uncomplicated cystitis. *Klebsiella pneumoniae* - _Klebsiella pneumoniae_ is more commonly associated with **hospital-acquired UTIs**, complicated UTIs, or infections in patients with underlying medical conditions, such as diabetes. - It is a much less common cause of **uncomplicated community-acquired cystitis** in healthy young women compared to _E. coli_.

Question 2: A 62-year-old woman presents to the emergency department with a 2-hour history of sharp chest pain. She says that the pain is worse when she inhales and is relieved by sitting up and leaning forward. Her past medical history is significant for rheumatoid arthritis, myocardial infarction status post coronary artery bypass graft, and radiation for breast cancer 20 years ago. Physical exam reveals a rubbing sound upon cardiac auscultation as well as increased jugular venous distention on inspiration. Pericardiocentesis is performed revealing grossly bloody fluid. Which of the following is most specifically associated with this patient's presentation?

A. Myocardial infarction
B. Malignancy (Correct Answer)
C. Uremia
D. Rheumatoid arthritis
E. Viral illness

Explanation: ***Malignancy*** - The presence of **grossly bloody (hemorrhagic) pericardial fluid** is the key finding that most specifically points to **malignancy** as the underlying cause. - **Hemorrhagic pericardial effusion** is most commonly associated with: (1) malignancy, (2) tuberculosis, or (3) trauma. Given the patient's **history of radiation therapy for breast cancer 20 years ago**, malignancy (either metastatic breast cancer or radiation-induced secondary malignancy) is the most likely cause. - Clinical features like **chest pain** worse on inspiration and relieved by leaning forward, a **pericardial friction rub**, and **increased jugular venous distention on inspiration (Kussmaul sign)** indicate pericarditis with possible cardiac tamponade. *Myocardial infarction* - While myocardial infarction can lead to pericarditis (acute post-MI pericarditis or delayed Dressler's syndrome), the pericardial fluid is typically **serous or serosanguinous, not grossly bloody**. - The patient's history of prior MI and CABG makes this less likely to be the cause of this acute presentation with hemorrhagic effusion. - Post-MI pericarditis usually occurs within days to weeks after the MI event. *Uremia* - **Uremic pericarditis** occurs in patients with severe kidney failure (uremia) and typically presents with **serofibrinous exudate**, not grossly bloody effusion. - There is no clinical indication of renal failure or uremia in this patient's presentation. *Rheumatoid arthritis* - **Rheumatoid pericarditis** can occur in patients with RA, but the pericardial effusion is usually **sterile and serofibrinous**, rarely resulting in frankly hemorrhagic fluid. - While this patient has RA, the **grossly bloody fluid** and **history of breast cancer radiation** make malignancy a much more specific and likely diagnosis. *Viral illness* - **Viral pericarditis** is a common cause of acute pericarditis and typically presents with chest pain and a pericardial friction rub. - However, viral pericarditis usually produces **serous or serofibrinous effusions, not grossly bloody fluid**. - There is no mention of prodromal viral symptoms, and the hemorrhagic nature of the fluid strongly argues against a viral etiology.

Question 3: A 38-year-old woman presents with fever and acute onset chest pain for the past 12 hours. She describes the pain as severe, sharp and stabbing in character, and localized to the retrosternal area. She also says the pain is worse when she breathes deeply or coughs. Past medical history is significant for recently diagnosed systemic lupus erythematosus (SLE). Her vital signs include: blood pressure 110/75 mm Hg, pulse 95/min, and temperature 38.0°C (100.4°F). Physical examination is significant for a friction rub heard best at the lower left sternal border. Which of the following is the most likely diagnosis in this patient?

A. Acute myocardial infarction
B. Septic shock
C. Pericardial tamponade
D. Constrictive pericarditis
E. Acute pericarditis (Correct Answer)

