Hypersensitivity pneumonitis US Medical PG Practice Questions and MCQs
Practice US Medical PG questions for Hypersensitivity pneumonitis. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Hypersensitivity pneumonitis US Medical PG Question 1: A 7-year-old boy is rushed to the urgent care department from a friend’s birthday party with breathing trouble. He is immediately placed on supplemental oxygen therapy. The patient’s father explains that peanut butter treats were served at the event, but he reported not having witnessed his son actually eat one. During the party, the patient approached his father with facial flushing, difficulty breathing, and itching of his face and neck. The patient was born at 40 weeks gestation via spontaneous vaginal delivery. He has met all age-related developmental milestones and is fully vaccinated. His past medical history is significant for peanut allergy and asthma. He carries an emergency inhaler. Family history is noncontributory. The patient’s vitals signs include a blood pressure of 110/85 mm Hg, a heart rate of 110/min, a respiratory rate of 25/min, and a temperature of 37.2°C (99.0°F). Physical examination reveals severe facial edema and severe audible stridor in both lungs. Which of the following types of hypersensitivity reaction is the most likely in this patient?
- A. Type 4–cell-mediated (delayed) hypersensitivity reaction
- B. Type 3–immune complex-mediated hypersensitivity reaction
- C. Mixed anaphylactic and cytotoxic hypersensitivity reaction
- D. Type 2–cytotoxic hypersensitivity reaction
- E. Type 1–anaphylactic hypersensitivity reaction (Correct Answer)
Hypersensitivity pneumonitis Explanation: ***Type 1–anaphylactic hypersensitivity reaction***
- This patient's symptoms (facial flushing, difficulty breathing, itching, facial edema, stridor) occurring rapidly after suspected **peanut exposure** are classic for a **Type 1 hypersensitivity reaction**, also known as **anaphylaxis**.
- Type 1 reactions are **IgE-mediated**, leading to mast cell and basophil degranulation and the release of mediators like **histamine**, causing immediate allergic symptoms.
*Type 4–cell-mediated (delayed) hypersensitivity reaction*
- **Type 4 reactions** are **delayed**, typically manifesting 24-72 hours after exposure, and are mediated by **T-cells**, not antibodies.
- Examples include contact dermatitis (e.g., poison ivy) or the tuberculin skin test, which do not fit the acute, severe presentation described.
*Type 3–immune complex-mediated hypersensitivity reaction*
- **Type 3 reactions** involve the formation of **immune complexes** (antigen-antibody complexes) that deposit in tissues, leading to inflammation.
- These reactions can cause conditions like serum sickness or lupus nephritis and typically have a slower onset and different symptom profile than acute anaphylaxis.
*Mixed anaphylactic and cytotoxic hypersensitivity reaction*
- While a patient can experience multiple types of responses over time, a **mixed reaction** implies a simultaneous presentation of distinct **Type 1** and **Type 2** features. The primary and overwhelming presentation here is clearly Type 1 anaphylaxis.
- There is no specific evidence presented to suggest a significant **cytotoxic (Type 2)** component in this acute presentation.
*Type 2–cytotoxic hypersensitivity reaction*
- **Type 2 reactions** involve **antibodies** (IgG or IgM) binding to antigens on cell surfaces, leading to cell destruction via complement activation or antibody-dependent cellular cytotoxicity.
- Examples include hemolytic transfusion reactions or autoimmune hemolytic anemia, which do not align with the patient's acute allergic symptoms and stridor.
Hypersensitivity pneumonitis US Medical PG Question 2: A 23-year-old man presents to the emergency department with shortness of breath. The patient was at a lunch hosted by his employer. He started to feel his symptoms begin when he started playing football outside with a few of the other employees. The patient has a past medical history of atopic dermatitis and asthma. His temperature is 98.3°F (36.8°C), blood pressure is 87/58 mmHg, pulse is 150/min, respirations are 22/min, and oxygen saturation is 85% on room air. Which of the following is the best next step in management?
- A. Albuterol and prednisone
- B. IV epinephrine
- C. IV fluids and 100% oxygen
- D. Albuterol and norepinephrine
- E. IM epinephrine (Correct Answer)
Hypersensitivity pneumonitis Explanation: ***IM epinephrine***
- The patient presents with **signs of anaphylaxis**, including acute onset shortness of breath, hypotension (BP 87/58 mmHg), tachycardia (HR 150/min), and hypoxia (SpO2 85%). Given his history of atopic dermatitis and asthma, he is at high risk for severe allergic reactions.
