A 72-year-old man has progressive fatigue, massive splenomegaly, and mild hepatomegaly. CBC shows hemoglobin 7.8 g/dL, WBC 4,000/uL, platelets 90,000/uL. Peripheral smear shows frequent teardrop-shaped red cells and occasional nucleated red cells with a leucoerythroblastic picture. Bone marrow aspiration yields no material. Which molecular finding would be expected in the majority of such patients?

• A BCR-ABL1 fusion transcript
• B JAK2 V617F mutation ✓
• C CALR frameshift mutation in BCR-ABL1-negative cases only if JAK2 and MPL are wild type
• D t(9;22)(q34;q11)

Explanation

Primary myelofibrosis presents in older adults with massive splenomegaly, teardrop red cells, a leucoerythroblastic smear, and a dry tap from marrow fibrosis. JAK2 V617F is found in approximately 50 to 60 percent of patients, making it the single most common driver mutation. CALR mutations predominate among the JAK2-negative fraction, while BCR-ABL1 fusion and t(9;22) define CML, excluded here by the dry tap and teardrop cells.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.