Family Medicine Board Review · Case-Based · Difficult Level

Polycythemia Vera — Clinical Vignette MCQs

Board-style cases built from the PV summary — diagnostic criteria, the JAK2/EPO algorithm, primary vs. secondary erythrocytosis, treatment thresholds, risk stratification, and pregnancy management. Tap "Reveal Answer" on each, then read the pearl.

15 Questions ●●●● Difficult Single Best Answer

Q1WHO Diagnostic Criteria●●●●● Extreme

A 58-year-old man has a hemoglobin of 172 g/L (17.2 g/dL) and a JAK2 V617F mutation detected on peripheral blood testing. Bone marrow biopsy shows hypercellularity with trilineage proliferation and pleomorphic megakaryocytes. Serum erythropoietin is low. Does this patient meet WHO diagnostic criteria for polycythemia vera?

A. No, because a red cell mass study was not performed
B. Yes — he meets all three major criteria (elevated Hb, characteristic bone marrow findings, and by extension the JAK2 mutation criterion)
C. No, because erythropoietin should be elevated, not low, to diagnose PV
D. Yes, but only because his hemoglobin exceeds 200 g/L
E. No, additional cytogenetic testing beyond JAK2 is mandatory in all cases

Reveal Answer

Correct answer: B

He meets the major criteria: (1) hemoglobin >165 g/L in men, (2) bone marrow hypercellularity with trilineage proliferation and pleomorphic megakaryocytes, and (3) presence of a JAK2 mutation. His low erythropoietin further supports (and is consistent with) the diagnosis, even though it functions as the minor criterion when needed rather than a required major finding here.

Why the others are wrong A — a formal red cell mass study is not required when the hemoglobin/hematocrit and other criteria are already satisfied; it's an alternative pathway (increased red cell mass), not a mandatory universal test. C — low, not high, erythropoietin is expected/supportive in PV; high EPO points toward secondary erythrocytosis instead. D — his hemoglobin of 172 g/L already exceeds the >165 g/L threshold for men; 200 g/L is not the specific cutoff required. E — JAK2 testing (V617F, or exon 12 if negative) is the key genetic criterion; broader cytogenetic testing isn't described as mandatory for diagnosis.

Exam Pearl WHO PV diagnosis = all 3 major criteria, OR first 2 major + the minor criterion (low EPO). Know the exact Hb/Hct thresholds: >165 g/L (16.5 g/dL) men, >160 g/L (16.0 g/dL) women for hemoglobin, or hematocrit >49% men / >48% women.

Q2Primary vs. Secondary — EPO Trap●●●●● Extreme

A 65-year-old man with severe COPD and chronic hypoxemia is found to have a hemoglobin of 178 g/L. He has no splenomegaly, and peripheral smear shows no abnormalities. What laboratory finding would be most expected in this patient's erythropoietin level, and what does it suggest about the underlying process?

A. Low erythropoietin, consistent with primary polycythemia vera
B. High erythropoietin, consistent with secondary erythrocytosis driven by chronic hypoxia
C. Erythropoietin level is irrelevant in distinguishing these conditions
D. Normal erythropoietin, ruling out any erythrocytosis-related process
E. Erythropoietin cannot be measured in patients with lung disease

Reveal Answer

Correct answer: B

Chronic hypoxia from COPD is a classic cause of secondary erythrocytosis — the body appropriately increases erythropoietin production in response to low oxygen, driving up red cell production. In secondary causes, erythropoietin is expected to be HIGH (in contrast to PV, where it is low).

Why the others are wrong A — low EPO is the PV pattern, not the expected finding in hypoxia-driven secondary erythrocytosis. C — EPO level is specifically the single most useful discriminator between primary and secondary erythrocytosis. D — a normal EPO wouldn't be the expected finding given his significant chronic hypoxemia, which should drive an elevated compensatory response. E — erythropoietin can and should be measured in this clinical scenario; lung disease doesn't preclude testing.

Exam Pearl Cardiopulmonary disease (chronic hypoxia) is a classic secondary erythrocytosis cause. Secondary → EPO high; PV → EPO low. This single fact resolves the majority of primary-vs-secondary erythrocytosis board questions.