- **Intramuscular epinephrine** is the first-line treatment for anaphylaxis as it acts rapidly to constrict blood vessels, relax airway smooth muscle, and reduce swelling, addressing both cardiovascular collapse and respiratory distress.
*Albuterol and prednisone*
- While **albuterol** (a bronchodilator) might help with bronchoconstriction, and **prednisone** (a corticosteroid) can reduce inflammation, these are not the immediate priority for severe anaphylaxis.
- They act too slowly to counteract the rapid, systemic effects of anaphylaxis, particularly the life-threatening hypotension and airway compromise.
*IV epinephrine*
- **Intravenous epinephrine** is reserved for severe, refractory cases of anaphylaxis, or for patients already receiving IV infusions in a critical care setting.
- Administering IV epinephrine requires careful titration due to the risk of arrhythmias and hypertension, and IM administration is preferred as the initial rapid response.
*IV fluids and 100% oxygen*
- **IV fluids** are crucial to address the distributive shock and hypotension in anaphylaxis, and **100% oxygen** is essential for hypoxia, but these are supportive measures.
- They do not address the underlying immunological mechanism driving the severe allergic reaction as directly and effectively as epinephrine.
*Albuterol and norepinephrine*
- **Albuterol** can help with bronchospasm, but it is insufficient for systemic anaphylaxis. **Norepinephrine** is a potent vasopressor used for severe shock.
- While norepinephrine can raise blood pressure, it does not have the broader beneficial effects of epinephrine on mast cell degranulation, airway dilation, and stabilization of vascular permeability, making it a secondary agent.
Hypersensitivity pneumonitis US Medical PG Question 3: A 55-year-old man with a history of fatigue and exertional dyspnea presents to the urgent care clinic following an acute upper respiratory illness. On physical examination, his pulses are bounding, his complexion is very pale, and scleral icterus is apparent. The spleen is moderately enlarged. Oxygen saturation is 79% at rest, with a new oxygen requirement of 9 L by a non-rebreather mask. Laboratory analysis results show a hemoglobin level of 6.8 g/dL. Of the following options, which hypersensitivity reaction does this condition represent?
- A. Type III–immune complex-mediated hypersensitivity reaction
- B. Type I–anaphylactic hypersensitivity reaction
- C. Type IV–cell-mediated (delayed) hypersensitivity reaction
- D. Type II–cytotoxic hypersensitivity reaction (Correct Answer)
- E. Type II and III–mixed cytotoxic and immune complex hypersensitivity reaction
Hypersensitivity pneumonitis Explanation: ***Type II–cytotoxic hypersensitivity reaction***
- The patient's symptoms, including **fatigue**, **exertional dyspnea**, **pale complexion**, **scleral icterus**, and **splenomegaly**, along with a **low hemoglobin** of 6.8 g/dL, strongly suggest **hemolytic anemia**.
- Following an **upper respiratory illness**, this presentation is consistent with **autoimmune hemolytic anemia (AIHA)**, where antibodies (mainly IgG or IgM) mistakenly target and destroy red blood cells, which is a classic example of a **Type II hypersensitivity reaction**.
*Type III–immune complex-mediated hypersensitivity reaction*
- This reaction involves the formation of **immune complexes** that deposit in tissues, leading to inflammation and damage, as seen in conditions like **serum sickness** or **lupus nephritis**.
- The patient's primary symptoms of **hemolysis** and **anemia** are not characteristic of immune complex deposition.
*Type I–anaphylactic hypersensitivity reaction*
- This type involves **IgE-mediated mast cell degranulation**, leading to rapid onset symptoms like **urticaria**, **angioedema**, **bronchospasm**, and **hypotension**.
- The patient's presentation of gradual onset fatigue, anemia, and icterus does not align with the acute, systemic allergic reaction seen in Type I hypersensitivity.
*Type IV–cell-mediated (delayed) hypersensitivity reaction*
- This reaction is mediated by **T cells** and **macrophages**, with a delayed onset (24-72 hours), as seen in **contact dermatitis** or **tuberculosis skin tests**.
