What is the appropriate diagnostic work‑up and management for a middle‑aged adult presenting with unexplained cytopenias, a leuko‑erythroblastic peripheral smear, palpable splenomegaly, and suspected primary myelofibrosis?

Primary Myelofibrosis: Diagnostic Work-up and Management

Diagnostic Approach

In a middle-aged adult presenting with unexplained cytopenias, leukoerythroblastic peripheral smear, and palpable splenomegaly, proceed directly to bone marrow aspiration and biopsy with comprehensive ancillary testing to confirm primary myelofibrosis and exclude other myeloid neoplasms. 1

Essential Clinical Features Supporting PMF Diagnosis

The clinical presentation described meets key diagnostic criteria for PMF, which requires integration of peripheral blood findings, bone marrow morphology, and molecular studies 1, 2:

• Leukoerythroblastosis (immature granulocytes and nucleated red blood cells in peripheral blood) is one of four PMF-characteristic features required by WHO criteria 1
• Palpable splenomegaly represents another cardinal diagnostic feature, resulting from extramedullary hematopoiesis 1, 2
• Cytopenias (particularly anemia) are typical manifestations of ineffective hematopoiesis in PMF 2, 3

Mandatory Bone Marrow Examination

Bone marrow aspiration and biopsy must be performed and should include:

• Morphologic assessment evaluating for proliferation of abnormal megakaryocytes (small to large with aberrant nuclear/cytoplasmic ratio, hyperchromatic, bulbous or irregularly folded nuclei, often in tight clusters) and granulocytic proliferation with left-shifted forms 1, 4
• Reticulin and collagen fibrosis grading (grade 2-3 on 0-3 scale defines overt PMF; grade 0-1 suggests prefibrotic PMF) 1, 4
• Assessment of cellularity (marked hypercellularity typical in prefibrotic PMF) 1
• Blast enumeration to exclude accelerated phase or leukemic transformation 2, 3

Required Molecular and Cytogenetic Testing

The following studies are mandatory at diagnosis:

• JAK2 V617F mutation testing (positive in ~60% of PMF patients) 1, 2
• CALR exon 9 mutation analysis (positive in 60-80% of JAK2/MPL-negative cases) 1, 3
• MPL W515 mutation testing (positive in 5-8% of PMF) 1, 2
• Conventional karyotyping to identify prognostically significant abnormalities and exclude Philadelphia chromosome 1, 2
• BCR-ABL1 testing to definitively exclude chronic myeloid leukemia 1, 5

Approximately 90% of PMF patients harbor JAK2, CALR, or MPL mutations; the remaining 10% are "triple-negative" but can still be diagnosed based on morphology and clinical criteria 2, 4, 3

Additional Prognostic Molecular Testing

Next-generation sequencing should be performed to detect high-risk mutations:

• ASXL1 and SRSF2 mutations predict inferior survival independent of clinical risk scores 2, 3, 6
• U2AF1-Q157 mutations also confer adverse prognosis 3
• Type 1/like CALR mutations are associated with superior survival compared to other driver mutations 2, 3, 7
• RAS/CBL mutations predict resistance to ruxolitinib therapy 3

Approximately 93% of patients harbor at least one somatic mutation detectable by targeted sequencing 5

Cytogenetic Risk Stratification

Karyotype analysis defines three prognostic categories 3, 6:

• Very high-risk abnormalities: -7, inv(3), i(17q), +21, +19, 12p-, 11q-, or complex karyotype
• Unfavorable karyotype (DIPSS-plus): complex karyotype or sole/two abnormalities including +8, -7/7q-, i(17q), inv(3), -5/5q-, 12p-, or 11q23 rearrangement 2
• Favorable abnormalities: normal karyotype, isolated +9, 13q-, 20q-, 1q abnormalities, or loss of Y chromosome

The presence of del(13)(q11-13q14-22) or der(6)t(1,6)(q21-23;p21.3) is strongly suggestive of PMF 1

Risk Stratification

Two contemporary prognostic systems should be applied:

MIPSS70+ Version 2.0 (Preferred for Treatment Decisions)

