Immunopathology Practice Questions

Q: A 3-year-old child presented with fatigue, malaise, fever, sore throat, headache, nausea, abdominal pain, and myalgia. On examination, generalized lymphadenopathy, hepatosplenomegaly, tonsillar enlargement, palatal petechiae, rashes, and edema of the eyelids were noted. In which of the following conditions would this presentation NOT occur?

X-linked agammaglobulinemia. **Explanation:** The clinical presentation described—fever, sore throat, generalized lymphadenopathy, hepatosplenomegaly, tonsillar enlargement, and palatal petechiae—is classic for **Infectious Mononucleosis (IM)**, most commonly caused by the **Epstein-Barr Virus (EBV)**. **Why X-linked Agammaglobulinemia (XLA) is the correct answer:** EBV specifically infects **B-lymphocytes** by binding to the **CD21 receptor**. In X-linked Agammaglobulinemia (Bruton’s), there is a mutation in the *BTK* gene, leading to a failure of B-cell maturation. Consequently, patients with XLA have a near-total **absence of circulating B-cells**. Since the host cells required for EBV infection and replication are missing, these patients do not manifest the typical clinical syndrome of Infectious Mononucleosis. **Analysis of Incorrect Options:** * **Multiple Myeloma:** While a plasma cell dyscrasia, these patients still possess B-lymphocytes that can be infected by EBV. * **DiGeorge Syndrome:** This is a T-cell deficiency (thymic hypoplasia). Since B-cell numbers are generally preserved, EBV can infect the B-cells and produce the described clinical features. * **Wiskott-Aldrich Syndrome:** This is a combined immunodeficiency affecting both T and B cells, but B-cells are present; therefore, the clinical manifestation of IM can occur. **High-Yield Clinical Pearls for NEET-PG:** * **EBV Triad:** Fever, Pharyngitis, and Lymphadenopathy (typically posterior cervical). * **Hoagland Sign:** Early transient bilateral upper eyelid edema (seen in ~10-15% of IM cases). * **Diagnostic Test:** Monospot test (Heterophile antibodies) or atypical lymphocytosis (Downey cells) on peripheral smear. * **Warning:** Administration of Ampicillin/Amoxicillin in a patient with IM often results in a characteristic maculopapular rash.

Q: Which of the following immunoglobulins is absent in Ataxia telangiectasia?

IgA. ### Explanation **Ataxia-Telangiectasia (AT)** is an autosomal recessive multisystem disorder caused by a mutation in the **ATM (Ataxia-Telangiectasia Mutated) gene** on chromosome 11 [1]. This gene is responsible for repairing double-stranded DNA breaks. #### Why IgA is the Correct Answer: The hallmark of AT is a combined immunodeficiency affecting both humoral and cellular immunity. The most characteristic laboratory finding is a **selective deficiency of IgA**, which occurs in approximately 70% of patients [1]. This occurs because the defective DNA repair mechanism impairs **class-switch recombination**, the process required to switch from IgM to other isotypes like IgA or IgE. #### Analysis of Incorrect Options: * **IgG:** While some subclasses of IgG (like IgG2) may be decreased, total IgG is usually normal or only mildly reduced compared to the profound absence of IgA. * **IgM:** IgM levels are typically **normal or elevated**. Since IgM is the first antibody produced and does not require class-switching, it remains unaffected by the ATM mutation. * **IgD:** IgD deficiency is not a clinical feature of AT and does not carry diagnostic significance for this condition. #### High-Yield Clinical Pearls for NEET-PG: * **Clinical Triad:** 1. Progressive cerebellar **ataxia** (early childhood), 2. Oculocutaneous **telangiectasia** (conjunctival "bloodshot" eyes), 3. Recurrent sinopulmonary infections [1]. * **Diagnostic Marker:** Elevated **Alpha-fetoprotein (AFP)** levels after age 2 are highly suggestive of AT. * **Malignancy Risk:** Patients have a 100x higher risk of developing lymphomas and leukemias due to genomic instability [1]. * **Radiosensitivity:** Patients are hypersensitive to **ionizing radiation** (X-rays/CT scans), which causes catastrophic DNA damage. **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: A patch test is what type of hypersensitivity?

