Hematopathology Practice Questions

Q: What is the most common site of histiocytosis?

Bone. **Explanation:** **Langerhans Cell Histiocytosis (LCH)**, formerly known as Histiocytosis X, is a proliferative disorder of dendritic cells (Langerhans cells) [1]. **1. Why Bone is the Correct Answer:** Bone is the most frequently involved organ in LCH, occurring in approximately **80% of cases**. It typically presents as a **solitary osteolytic lesion** (Eosinophilic Granuloma), most commonly involving the **skull**, followed by the femur, ribs, and mandible. In pediatric populations, it is a classic cause of a "punched-out" radiolucent lesion on a skull X-ray. **2. Why Other Options are Incorrect:** * **B. Skin:** This is the second most common site (approx. 30-40%). It often presents as a seborrheic dermatitis-like rash, especially in the Letterer-Siwe disease variant. * **C. Lung:** While common in adult smokers (Pulmonary LCH), it is less frequent than bone involvement across the general disease spectrum. * **D. Liver:** Involvement of the liver, spleen, or bone marrow indicates "high-risk" multisystem disease (Letterer-Siwe) but is statistically less common than skeletal involvement. **3. NEET-PG High-Yield Pearls:** * **Pathognomonic Marker:** **Birbeck Granules** (tennis-racket shaped pentalaminar structures) seen on Electron Microscopy [1]. * **Immunohistochemistry (IHC):** Positive for **CD1a**, **S100**, and **Langerin (CD207)** [1]. Langerin is the most specific marker. * **Clinical Triad (Hand-Schüller-Christian disease):** Calvarial bone defects, Exophthalmos, and Diabetes Insipidus. * **Mutation:** Frequently associated with the **BRAF V600E** mutation (approx. 50% of cases) [1]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of White Blood Cells, Lymph Nodes, Spleen, and Thymus, pp. 629-630.

Q: Which coagulation pathway(s) does the Prothrombin Time (PT) test evaluate?

Extrinsic and common pathway. **Explanation:** The **Prothrombin Time (PT)** test measures the time it takes for plasma to clot after the addition of Tissue Factor (Factor III) and Calcium [1]. It is the primary screening test for the **Extrinsic and Common pathways** of the coagulation cascade [1]. 1. **Why Option A is correct:** The PT test specifically monitors the activity of **Factor VII** (Extrinsic pathway) and the shared factors of the **Common pathway: Factors X, V, II (Prothrombin), and I (Fibrinogen).** Because Factor VII has the shortest half-life of all clotting factors, PT is highly sensitive to early vitamin K deficiency and liver dysfunction. 2. **Why Options B and C are incorrect:** The **Intrinsic pathway** (Factors XII, XI, IX, VIII) is evaluated by the **Activated Partial Thromboplastin Time (aPTT)** test, not PT [1]. 3. **Why Option D is incorrect:** While PT does evaluate the extrinsic pathway, it cannot function without the common pathway. A deficiency in Factor X, V, or II will also result in a prolonged PT; therefore, the test encompasses both. **High-Yield Clinical Pearls for NEET-PG:** * **Warfarin Monitoring:** PT (reported as **INR**) is used to monitor Warfarin therapy because Warfarin inhibits Vitamin K-dependent factors (II, VII, IX, X), and Factor VII is the first to decline. * **Liver Disease:** PT is one of the best indicators of the liver's synthetic function. * **Mnemonic for PT vs. aPTT:** * **PeT** (3 letters) = Extrinsic pathway (shorter name). * **PiiTT** (4 letters) = Intrinsic pathway (longer name). * **Mixing Study:** If PT is prolonged, a mixing study is performed. If it corrects, it indicates a factor deficiency; if it doesn't, it indicates the presence of an inhibitor (e.g., Lupus anticoagulant). **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Hemodynamic Disorders, Thromboembolic Disease, and Shock, pp. 128-130.

Q: Which of the following is false regarding Chediak-Higashi syndrome?