This system integrates clinical, cytogenetic, and molecular variables and requires an online calculator (http://www.mipss70score.it) 3, 6:

• Very low risk: 10-year survival 92%
• Low risk: 10-year survival 56%
• Intermediate risk: 10-year survival 30%
• High risk: 10-year survival 13%
• Very high risk: 10-year survival 0%

GIPSS (Genetically-Inspired Prognostic Scoring System)

Based exclusively on mutations and karyotype, offering lower complexity 3, 6

DIPSS-Plus (Alternative System)

Uses eight clinical predictors: age >65 years, hemoglobin <10 g/dL, leukocytes >25 × 10⁹/L, circulating blasts ≥1%, constitutional symptoms, red cell transfusion dependency, platelet count <100 × 10⁹/L, and unfavorable karyotype 2

Management Algorithm

Very Low and Low Risk (MIPSS70+ v2.0)

Observation alone is appropriate for asymptomatic patients with estimated 10-year survival 56-92%, especially in the absence of high-risk mutations 3, 6

Intermediate Risk

Treatment-requiring patients are best served by participating in clinical trials given estimated 10-year survival of 30% 3, 6

Allogeneic hematopoietic stem cell transplant (AHSCT) should be considered in carefully selected younger patients, as this is the only potentially curative therapy 1, 2, 3

High and Very High Risk

Allogeneic stem cell transplant is the preferred treatment for transplant-eligible patients with estimated 10-year survival 0-13% 3, 6

All patients with high/intermediate-2 risk disease or those harboring high-risk mutations (ASXL1, SRSF2, U2AF1-Q157) should be considered for stem cell transplant 2, 3

The risk of transplant-related complications is justified when median survival is expected to be less than 5 years 1

Palliative Pharmacotherapy (Non-Transplant Candidates)

JAK2 inhibitors are indicated for symptomatic splenomegaly and constitutional symptoms but do not modify disease natural history:

• Ruxolitinib (first-line JAK2 inhibitor) 3, 6
• Fedratinib (for patients failing ruxolitinib) 3
• Pacritinib (for patients with platelet count <50 × 10⁹/L) 3
• Momelotinib (shows erythropoietic benefits in addition to spleen/symptom responses) 3

JAK2 inhibitors have not been shown to induce complete remissions, affect mutant allele burden significantly, or prolong survival 2, 3

Anemia management options include:

• Androgens (e.g., danazol) 6
• Prednisone 6
• Thalidomide 6
• Erythropoiesis-stimulating agents 1
• Immunomodulators 1

Hydroxyurea is first-line treatment for symptomatic splenomegaly in patients not requiring JAK2 inhibitors 1, 6

Interventional Therapies

• Splenectomy is indicated for drug-refractory painful splenomegaly, symptomatic portal hypertension, or frequent red cell transfusions 1, 2, 3
• Involved field radiotherapy is useful for post-splenectomy hepatomegaly, non-hepatosplenic extramedullary hematopoiesis, PMF-associated pulmonary hypertension, and extremity bone pain 2, 3, 6

Critical Diagnostic Pitfalls to Avoid

• Failure to distinguish prefibrotic PMF from essential thrombocythemia on bone marrow morphology, which has significant prognostic implications for survival and myelofibrotic transformation 1
• Omitting cytogenetic analysis, which is essential for diagnosis, prognostication, and excluding Philadelphia chromosome-positive chronic myeloid leukemia 1, 2
• Not performing comprehensive mutation analysis including ASXL1, SRSF2, and U2AF1, which provide DIPSS-plus-independent prognostic information 2, 3
• Misclassifying triple-negative PMF as reactive myelofibrosis; triple-negative patients have higher leukemic transformation rates and lower survival than CALR/JAK2-mutant patients 7
• Inadequate bone marrow morphologic assessment failing to recognize the characteristic abnormal megakaryocyte morphology (hyperchromatic, bulbous, irregularly folded nuclei in tight clusters) that distinguishes PMF from essential thrombocythemia 1, 4
• Starting JAK2 inhibitors in asymptomatic low-risk patients, as these agents are purely palliative and should only be used with clear treatment indications 6