Q3Symptom Frequency Trap●●●● Very Hard

A 61-year-old woman newly diagnosed with polycythemia vera asks which symptom she is statistically most likely to have already been experiencing prior to diagnosis. A resident suggests "itching after a hot shower" (aquagenic pruritus) is the most common presenting symptom. Is this accurate?

A. Yes — pruritus is the single most common presenting symptom in PV
B. No — fatigue is actually the most common presenting symptom (91%), more common than pruritus, insomnia, or concentration problems
C. No — splenomegaly is the most common presenting finding
D. No — arterial thrombosis is the most common presenting finding
E. Yes, but only in patients over age 70

Reveal Answer

Correct answer: B

Fatigue is reported in 91% of patients at presentation — the most common finding, ahead of insomnia (68%), concentration problems (61%), and aquagenic pruritus (36–68%). While pruritus is the more "iconic" textbook symptom, it is not the statistically most common one.

Why the others are wrong A — this is the common misconception the question is testing; pruritus, while classic, is less frequent than fatigue. C — splenomegaly occurs in about 36% of patients, well below fatigue's 91%. D — arterial thrombosis occurs in only about 16% of patients, a minority finding, not the most common. E — there's no age-based exception described that would make pruritus more common than fatigue.

Exam Pearl Presenting symptom frequency ranking: fatigue (91%) > insomnia (68%) > concentration problems (61%) > pruritus (36–68%) > splenomegaly (36%) > erythromelalgia (29%) > arterial thrombosis (16%) > venous thrombosis (7.4%) > major hemorrhage (4.2%). Don't let the "classic" symptom (pruritus) fool you into thinking it's the most frequent.

Q4Evaluation Algorithm●●●●● Extreme

A 55-year-old man has an elevated hematocrit of 51%. JAK2 V617F testing returns positive, and serum erythropoietin is reported as normal. What is the most appropriate next step?

A. Diagnose PV immediately and begin phlebotomy without further testing
B. Repeat both the JAK2 V617F and erythropoietin testing; pursue bone marrow examination if results remain unchanged
C. Conclude PV is excluded since erythropoietin is not low
D. Order JAK2 exon 12 testing only, skipping repeat of the initial tests
E. No further workup needed; classify as secondary erythrocytosis

Reveal Answer

Correct answer: B

When JAK2 V617F is positive but erythropoietin is normal or high (rather than the expected low value), the algorithm calls for repeating both tests; if results remain unchanged, bone marrow examination becomes necessary to clarify the diagnosis.

Why the others are wrong A — a positive JAK2 with a discordant (normal) EPO doesn't immediately confirm PV; the algorithm specifically calls for repeat testing first. C — a normal EPO with positive JAK2 doesn't exclude PV outright; it triggers repeat testing/further workup rather than exclusion. D — exon 12 testing is the pathway when JAK2 V617F is negative with low EPO, not the situation described here (V617F positive). E — this discordant result specifically requires further evaluation, not an immediate secondary erythrocytosis label.

Exam Pearl Learn all four algorithm branches: V617F(+)/EPO low → PV probable, biopsy encouraged; V617F(+)/EPO normal-high → repeat both, biopsy if unchanged; V617F(−)/EPO low → PV possible, consider exon 12 + biopsy; V617F(−)/EPO normal-high → PV unlikely, consider secondary cause.

Q5JAK2 Exon 12●●●●● Extreme

A 49-year-old woman has hematocrit of 52%, a negative JAK2 V617F test, and a low serum erythropoietin level. A colleague states that PV is now excluded given the negative JAK2 V617F result. Is this correct?

A. Yes, a negative JAK2 V617F test always excludes PV
B. No — PV remains possible; JAK2 exon 12 mutation testing and bone marrow examination should be considered given her low erythropoietin
C. Yes, because low erythropoietin only occurs in secondary causes
D. No, but no further testing is available or indicated
E. Yes, unless she has splenomegaly

Reveal Answer

Correct answer: B

A negative JAK2 V617F combined with low erythropoietin places her in the "PV possible" category — a rarer JAK2 exon 12 mutation may be responsible, and bone marrow examination should be considered to further evaluate.

Why the others are wrong A — this is the exact misconception being tested; V617F negativity does not fully exclude PV when EPO is low. C — low EPO is actually the pattern seen in PV, not secondary causes (secondary causes have high EPO); this statement reverses the correct relationship. D — additional testing (exon 12, bone marrow exam) is specifically available and indicated in this scenario. E — the decision to pursue further testing isn't contingent on the presence of splenomegaly.

