A 55-year-old man presents with fatigue, splenomegaly 18 cm, WBC 2.4 × 10⁹/L, Hb 8.2 g/dL, platelet count 68 × 10⁹/L and a leukoerythroblastic blood film. Bone marrow biopsy shows dry tap with reticulin grade MF-3. JAK2 V617F is positive. The diagnosis and its DIPSS-plus classification are being determined. Which factor is NOT included in the DIPSS-plus scoring for primary myelofibrosis?
- A JAK2 V617F mutation status ✓
- B Platelet count <100 × 10⁹/L
- C Need for red cell transfusion
- D Unfavourable karyotype
Correct answer: A. JAK2 V617F mutation status
Explanation
The DIPSS-plus score for primary myelofibrosis includes all DIPSS factors (age >65, constitutional symptoms, Hb <10 g/dL, leukocyte count >25 × 10⁹/L, circulating blasts ≥1%) plus three additional variables: thrombocytopenia (platelets <100 × 10⁹/L), RBC transfusion dependence, and unfavourable karyotype (e.g., complex karyotype, +8, −7). JAK2 V617F mutation status, though diagnostically important and present in ~60% of PMF cases, is not a component of the DIPSS-plus prognostic model.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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