Explanation: ***Acute pericarditis*** - This patient's symptoms of **acute onset, sharp, retrosternal chest pain** that is **worse with deep breathing or coughing**, accompanied by a **pericardial friction rub** and fever, are classic for **acute pericarditis**. - The history of **systemic lupus erythematosus (SLE)** is a significant risk factor for pericarditis, as SLE can cause serositis (inflammation of serous membranes including the pericardium). *Acute myocardial infarction* - While chest pain is present, the description of **sharp, stabbing pain worse with breathing** is more typical of pericarditis than the **crushing, pressure-like pain of an MI** that often radiates to the arm or jaw. - The presence of a **pericardial friction rub** is highly suggestive of pericarditis and not typically found in MI. *Septic shock* - This patient's vital signs, including a blood pressure of **110/75 mmHg**, do not indicate **hypotension** as seen in septic shock. - While fever is present, the primary presentation is **chest pain** and a **friction rub**, not generalized signs of severe infection and organ dysfunction. *Pericardial tamponade* - Pericardial tamponade would present with signs of **hemodynamic compromise** such as **hypotension**, **tachycardia**, **muffled heart sounds**, and **jugular venous distention (Beck's triad)**, which are not described. - The primary symptom is **chest pain** and a **friction rub** indicative of inflammation, not significant fluid accumulation causing cardiac compression. *Constrictive pericarditis* - **Constrictive pericarditis** typically presents with signs of **chronic right-sided heart failure** such as **peripheral edema**, **ascites**, and **jugular venous distention**, often after a prolonged course of pericardial inflammation. - This patient presents with **acute symptoms** and signs of **active inflammation** (fever, friction rub), which is not consistent with the chronic nature of constrictive pericarditis.

Question 4: A 62-year-old man comes to the physician because of an oozing skin ulceration on his foot for 1 week. He has a history of type 2 diabetes mellitus and does not adhere to his medication regimen. Physical exam shows purulent discharge from an ulcer on the dorsum of his left foot. Pinprick sensation is decreased bilaterally to the level of the mid-tibia. A culture of the wound grows beta-hemolytic, coagulase-positive cocci in clusters. The causal organism most likely produces which of the following virulence factors?

A. Exotoxin A
B. M protein
C. P fimbriae
D. IgA protease
E. Protein A (Correct Answer)

Explanation: ***Protein A*** - The culture finding of **beta-hemolytic, coagulase-positive cocci in clusters** is characteristic of ***Staphylococcus aureus***. - ***Staphylococcus aureus*** produces **Protein A**, which binds to the Fc region of IgG, preventing opsonization and phagocytosis, thereby hindering the immune response. *Exotoxin A* - **Exotoxin A** is a virulence factor primarily produced by ***Pseudomonas aeruginosa***, particularly associated with deep tissue infections and sepsis. - It functions as an **ADP-ribosylating toxin** that inhibits protein synthesis, but it is not characteristic of the organism isolated in this patient. *M protein* - **M protein** is a key virulence factor of ***Streptococcus pyogenes*** (Group A Streptococcus), responsible for preventing phagocytosis and promoting adhesion. - ***S. pyogenes*** is beta-hemolytic but typically grows in **chains**, not clusters, and is **coagulase-negative**. *P fimbriae* - **P fimbriae** (pyelonephritis-associated pilus) are virulence factors predominantly found in uropathogenic strains of ***Escherichia coli***, mediating adhesion to uroepithelial cells. - These fimbriae are associated with urinary tract infections, not typically with skin ulcers from **Gram-positive cocci in clusters**. *IgA protease* - **IgA protease** is a virulence factor produced by several pathogenic bacteria such as ***Neisseria gonorrhoeae***, ***Haemophilus influenzae***, and ***Streptococcus pneumoniae***. - It cleaves IgA at hinge regions, allowing the bacteria to evade mucosal immunity, but it is not a primary virulence factor of ***Staphylococcus aureus*** or commonly associated with skin ulcers.

Question 5: A 45-year-old immigrant presents with unintentional weight loss, sleep hyperhidrosis, and a persistent cough. He says these symptoms have been present for quite some time. Upon imaging, many granulomas in the upper lobes are present. It is noted that these apical granulomas have centers of necrosis that appear cheese-like in appearance. Encircling the area of necrosis are large cells with cytoplasms pale in color. Of the following surface markers, which one is most closely associated with these cells?

