Immunopathology Practice Questions

Q: A 25-year-old woman presents with a history of recurrent shortness of breath and severe wheezing. Laboratory studies demonstrate that she has a deficiency of C1 inhibitor, an esterase inhibitor that regulates the activation of the classical complement pathway. What is the diagnosis?

Hereditary angioedema. **Explanation:** **Hereditary Angioedema (HAE)** is the correct diagnosis. It is an autosomal dominant disorder caused by a deficiency or dysfunction of **C1 inhibitor (C1-INH)**. * **Mechanism:** C1-INH is a serine protease inhibitor that normally regulates the classical complement pathway by inhibiting C1. Crucially, it also inhibits the **kinin system** (specifically kallikrein and factor XII). * **Pathophysiology:** Without C1-INH, there is uncontrolled activation of the kinin system, leading to excessive production of **bradykinin**. Bradykinin increases vascular permeability, resulting in episodic, non-pitting edema of the skin, gastrointestinal tract (abdominal pain), and larynx (causing life-threatening airway obstruction/wheezing). **Why other options are incorrect:** * **Chronic Granulomatous Disease (A):** Caused by a defect in **NADPH oxidase**, leading to impaired respiratory burst and recurrent infections with catalase-positive organisms. * **Myeloperoxidase Deficiency (C):** A defect in the MPO-H2O2 system; patients are usually asymptomatic but may have increased susceptibility to *Candida* infections. * **Selective IgA Deficiency (D):** The most common primary immunodeficiency; characterized by recurrent sinopulmonary infections and risk of anaphylaxis during blood transfusions. **NEET-PG High-Yield Pearls:** * **Biochemical Marker:** Low levels of **C4** are a classic screening finding (due to continuous consumption by unregulated C1). * **Clinical Trigger:** Attacks are often precipitated by trauma, dental procedures, or stress. * **Treatment:** Acute attacks are treated with C1-INH concentrate or **Icatibant** (bradykinin B2 receptor antagonist). **Danazol** (androgen) is used for prophylaxis as it increases hepatic synthesis of C1-INH. * **Key Contraindication:** ACE inhibitors are contraindicated as they prevent bradykinin breakdown, worsening the edema.

Question 1

In Henoch-Schonlein purpura, which immunoglobulins and complement components are involved?

Accepted Answer

IgA, C3

Answer

IgG, C3

Answer

IgA, C1

Answer

IgG, C1

Question 2

Which of the following statements about macrophages is false?

Accepted Answer

Involved in Type III hypersensitivity

Answer

Derived from monocytes

Answer

Harbor Mycobacteria

Answer

Produce TNF and interleukins

Question 3

A boy presents with shortness of breath after being injected with penicillin, with no prior history of allergy. Examination 48 hours later reveals destruction of his RBCs, leading to a diagnosis of autoimmune hemolytic anemia (AIHA). What type of hypersensitivity reaction is responsible?

Accepted Answer

Type II

Answer

Type I

Answer

Type III

Answer

Type IV

Question 4

A 46-year-old man is on a waiting list to secure a renal transplant. What is the genetic locus of transplant antigens in humans known as?

Accepted Answer

Human leukocyte antigen (HLA)

Answer

Rhesus (Rh)

Answer

Immunoglobulin A and IgM

Answer

ABO

Question 5

Which of the following conditions is not related to immunity?

Accepted Answer

Diabetic nephropathy

Answer

Membranoproliferative glomerulonephritis (MPGN)

Answer

Post-streptococcal glomerulonephritis (PSGN)

Answer

IgA nephropathy

Question 6

A 25-year-old woman presents with a history of recurrent shortness of breath and severe wheezing. Laboratory studies demonstrate that she has a deficiency of C1 inhibitor, an esterase inhibitor that regulates the activation of the classical complement pathway. What is the diagnosis?

Accepted Answer

Hereditary angioedema

Answer

Chronic granulomatous disease

Answer

Myeloperoxidase deficiency

Answer

Selective IgA deficiency

Question 7

Which of the following statements is not true regarding NETosis?

Accepted Answer

Chromatin condensation

Answer

Causes death of neutrophils

Answer

Detected in blood in patients with sepsis

Answer

Plays a role in the pathogenesis of SLE

Question 8

All of the following statements regarding mast cells are true except?

Accepted Answer

Disodium cromoglycate inhibits their degranulation.

Answer

They contain heparin proteoglycan.

Answer

Their number is increased in patients with bronchial asthma.

Answer

They possess receptors for the Fc portion of IgE.

Question 9

DiGeorge syndrome is characterized by which of the following?

Accepted Answer

Thymic aplasia

Answer

Thyroid aplasia

Answer

Lymph node aplasia

Answer

Bone marrow aplasia

Question 10

Macrophage activation syndrome is characterized by all of the following except which one?

Accepted Answer

Hypoferritinemia

Answer

Hemophagocytosis

Answer

Hypofibrinogenemia

Answer

Hyperglycidemia

Immunopathology — MCQs

Immunopathology — MCQs

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