A 40-year-old farmer from Ohio seeks evaluation at a clinic with complaints of a chronic cough, fevers, and anorexia of several months duration. On examination, he has generalized lymphadenopathy with hepatosplenomegaly. A chest radiograph reveals local infiltrates and patchy opacities involving all lung fields. Fine needle aspiration of an enlarged lymph node shows the presence of intracellular yeast. A fungal culture shows the presence of smooth, thin-walled microconidia and tuberculate macroconidia. Which of the following is the most likely diagnosis?
Q12
A 32-year-old man comes to the physician because of a 1-week history of fever, weakness, diffuse abdominal pain, and multiple lumps on his body. He has recently returned to the USA from a 3-month agricultural internship in South America. Physical examination shows enlarged superficial cervical and inguinal lymph nodes. There is tender hepatomegaly. A photomicrograph of a liver biopsy sample after methenamine silver staining is shown. Which of the following is the most likely diagnosis?
Q13
A 58-year-old woman visits a physician because of fever, chills, dry cough, and a few enlarging masses on her cheeks and neck. Wart-like lesions are present on the nose as shown in the photograph. She reports that she visited the Mississippi area a few months before on a business trip. Her temperature is 38.1°C (100.6°F), the pulse is 80/min, and the blood pressure is 121/78 mm Hg. A fine needle aspirate of the lymph node is sent for pathological investigation. Culture growth shows white colonies on Sabouraud glucose agar (SGA). Which of the following is the most likely causal organism?
Q14
A young woman from the Ohio River Valley in the United States currently on corticosteroid therapy for ulcerative colitis presented to a clinic complaining of fever, sweat, headache, nonproductive cough, malaise, and general weakness. A chest radiograph revealed patchy pneumonia in the lower lung fields, together with enlarged mediastinal and hilar lymph nodes. Skin changes suggestive of erythema nodosum (i.e. an acute erythematous eruption) were noted. Because the patient was from a region endemic for fungal infections associated with her symptoms and the patient was in close contact with a person presenting similar symptoms, the attending physician suspected that systemic fungal infection might be responsible for this woman’s illness. Which of the following laboratory tests can the physician use to ensure early detection of the disease, and also effectively monitor the treatment response?
Q15
An investigator is studying growth patterns of various fungal pathogens. Incubation of an isolated fungus at 25°C shows branching hyphae with rosettes of conidia under light microscopy. After incubation at 37°C, microscopic examination of the same organism instead shows smooth, white colonies with rounded, elongated cells. Infection with the investigated pathogen is most likely to cause which of the following conditions?
Q16
A 50-year-old man from India visits his physician complaining of worsening respiratory symptoms. He states that he was diagnosed with emphysema 4 years ago and that, over the past several months, he has developed a chronic productive cough, dyspnea, fatigue, unexplained weight loss, and night sweats. He notes that he also has other complaints aside from his lung problems, including sharp, intermittent chest pain and joint pain in his elbows and knees. There is also an erythematous rash on both the lower extremities that features raised lesions; it is determined to be erythema nodosum. Cardiac examination reveals a friction rub, and a computed tomography (CT) scan of the chest reveals cavitation of both lung apices. The patient is isolated for the suspicion of active tuberculosis (TB) infection. A purified protein derivative (PPD) test is negative. Sputum sample staining fails to reveal acid-fast bacilli, but it does reveal yeast forms that are replicating by narrow-based budding. Which of the following would aid in making a correct diagnosis in this patient?
Q17
A 16-year-old boy presents to his pediatrician because he has noticed white plaques forming on his tongue over the last 5 days. He recently returned from a boy scout trip where he traveled across the country and hiked through the woods. His past medical history is significant for asthma for which he uses an inhaler as needed. He says that during the trip he felt short of breath several times and had to use the inhaler. He also says that several of his friends appeared to get sick on the same trip and were coughing a lot. He has not experienced any other symptoms since returning from the trip. On presentation, he is found to have white plaques on the tongue that can be scraped off. Which of the following is a characteristic of the most likely cause of this patient's disease?
Q18
A 44-year-old man comes to the physician because of a 3-week history of productive cough, fever, and lethargy. He also has several skin lesions over his body. His symptoms began 3 weeks after he returned from a camping trip in Kentucky. Three years ago, he underwent kidney transplantation for polycystic kidney disease. Current medications include sirolimus and prednisone. His temperature is 38°C (100.4°F). Diffuse crackles are heard over the lung fields. There are 4 white, verrucous skin patches over his chest and upper limbs. A photomicrograph of a skin biopsy specimen from one of the lesions is shown. Which of the following is the most likely diagnosis?
