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 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.

Q: The arrow shows:

Cabot's rings seen in pernicious anemia. ***Cabot's rings seen in pernicious anemia*** - **Cabot's rings** are thin, blue to purple ring-like or figure-of-eight structures within red blood cells, representing remnants of the **mitotic spindle**. - They are classically associated with **megaloblastic anemia**, particularly **pernicious anemia**, due to impaired DNA synthesis from **B12/folate deficiency**. *Howell-Jolly bodies seen in pernicious anemia* - **Howell-Jolly bodies** are small, round **nuclear remnants** (DNA fragments) that appear as dark purple inclusions in red blood cells. - They are primarily associated with **asplenia** or **splenic dysfunction**, not specifically with pernicious anemia morphology. *Rushton bodies seen in iron deficiency anemia* - **Rushton bodies** are **eosinophilic hyaline bodies** found in **odontogenic cysts**, particularly radicular cysts, not in blood cells. - They are completely unrelated to **hematological conditions** and have no association with iron deficiency anemia. *None of the above* - This option is incorrect as **Cabot's rings** are indeed the correct identification of the arrow-indicated structure. - The morphological description and clinical association with **pernicious anemia** make this option inappropriate.

Q: Which is the most common antigen implicated in hemolytic disease of the newborn?

D antigen in Rh group. **Explanation:** Hemolytic Disease of the Newborn (HDN) occurs due to the transplacental passage of maternal IgG antibodies that target fetal red blood cell antigens, leading to hemolysis. **Why Option B is Correct:** The **D antigen** of the Rh blood group system is the most potent immunogen among all human blood group antigens. Rh incompatibility occurs when an Rh-negative mother (d/d) carries an Rh-positive fetus (D/d). Sensitization usually happens during delivery; in subsequent pregnancies, maternal anti-D antibodies cross the placenta, causing immune-mediated hemolysis. Despite the use of Anti-D prophylaxis (RhoGAM), the D antigen remains the **most common and most severe** cause of significant Rh-related HDN. **Why Other Options are Incorrect:** * **Options A & C (C and E antigens):** These are "minor" Rh antigens. While they can cause HDN, they are significantly less immunogenic than the D antigen and are much rarer causes of clinical disease. * **Option D (Duffy antigen):** This is a minor blood group system. While anti-Duffy antibodies can cause HDN or transfusion reactions, they are extremely rare compared to Rh or ABO incompatibilities. **High-Yield Clinical Pearls for NEET-PG:** * **Most common cause of HDN overall:** ABO incompatibility (usually Mother 'O' and Baby 'A' or 'B'). It is often milder and can occur in the first pregnancy. * **Most common cause of SEVERE HDN:** Rh (D) incompatibility. * **Standard Prophylaxis:** 300 mcg of Anti-D is given to Rh-negative unsensitized mothers at 28 weeks gestation and within 72 hours of delivery. * **Diagnosis:** The **Direct Coombs Test (DCT)** on fetal/neonatal cord blood is the gold standard for confirming immune-mediated hemolysis.

Question 1

Which of the following is involved in hereditary spherocytosis?

Accepted Answer

Ankyrin

Answer

Troponin

Answer

Pyrin

Answer

Actin

Question 2

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 3

Routine Rh typing includes testing for which antigen?

Accepted Answer

D antigen

Answer

A antigen

Answer

B antigen

Answer

C antigen

Question 4

A 25-year-old man involved in a motorcycle accident incurs a laceration to his thigh. The bleeding is stabilized en route to the hospital, but on arrival, he is noted to have orthostatic hypotension and his hematocrit is 21%. He receives 2 units of PRBCs. As the first unit is nearly finished transfusing, he becomes febrile and hypotensive. Urine output ceases. The serum above the clot in a red top phlebotomy tube is pink. Which of the following complications of transfusion has most likely occurred in this man?

Accepted Answer

Mislabeled specimens were processed in the laboratory

Answer

Donor antibodies were directed against his granulocytes

Answer

Donor blood was contaminated with hepatitis C virus

Answer

Fluid overload led to congestive heart failure

Question 5

Hematopoietic stem cells differ from progenitor stem cells in that they can:

Accepted Answer

Long-term reconstitution of bone marrow

Answer

Form terminally differentiated cells

Answer

Produce growth factors

Answer

Have receptors for anchoring proteins

Question 6

What is the most common site of histiocytosis?

Accepted Answer

Bone

Answer

Skin

Answer

Lung

Answer

Liver

Question 7

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 8

What is the expected reticulocyte count in hemolytic jaundice?

Accepted Answer

2.50%

Answer

0.50%

Answer

1%

Answer

1.50%

Question 9

The arrow shows:

Accepted Answer

Cabot's rings seen in pernicious anemia

Answer

Howell-Jolly bodies seen in pernicious anemia

Answer

Rushton bodies seen in iron deficiency anemia

Answer

None of the above

Question 10

Which is the most common antigen implicated in hemolytic disease of the newborn?

Accepted Answer

D antigen in Rh group

Answer

C antigen in Rh group

Answer

E antigen in Rh group

Answer

Duffy antigen

Hematopathology — MCQs

Hematopathology — MCQs

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