A. CD20
B. CD3
C. CD4
D. CD14 (Correct Answer)
E. CD8

Explanation: ***CD14*** - The description of **caseating granulomas** in the upper lobes with large cells having pale cytoplasm points towards **tuberculosis** and the presence of **epithelioid macrophages**. - **CD14** is a surface marker commonly found on **monocytes** and **macrophages**, making it the most appropriate choice among the given options. - Note: While epithelioid macrophages (the activated form seen in granulomas) may downregulate CD14 compared to circulating monocytes, CD14 remains the most closely associated macrophage marker among these choices. **CD68** would be the ideal marker for tissue macrophages, but it is not listed. *CD20* - **CD20** is a surface marker characteristic of **B lymphocytes**. - While B cells might be present in inflammatory lesions, they are not the predominant cell type described as "large cells with pale cytoplasm" forming the granuloma. *CD3* - **CD3** is a pan T-cell marker, indicating the presence of all types of **T lymphocytes**. - While T cells (specifically CD4+ T helper cells) are crucial in granuloma formation, the "large cells with pale cytoplasm" encasing the necrosis specifically refer to epithelioid macrophages, not T cells. *CD4* - **CD4** is a surface marker for **helper T lymphocytes**. - **CD4+ T cells** play a critical role in orchestrating the immune response and granuloma formation in tuberculosis through IFN-γ secretion, but the description of the large cells with pale cytoplasm refers to macrophages, not lymphocytes. *CD8* - **CD8** is a surface marker for **cytotoxic T lymphocytes**. - **CD8+ T cells** are also involved in the immune response to mycobacterial infection but are not the primary cell type described as forming the bulk of the granuloma's characteristic "large cells with pale cytoplasm."

Question 6: A 30-year-old man comes to the physician because of an episode of bloody vomiting this morning and a 1-week history of burning upper abdominal pain. Two weeks ago, he sustained a head injury and was in a coma for 3 days. An endoscopy shows multiple, shallow hemorrhagic lesions predominantly in the gastric fundus and greater curvature. Biopsies show patchy loss of epithelium and an acute inflammatory infiltrate in the lamina propria that does not extend beyond the muscularis mucosa. Which of the following is the most likely diagnosis?

A. Type B gastritis
B. Cushing ulcer (Correct Answer)
C. Erosive gastritis
D. Dieulafoy lesion
E. Penetrating ulcer

Explanation: ***Cushing ulcer*** - A **Cushing ulcer** is a type of **stress ulcer** specifically associated with **intracranial injury**, which causes increased vagal stimulation leading to hypersecretion of gastric acid. - The patient's history of a **head injury** followed by **bloody vomiting** and **upper abdominal pain**, along with endoscopic findings of shallow, hemorrhagic lesions, is highly consistent with a Cushing ulcer. *Type B gastritis* - **Type B gastritis** is primarily caused by **Helicobacter pylori infection**, often leading to chronic inflammation and sometimes ulcers, not acute stress-related lesions after a head injury. - While it can cause epigastric pain and bleeding, the strong association with a recent head injury makes Cushing ulcer a more specific diagnosis. *Erosive gastritis* - **Erosive gastritis** is a broad term encompassing various causes of gastric mucosal erosions, including NSAIDs, alcohol, and stress. - While Cushing ulcer represents a specific form of stress-related erosive gastritis, **Cushing ulcer is the most specific and accurate diagnosis** given the distinct history of intracranial injury and coma. - The temporal relationship between head trauma and gastric symptoms is pathognomonic for Cushing ulcer. *Dieulafoy lesion* - A **Dieulafoy lesion** is characterized by an abnormally large submucosal artery that erodes the overlying mucosa, leading to sudden, massive gastrointestinal bleeding. - This condition is typically isolated, not presenting with multiple, shallow hemorrhagic lesions across the gastric fundus and greater curvature, and is not directly linked to head injury. *Penetrating ulcer* - A **penetrating ulcer** is a complication of a chronic peptic ulcer where the ulcer extends beyond the muscularis propria into adjacent organs. - The biopsy findings of inflammation not extending beyond the **muscularis mucosa** indicate superficial damage (erosions), not a deep penetrating ulcer.

Question 7: An 18-year-old man presents with bloody diarrhea and weight loss. He undergoes endoscopic biopsy which shows pseudopolyps. Biopsies taken during the endoscopy show inflammation only involving the mucosa and submucosa. He is diagnosed with an inflammatory bowel disease. Which of the following characteristics was most likely present?

