![A previously healthy 28-year-old man presented to the emergency department with chest pain and petechiae on his extremities. Labs revealed elevated troponin level (6.86 ng/mL), acute kidney injury (Cr, 1.95 mg/dL), and eosinophilia (WBC, 22 400/µL, 57% eosinophils). Transthoracic and transesophageal echocardiograms were negative for valvular pathology/endocarditis, but a cardiac magnetic resonance image was consistent with myocarditis. Fluorescence in situ hybridization (FISH) from peripheral blood revealed PDGFRA gene rearrangement with FIP1L1-PDGFRA fusion in 75% of interphase cells (panel D; tricolor rearrangement FISH probe, peripheral blood). The serum tryptase level was elevated to 30.9 ng/mL. A bone marrow biopsy demonstrated hypercellular marrow (panel B; hematoxylin and eosin [H&E]-stained bone marrow, 2× objective, ×20 magnification) with granulocytic hyperplasia, increased eosinophilic precursors with maturation (panel A; H&E-stained bone marrow, 40× objective, ×400 magnification), increased mast cells (panel C; tryptase-stained bone marrow, 20× objective, ×200 magnification), increased reticulin network (MF-1 to MF-2 fibrosis), and PDGFRA gene rearrangement. He was diagnosed with hypereosinophilic syndrome secondary to FIP1L1-PDGFRA–positive myeloid/lymphoid neoplasm with eosinophilia and was started on steroids and imatinib treatment. After 2 weeks of therapy, he achieved a complete hematologic response with an undetectable eosinophil count. His troponin eventually normalized, and his creatinine improved to 1.75 mg/dL.](https://ash.silverchair-cdn.com/ash/content_public/journal/blood/138/12/10.1182_blood.2021011930/4/m_bloodbld2021011930f1.png?Expires=1735811689&Signature=zA0jtICAFLucLgWAdsEeVAJhjPSP7INJHauj4DhKbqEQFTe7AFvDARs7P3uhY6KSkOAITDHWUWULRfKW7Y5p~PMV6gZR5w~HtaCe7Wy7C0Lwqn5Xnm7k3kEndGgt~9S3rTvTkHJBzYCmJUwBRyNsHXRJdasSpUVZegHGeffCy-~MlJoqnxP2MFIPkkmRah8VPvaE2NqjbR8KBrwhr92cRxAx58v5JG1mm5WPYJJ30oAfMUKMyjunnVGlGNRCAFaGkjemdZtMIoASvIJoLkg~UvtNkDkFG4YAhnOT0Q0mIiCJv-441vw7C~l2YllLVgrsYCkyTBdmBx3EXgXt2rda0Q__&Key-Pair-Id=APKAIE5G5CRDK6RD3PGA)
A previously healthy 28-year-old man presented to the emergency department with chest pain and petechiae on his extremities. Labs revealed elevated troponin level (6.86 ng/mL), acute kidney injury (Cr, 1.95 mg/dL), and eosinophilia (WBC, 22 400/µL, 57% eosinophils). Transthoracic and transesophageal echocardiograms were negative for valvular pathology/endocarditis, but a cardiac magnetic resonance image was consistent with myocarditis. Fluorescence in situ hybridization (FISH) from peripheral blood revealed PDGFRA gene rearrangement with FIP1L1-PDGFRA fusion in 75% of interphase cells (panel D; tricolor rearrangement FISH probe, peripheral blood). The serum tryptase level was elevated to 30.9 ng/mL. A bone marrow biopsy demonstrated hypercellular marrow (panel B; hematoxylin and eosin [H&E]-stained bone marrow, 2× objective, ×20 magnification) with granulocytic hyperplasia, increased eosinophilic precursors with maturation (panel A; H&E-stained bone marrow, 40× objective, ×400 magnification), increased mast cells (panel C; tryptase-stained bone marrow, 20× objective, ×200 magnification), increased reticulin network (MF-1 to MF-2 fibrosis), and PDGFRA gene rearrangement. He was diagnosed with hypereosinophilic syndrome secondary to FIP1L1-PDGFRA–positive myeloid/lymphoid neoplasm with eosinophilia and was started on steroids and imatinib treatment. After 2 weeks of therapy, he achieved a complete hematologic response with an undetectable eosinophil count. His troponin eventually normalized, and his creatinine improved to 1.75 mg/dL.
The FIP1L1-PDGFRA fusion protein is a tyrosine kinase that results from a deletion of CHIC2 on chromosome 4q12 and causes transformation of hematopoietic stem cells. Patients with this mutation typically respond well to tyrosine kinase inhibitors, such as imatinib.
A previously healthy 28-year-old man presented to the emergency department with chest pain and petechiae on his extremities. Labs revealed elevated troponin level (6.86 ng/mL), acute kidney injury (Cr, 1.95 mg/dL), and eosinophilia (WBC, 22 400/µL, 57% eosinophils). Transthoracic and transesophageal echocardiograms were negative for valvular pathology/endocarditis, but a cardiac magnetic resonance image was consistent with myocarditis. Fluorescence in situ hybridization (FISH) from peripheral blood revealed PDGFRA gene rearrangement with FIP1L1-PDGFRA fusion in 75% of interphase cells (panel D; tricolor rearrangement FISH probe, peripheral blood). The serum tryptase level was elevated to 30.9 ng/mL. A bone marrow biopsy demonstrated hypercellular marrow (panel B; hematoxylin and eosin [H&E]-stained bone marrow, 2× objective, ×20 magnification) with granulocytic hyperplasia, increased eosinophilic precursors with maturation (panel A; H&E-stained bone marrow, 40× objective, ×400 magnification), increased mast cells (panel C; tryptase-stained bone marrow, 20× objective, ×200 magnification), increased reticulin network (MF-1 to MF-2 fibrosis), and PDGFRA gene rearrangement. He was diagnosed with hypereosinophilic syndrome secondary to FIP1L1-PDGFRA–positive myeloid/lymphoid neoplasm with eosinophilia and was started on steroids and imatinib treatment. After 2 weeks of therapy, he achieved a complete hematologic response with an undetectable eosinophil count. His troponin eventually normalized, and his creatinine improved to 1.75 mg/dL.
The FIP1L1-PDGFRA fusion protein is a tyrosine kinase that results from a deletion of CHIC2 on chromosome 4q12 and causes transformation of hematopoietic stem cells. Patients with this mutation typically respond well to tyrosine kinase inhibitors, such as imatinib.
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