Isolated molecular relapse in FIP1L1-PDGFRalpha hypereosinophilic syndrome after discontinuation and single weekly dose of imatinib: need of quantitative molecular procedures to modulate imatinib dose.

Imatinib is the treatment of choice for FIP1L1-PDGFRalpha (F/P+) positive myeloproliferative neoplasms, but little is known about optimal dose and duration of treatment to maintain complete molecular remission once achieved. We describe a case of F/P+ patients who started imatinib and reached a molecular remission, but did relapse after 15 months of therapy for poor adherence to therapy, and re-obtained remission only with standard dose of 400 mg/day. We reviewed the literature and highlights the need of quantitative molecular procedures to modulate imatinib dose.