A. Cobblestone mucosa
B. Skip lesions
C. Fistulas and strictures
D. Noncaseating granuloma
E. Rectal involvement (Correct Answer)

Explanation: **_Rectal involvement_** - The description of **bloody diarrhea** and **pseudopolyps** on endoscopy, along with inflammation limited to the **mucosa and submucosa**, is highly characteristic of **ulcerative colitis (UC)**. UC invariably involves the rectum and extends proximally in a continuous fashion. - The presence of **pseudopolyps** is common in UC due to cycles of mucosal ulceration and regeneration. *Cobblestone mucosa* - **Cobblestone mucosa** is a classic endoscopic finding in **Crohn's disease**, resulting from deep ulcerations interspersed with islands of edematous, non-ulcerated mucosa. - This feature points to a transmural pattern of inflammation, which is inconsistent with the superficial inflammation confined to the **mucosa and submucosa** described. *Skip lesions* - **Skip lesions** refer to discontinuous areas of inflammation separated by healthy tissue, a hallmark feature of **Crohn's disease**. - **Ulcerative colitis** (implied by the superficial inflammation) is characterized by continuous inflammation extending proximally from the rectum without skipped areas. *Fistulas and strictures* - **Fistulas** (abnormal connections between organs or to the skin) and **strictures** (narrowing of the intestinal lumen) are complications typically associated with **Crohn's disease**, due to its **transmural inflammation**. - These are rare in **ulcerative colitis**, which primarily affects the superficial layers of the colon. *Noncaseating granuloma* - The presence of **noncaseating granulomas** on biopsy is a key histological feature distinguishing **Crohn's disease** from ulcerative colitis. - The inflammation described as restricted to the **mucosa and submucosa** makes granulomas less likely, as they often imply a transmural process.

Question 8: A 34-year-old woman comes to the physician because of a 6-week history of fever and productive cough with blood-tinged sputum. She has also had a 4-kg (8.8-lb) weight loss during the same time period. Examination shows enlarged cervical lymph nodes. An x-ray of the chest shows a 2.5-cm pulmonary nodule in the right upper lobe. A biopsy specimen of the lung nodule shows caseating granulomas with surrounding multinucleated giant cells. Which of the following is the most likely underlying cause of this patient's pulmonary nodule?

A. Combined type III/IV hypersensitivity reaction
B. IgE-mediated mast cell activation
C. Immune complex deposition
D. Antibody-mediated cytotoxic reaction
E. Delayed T cell-mediated reaction (Correct Answer)

Explanation: ***Delayed T cell-mediated reaction*** - The presence of **caseating granulomas** with **multinucleated giant cells** is characteristic of tuberculosis, which is mediated by a **Type IV hypersensitivity reaction**. - This reaction involves **T cells** and **macrophages** forming granulomas to wall off persistent intracellular pathogens. *Combined type III/IV hypersensitivity reaction* - While granulomas can sometimes involve aspects of **Type III hypersensitivity** (immune complex deposition), **caseating granulomas** are primarily a feature of **Type IV (delayed T cell-mediated) hypersensitivity**. - **Type III reactions** are more typically associated with vasculitis or glomerulonephritis, which are not the primary features here. *IgE-mediated mast cell activation* - This describes a **Type I hypersensitivity reaction**, responsible for immediate allergic reactions like asthma or anaphylaxis. - The patient's symptoms (fever, weight loss, productive cough, granulomas) are not consistent with an **IgE-mediated response**. *Immune complex deposition* - This is characteristic of a **Type III hypersensitivity reaction**, where antigen-antibody complexes deposit in tissues, leading to inflammation and damage. - While Type III reactions can cause inflammation, they typically don't manifest as **caseating granulomas** and the chronic, progressive symptoms described. *Antibody-mediated cytotoxic reaction* - This describes a **Type II hypersensitivity reaction**, where antibodies directly bind to antigens on cell surfaces, leading to cell lysis (e.g., autoimmune hemolytic anemia). - The clinical picture of **granulomatous inflammation** is not consistent with a direct **antibody-mediated cytotoxic reaction**.

Question 9: A 60-year-old man comes to the office because of an 8-month history of cough, night sweats, shortness of breath, and fatigue. He has also had a 9-kg (19.8-lb) weight loss during this time. He appears pale. Abdominal examination shows hepatosplenomegaly. His leukocyte count is 80,000/mm3 and his leukocyte alkaline phosphatase level is increased. A peripheral blood smear shows > 82% neutrophils with band forms and immature and mature neutrophil precursors. An x-ray of the chest shows a 9-mm right hilar nodule. Which of the following is the most likely cause of this patient's laboratory findings?