- The patient's rapid development of severe anemia and an acute hemolytic picture is not consistent with a T-cell-mediated delayed reaction.
*Type II and III–mixed cytotoxic and immune complex hypersensitivity reaction*
- While some autoimmune conditions can involve elements of both Type II and Type III reactions, the overwhelming clinical picture in this patient points to direct **antibody-mediated destruction of red blood cells (Type II)**.
- There are no specific features mentioned, such as vasculitis or nephritis, that would strongly suggest **immune complex deposition** in addition to the prominent hemolytic anemia.
Hypersensitivity pneumonitis US Medical PG Question 4: A 51-year-old man presents to the clinic with a history of hematuria and hemoptysis following pneumonia several weeks ago. He works as a hotel bellhop. His medical history is significant for gout, hypertension, hypercholesterolemia, diabetes mellitus type II, and mild intellectual disability. He currently smokes 2 packs of cigarettes per day and denies any alcohol use or any illicit drug use. His vital signs include: temperature 36.7°C (98.0°F), blood pressure 126/74 mm Hg, heart rate 87/min, and respiratory rate 23/min. Physical examination shows minimal bibasilar rales, but otherwise clear lungs on auscultation, grade 2/6 holosystolic murmur, and benign abdominal findings. Pulmonary function tests demonstrate a restrictive pattern and a current chest radiograph shows bibasilar alveolar infiltrates. Clinical pathology analysis reveals antiglomerular basement membrane antibody, and his renal biopsy shows a linear immunofluorescence pattern. Of the following options, which type of hypersensitivity reaction underlies this patient’s diagnosis?
- A. Type I and IV–mixed anaphylactic and cell-mediated hypersensitivity reaction
- B. Type IV–cell-mediated (delayed) hypersensitivity reaction
- C. Type I–anaphylactic hypersensitivity reaction
- D. Type III–immune complex-mediated hypersensitivity reaction
- E. Type II–cytotoxic hypersensitivity reaction (Correct Answer)
Hypersensitivity pneumonitis Explanation: ***Type II–cytotoxic hypersensitivity reaction***
- The presence of **antiglomerular basement membrane (anti-GBM) antibodies** targeting kidney and lung tissues (causing hematuria and hemoptysis) is characteristic of **Goodpasture syndrome**, which is a classic example of a **Type II hypersensitivity reaction**.
- In Type II reactions, antibodies (IgG or IgM) bind to antigens on the surface of cells or within tissues, leading to **complement activation** and cell destruction (cytotoxicity) or dysfunction.
*Type I and IV–mixed anaphylactic and cell-mediated hypersensitivity reaction*
- This option describes a mixed reaction that doesn't fit the clinical picture of **anti-GBM disease**. Type I involves IgE-mediated mast cell degranulation, and Type IV involves T-cell-mediated delayed responses.
- While infections often precede Goodpasture syndrome, the direct pathology from **anti-GBM antibodies** is distinct from typical mixed allergic or delayed-type reactions.
*Type IV–cell-mediated (delayed) hypersensitivity reaction*
- Type IV reactions are characterized by **T-cell-mediated inflammation** and do not involve antibodies binding to tissue antigens; examples include tuberculosis skin tests or contact dermatitis.
- The presence of specific **anti-GBM antibodies** and a **linear immunofluorescence pattern** on renal biopsy clearly indicate an antibody-mediated process, ruling out a purely cell-mediated reaction.
*Type I–anaphylactic hypersensitivity reaction*
- Type I reactions involve **IgE antibodies** binding to mast cells and basophils, leading to histamine release and immediate allergic responses like anaphylaxis, asthma, or hives.
- The symptoms of hematuria and hemoptysis due to **glomerular basement membrane damage** are inconsistent with an immediate IgE-mediated allergic reaction.
*Type III–immune complex-mediated hypersensitivity reaction*
- Type III reactions involve the formation of **soluble immune complexes** (antigen-antibody complexes) that deposit in tissues, leading to inflammation (e.g., lupus nephritis, serum sickness).
- While antibodies are involved, the defining feature of Goodpasture syndrome is antibodies directly targeting and binding to fixed antigens on the **glomerular and alveolar basement membranes**, not circulating immune complex deposition, which would typically show a **granular immunofluorescence pattern**.
