A 25-year-old G2P1 woman at 12 weeks gestational age presents to the office to discuss the results of her routine prenatal screening labs, which were ordered during her 1st prenatal visit. She reports taking a daily prenatal vitamin but no other medications. She complains of mild fatigue and appears pale on exam. Her complete blood count (CBC) shows the following: Hemoglobin (Hb) 9.5 g/dL Hematocrit 29% Mean corpuscular volume (MCV) 75 µm3 Which of the following are the most likely hematologic states of the patient and her fetus?

Iron deficiency anemia in the mother; normal Hb levels in the fetus

Iron deficiency anemia in both the mother and the fetus

Pernicious anemia in the mother; normal Hb levels in the fetus

Physiologic anemia in the mother; normal Hb levels in the fetus

Folate deficiency anemia in both the mother and the fetus

A 37-year-old man, otherwise healthy, has a routine CBC done prior to donating blood for the first time. The results are as follows: Hemoglobin 10.8 g/dL Mean corpuscular volume (MCV) 82 μm3 Mean corpuscular hemoglobin concentration (MCHC) 42% Reticulocyte count 3.2% White blood cell count 8,700/mm3 Platelet count 325,000/mm3 The patient is afebrile and his vital signs are within normal limits. On physical examination, his spleen is just palpable. A peripheral blood smear is shown in the exhibit (see image). A direct antiglobulin test (DAT) is negative. Which of the following best describes the etiology of this patient’s most likely diagnosis?

Inherited membrane abnormality of red cells

A 32-year-old woman complains of fatigue and pallor. She says symptoms that started several months ago and have been becoming more serious with time. She reports that she has been exercising regularly and has been adhering to a strict vegan diet. The patient has no significant past medical history and takes no current medications. She denies any smoking history, alcohol use, or recreational drug use. She is tachycardic, but otherwise, her physical examination is unremarkable. A complete blood count (CBC) shows anemia with a low MCV (mean corpuscular volume), and a peripheral blood smear shows small erythrocytes. Which of the following is the most likely diagnosis in this patient?

Glucose-6-phosphate dehydrogenase deficiency

A 35-year-old woman is involved in a car accident and presents with an open fracture of the left femur and severe bleeding from the left femoral artery. No past medical history or current medications. Her blood pressure is 90/60 mm Hg, pulse is 110/min, and respirations are 21/min. On physical examination, the patient is lethargic, confused, and poorly responds to commands. Peripheral pulses are 1+ in the left lower extremity below the level of the knee and 2+ elsewhere. When she arrives at the hospital, a stat hemoglobin level shows 6 g/dL. Which of the following is most correct about the patient’s condition?

This patient’s laboratory findings will likely demonstrate a normocytic anemia

Hemoglobin concentration will be significantly decreased immediately after the acute bleeding begins

This patient will likely be diagnosed with iron deficiency anemia

Hematocrit is expected to accurately reflect the degree of blood loss immediately after acute hemorrhage

Her reticulocyte count is expected to be elevated at this time

A 62-year-old man, a retired oil pipeline engineer, presents to his primary care physician with complaints of headaches, fatigue, and constant ringing in his ears. Recurrently he has developed pruritus, usually after a hot shower. He also noted a constant burning sensation in his fingers and toes, independent of physical activity. On examination, he has a red face and his blood pressure levels are 147/89 mm Hg. A CBC revealed that his Hb is 19.0 g/dL and Hct is 59%. Because of his condition, his physician prescribes him 81 mg of aspirin to be taken daily in addition to therapeutic phlebotomy. Which of the statements below is true about this patient’s condition?

Mutation of the JAK2 gene is commonly seen in this condition.

Warfarin and phlebotomy are the preferred course of treatment.

The patient has a decreased risk of developing myelofibrosis.

Serum erythropoietin is expected to be high.

Arterial oxygen saturation is usually higher than normal values in this condition.

A 43-year-old man comes to the physician for a 1-week history of swelling around his eyes and decreased urination. His pulse is 87/min, and blood pressure is 152/95 mm Hg. Physical examination shows 1+ periorbital and pretibial edema. Serum studies show a urea nitrogen concentration of 21 mg/dL and a creatinine concentration of 1.4 mg/dL. Urinalysis shows 3+ blood and 1+ protein. Further evaluation of this patient is most likely to show which of the following?