It is inherited in an autosomal dominant pattern.. **Explanation:** **Chediak-Higashi Syndrome (CHS)** is a rare, multisystem disorder caused by a mutation in the **LYST gene** (Lysosomal Trafficking Regulator). 1. **Why Option A is the correct answer (False statement):** Chediak-Higashi syndrome is inherited in an **autosomal recessive** pattern, not autosomal dominant [1]. The mutation leads to defective vesicle fusion and intracellular protein trafficking, resulting in the formation of pathognomonic **giant granules** in various cells [1]. 2. **Why the other options are true:** * **Option B:** The primary cellular defect is the failure of **phagosome-lysosome fusion** [1]. This prevents the effective killing of phagocytosed bacteria, leading to recurrent pyogenic infections (primarily by *Staphylococcus* and *Streptococcus*). * **Option C:** Melanocytes are affected because **melanosomes** (specialized lysosomes) fail to distribute melanin properly [1]. This results in **oculocutaneous albinism**, a hallmark clinical feature. * **Option D:** Platelets contain "dense bodies" (delta granules) which are lysosome-like organelles. Defective trafficking leads to a **storage pool deficiency**, resulting in platelet dysfunction and bleeding tendencies [1]. **NEET-PG High-Yield Pearls:** * **Peripheral Smear:** Look for **giant peroxidase-positive granules** in neutrophils and precursors [1]. * **Clinical Tetrad:** Partial albinism, recurrent infections, peripheral neuropathy, and mild bleeding [1]. * **Accelerated Phase:** A life-threatening "lymphoma-like" syndrome characterized by hemophagocytic lymphohistiocytosis (HLH), hepatosplenomegaly, and pancytopenia. * **Diagnosis:** Confirmed by genetic testing (LYST gene) or seeing giant granules on a blood film [1]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 245-246.

Question 1

Which of the following is an example of a chronic myeloproliferative disorder?

Accepted Answer

Essential thrombocythaemia

Answer

Neutrophilic leukaemoid reaction

Answer

Plasmacytosis

Answer

Hairy cell leukaemia

Question 2

Routine Rh typing includes testing for which antigen?

Accepted Answer

D antigen

Answer

A antigen

Answer

B antigen

Answer

C antigen

Question 3

Which is the diagnostic test for Disseminated Intravascular coagulation?

Accepted Answer

D-Dimer assay

Answer

Prothrombin Time (PT)

Answer

Activated Partial Thromboplastin Time (APTT)

Answer

Bleeding Time (BT)

Question 4

What is the most common site of histiocytosis?

Accepted Answer

Bone

Answer

Skin

Answer

Lung

Answer

Liver

Question 5

Differential diagnosis for pancytopenia with cellular bone marrow includes the following except?

Accepted Answer

Congenital dyserythropoietic anemia

Answer

Megaloblastic anemia

Answer

Myelodysplasia

Answer

Paroxysmal Nocturnal Hemoglobinuria

Question 6

Bence Jones proteins are:

Accepted Answer

Light chains

Answer

Heavy chains

Answer

Heavy and light chains

Answer

Immunoglobulins

Question 7

In Acute Myeloid Leukemia (AML), which subtype is associated with the best prognosis?

Accepted Answer

Acute promyelocytic leukemia (M3)

Answer

Acute megakaryocytic leukemia

Answer

Acute monocytic leukemia

Answer

Erythroleukemia

Question 8

Which coagulation pathway(s) does the Prothrombin Time (PT) test evaluate?

Accepted Answer

Extrinsic and common pathway

Answer

Intrinsic and common pathway

Answer

Intrinsic pathway

Answer

Extrinsic pathway

Question 9

Which of the following is false regarding Chediak-Higashi syndrome?

Accepted Answer

It is inherited in an autosomal dominant pattern.

Answer

There is a defect in the fusion of phagosomes and lysosomes.

Answer

Abnormalities are present in melanocytes.

Answer

Platelet abnormalities are present.

Question 10

What is the expected reticulocyte count in hemolytic jaundice?

Accepted Answer

2.50%

Answer

0.50%

Answer

1%

Answer

1.50%

Hematopathology — MCQs

Hematopathology — MCQs

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