Hypersensitivity pneumonitis US Medical PG Question 5: 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)
Hypersensitivity pneumonitis 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**.
Hypersensitivity pneumonitis US Medical PG Question 6: A 48-year-old woman with alpha-1-antitrypsin deficiency undergoes a lung transplant. She tolerates the surgery well, but 3 years later develops inflammation and fibrosis in her terminal bronchioles. Which of the following best describes the pathophysiology of this patient's deterioration?
- A. Proliferation of grafted immunocompetent T cells
- B. Staphylococcus aureus pneumonia
- C. Lymphocytic inflammation of the bronchiolar wall (Correct Answer)
- D. T-cell mediated vascular damage
- E. Cytotoxic T lymphocytes reacting against foreign MHCs
Hypersensitivity pneumonitis Explanation: ***Lymphocytic inflammation of the bronchiolar wall***
- The development of inflammation and fibrosis in the **terminal bronchioles** years after a lung transplant, despite initial success, is highly suggestive of **chronic rejection**, also known as **bronchiolitis obliterans syndrome (BOS)**.
- Chronic rejection in lung transplantation is primarily characterized by **lymphocytic inflammation** leading to fibrosis and obliteration of the small airways, consistent with the patient's presentation.
*Proliferation of grafted immunocompetent T cells*
- This mechanism describes **graft-versus-host disease (GVHD)**, which occurs when immunocompetent cells in the graft attack recipient tissues.
- While GVHD can occur in organ transplantation, it is more commonly associated with **hematopoietic stem cell transplantation** and typically presents with a broader range of systemic symptoms, not primarily localized bronchiolar inflammation and fibrosis.
*Staphylococcus aureus pneumonia*
- **Bacterial pneumonia** would typically present with acute symptoms such as fever, cough with purulent sputum, and acute infiltrates on imaging.
- While infections are a risk post-transplant, a subacute process leading to **fibrosis** over 3 years is less typical for a bacterial pneumonia, which tends to be more acute and responsive to antibiotics.
*T-cell mediated vascular damage*
- This mechanism is characteristic of **acute humoral rejection** (antibody-mediated rejection) or some forms of acute cellular rejection, which often target the **vasculature** of the graft.
- While vascular damage can occur, the primary pathology described by inflammation and fibrosis in the **bronchioles** specifically points more towards chronic rejection affecting the airways themselves rather than predominantly the blood vessels.
*Cytotoxic T lymphocytes reacting against foreign MHCs*
- This describes the fundamental mechanism for **acute cellular rejection** in transplantation, where recipient T cells recognize foreign **MHC molecules** on donor cells.
- Acute cellular rejection typically occurs earlier (within weeks to months) post-transplant and involves prominent lymphocytic infiltrates, but the primary long-term fibrotic obstructive pathology of the bronchioles (BOS) is specifically the chronic form of T-cell mediated injury.
Hypersensitivity pneumonitis US Medical PG Question 7: A 28-year-old man comes to his general practitioner for a regular checkup. He has had trouble breathing lately with coughing, shortness of breath, and wheezing. Problems first started when he went running (outside), but he is also observing the problems when taking a light walk or resting. As a child, he suffered from atopic dermatitis, just like his father and sister. He also has a history of hay fever. What is the most likely cause of his symptoms?
- A. Smoking
- B. Chronic obstructive pulmonary disease
- C. Type I hypersensitivity (Correct Answer)
- D. Type IV hypersensitivity
- E. Exercise
Hypersensitivity pneumonitis Explanation: ***Type I hypersensitivity***
- The patient's presentation with **coughing, shortness of breath, and wheezing** suggests **bronchial asthma**, which is a classic manifestation of **Type I hypersensitivity** (allergic reaction).
- The history of **atopic dermatitis** (eczema) and **hay fever** indicates an **atopic diathesis**, which is a strong predisposing factor for allergic asthma. This forms the **atopic triad**.
*Smoking*
- While smoking can cause respiratory symptoms like coughing and shortness of breath, it typically does not cause acute wheezing that improves with rest in a young, otherwise healthy individual.
- The patient's personal history of atopic dermatitis and hay fever, and running in the family does not suggest smoking.