Q19
A 46-year-old woman comes to the physician for a 6-month history of worsening bronchial asthma control. Before this issue began, she only used her salbutamol inhaler once a day. Now, she has to use it multiple times daily and also reports frequent nighttime awakening. Seven months ago, she moved to an apartment that is damp and has mold on some of the walls. The physician injects 0.1 mL of Candida albicans extract on the mid-volar surface of the right arm intradermally. After 48 hours there is a palpable induration of 17 mm. This reaction is most likely a result of release of which of the following substances?
Dimorphic fungi US Medical PG Practice Questions and MCQs
Question 11: A 40-year-old farmer from Ohio seeks evaluation at a clinic with complaints of a chronic cough, fevers, and anorexia of several months duration. On examination, he has generalized lymphadenopathy with hepatosplenomegaly. A chest radiograph reveals local infiltrates and patchy opacities involving all lung fields. Fine needle aspiration of an enlarged lymph node shows the presence of intracellular yeast. A fungal culture shows the presence of smooth, thin-walled microconidia and tuberculate macroconidia. Which of the following is the most likely diagnosis?
A. Coccidioidomycosis
B. Blastomycosis
C. Cryptococcosis
D. Histoplasmosis (Correct Answer)
E. Sporotrichosis
Explanation: ***Histoplasmosis***
- **Histoplasmosis** is characterized by the presence of **intracellular yeast** in tissue samples and **tuberculate macroconidia** in fungal cultures, which are key diagnostic findings in this case.
- The patient's presentation with chronic cough, fevers, anorexia, generalized lymphadenopathy, hepatosplenomegaly, and lung infiltrates, along with geographic exposure in **Ohio** (part of the Ohio River Valley endemic area), is highly consistent with disseminated histoplasmosis.
*Coccidioidomycosis*
- While coccidioidomycosis can cause lung infiltrates, it is typically endemic to the **southwestern United States** and Mexico, not Ohio.
- Microscopic examination would reveal **spherules** containing endospores, not intracellular yeast with tuberculate macroconidia.
*Blastomycosis*
- Blastomycosis is also endemic to the Ohio River Valley, but it is characterized by **broad-based budding yeast** in tissue, and its cultures typically do not show tuberculate macroconidia.
- While it causes pulmonary and disseminated disease, the specific microscopic and culture findings differentiate it from histoplasmosis.
*Cryptococcosis*
- Cryptococcosis primarily affects immunocompromised individuals and is characterized by encapsulated yeast, which would be visible with India ink stain.
- It typically presents as **meningitis** or pneumonia, and its culture morphology does not include tuberculate macroconidia.
*Sporotrichosis*
- Sporotrichosis is commonly associated with **cutaneous lesions** following traumatic inoculation of spores from soil or vegetation, and it rarely causes disseminated disease with extensive systemic symptoms like those described.
- The yeast forms in tissue are typically smaller and cigar-shaped, and the culture morphology differs significantly from what is described.
Question 12: A 32-year-old man comes to the physician because of a 1-week history of fever, weakness, diffuse abdominal pain, and multiple lumps on his body. He has recently returned to the USA from a 3-month agricultural internship in South America. Physical examination shows enlarged superficial cervical and inguinal lymph nodes. There is tender hepatomegaly. A photomicrograph of a liver biopsy sample after methenamine silver staining is shown. Which of the following is the most likely diagnosis?
A. Aspergillosis
B. Paracoccidioidomycosis (Correct Answer)
C. Blastomycosis
D. Malaria
E. Histoplasmosis
Explanation: **Paracoccidioidomycosis**
- The patient's presentation with **fever**, **weakness**, **abdominal pain**, **multiple body lumps**, **diffuse lymphadenopathy**, and **hepatomegaly** after returning from **South America** is highly suggestive of a systemic fungal infection.
- The liver biopsy showing **yeast forms** with **multiple budding cells** (often described as a **"mariner's wheel"** or **"Mickey Mouse ears"** appearance on methenamine silver stain) is characteristic of *Paracoccidioides brasiliensis*, the causative agent of paracoccidioidomycosis.
*Aspergillosis*
- Generally presents with **pulmonary infections** (e.g., aspergilloma, allergic bronchopulmonary aspergillosis, invasive aspergillosis) or disseminated disease in immunocompromised individuals.