A. Sarcoidosis
B. Acute lymphoblastic leukemia
C. Leukemoid reaction (Correct Answer)
D. Tuberculosis
E. Chronic myeloid leukemia

Explanation: ***Leukemoid reaction*** - The combination of **leukocytosis** (>50,000/mm³), **immature granulocytes**, and **elevated leukocyte alkaline phosphatase (LAP) score** in the presence of an underlying inflammatory or infectious process (such as the suspected lung lesion) strongly suggests a leukemoid reaction. - A leukemoid reaction is a reactive **increase in white blood cells**, often in response to severe infection or malignancy, mimicking leukemia but distinct from it due to the high LAP score and lack of specific chromosomal translocations. *Sarcoidosis* - Sarcoidosis typically presents with **non-caseating granulomas**, often affecting the lungs and lymph nodes, but does not usually cause such a profound leukocytosis with immature forms. - While a **hilar nodule** can be seen, the described hematological findings, especially the high LAP score and pronounced neutrophilia, are not characteristic of sarcoidosis. *Acute lymphoblastic leukemia* - This condition involves a proliferation of **lymphoblasts**, not mature or immature neutrophils; therefore, the peripheral smear would show a predominance of blasts and not mature neutrophil precursors. - While it can cause leukocytosis, the specific cell types and the **elevated LAP score** (LAP is typically low in ALL) rule it out. *Tuberculosis* - Tuberculosis can cause fever, night sweats, weight loss, and lung findings, but it typically does not lead to a **leukocyte count of 80,000/mm³** with such a high proportion of immature neutrophils. - While it can cause a **leukemoid reaction**, the LAP score and specific granulocyte morphology help differentiate it from other causes, and the primary diagnosis here is the reaction itself, which would be *caused* by something like TB. *Chronic myeloid leukemia* - CML also presents with marked leukocytosis and **immature myeloid cells** but is characterized by a **low leukocyte alkaline phosphatase (LAP) score** and the presence of the **Philadelphia chromosome (BCR-ABL1 fusion gene)**, which contradicts the elevated LAP score found in this patient. - While hepatosplenomegaly and constitutional symptoms align, the LAP score is a key differentiating factor.

Question 10: A 32-year-old man who recently emigrated from Somalia comes to the physician because of a 4-week history of fever, cough, and chest pain. He has had a 5-kg (11-lb) weight loss over the last 3 months despite no changes in appetite. His temperature is 38.1°C (100.6°F). Physical examination shows enlarged cervical lymph nodes. The lungs are clear to auscultation. The results of an interferon-γ release assay are positive. An x-ray of the chest shows bilateral mediastinal lymphadenopathy. A transbronchial needle aspiration biopsy of a mediastinal lymph node is performed; a photomicrograph of the specimen is shown. The structure indicated by the arrow is most likely comprised of which of the following types of cells?

A. Natural killer cells
B. B cells
C. Fibroblasts
D. Neutrophils
E. Macrophages (Correct Answer)

Explanation: ***Macrophages*** - The photomicrograph shows a **granuloma**, characterized by collections of **epithelioid histiocytes** (modified macrophages) and **multinucleated giant cells**, which are essentially fused macrophages. - This morphology, coupled with the clinical picture of fever, cough, weight loss, positive interferon-γ release assay, and mediastinal lymphadenopathy in a patient from an endemic area, is highly suggestive of **tuberculosis**, a classic granulomatous disease. *Natural killer cells* - Natural killer cells are part of the innate immune system and are primarily involved in **killing virally infected cells** and **tumor cells**. - They are not the primary cellular component forming the characteristic structure of a granuloma. *B cells* - B cells are responsible for **antibody production** and antigen presentation. - While B cells may be present in the periphery of a granuloma, they do not form the core epithelioid and giant cell components. *Fibroblasts* - Fibroblasts produce **collagen** and the extracellular matrix, playing a role in **scar formation** and the fibrotic wall that can surround chronic granulomas. - They do not constitute the primary cellular components of the inflammatory core of a granuloma. *Neutrophils* - Neutrophils are typically associated with **acute inflammation** and bacterial infections, characterized by pus formation. - They are not the predominant cell type in the organized structure of a **granuloma** found in tuberculosis.

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