Immunopathology Practice Questions

Q: All of the following statements are true about Wiskott-Aldrich syndrome, except:

Autosomal recessive disorder. **Explanation:** Wiskott-Aldrich Syndrome (WAS) is a rare immunodeficiency characterized by the triad of **thrombocytopenia, eczema, and recurrent infections** [1]. **Why Option A is the correct answer (The Exception):** Wiskott-Aldrich Syndrome is an **X-linked recessive** disorder [1], not autosomal recessive. It is caused by a mutation in the *WAS* gene located on the short arm of the X chromosome (Xp11.23) [1]. This gene encodes the Wiskott-Aldrich Syndrome Protein (WASP), which is essential for actin cytoskeleton remodeling in hematopoietic cells. **Analysis of other options:** * **Option B (Low IgM):** Patients typically show a characteristic "inverted" immunoglobulin pattern: **Low IgM**, normal to high IgG, and **elevated IgA and IgE** levels [1]. * **Option C (Thrombocytopenia):** This is a hallmark feature. Patients present with micro-thrombocytopenia (small platelets) and are at high risk for mucosal bleeding and intracranial hemorrhage. * **Option D (Eczema):** Severe atopic dermatitis (eczema) is a classic component of the clinical triad, usually appearing in early infancy. **High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic (TIE):** **T**hrombocytopenia, **I**mmunodeficiency, **E**czema. * **Cellular Defect:** Impaired formation of the **immunological synapse** and defective migration of white blood cells [1]. * **Complications:** Increased risk for **B-cell lymphomas** [1] and autoimmune hemolytic anemia. * **Treatment:** Hematopoietic stem cell transplant (HSCT) is the definitive treatment [1]. * **Laboratory finding:** Small-sized platelets on peripheral smear (unique to WAS). **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 250-251.

Q: Which of the following diseases is characterized by the features presented?

Systemic Lupus Erythematosus (SLE). ***Systemic Lupus Erythematosus (SLE)*** - **Wire-loop lesions** on renal biopsy are pathognomonic of **lupus nephritis**, specifically seen in Class IV diffuse endocapillary/extracapillary proliferative glomerulonephritis - The characteristic **subendothelial immune complex deposits** create the distinctive wire-loop appearance under light microscopy, indicating active **Type III hypersensitivity** reaction *Rheumatoid Arthritis (RA)* - Primarily affects **synovial joints** with pannus formation, not typically associated with glomerular wire-loop lesions - Renal involvement in RA is usually secondary to **drug toxicity** (NSAIDs, DMARDs) rather than immune complex nephritis *Autoimmune hepatitis* - Characterized by **hepatocellular necrosis** and **portal inflammation** with plasma cell infiltration in liver tissue - Does not cause **glomerular pathology** or wire-loop lesions, as it primarily targets hepatocytes *Human Immunodeficiency Virus (HIV)* - Associated with **HIV-associated nephropathy (HIVAN)** showing collapsing focal segmental glomerulosclerosis, not wire-loop lesions - Causes **immunosuppression** rather than autoimmune complex-mediated glomerular damage typical of SLE

Q: Leukocyte adhesion deficiency type 1 is associated with which chromosome?

21. **Explanation:** **Leukocyte Adhesion Deficiency Type 1 (LAD-1)** is an autosomal recessive disorder characterized by a defect in the process of leukocyte migration. 1. **Why Option C is Correct:** LAD-1 is caused by a mutation in the **ITGB2 gene**, which is located on **Chromosome 21 (21q22.3)**. This gene encodes the **CD18** protein, which is the common $\beta_2$-integrin subunit. CD18 normally pairs with various $\alpha$-subunits (CD11a, CD11b, CD11c) to form functional integrins (like LFA-1 and Mac-1) on the surface of leukocytes. Without CD18, leukocytes cannot adhere firmly to the vascular endothelium, preventing them from migrating into tissues to fight infection. 2. **Why Other Options are Incorrect:** * **Option A (Chr 1):** While many genes are on Chromosome 1, it is not the locus for the ITGB2 gene. * **Option B (Chr 5):** Chromosome 5 is associated with conditions like Cri-du-chat syndrome or Familial Adenomatous Polyposis (APC gene), not LAD-1. * **Option D (Chr X):** LAD-1 is autosomal recessive, not X-linked. However, Chronic Granulomatous Disease (CGD) is frequently X-linked. **High-Yield Clinical Pearls for NEET-PG:** * **Classic Triad:** Delayed separation of the umbilical cord (>30 days), recurrent bacterial infections (skin/mucosa), and **absent pus formation** at infection sites. * **Laboratory Finding:** Marked **neutrophilia** (leukocytosis) even during health, because neutrophils cannot exit the bloodstream into the tissues. * **LAD Type 2:** Defect in **Sialyl-Lewis X** (ligand for selectins) due to a mutation in the GDP-fucose transporter (Chromosome 11). * **Diagnosis:** Flow cytometry showing decreased expression of **CD11/CD18** on leukocytes.

Question 1

All of the following statements are true about Wiskott-Aldrich syndrome, except:

Accepted Answer

Autosomal recessive disorder

Answer

Low serum IgM level

Answer

Thrombocytopenia

Answer

Eczema

Question 2

Which of the following diseases is characterized by the features presented?

Accepted Answer

Systemic Lupus Erythematosus (SLE)

Answer

Rheumatoid Arthritis (RA)

Answer

Autoimmune hepatitis

Answer

Human Immunodeficiency Virus (HIV)

Question 3

Which type of collagen is primarily affected in Goodpasture syndrome?

Accepted Answer

Type IV

Answer

Type I

Answer

Type II

Answer

Type III

Question 4

Leukocyte adhesion deficiency type 1 is associated with which chromosome?

Accepted Answer

21

Answer

1

Answer

5

Answer

X

Question 5

A 45-year-old woman with autoimmune hemolytic anemia presents with increasing fatigue. Which of the following mediators of inflammation is primarily responsible for antibody-mediated hemolysis in this patient?

Accepted Answer

Complement proteins

Answer

Arachidonic acid metabolites

Answer

Coagulation proteins

Answer

Kallikrein and kinins

Question 6

DiGeorge's syndrome is due to which of the following?

Accepted Answer

Congenital thymic aplasia

Answer

Deficiency of complement factors

Answer

Inborn error of metabolism

Answer

Chromosomal anomaly

Question 7

Which of the following conditions is an example of Type II hypersensitivity?

Accepted Answer

Pernicious anaemia

Answer

Serum sickness

Answer

Arthus phenomenon

Answer

Pathergy phenomenon

Question 8

A patient with recurrent bacterial infections is diagnosed to have a genetic deficiency in myeloperoxidase. What is the cause of this increased susceptibility to infections?

Accepted Answer

An inability to produce hydroxyhalide radicals

Answer

Defective neutrophil degranulation

Answer

Defective production of prostaglandins

Answer

Decreased oxygen consumption after phagocytosis

Question 9

Which of the following hypersensitivity types cannot be detected by a skin test?

Accepted Answer

Type 2

Answer

Type 1

Answer

Type 3

Answer

Type 4

Question 10

A 42-year-old man develops urticaria, stridor, and hypotension during a blood transfusion, requiring IV epinephrine. He has a history of frequent sinusitis and bronchitis. Which is the most likely immunologic deficiency?

Accepted Answer

Immunoglobulin A deficiency

Answer

Wiskott-Aldrich syndrome

Answer

Ataxia telangiectasia

Answer

DiGeorge syndrome

Immunopathology — MCQs

Immunopathology — MCQs

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