Exam Pearl JAK2 V617F negative does NOT rule out PV when erythropoietin is low — always consider JAK2 exon 12 testing as the next step in this specific combination, rather than concluding the workup.

Q6Phlebotomy Math●●●●● Extreme

A 60-year-old man with newly diagnosed PV has a hematocrit of 57%. His treatment goal is a hematocrit below 45%. Approximately how many 500 mL units of blood will need to be phlebotomized to reach his goal, assuming an average-sized adult and a linear ~3% hematocrit drop per unit?

A. 1 unit
B. 2 units
C. 4 units
D. 10 units
E. No phlebotomy is needed since he is asymptomatic

Reveal Answer

Correct answer: C

He needs to drop his hematocrit from 57% to below 45% — a decrease of at least 12 percentage points. At approximately 3% drop per 500 mL unit, this requires roughly 12 ÷ 3 = 4 units to reach goal.

Why the others are wrong A/B — 1–2 units would only drop his hematocrit by 3–6%, leaving him well above the 45% goal (54% or 51%). D — 10 units would be a substantial overshoot, dropping hematocrit by roughly 30 points, far beyond what's needed and clinically excessive. E — all PV patients, symptomatic or not, should receive phlebotomy to reach the hematocrit goal, since hematocrit control is central to reducing thrombotic risk.

Exam Pearl Phlebotomy math: each 500 mL unit drops hematocrit by ~3% in an average adult. Practice this calculation — boards can present it as a straightforward arithmetic application of a memorized fact.

Q7Aspirin — Platelet Cutoff●●●●● Extreme

A 52-year-old woman with PV has a platelet count of 1,250 × 10⁹/L. Her physician is considering starting low-dose aspirin for thromboprophylaxis. What is the most appropriate approach?

A. Start aspirin 81 mg daily as in all PV patients without hesitation
B. Avoid aspirin given her extreme thrombocytosis (>1,000 × 10⁹/L), due to increased bleeding risk from acquired von Willebrand disease
C. Double the aspirin dose to compensate for her elevated platelet count
D. Switch immediately to warfarin instead of addressing the platelet count
E. Aspirin dosing is unaffected by platelet count in PV

Reveal Answer

Correct answer: B

Aspirin should be avoided in patients with extreme thrombocytosis (>1,000 × 10⁹/L) because of an increased bleeding risk from acquired von Willebrand disease that can occur at very high platelet counts, paradoxically raising bleeding risk despite the elevated platelet count.

Why the others are wrong A — aspirin is standard in most PV patients, but this specific platelet threshold is an exception where it should be avoided. C — doubling the dose would worsen bleeding risk, not address the underlying concern. D — switching to warfarin isn't the described management approach for this specific extreme thrombocytosis scenario; the concern is specifically about aspirin's bleeding risk at this platelet level, not a signal to anticoagulate instead. E — platelet count directly affects the aspirin decision at this specific extreme threshold.

Exam Pearl Memorize the exact cutoff: avoid aspirin if platelets >1,000 × 10⁹/L due to acquired von Willebrand disease risk — a counterintuitive but frequently tested exception to the "everyone gets aspirin" default in PV.

Q8Hydroxyurea in Young Patients●●●● Very Hard

A 34-year-old man with high-risk PV (history of arterial thrombosis) requires cytoreductive therapy. His hematologist expresses caution about starting hydroxyurea given his age. What is the most accurate rationale for this caution?

A. Hydroxyurea is completely contraindicated in all patients under age 40
B. There are leukemogenic concerns with long-term hydroxyurea use in younger patients, given their longer expected treatment duration
C. Hydroxyurea only works in patients over age 60
D. Young age eliminates the need for any cytoreductive therapy regardless of risk status
E. Hydroxyurea causes immediate irreversible renal failure in young adults

Reveal Answer

Correct answer: B

In patients younger than 40 years, caution is recommended with hydroxyurea use because of leukemogenic concerns with long-term use — younger patients face a longer cumulative exposure duration if started early, raising theoretical long-term leukemia transformation risk.