Renal interstitial inflammation

Detached renal tubular epithelial cells

Red blood cell disorders for USMLE Step 2 CK: High-Yield Pathology Lessons

RBC Indices & Basics - Know Your Doughnuts

Normal red blood cells in peripheral blood smear

MCV (Mean Corpuscular Volume): Average RBC size. Defines anemias:
- - Microcytic: <80 fL
- - Normocytic: 80-100 fL
- - Macrocytic: >100 fL
MCHC (Mean Corpuscular Hemoglobin Conc.): Avg. Hb concentration. ↑ in spherocytosis.
RDW (Red Cell Distribution Width): Measures size variation (anisocytosis).

⭐ RDW is typically normal in thalassemia trait but elevated in iron deficiency anemia, helping differentiate these two microcytic anemias.

Microcytic Anemias - Small Cells, Big Problems

Defined by Mean Corpuscular Volume (MCV) < 80 fL. Common causes are due to defective heme or globin synthesis.
📌 Mnemonic: TAILS
- Thalassemia
- Anemia of chronic disease
- Iron deficiency
- Lead poisoning
- Sideroblastic anemia

Microcytic hypochromic anemia with target cells

Condition	Iron	TIBC	Ferritin	Key Features
Iron Deficiency	↓	↑	↓	Pica, koilonychia
Anemia of Chronic Disease	↓	↓	↑ / N	↑ Hepcidin
Thalassemias (α & β)	↑	N	↑	Target cells, normal RDW
Sideroblastic Anemia	↑	N	↑	Ring sideroblasts, basophilic stippling

Macrocytic Anemias - Large & In Charge

Anemia with Mean Corpuscular Volume (MCV) > 100 fL. Key division: Megaloblastic vs. Non-megaloblastic.
Megaloblastic Anemia: Impaired DNA synthesis → delayed nuclear maturation.
- Causes: Folate (B9) & Cobalamin (B12) deficiency.
- Labs: ↑ Homocysteine. In B12 deficiency, also ↑ Methylmalonic Acid (MMA).
- Smear: Hypersegmented neutrophils (>5 lobes), macro-ovalocytes.
⭐ Neurological symptoms (subacute combined degeneration) are specific to B12 deficiency, not folate!
Non-Megaloblastic Anemia: Normal DNA synthesis.
- Causes: Liver disease, alcoholism, hypothyroidism.

Hypersegmented neutrophil and macro-ovalocytes

Normocytic Anemias - Just Right, Still Wrong

Definition: Anemia with normal-sized red blood cells (MCV 80-100 fL), but ↓ total RBC count. The primary distinction is whether the bone marrow is responding appropriately (↑ reticulocytes).

Hereditary Spherocytosis: Autosomal dominant defect in spectrin or ankyrin. Leads to loss of membrane, creating spherocytes. Diagnosed with osmotic fragility test. ↑ MCHC is characteristic.

⭐ Paroxysmal Nocturnal Hemoglobinuria (PNH): The only hemolytic anemia caused by an acquired genetic defect (PIGA gene). Presents with a classic triad of hemolytic anemia, pancytopenia, and venous thrombosis.

Polycythemia - Too Much of a Good Thing

Definition: Increased RBC mass, with Hematocrit >49% in males, >48% in females.
Primary (Polycythemia Vera): Neoplastic proliferation of myeloid cells.
- JAK2 V617F mutation is key.
- Features ↓ EPO, generalized pruritus (especially post-shower), plethora, and splenomegaly.
Secondary: Response to ↑ EPO.
- Physiologic: High altitude, COPD.
- Pathologic: EPO-secreting tumors (Renal Cell Carcinoma).
Relative: ↓ plasma volume (e.g., dehydration).

⭐ In Polycythemia Vera, despite low EPO levels, RBC production is autonomous and uncontrolled due to the JAK2 mutation.

High‑Yield Points - ⚡ Biggest Takeaways

Iron deficiency anemia, the most common type, presents with microcytic, hypochromic cells and low ferritin.

Anemia of chronic disease shows normocytic cells, high ferritin, and is driven by hepcidin.

Megaloblastic anemias (B12/folate) feature macrocytic RBCs and hypersegmented neutrophils; only B12 causes neurologic deficits.

Sickle cell anemia results from a β-globin point mutation, leading to vaso-occlusive crises and autosplenectomy.

G6PD deficiency is an X-linked disorder causing hemolysis with oxidative triggers, showing Heinz bodies and Bite cells.

Hereditary spherocytosis is an autosomal dominant defect causing spherocytes and an increased MCHC.

Continue reading on Oncourse

CONTINUE READING — FREE

or get the app

App Store|Google Play