- Microscopic findings would show **hyphae with acute-angle branching septate forms**, not budding yeast.
*Blastomycosis*
- Typically found in the **Mississippi and Ohio River basins** and Great Lakes region of North America.
- Microscopic examination reveals **broad-based budding yeast** cells, often larger than *Paracoccidioides*, without the characteristic multiple budding pattern.
*Malaria*
- Caused by a **parasite** (*Plasmodium*) transmitted by mosquitos, and would present with cyclical fevers, chills, anemia, and splenomegaly.
- A definitive diagnosis is made by **blood smear** showing parasites within red blood cells, not fungal elements in a tissue biopsy.
*Histoplasmosis*
- Endemic in the **Ohio and Mississippi River Valleys** and parts of Central and South America.
- Microscopic findings would show **small, oval yeast cells** within macrophages, often much smaller than *Paracoccidioides* and without multiple budding, making disseminated disease a possibility, but less likely given the specific biopsy findings.
Question 13: A 58-year-old woman visits a physician because of fever, chills, dry cough, and a few enlarging masses on her cheeks and neck. Wart-like lesions are present on the nose as shown in the photograph. She reports that she visited the Mississippi area a few months before on a business trip. Her temperature is 38.1°C (100.6°F), the pulse is 80/min, and the blood pressure is 121/78 mm Hg. A fine needle aspirate of the lymph node is sent for pathological investigation. Culture growth shows white colonies on Sabouraud glucose agar (SGA). Which of the following is the most likely causal organism?
A. Histoplasma capsulatum
B. Malassezia furfur
C. Blastomyces dermatitidis (Correct Answer)
D. Coccidioides immitis
E. Aspergillus fumigatus
Explanation: ***Blastomyces dermatitidis***
- The patient's symptoms, including **fever, chills, dry cough, enlarging masses on cheeks and neck, and wart-like lesions on the nose**, along with a history of travel to the **Mississippi area**, are highly characteristic of **blastomycosis**.
- **_Blastomyces dermatitidis_** is a dimorphic fungus endemic to the **Ohio and Mississippi River valleys** and the Great Lakes region, often causing pulmonary disease that can disseminate to the skin, bones, and other organs, producing lesions such as those described.
*Histoplasma capsulatum*
- This fungus is also endemic to the **Ohio and Mississippi River valleys** but typically causes **histoplasmosis**, which often presents with asymptomatic lung infection, or in severe cases, disseminated disease with **hepatosplenomegaly** and **oral ulcers**, rather than aggressive cutaneous **wart-like lesions**.
- While it can cause pulmonary symptoms, the prominent **skin lesions** and masses described are less typical for disseminated histoplasmosis compared to **blastomycosis**.
*Malassezia furfur*
- **_Malassezia furfur_** is associated with superficial fungal infections like **tinea versicolor** (pityriasis versicolor), which presents as hypopigmented or hyperpigmented patches on the skin, mainly on the trunk and upper extremities.
- It does not typically cause **deep-seated infections** with systemic symptoms (fever, chills, cough) or **wart-like lesions** on the nose and neck masses.
*Coccidioides immitis*
- **_Coccidioides immitis_** is endemic to the **southwestern United States** (e.g., California, Arizona) and is the causative agent of **Coccidioidomycosis** (Valley Fever).
- While it can cause pulmonary symptoms and disseminate, the classic dermatological manifestations are often **erythema nodosum** or **erythema multiforme**, not the wart-like, verrucous lesions described in this case, and its endemic region does not fit the patient's travel history to Mississippi.
*Aspergillus fumigatus*
- **_Aspergillus fumigatus_** is an opportunistic mold that primarily causes allergic bronchopulmonary aspergillosis (ABPA), aspergilloma (fungus ball in pre-existing lung cavities), or invasive aspergillosis in **immunocompromised individuals**.
- It is not typically associated with cutaneous **wart-like lesions** or the specific endemic pattern and systemic symptoms described in an otherwise seemingly immunocompetent individual in the Mississippi region.
Question 14: A young woman from the Ohio River Valley in the United States currently on corticosteroid therapy for ulcerative colitis presented to a clinic complaining of fever, sweat, headache, nonproductive cough, malaise, and general weakness. A chest radiograph revealed patchy pneumonia in the lower lung fields, together with enlarged mediastinal and hilar lymph nodes. Skin changes suggestive of erythema nodosum (i.e. an acute erythematous eruption) were noted. Because the patient was from a region endemic for fungal infections associated with her symptoms and the patient was in close contact with a person presenting similar symptoms, the attending physician suspected that systemic fungal infection might be responsible for this woman’s illness. Which of the following laboratory tests can the physician use to ensure early detection of the disease, and also effectively monitor the treatment response?
