General Pathology Practice Questions

Q: Which of the following is NOT an inherited coagulation disorder?

Lupus anticoagulant. **Explanation:** The distinction between inherited and acquired thrombophilias is a high-yield topic in NEET-PG. **1. Why Lupus Anticoagulant is the correct answer:** **Lupus Anticoagulant (LA)** is an **acquired** autoimmune condition [1]. It is a type of antiphospholipid antibody (aPL) found in Antiphospholipid Antibody Syndrome (APS). Despite its name, it is a pro-thrombotic agent *in vivo*, leading to venous and arterial thrombosis, though it paradoxically prolongs the Activated Partial Thromboplastin Time (aPTT) *in vitro* [1]. **2. Why the other options are incorrect:** * **Factor V Leiden Mutation (Option C):** This is the **most common inherited cause** of hypercoagulability [1]. It involves a point mutation (G1691A) in the Factor V gene, making Factor V resistant to cleavage by activated Protein C (APC resistance) [1]. * **Protein C and S Deficiencies (Options A & B):** These are **autosomal dominant** inherited disorders. Protein C and S are natural anticoagulants (Vitamin K dependent) [2]. Their deficiency leads to an inability to inactivate Factors Va and VIIIa, resulting in a hypercoagulable state. **Clinical Pearls for NEET-PG:** * **Most common inherited thrombophilia:** Factor V Leiden [1]. * **Most common acquired thrombophilia:** Antiphospholipid Antibody Syndrome (APS) [1]. * **Warfarin-induced skin necrosis:** Classically seen in patients with **Protein C deficiency** when starting Warfarin without heparin bridging. * **Mixing Study:** Used to differentiate LA from factor deficiencies; LA will **not** correct upon mixing with normal plasma. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Hemodynamic Disorders, Thromboembolic Disease, and Shock, pp. 133-135. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Blood And Bone Marrow Disease, pp. 624-625.

Q: Two siblings have osteogenesis imperfecta, but their parents are normal. What is the mechanism of inheritance?

Germline mosaicism. **Explanation:** The correct answer is **Germline Mosaicism** (also known as Gonadal Mosaicism). **Why it is correct:** In this scenario, the parents are phenotypically normal (they do not carry the mutation in their somatic cells), yet they have **two** children with an autosomal dominant condition (Osteogenesis Imperfecta). If it were a simple "new mutation," it would be highly improbable for it to occur twice in the same family. Germline mosaicism occurs when a mutation happens post-zygotically during the parent's embryonic development, affecting only a subset of germ cells (sperm or eggs) but not the somatic cells [1]. Thus, the parent is healthy but can pass the mutation to multiple offspring. **Why other options are incorrect:** * **Anticipation:** Refers to the increasing severity or earlier onset of a disease in successive generations, typically seen in trinucleotide repeat disorders (e.g., Huntington’s, Fragile X). * **Genomic Imprinting:** Involves differential expression of a gene depending on whether it is inherited from the mother or father (e.g., Prader-Willi and Angelman syndromes). * **New Mutation (De novo):** While Osteogenesis Imperfecta often results from new mutations, a single new mutation cannot explain why **two** siblings are affected if the parents are normal. **NEET-PG High-Yield Pearls:** * **Classic Example:** Germline mosaicism is the most common explanation when healthy parents have multiple children with **Osteogenesis Imperfecta** or **Duchenne Muscular Dystrophy (DMD)**. * **Recurrence Risk:** In germline mosaicism, the recurrence risk for siblings is significantly higher than the general population risk, despite normal parental testing. * **Definition:** Presence of two or more genetically different cell lines in the gonads [1]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Genetic Disorders, pp. 170-171.

Q: Which of the following conditions is not primarily caused by a genetic mutation?

Diabetes mellitus type II. The core concept tested here is the distinction between **monogenic (Mendelian) disorders** and **multifactorial (polygenic) diseases**. [1] **Why Diabetes Mellitus Type II (DM-II) is the correct answer:** DM-II is a **multifactorial disease**. While it has a strong genetic predisposition (often stronger than Type I), it is not caused by a single primary mutation. Instead, it results from a complex interplay between **polygenic susceptibility** (multiple gene variants) and **environmental triggers** such as obesity, sedentary lifestyle, and aging. [1] It does not follow a classic Mendelian inheritance pattern. **Why the other options are incorrect:** * **Cystic Fibrosis:** A classic **Autosomal Recessive** disorder caused by mutations in the *CFTR* gene on chromosome 7. [2] * **Hemophilia:** An **X-linked Recessive** bleeding disorder caused by mutations in genes encoding Factor VIII (Hemophilia A) or Factor IX (Hemophilia B). * **Alpha-1 Antitrypsin Deficiency:** An **Autosomal Codominant** disorder caused by mutations in the *SERPINA1* gene, leading to emphysema and liver cirrhosis. **NEET-PG High-Yield Pearls:** * **Strongest Genetic Link:** Between DM-I and DM-II, **DM-II** has a higher concordance rate in monozygotic twins (up to 90%). * **MODY (Maturity Onset Diabetes of the Young):** Unlike DM-II, MODY is **monogenic** (Autosomal Dominant). The most common type is **MODY 3** (*HNF1-alpha* mutation). * **Polygenic vs. Monogenic:** Most common chronic diseases (HTN, DM-II, CAD) are polygenic, whereas rare "textbook" diseases are usually monogenic. [1]

Q: Cystic fibrosis affects all systems EXCEPT:

