A case of myeloid neoplasm with FIP1L1-PDGFRA rearrangement without marked peripheral blood eosinophilia.

We report a 29-year-old man with double hip pain and lower limb weakness for 6 months with myeloid neoplasm with FIP1L1-PDGFRA rearrangement without marked peripheral blood eosinophilia. Nested reverse transcription polymerase chain reaction demonstrated that bone marrow was positive for FIP1L1-PDGFRA rearrangement. The patient consequently received imatinib treatment at a dosage of 100 mg daily. Two weeks later, white blood cell counts were normalized. The double hip pain disappeared gradually. FIP1L1-PDGFRA fusion by reverse transcription polymerase chain reaction was still positive at 3 months. His 9-month post-treatment complete blood cell count, peripheral blood and bone marrow biopsy were all normal. FIP1L1 was unrearranged. The patient continues to be treated with imatinib 100 mg daily for more than 2 years with no recurrence. The presence of PDGFRA rearrangement in this case conferred a high sensitivity to imatinib treatment and a favorable clinical outcome.