Why the others are wrong A — it's not an absolute contraindication, but rather a scenario requiring caution/careful risk-benefit discussion, especially in high-risk patients like this one with a thrombosis history. C — hydroxyurea's efficacy isn't age-restricted in this way. D — this patient is high-risk (history of thrombosis) and still requires cytoreductive therapy consideration despite his age; young age doesn't eliminate the indication, it just adds a caution to the specific agent choice. E — immediate irreversible renal failure is not the described concern; leukemogenesis with long-term use is.

Exam Pearl Age <40 + hydroxyurea = leukemogenic caution, not an absolute contraindication. This nuance matters in high-risk younger patients who still need cytoreductive therapy — alternatives like pegylated interferon-alfa are often preferred in this age group.

Q9Risk Stratification Scoring●●●●● Extreme

A 69-year-old man with PV has a leukocyte count of 17 × 10⁹/L and a history of deep venous thrombosis 2 years ago. Using the risk factor-based survival prediction points system, what is his total risk score, and which risk group does he fall into?

A. 5 points; low-risk group
B. 7 points; high-risk group
C. 6 points; intermediate-risk group
D. 2 points; intermediate-risk group
E. 3 points; low-risk group

Reveal Answer

Correct answer: B

Scoring: age ≥67 years = 5 points; leukocyte count ≥15 × 10⁹/L = 1 point; history of venous thromboembolism = 1 point. Total = 5 + 1 + 1 = 7 points, which falls into the high-risk group (3+ points), corresponding to a median survival of approximately 11 years.

Why the others are wrong A — 5 points alone (age only, ignoring his other two risk factors) would already place him in the high-risk category (3+), so "low-risk" is incorrect regardless, and it also undercounts his total. C/D — both miscategorize him as intermediate-risk; his correctly-summed score of 7 places him solidly in the high-risk (3+) group. E — 3 points would still fall in the high-risk category, not low-risk, so this option is internally inconsistent, and also undercounts his actual score.

Exam Pearl Risk score components: age ≥67 = 5 pts; age 57–66 = 2 pts; leukocytes ≥15 ×10⁹/L = 1 pt; history of VTE = 1 pt. Risk groups: low (0) = 28 yr median survival; intermediate (1–2) = 19 yr; high (3+) = 11 yr. Any patient with advanced age alone (≥67 = 5 points) is already automatically high-risk.

Q10Pruritus Management●●●○ Hard

A 57-year-old woman with PV on phlebotomy and low-dose aspirin continues to have bothersome aquagenic pruritus. Which additional agent is specifically recommended as first-line therapy for this symptom?

A. High-dose systemic corticosteroids
B. Antihistamines and paroxetine, in addition to her current aspirin
C. Immediate initiation of ruxolitinib regardless of other symptoms
D. Increasing her phlebotomy frequency alone, with no medication changes
E. Topical capsaicin as the sole recommended therapy

Reveal Answer

Correct answer: B

First-line therapy for PV-associated pruritus includes aspirin, antihistamines, and paroxetine (Paxil). Since she's already on aspirin, adding antihistamines and paroxetine is the appropriate next step.

Why the others are wrong A — high-dose systemic corticosteroids are not the described first-line pruritus therapy in PV. C — ruxolitinib is reserved for specific higher-level cytoreductive scenarios (e.g., resistance/intolerance to hydroxyurea with symptomatic splenomegaly), not first-line isolated pruritus management. D — phlebotomy alone, without addressing the specific pruritus-targeted medications, isn't the complete first-line approach described. E — topical capsaicin isn't the specifically recommended first-line agent in this framework.

Exam Pearl PV pruritus first-line triad: aspirin + antihistamines + paroxetine. The SSRI (paroxetine) inclusion is a somewhat unexpected but testable detail — don't default to antihistamines alone.

Q11Pregnancy Management●●●●● Extreme

A 30-year-old woman with PV on hydroxyurea is planning to conceive in 2 months with her partner. She is currently 4 weeks pregnant, having conceived unexpectedly while still on hydroxyurea. What is the most appropriate immediate management, and what agent should be used if cytoreductive therapy remains necessary during pregnancy?