*Chronic obstructive pulmonary disease*
- **COPD** usually develops in older individuals, often with a history of significant smoking or environmental exposure, and is characterized by **progressive, non-reversible airflow limitation**.
- The patient's young age and history of atopic conditions make COPD a less likely diagnosis compared to asthma.
*Type IV hypersensitivity*
- **Type IV hypersensitivity**, or **delayed-type hypersensitivity**, typically manifests as contact dermatitis (e.g., poison ivy) or granulomatous reactions, which are T-cell mediated and develop over 24-72 hours.
- It does not cause acute respiratory symptoms like wheezing, nor is it linked to atopic conditions such as hay fever and asthma.
*Exercise*
- Exercise can trigger **exercise-induced bronchoconstriction (asthma)**, which presents as shortness of breath and wheezing during or after physical activity.
- However, the patient also experiences symptoms during light walks or at rest, and has a strong atopic history, indicating that exercise is a trigger for underlying asthma (Type I hypersensitivity) rather than the sole cause of symptoms.
Hypersensitivity pneumonitis US Medical PG Question 8: A 3-year-old boy is brought to the emergency department by his mother because of a cough and mild shortness of breath for the past 12 hours. He has not had fever. He has been to the emergency department 4 times during the past 6 months for treatment of asthma exacerbations. His 9-month-old sister was treated for bronchiolitis a week ago. His father has allergic rhinitis. Current medications include an albuterol inhaler and a formoterol-fluticasone inhaler. He appears in mild distress. His temperature is 37.5°C (99.5°F), pulse is 101/min, respirations are 28/min, and blood pressure is 86/60 mm Hg. Examination shows mild intercostal and subcostal retractions. Pulmonary examination shows decreased breath sounds and mild expiratory wheezing throughout the right lung field. Cardiac examination shows no abnormalities. An x-ray of the chest shows hyperlucency of the right lung field with decreased pulmonary markings. Which of the following is the next best step in management?
- A. Azithromycin therapy
- B. Racemic epinephrine
- C. Albuterol nebulization
- D. CT of the lung
- E. Bronchoscopy (Correct Answer)
Hypersensitivity pneumonitis Explanation: ***Bronchoscopy***
- The patient's history of recurrent respiratory symptoms, unilateral wheezing and decreased breath sounds, and radiological findings of **unilateral hyperlucency** and **decreased pulmonary markings** strongly suggest a **foreign body aspiration**.
- **Bronchoscopy** is both diagnostic and therapeutic in this situation, allowing for direct visualization and removal of the foreign body.
*Azithromycin therapy*
- This is an **antibiotic** and would be used for bacterial infections, which are not indicated here given the clinical picture of a suspected foreign body.
- Antibiotics are not effective for mechanical obstruction of the airway.
*Racemic epinephrine*
- Racemic epinephrine is used for conditions like **croup** to reduce airway edema.
- It would not address an inhaled **foreign body**, which is a mechanical obstruction.
*Albuterol nebulization*
- While albuterol is used for bronchospasm, the unilateral nature of the findings and the history of recurrent issues point away from simple asthma exacerbation.
- Albuterol would likely not relieve the obstruction caused by a **foreign body**.
*CT of the lung*
- While CT could help identify a foreign body, it exposes the child to **radiation** and is not the definitive treatment.
- Bronchoscopy offers both diagnosis and immediate treatment, making it superior to CT as the *next best step*.
Hypersensitivity pneumonitis US Medical PG Question 9: A 70-year-old man comes to the physician because of intermittent shortness of breath while going up stairs and walking his dog. It began about 1 month ago and seems to be getting worse. He has also developed a dry cough. He has not had any wheezing, fevers, chills, recent weight loss, or shortness of breath at rest. He has a history of Hodgkin lymphoma, for which he was treated with chemotherapy and radiation to the chest 7 years ago. He also has hypertension, for which he takes lisinopril. Ten years ago, he retired from work in the shipbuilding industry. He has smoked half a pack of cigarettes daily since the age of 21. Vital signs are within normal limits. On lung auscultation, there are mild bibasilar crackles. A plain x-ray of the chest shows bilateral ground-glass opacities at the lung bases and bilateral calcified pleural plaques. Which of the following is the greatest risk factor for this patient's current condition?
