Pathophysiology Test- Hematology Study Guide

What You Need to Know for Your Hematology Pathophysiology Exam

Let's cut the nonsense. Your pathophysiology test is coming up, and hematology is a big chunk of it. This guide gives you exactly what you need to memorize and understand—not fluff, not filler.

You need to know blood cell disorders, anemia classifications, coagulation cascade basics, and clinical presentations. That's it. Let's get to it.

Blood Cell Lines: The Foundation

Every hematology question traces back to these three cell lines. Know them cold.

Erythrocytes (Red Blood Cells)

RBCs carry oxygen using hemoglobin. Each RBC lives about 120 days. The bone marrow pumps out millions daily.

Key lab values to memorize:

• Normal RBC count: 4.5-5.5 million/μL
• Hemoglobin: 12-16 g/dL (women), 14-18 g/dL (men)
• Hematocrit: 36-48% (women), 42-52% (men)
• MCV: 80-100 fL (tells you cell size)

Leukocytes (White Blood Cells)

WBCs are your immune army. Five types, each with specific functions.

• Neutrophils (50-70%) — First responders to bacterial infection. Kill bacteria by phagocytosis. Elevated in bacterial infections, stress, inflammation.
• Lymphocytes (20-40%) — Adaptive immunity. B-cells make antibodies, T-cells attack infected cells. Elevated in viral infections.
• Monocytes (2-8%) — Macrophages in tissue. Clean up debris, present antigens. Rise in chronic infections.
• Eosinophils (1-4%) — Fight parasites, involved in allergic reactions. Elevated with allergies, parasitic infections.
• Basophils (0.5-1%) — Release histamine. Low counts are usually nothing. Elevated in myeloproliferative disorders.

Left shift means more immature neutrophils (bands) are circulating. This signals acute bacterial infection. You'll see this on almost every clinical scenario question.

Thrombocytes (Platelets)

Platelets stop bleeding. Normal count is 150,000-400,000/μL. Below 50,000, you're looking at spontaneous bleeding risk. Below 20,000, you need transfusion.

Platelets adhere to damaged endothelium, aggregate, and form the platelet plug. Vitamin K-dependent factors help stabilize the clot.

Anemia: Classification and Pathophysiology

Anemia is low hemoglobin or RBC count. The MCV classification is how most exams test this.

Microcytic Anemia (MCV < 80)

Small cells. Think TAILS:

• Thalassemia — Genetic defect in globin chain synthesis. Common in Mediterranean, African, Asian populations.
• Anemia of chronic disease — Can be microcytic in long-standing cases (though usually normocytic).
Iron deficiency — Most common cause worldwide. Due to blood loss, poor intake, or malabsorption.
• Lead poisoning — Industrial exposure. Basophilic stippling on blood smear.
• Sideroblastic anemia — Defect in heme synthesis. Ring sideroblasts in bone marrow.

Iron studies in iron deficiency: Low ferritin, low iron, high TIBC. That's the pattern you need to recognize.

Normocytic Anemia (MCV 80-100)

These are the tricky ones. Causes include:

• Acute blood loss
• Anemia of chronic disease
• Hemolytic anemia
• Bone marrow failure
• Early iron deficiency or B12/folate deficiency

Hemolytic anemia breaks down into intrinsic (membrane defects, enzyme deficiencies) and extrinsic (immune-mediated, mechanical trauma).

Lab clues for hemolysis: Elevated LDH, elevated indirect bilirubin, low haptoglobin, reticulocytosis. The reticulocyte count is key—if it's high, your bone marrow is responding appropriately. If it's low, your marrow isn't making new cells.

Macrocytic Anemia (MCV > 100)

Big cells. Two main categories:

• Megaloblastic — B12 or folate deficiency. DNA synthesis is impaired. You'll see hypersegmented neutrophils on smear, oval macrocytes, and pancytopenia. Causes include pernicious anemia (autoimmune against intrinsic factor), malabsorption, alcoholism, certain medications.
• Non-megaloblastic — Liver disease, hypothyroidism, alcoholism (direct toxicity), reticulocytosis, myelodysplasia.

For B12 deficiency, know the subacute combined degeneration—posterior column and lateral corticospinal tract involvement. Numbness, tingling, ataxia, weakness.

Key Hematologic Disorders You Must Know

Sickle Cell Disease

Point mutation in beta globin gene. HbS polymerizes when deoxygenated, causing RBCs to sickle. These get trapped in microvasculature.