A. Continue hydroxyurea throughout pregnancy without changes, since it's the first-line cytoreductive agent
B. Stop hydroxyurea immediately given the unplanned pregnancy; if cytoreductive therapy is still needed, interferon-alfa is the drug of choice during pregnancy
C. Switch to busulfan as the preferred pregnancy-safe cytoreductive agent
D. No cytoreductive therapy is ever appropriate during pregnancy under any circumstances
E. Continue hydroxyurea but add high-dose aspirin to offset any teratogenic risk

Reveal Answer

Correct answer: B

Hydroxyurea should ideally be stopped 3 months before conception given its teratogenic potential; in this case of unplanned pregnancy while on therapy, it should be stopped immediately upon recognition of pregnancy. If cytoreductive therapy remains necessary during pregnancy, interferon-alfa is the drug of choice, as it does not carry the same teratogenic profile.

Why the others are wrong A — continuing a teratogenic agent through pregnancy contradicts the specific preconception stop recommendation. C — busulfan is not described as the pregnancy-safe choice; interferon-alfa holds that role. D — cytoreductive therapy can still be used during pregnancy when needed — interferon-alfa is specifically the preferred agent in that circumstance, so it's not universally prohibited. E — adding aspirin does not offset teratogenic risk from an unrelated agent; this doesn't address the core issue.

Exam Pearl Pregnancy + PV: stop hydroxyurea (teratogenic) at least 3 months preconception; if cytoreductive therapy is needed during pregnancy, interferon-alfa is the agent of choice. All pregnant PV patients should also receive low-dose aspirin, and postpartum enoxaparin for 6 weeks if no contraindications.

Q12Prognosis — Treated vs. Untreated●●●● Very Hard

A newly diagnosed 62-year-old man with PV asks about his prognosis with and without treatment. What is the most accurate counseling regarding expected survival and cause of death?

A. Without treatment, death typically occurs within 2 years, mostly from thrombotic events; with standard treatment (aspirin + hydroxyurea), median survival is approximately 13.5 years
B. Without treatment, survival is unaffected; PV has no impact on life expectancy regardless of therapy
C. With treatment, most patients die from bleeding complications rather than thrombosis
D. Without treatment, death typically occurs within 10 years, primarily from infection
E. Treatment does not meaningfully extend survival compared to no treatment

Reveal Answer

Correct answer: A

Without treatment, death from PV typically occurs within 2 years, predominantly from thrombotic events. With standard-of-care treatment (aspirin + hydroxyurea), median survival extends to approximately 13.5 years — a dramatic and clinically important difference that underscores the importance of treatment adherence.

Why the others are wrong B — untreated PV significantly shortens survival; this statement is factually incorrect. C — thrombosis, not bleeding, remains the dominant cause of concern/death driving the treatment approach (phlebotomy and aspirin specifically target thrombosis prevention). D — untreated survival is much shorter (2 years, not 10), and the primary cause is thrombosis, not infection. E — treatment dramatically extends survival (2 years untreated vs. 13.5 years treated), a very meaningful difference.

Exam Pearl Memorize both survival figures: untreated ≈ 2 years (death mostly from thrombosis) vs. treated (aspirin + hydroxyurea) ≈ 13.5 years median survival. This dramatic gap is a classic isolated board fact.

Q13Secondary Erythrocytosis — Tumor●●●●● Extreme

A 68-year-old man presents with hematuria, flank pain, and an elevated hemoglobin of 185 g/L. CT abdomen reveals a renal mass. What is the most likely explanation for his elevated hemoglobin?

A. Concurrent polycythemia vera, unrelated to the renal mass
B. Paraneoplastic erythropoietin production from renal cell carcinoma, causing secondary erythrocytosis
C. Iron deficiency anemia masking as erythrocytosis
D. JAK2 mutation acquired from the renal tumor itself
E. Dehydration alone fully explains the finding, unrelated to the mass

Reveal Answer

Correct answer: B

Renal cell carcinoma is a classic erythropoietin-producing tumor, causing secondary erythrocytosis via paraneoplastic EPO secretion. This fits his presentation of hematuria, flank pain, a renal mass, and elevated hemoglobin.

Why the others are wrong A — the more parsimonious and classic explanation given the renal mass is paraneoplastic EPO production, not an unrelated coincidental PV diagnosis. C — iron deficiency causes anemia, not erythrocytosis; this doesn't fit an elevated hemoglobin picture. D — JAK2 mutations are associated with primary myeloproliferative neoplasms like PV, not acquired from renal tumors. E — while dehydration can mildly concentrate hemoglobin, it doesn't fully explain this clinical picture in the presence of a renal mass with classic paraneoplastic potential.