A. Skin tests
B. Fungal staining
C. Antigen detection (Correct Answer)
D. Culture method
E. Antibody testing
Explanation: ***Antigen detection***
- **Antigen detection assays** (e.g., *Histoplasma galactomannan antigen*) are highly sensitive for **disseminated histoplasmosis**, especially in immunosuppressed patients like this one on corticosteroids.
- They provide **early diagnosis** and are effective for **monitoring treatment response**, as antigen levels typically decrease with successful therapy.
*Skin tests*
- **Skin tests** (e.g., *histoplasmin skin test*) indicate **prior exposure** to the fungus and are not useful for diagnosing active, acute infection.
- A positive skin test does not differentiate between past exposure and current disease, making it unsuitable for early detection or monitoring.
*Fungal staining*
- **Fungal staining** of patient samples (e.g., sputum, biopsy) can reveal fungal elements but has **limited sensitivity** and may not identify the specific pathogen.
- It often requires **invasive procedures** to obtain suitable specimens and is not ideal for routine monitoring of treatment response due to variability.
*Culture method*
- **Fungal cultures** are a **definitive diagnostic method** but can take **several weeks** to yield results, which is too slow for early detection in an acutely ill patient.
- While useful for species identification and susceptibility testing, the **delayed turnaround time** makes it impractical for monitoring rapid treatment changes.
*Antibody testing*
- **Antibody tests** for fungal infections can be useful but may show **false negatives in immunocompromised patients** (like this patient on corticosteroids) due to a blunted immune response.
- Seroconversion or a significant rise in antibody titers can indicate infection, but antibodies may **persist long after resolution**, making them less reliable for monitoring acute treatment efficacy.
Question 15: An investigator is studying growth patterns of various fungal pathogens. Incubation of an isolated fungus at 25°C shows branching hyphae with rosettes of conidia under light microscopy. After incubation at 37°C, microscopic examination of the same organism instead shows smooth, white colonies with rounded, elongated cells. Infection with the investigated pathogen is most likely to cause which of the following conditions?
A. Pityriasis versicolor
B. Candidiasis
C. Cryptococcosis
D. Sporotrichosis (Correct Answer)
E. Coccidioidomycosis
Explanation: ***Sporotrichosis***
- The description of a fungal pathogen exhibiting **thermal dimorphism** (different forms at 25°C and 37°C) is characteristic of **Sporothrix schenckii**.
- At 25°C, it typically grows as **mold with branching hyphae and conidia in rosettes**, and at 37°C, it grows as **yeast-like cells (cigar-shaped bodies in tissue)**, which can appear rounded and elongated.
*Pityriasis versicolor*
- Caused by **Malassezia globosa**, which is a **lipophilic yeast** and does not exhibit thermal dimorphism described here.
- Characterized by **hypo- or hyperpigmented skin patches**, not deep tissue infection with dimorphic growth.
*Candidiasis*
- Caused by **Candida species**, which are **opportunistic yeasts** that can form pseudohyphae and true hyphae but do not display the specific dimorphism with rosettes of conidia at 25°C.
- Infections range from superficial mucocutaneous to systemic, but the fungal morphology described does not fit.
*Cryptococcosis*
- Caused by **Cryptococcus neoformans** or **Cryptococcus gattii**, which are **encapsulated yeasts** and do not exhibit dimorphism (mold at 25°C, yeast at 37°C).
- Primarily causes **meningoencephalitis** or pulmonary disease, and is identified by its capsule and yeast form.
*Coccidioidomycosis*
- Caused by **Coccidioides immitis** or **Coccidioides posadasii**, which are **thermally dimorphic fungi**, but their morphology differs from the description.
- At 25°C, they grow as molds with **arthroconidia**, and at 37°C, they form **spherules containing endospores** in tissue, not smooth, white colonies with rounded, elongated cells.
Question 16: A 50-year-old man from India visits his physician complaining of worsening respiratory symptoms. He states that he was diagnosed with emphysema 4 years ago and that, over the past several months, he has developed a chronic productive cough, dyspnea, fatigue, unexplained weight loss, and night sweats. He notes that he also has other complaints aside from his lung problems, including sharp, intermittent chest pain and joint pain in his elbows and knees. There is also an erythematous rash on both the lower extremities that features raised lesions; it is determined to be erythema nodosum. Cardiac examination reveals a friction rub, and a computed tomography (CT) scan of the chest reveals cavitation of both lung apices. The patient is isolated for the suspicion of active tuberculosis (TB) infection. A purified protein derivative (PPD) test is negative. Sputum sample staining fails to reveal acid-fast bacilli, but it does reveal yeast forms that are replicating by narrow-based budding. Which of the following would aid in making a correct diagnosis in this patient?