Clinical features:

• Vaso-occlusive crises (pain crises)
• Aplastic crises (Parvovirus B19 infection)
• Acute chest syndrome
• Stroke risk
• Chronic hemolytic anemia

Smear shows sickle cells, target cells. Hydrops fetalis occurs with homozygous HbS and alpha thalassemia.

Leukemia Classification

Acute vs. chronic. Lymphoid vs. myeloid. Four main types:

For AML, remember Auer rods—crystallized granules. Positive in AML, especially M3 (APL). APL has t(15;17) and responds to ATRA.

Lymphoma: Hodgkin vs. Non-Hodgkin

Hodgkin lymphoma—Reed-Sternberg cells (owl eyes). Bimodal age distribution. Contiguous spread. B symptoms (fever, night sweats, weight loss >10%) matter for staging.

Non-Hodgkin lymphoma—Diffuse spread. More common overall. Includes Burkitt (jaw lesions in Africa, "starry sky" pattern), follicular, mantle cell, and DLBCL. Categorized as indolent vs. aggressive.

Multiple Myeloma

Malignant plasma cells in bone marrow. Produces monoclonal immunoglobulin (usually IgG or IgA).

CRAB criteria for diagnosis:

• Calcium elevation
• Renal insufficiency
• Anemia
• Bone lesions (lytic, "punched out")

Also watch for recurrent infections (hypogammaglobulinemia) and hyperviscosity syndrome. Bence Jones proteins are light chains in urine.

Coagulation: What You Actually Need

The cascade looks intimidating. Focus on what matters for pathophysiology.

Intrinsic vs. Extrinsic Pathways

The extrinsic pathway is Factor VII and tissue factor. The intrinsic pathway is Factors XII, XI, IX, VIII. Both feed into Factor X, then common pathway (V, II, I, XIII).

Vitamin K is needed for Factors II, VII, IX, X (and protein C, S). Warfarin blocks vitamin K epoxide reductase. That's why PT/INR monitors warfarin—the extrinsic pathway Factor VII has the shortest half-life.

Platelet Disorders

Qualitative platelet defects: Aspirin (irreversible COX inhibition), uremia, liver disease.

Quantitative: Thrombocytopenia causes:

• Decreased production (bone marrow failure, chemo, radiation)
• Increased destruction (ITP, TTP, HUS, DIC, heparin-induced)
• Sequestration (splenomegaly)

ITP (Immune Thrombocytopenic Purpura) — Autoantibodies against platelets. Isolated thrombocytopenia. Chronic in adults, acute in children (often post-viral).

TTP (Thrombotic Thrombocytopenic Purpura) — ADAMTS13 deficiency. Pentad: thrombocytopenia, microangiopathic hemolytic anemia, neurological symptoms, renal dysfunction, fever. Plasma exchange is treatment.

DIC (Disseminated Intravascular Coagulation) — Widespread activation of coagulation. Consumes clotting factors and platelets. Causes both thrombosis and bleeding. Associated with sepsis, trauma, malignancy, obstetric complications.

Getting Started: How to Study This Material

Don't just read. Active recall works better for pathophysiology.

• Make flashcards for each disorder: cause, pathophysiology, labs, treatment. Quiz yourself on the clinical presentation before reading the answer.
• Draw the coagulation cascade from memory. Redraw it until you can do it without looking.
• Practice RBC index calculations. Given Hgb, Hct, MCV—classify the anemia before you check answers.
• Match clinical scenarios to diagnoses. "65-year-old with anemia, bone pain, renal failure"—that's multiple myeloma until proven otherwise.
• Use practice questions. Pathophysiology exams love clinical vignettes. Work through as many as possible.

Focus your review time on anemia classification, leukemia differentiation, and coagulation disorders. These three areas will dominate your exam.

Quick Reference: High-Yield Associations

• Bite cells, Heinz bodies → G6PD deficiency
• Howell-Jolly bodies → Asplenia or hyposplenia
• Target cells → Liver disease, thalassemia, hemoglobin C
• Schistocytes → Microangiopathic hemolytic anemia (TTP, HUS, DIC)
• Teardrop cells → Myelofibrosis, bone marrow infiltration
• Pappenheimer bodies → Sideroblastic anemia
• Hypersegmented neutrophils → B12 or folate deficiency

That's your hematology pathophysiology coverage. Know these concepts, memorize the key associations, and practice applying them to clinical scenarios. The rest is detail you can fill in if you understand the framework.