Type 4. **Explanation:** The correct answer is **Type 4 Hypersensitivity**, also known as **Delayed-Type Hypersensitivity (DTH)**. **Why Type 4 is correct:** A patch test is the gold standard for diagnosing **Allergic Contact Dermatitis** (e.g., sensitivity to nickel, poison ivy, or cosmetics). Unlike other hypersensitivities, Type 4 is **cell-mediated**, involving T-lymphocytes (specifically Th1 cells and CD8+ T-cells) rather than antibodies. When an allergen is applied to the skin via a patch, sensitized T-cells take **48 to 72 hours** to migrate to the site and release cytokines, causing a localized inflammatory response (induration and erythema). This delay in reaction is why it is termed "delayed." **Why other options are incorrect:** * **Type 1 (Immediate):** Mediated by **IgE antibodies** and mast cell degranulation (e.g., Anaphylaxis, Asthma). Reactions occur within minutes. The diagnostic test for this is the **Skin Prick Test**, not the Patch Test. * **Type 2 (Cytotoxic):** Mediated by **IgG or IgM** antibodies directed against antigens on cell surfaces (e.g., Rheumatic fever, Goodpasture syndrome). * **Type 3 (Immune-Complex):** Caused by the deposition of **antigen-antibody complexes** in tissues (e.g., SLE, Serum sickness, Arthus reaction). **High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic for Hypersensitivity (Gell & Coombs):** **ACID** (Type 1: **A**llergic/Anaphylactic; Type 2: **C**ytotoxic; Type 3: **I**mmune-complex; Type 4: **D**elayed). * **Other Type 4 examples:** Mantoux (Tuberculin) test, Lepromin test, Graft rejection, and Granuloma formation (Sarcoidosis, TB). * **Key Cells:** Type 4 is the only hypersensitivity that **does not involve antibodies**. It is mediated by T-cells and Macrophages.

Question 1

Onion skin spleen is seen in which of the following conditions?

Accepted Answer

Systemic Lupus Erythematosus (SLE)

Answer

Sjogren's syndrome

Answer

Thrombotic thrombocytopenic purpura

Answer

Henoch Schonlein purpura

Question 2

NADPH oxidase deficiency causes impaired immunity. Which of the following processes is affected?

Accepted Answer

Chronic granulomatous disease

Answer

Chediak-Higashi syndrome

Answer

Leukocyte adhesion defect type 1

Answer

Leukocyte adhesion defect type 2

Question 3

A 3-year-old child presented with fatigue, malaise, fever, sore throat, headache, nausea, abdominal pain, and myalgia. On examination, generalized lymphadenopathy, hepatosplenomegaly, tonsillar enlargement, palatal petechiae, rashes, and edema of the eyelids were noted. In which of the following conditions would this presentation NOT occur?

Accepted Answer

X-linked agammaglobulinemia

Answer

Multiple myeloma

Answer

DiGeorge syndrome

Answer

Wiskott-aldrich syndrome

Question 4

Which of the following immunoglobulins is absent in Ataxia telangiectasia?

Accepted Answer

IgA

Answer

IgG

Answer

IgM

Answer

IgD

Question 5

A patch test is what type of hypersensitivity?

Accepted Answer

Type 4

Answer

Type 1

Answer

Type 2

Answer

Type 3

Question 6

A 1-year-old child presents with cyanosis during breastfeeding, which resolves upon squatting. A cleft palate is noted on examination, and laboratory tests reveal hypocalcemia. Which of the following abnormalities are expected to be seen in the lymphoid organs?

Accepted Answer

Decreased size of the periaeriolar lymphoid sheath of the spleen

Answer

Increased size of splenic follicles

Answer

Increased size of paracortical areas of lymph nodes

Answer

Decreased size of germinal centers of lymph nodes

Question 7

A 23-year-old woman develops a skin rash after prolonged sun exposure and has a malar rash on physical examination. Laboratory studies show a positive ANA test result with a titer of 1:1024 and a "rim" pattern, along with a positive anti-double-stranded DNA test. Her hemoglobin is 12.1 g/dL, hematocrit is 35.5%, MCV is 89 mm
3, platelet count is 109,000/mm
3, and WBC count is 4500/mm
3. Which of the following findings is most likely to be shown by a WBC differential count?

Accepted Answer

Monocytosis

Answer

Basophilia

Answer

Eosinophilia

Answer

Neutrophilia

Question 8

Serum sickness is which type of hypersensitivity reaction?

Accepted Answer

Type III

Answer

Type I

Answer

Type II

Answer

Type IV

Question 9

Lymph node biopsy of an AIDS patient shows what finding?

Accepted Answer

All of the above

Answer

Wahin-Finkeldey cells

Answer

Marked follicular hyperplasia

Answer

'Moth-eaten appearance'

Question 10

What is the most common cause of death in primary amyloidosis?

Accepted Answer

Cardiac failure

Answer

Respiratory failure

Answer

Renal failure

Answer

Septicemia

Immunopathology — MCQs

Immunopathology — MCQs

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