A. India ink stain of sputum
B. HIV antibody screening
C. Urine histoplasma antigen (Correct Answer)
D. Fungal blood cultures
E. Coccidioidomycosis serology
Explanation: ***Urine histoplasma antigen***
- The patient's symptoms, including **chronic productive cough**, **dyspnea**, **fatigue**, **weight loss**, **night sweats**, cavitation on CT, **erythema nodosum**, and **joint pain**, are highly suggestive of disseminated **histoplasmosis**.
- A **positive urine histoplasma antigen test** is a rapid and highly sensitive method for diagnosing disseminated histoplasmosis, especially in patients with respiratory and extrapulmonary symptoms.
*India ink stain of sputum*
- An **India ink stain** is primarily used to detect *Cryptococcus neoformans*, which is characterized by a capsule and typically causes meningoencephalitis, not this constellation of symptoms.
- The sputum already reveals yeast forms with narrow-based budding, which is inconsistent with *Cryptococcus* but consistent with *Histoplasma*.
*HIV antibody screening*
- While HIV infection can predispose individuals to disseminated fungal infections, the primary step in diagnosis here is identifying the causative organism.
- An HIV test would provide information about immunodeficiency but not directly diagnose the current lung pathology.
*Fungal blood cultures*
- While fungal blood cultures can be useful, they often have **low sensitivity** and can take several days to yield results, delaying treatment.
- In cases of disseminated histoplasmosis, antigen testing is generally more rapid and sensitive.
*Coccidioidomycosis serology*
- **Coccidioidomycosis**, while a cause of fungal pneumonia, is endemic to the **Southwestern United States** and parts of Central and South America, not India.
- The yeast forms with **narrow-based budding** seen in the sputum are not characteristic of *Coccidioides*, which forms spherules in tissue.
Question 17: A 16-year-old boy presents to his pediatrician because he has noticed white plaques forming on his tongue over the last 5 days. He recently returned from a boy scout trip where he traveled across the country and hiked through the woods. His past medical history is significant for asthma for which he uses an inhaler as needed. He says that during the trip he felt short of breath several times and had to use the inhaler. He also says that several of his friends appeared to get sick on the same trip and were coughing a lot. He has not experienced any other symptoms since returning from the trip. On presentation, he is found to have white plaques on the tongue that can be scraped off. Which of the following is a characteristic of the most likely cause of this patient's disease?
A. Acute angle branching
B. Spherules containing endospores
C. Germ tube formation (Correct Answer)
D. Latex agglutination
E. Broad-based budding
Explanation: ***Germ tube formation***
- This patient presents with **oral thrush (candidiasis)**, characterized by **white plaques on the tongue that can be scraped off**. His history of **asthma and inhaler use** (likely corticosteroids) is a risk factor.
- **Germ tube formation** is a rapid diagnostic test for *Candida albicans*, the most common cause of oral thrush, where yeast cells produce filament-like extensions when incubated in serum.
*Acute angle branching*
- This is characteristic of **Aspergillus species**, which typically cause invasive mold infections in immunocompromised individuals, or allergic bronchopulmonary aspergillosis, not oral thrush.
- *Aspergillus* infections are not typically associated with easily scraped-off oral plaques.
*Spherules containing endospores*
- **Spherules containing endospores** are the characteristic tissue form of **Coccidioides immitis/posadasii**, a dimorphic fungus causing coccidioidomycosis (Valley fever), typically presenting as a pulmonary infection.
- This feature is not associated with *Candida albicans* or oral thrush, though the patient's travel history could suggest dimorphic fungal exposure.
*Latex agglutination*
- **Latex agglutination** is a serological test primarily used for detecting **cryptococcal capsular antigen** in cerebrospinal fluid or serum, indicating cryptococcosis.
- It is not a characteristic feature or primary diagnostic method for *Candida* infections like oral thrush.
*Broad-based budding*
- **Broad-based budding** is a microscopic characteristic of **Blastomyces dermatitidis**, a dimorphic fungus causing blastomycosis, typically a pulmonary infection that can disseminate to skin, bone, or other organs.