Exam Pearl EPO-producing tumors causing secondary erythrocytosis: hepatocellular carcinoma, renal cell carcinoma, hemangioblastoma, pheochromocytoma, uterine leiomyoma. Renal cell carcinoma is the classic one to recognize alongside hematuria/flank pain.

Q14Secondary Erythrocytosis — Lifestyle●●●○ Hard

A 45-year-old male smoker with obesity and loud snoring presents with an elevated hematocrit of 53%. He denies any known cardiopulmonary disease. Which combination of factors in his history could plausibly explain secondary erythrocytosis without invoking PV?

A. Smoking (chronic carbon monoxide exposure) and possible obstructive sleep apnea (chronic hypoxia) given his obesity and snoring
B. His age alone fully explains the elevated hematocrit
C. Only a JAK2 mutation could explain this finding
D. Elevated hematocrit in smokers is never clinically significant
E. Obesity alone, unrelated to any hypoxic mechanism, directly elevates hematocrit

Reveal Answer

Correct answer: A

Both smoking (via chronic carbon monoxide exposure, which reduces effective oxygen-carrying capacity and triggers compensatory erythropoiesis) and obesity with snoring suggestive of obstructive sleep apnea (chronic intermittent hypoxia) are recognized causes of secondary erythrocytosis, and both should be considered before attributing his findings to PV.

Why the others are wrong B — age alone isn't a described mechanism for secondary erythrocytosis in this framework. C — a JAK2 mutation would point toward PV (primary), not secondary erythrocytosis, and it's not the only possible explanation here — his lifestyle/exam findings suggest secondary causes first. D — smoking-related erythrocytosis is clinically significant and specifically listed as a secondary cause. E — obesity's contribution here is through its association with sleep apnea/hypoxia, not a direct, mechanism-independent effect on hematocrit.

Exam Pearl Lifestyle/exposure-related secondary erythrocytosis causes: smoking/chronic CO poisoning, high-altitude habitat, sleep apnea/obesity-hypoventilation/Pickwickian syndrome. Always screen for these before assuming a myeloproliferative process.

Q15Integrative — MPN Differential●●●●● Extreme

A 60-year-old man has elevated hemoglobin, leukocytosis, and thrombocytosis. His physician is considering several myeloproliferative neoplasms in the differential, including PV, essential thrombocytosis, primary myelofibrosis, and chronic myelogenous leukemia. Which single feature would be the LEAST helpful in distinguishing PV specifically from these other primary erythrocytosis-associated conditions on initial evaluation?

A. Serum erythropoietin level
B. JAK2 V617F mutation status
C. The mere presence of elevated white blood cell and platelet counts, since concurrent trilineage stimulation can be seen across this differential and isn't unique to PV
D. Bone marrow biopsy findings
E. Philadelphia chromosome / BCR-ABL1 testing

Reveal Answer

Correct answer: C

PV, essential thrombocytosis, primary myelofibrosis, and CML are grouped together as other myeloproliferative neoplasms under the primary erythrocytosis differential, and all can show elevations in more than one cell line to varying degrees. Simply noting elevated WBC and platelets alongside elevated Hb is not specific enough to pinpoint PV over these other related conditions — more specific testing is needed.

Why the others are wrong A — erythropoietin level is highly useful (low in PV) and helps separate PV from secondary causes, and is part of the standard workup. B — JAK2 V617F is a defining major criterion for PV and present in the vast majority of cases, making it a very useful distinguishing test. D — bone marrow biopsy findings (trilineage hyperplasia with pleomorphic megakaryocytes) are a major diagnostic criterion and help distinguish PV morphologically from the other MPNs. E — Philadelphia chromosome/BCR-ABL1 is specifically useful to identify or exclude CML, which is part of this same differential list.

Exam Pearl PV sits within a broader family of primary erythrocytosis/myeloproliferative neoplasms (essential thrombocytosis, primary myelofibrosis, CML, myelodysplastic syndrome). Nonspecific trilineage elevation alone doesn't distinguish between them — JAK2 testing, erythropoietin level, bone marrow findings, and BCR-ABL1 status are the specific discriminating tools.