Endocrine. **Explanation:** Cystic Fibrosis (CF) is an autosomal recessive disorder caused by mutations in the **CFTR gene**, which encodes a chloride channel [1]. This defect leads to the production of thick, viscid secretions in **exocrine glands**. **Why "Endocrine" is the correct answer:** The primary pathology of CF involves **exocrine dysfunction**. While CF frequently leads to "Cystic Fibrosis-Related Diabetes" (CFRD), this occurs because the thick secretions obstruct the pancreatic ducts, leading to secondary scarring and destruction of the islet cells (an **exocrine-driven** destruction of endocrine tissue). The endocrine system as a whole (pituitary, thyroid, adrenal) is not primarily affected by CFTR mutations. **Analysis of Incorrect Options:** * **Respiratory:** This is the most common cause of morbidity [2]. Thick mucus leads to bronchiectasis, recurrent infections (notably *Pseudomonas*), and nasal polyps [1]. * **Hepatobiliary:** Obstruction of bile ductules leads to focal biliary cirrhosis, neonatal cholestasis, and gallstones. * **Genitourinary:** Over 95% of males are infertile due to **Congenital Bilateral Absence of the Vas Deferens (CBAVD)** [1]. In females, thick cervical mucus can reduce fertility. **High-Yield Clinical Pearls for NEET-PG:** * **Gold Standard Diagnosis:** Sweat Chloride Test (>60 mEq/L). * **Most Common Mutation:** ΔF508 (Class II mutation - protein misfolding). * **Pancreatic Status:** 85-90% of patients have pancreatic exocrine insufficiency (malabsorption/steat同年rhea). * **GI Complication:** Meconium ileus is a classic presenting sign in neonates. * **Microbiology:** *Staphylococcus aureus* is common in early childhood; *Pseudomonas aeruginosa* is the dominant pathogen in adults.

Q: Which intermediate filament is characteristic of fibroblasts?

Vimentin. **Explanation:** Intermediate filaments (IFs) are crucial components of the cytoskeleton that provide mechanical strength to cells. They are highly tissue-specific, making them excellent immunohistochemical (IHC) markers in diagnostic pathology. **Why Vimentin is correct:** **Vimentin** is the characteristic intermediate filament of **mesenchymal cells**. Since fibroblasts are the prototypical cells of mesenchymal origin (connective tissue), they express vimentin. In tumor pathology, Vimentin is used as a primary marker for **sarcomas** (malignancies of mesenchymal origin). **Analysis of Incorrect Options:** * **Lamin A:** These are nuclear intermediate filaments found in the **nuclear lamina** (inner lining of the nuclear envelope) of most differentiated somatic cells, not specific to the cytoplasmic cytoskeleton of fibroblasts. * **Desmin:** This is the marker for **muscle cells** (skeletal, cardiac, and smooth muscle). It is used clinically to identify tumors like rhabdomyosarcomas or leiomyosarcomas. * **Cytokeratin:** This is the characteristic marker for **epithelial cells**. It is the primary IHC marker used to diagnose **carcinomas**. **NEET-PG High-Yield Pearls:** * **Vimentin** is also positive in Melanoma, Renal Cell Carcinoma (RCC), and Endometrial Carcinoma (exceptions where epithelial tumors show vimentin). * **Glial Fibrillary Acidic Protein (GFAP):** Marker for astrocytes and ependymal cells (Glial tumors/Gliomas). * **Neurofilaments:** Marker for neurons and neural tumors (e.g., Neuroblastoma). * **Synaptophysin/Chromogranin:** Markers for neuroendocrine tumors.

Question 1

All of the following are true of red infarction, except?

Accepted Answer

Occurs in end arterial occlusion

Answer

Occurs with venous occlusion

Answer

Seen in loose tissues

Answer

Occurs in previously congested tissue

Question 2

Which of the following is NOT an inherited coagulation disorder?

Accepted Answer

Lupus anticoagulant

Answer

Protein C deficiency

Answer

Protein S deficiency

Answer

Factor V Leiden mutation

Question 3

Two siblings have osteogenesis imperfecta, but their parents are normal. What is the mechanism of inheritance?

Accepted Answer

Germline mosaicism

Answer

Anticipation

Answer

Genomic imprinting

Answer

New mutation

Question 4

All endothelial cells produce thrombomodulin except those found in which of the following circulations?

Accepted Answer

Cerebral microcirculation

Answer

Hepatic circulation

Answer

Cutaneous circulation

Answer

Renal circulation

Question 5

Which of the following conditions is not primarily caused by a genetic mutation?

Accepted Answer

Diabetes mellitus type II

Answer

Cystic fibrosis

Answer

Hemophilia

Answer

Alpha 1 antitrypsin deficiency

Question 6

Which of the following is not typically seen in cystic fibrosis?

Accepted Answer

Limb anomalies

Answer

Meconium ileus

Answer

Female infertility

Answer

Lung infection

Question 7

Cystic fibrosis affects all systems EXCEPT:

Accepted Answer

Endocrine

Answer

Respiratory

Answer

Hepatobiliary

Answer

Genitourinary

Question 8

On sectioning of an organ at autopsy, a focal, wedge-shaped firm area is seen accompanied by extensive hemorrhage and a red appearance. The lesion has a base on the surface of the organ. This finding is typically of:

Accepted Answer

Lung with pulmonary thromboembolism

Answer

Liver with hypovolemic shock

Answer

Heart with coronary thrombosis

Answer

Kidney with septic embolus

Question 9

Edema is caused by all of the following mechanisms, EXCEPT:

Accepted Answer

Increased plasma proteins

Answer

Increased vascular permeability

Answer

Obstruction to lymphatic flow

Answer

Sodium retention

Question 10

Which intermediate filament is characteristic of fibroblasts?

Accepted Answer

Vimentin

Answer

Lamin A

Answer

Desmin

Answer

Cytokeratin

General Pathology — MCQs

General Pathology — MCQs

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