- A. Family history
- B. Smoking
- C. Radiation therapy
- D. Occupational exposure (Correct Answer)
- E. Advanced age
Hypersensitivity pneumonitis Explanation: ***Occupational exposure***
- The patient's history of working in the **shipbuilding industry** and the presence of **calcified pleural plaques** strongly suggest **asbestosis**, a chronic lung disease caused by inhaling asbestos fibers.
- **Asbestosis** typically presents with **progressive shortness of breath** and a **dry cough**, along with bibasilar crackles and ground-glass opacities, consistent with the patient's symptoms and chest X-ray findings.
*Family history*
- While genetics can play a role in some interstitial lung diseases (e.g., familial pulmonary fibrosis), there is no specific family history mentioned that would strongly link it to the patient's present illness.
- The patient's presentation with **pleural plaques** points away from a primary genetic cause and towards environmental exposure.
*Smoking*
- Smoking is a risk factor for various lung conditions, including **emphysema** and **lung cancer**, and can exacerbate other lung diseases. However, the presence of **pleural plaques** is not caused by smoking.
- While smoking can worsen the prognosis of asbestos-related diseases, it is not the primary cause of the pleural plaques or the most likely underlying condition in this specific clinical picture.
*Radiation therapy*
- **Radiation pneumonitis** and **fibrosis** can occur following chest radiation, and the patient received radiation for Hodgkin lymphoma 7 years ago. However, the **calcified pleural plaques** are highly characteristic of asbestos exposure, not radiation.
- Radiation-induced lung changes are typically more localized to the irradiated field and would not specifically cause pleural plaques.
*Advanced age*
- While the incidence of many chronic diseases increases with age, age itself is not a specific risk factor for the characteristic findings of **calcified pleural plaques** and the described clinical picture.
- The presence of specific radiological findings (pleural plaques) strongly points to an environmental exposure rather than simply advanced age.
Hypersensitivity pneumonitis US Medical PG Question 10: A 14-year-old boy presents to an urgent care clinic complaining of a runny nose that has lasted for a few weeks. He also reports sneezing attacks that last up to an hour, nasal obstruction, and generalized itching. He has similar episodes each year during the springtime that prevent him from going out with his friends or trying out for sports. His younger brother has a history of asthma. Which of the following diseases has a similar pathophysiology?
- A. Irritant contact dermatitis
- B. Dermatitis herpetiformis
- C. Allergic contact dermatitis
- D. Atopic dermatitis (Correct Answer)
- E. Systemic lupus erythematosus
Hypersensitivity pneumonitis Explanation: ***Atopic dermatitis***
- This patient's symptoms are highly suggestive of **allergic rhinitis**, a **type I hypersensitivity reaction** mediated by IgE antibodies, which also underlies atopic dermatitis.
- The family history of asthma (part of the **atopic triad** – allergic rhinitis, asthma, atopic dermatitis) further supports a common underlying allergic predisposition.
*Irritant contact dermatitis*
- This is a **non-allergic inflammatory reaction** caused by direct skin irritation from chemical or physical agents, not an immunological hypersensitivity.
- It does not involve IgE-mediated mechanisms or a systemic allergic predisposition like the patient's condition.
*Dermatitis herpetiformis*
- This is a **chronic blistering skin condition** strongly associated with **celiac disease** and characterized by IgA deposition in the skin.
- It involves an autoimmune response to gluten and is not related to the IgE-mediated allergic response seen in allergic rhinitis.
*Allergic contact dermatitis*
- This is a **type IV delayed-type hypersensitivity reaction** mediated by T cells, often occurring days after exposure to an allergen (e.g., poison ivy, nickel).
- It is distinct from the immediate IgE-mediated (type I) hypersensitivity responsible for allergic rhinitis.
*Systemic lupus erythematosus*
- This is a **chronic autoimmune disease** characterized by systemic inflammation and autoantibody production against various self-antigens, leading to diverse organ involvement.
- It is a complex autoimmune disorder with different immunological mechanisms (e.g., type III hypersensitivity) rather than the IgE-mediated allergy seen in this case.
More Hypersensitivity pneumonitis US Medical PG questions available in the OnCourse app. Practice MCQs, flashcards, and get detailed explanations.