- This feature is not associated with *Candida albicans* or oral thrush.
Question 18: A 44-year-old man comes to the physician because of a 3-week history of productive cough, fever, and lethargy. He also has several skin lesions over his body. His symptoms began 3 weeks after he returned from a camping trip in Kentucky. Three years ago, he underwent kidney transplantation for polycystic kidney disease. Current medications include sirolimus and prednisone. His temperature is 38°C (100.4°F). Diffuse crackles are heard over the lung fields. There are 4 white, verrucous skin patches over his chest and upper limbs. A photomicrograph of a skin biopsy specimen from one of the lesions is shown. Which of the following is the most likely diagnosis?
A. Coccidioidomycosis
B. Mucormycosis
C. Blastomycosis (Correct Answer)
D. Cryptococcosis
E. Histoplasmosis
Explanation: ***Blastomycosis***
- The patient's history of **camping in Kentucky**, along with the presence of **pulmonary symptoms** (productive cough, fever, crackles) and **verrucous skin lesions**, are classic for blastomycosis.
- The photomicrograph showing **broad-based budding yeast** is pathognomonic for *Blastomyces dermatitidis*.
*Coccidioidomycosis*
- This is typical in the **Southwestern United States and parts of Mexico**, not Kentucky.
- Microscopic examination would reveal **spherules containing endospores**, which are not seen in the provided image.
*Mucormycosis*
- This infection is characterized by **irregular, broad, non-septate hyphae** with **wide-angle branching**, often invading blood vessels, leading to tissue necrosis.
- It primarily affects immunocompromised patients but typically presents as **rhinocerebral** or **pulmonary infection**, less commonly with verrucous skin lesions of this type.
*Cryptococcosis*
- Primarily affects the **lungs and central nervous system**, especially in immunocompromised individuals.
- Microscopy typically shows **encapsulated yeast** cells, which would be visible with India ink stain, and are not represented by the broad-based budding in the image.
*Histoplasmosis*
- Prevalent in the **Ohio and Mississippi River Valleys**, which includes Kentucky, and is often associated with **bird or bat droppings**.
- On microscopy, it presents as **small intracellular yeast** within macrophages, which is morphologically distinct from the large, broad-based budding yeast shown.
Question 19: A 46-year-old woman comes to the physician for a 6-month history of worsening bronchial asthma control. Before this issue began, she only used her salbutamol inhaler once a day. Now, she has to use it multiple times daily and also reports frequent nighttime awakening. Seven months ago, she moved to an apartment that is damp and has mold on some of the walls. The physician injects 0.1 mL of Candida albicans extract on the mid-volar surface of the right arm intradermally. After 48 hours there is a palpable induration of 17 mm. This reaction is most likely a result of release of which of the following substances?
A. Interleukin-10
B. Superoxide anion
C. Tryptase
D. Interferon-γ (Correct Answer)
E. Lysozyme
Explanation: ***Interferon-γ***
- The patient's worsened asthma, fungal exposure, and positive delayed-type hypersensitivity (DTH) skin test to *Candida albicans* suggest a **Th1-mediated immune response**.
- **Interferon-γ (IFN-γ)** is a key cytokine produced by Th1 cells, crucial for activating macrophages and cell-mediated immunity, which drives the induration observed in DTH reactions.
*Interleukin-10*
- **Interleukin-10 (IL-10)** is primarily an **anti-inflammatory cytokine** that suppresses immune responses, particularly Th1 and Th2 activity.
- Its release is associated with downregulating, rather than mediating, the robust inflammatory reaction seen in a positive DTH test.
*Superoxide anion*
- **Superoxide anion** is a reactive oxygen species produced by phagocytes (e.g., neutrophils, macrophages) as part of the **respiratory burst** to kill ingested pathogens.
- While important for host defense, it is not the primary mediator responsible for the induration and cellular infiltration characteristic of a *Candida* DTH skin test.
*Tryptase*
- **Tryptase** is an enzyme released by **mast cells** upon activation, typically during **immediate hypersensitivity reactions (Type I)**.
- Its presence is indicative of allergic reactions mediated by IgE, which manifest as wheal and flare, not the delayed induration seen in this case.
*Lysozyme*
- **Lysozyme** is an enzyme found in secretions (e.g., tears, saliva) and phagocytes, which degrades bacterial cell walls.
- It plays a role in innate immunity against bacteria but is not directly involved in the mediation of a delayed-type hypersensitivity reaction to fungal antigens.
