Provided the high cost of these new therapies and the challenges in designing and implementing the clinical trials necessary for regulatory approval (and insurance reimbursement) in rare diseases, selection of the right drug for an individual patient is becoming increasingly important

Provided the high cost of these new therapies and the challenges in designing and implementing the clinical trials necessary for regulatory approval (and insurance reimbursement) in rare diseases, selection of the right drug for an individual patient is becoming increasingly important. Objectives Compare and contrast the most common agents used to treat hypereosinophilic syndrome Discuss recent advances in targeted therapies for eosinophilic disorders Introduction A 50-year-old woman with a history of urticaria, sinusitis with nasal polyps, and eosinophilia presented with dyspnea and palpitations. Absolute eosinophil count (AEC) was 23?400/L. Echocardiogram showed RI-2 severe mitral regurgitation, marked bilateral atrial enlargement, and severe pulmonary hypertension. A bone marrow biopsy performed several years earlier RI-2 was normocellular with increased eosinophils, but there was no evidence of myeloid neoplasia. Hypereosinophilic syndrome: definition and classification Since the first description of eosinophilic endomyocardial fibrosis by Loeffler in 1934,1 the definition and classification of hypereosinophilic syndromes (HESs) have evolved considerably. In 1975, Chusid et al2 described 14 cases of idiopathic HES defined by the presence of an AEC 1500/L for 6 months (or death before that time), the absence of a known secondary cause, and evidence of eosinophilic end organ manifestations. The patients in that study included individuals with Churgs eosinophilic granulomatosis (or eosinophilic granulomatosis with polyangiitis [EGPA]), idiopathic eosinophilia with gastrointestinal involvement (eosinophilic gastrointestinal disease), and eosinophilic leukemia, clearly showing the heterogeneity of HES. In the 40 years since their report, more effective therapies have become available, making the 6-month requirement to make a diagnosis increasingly problematic. Moreover, the identification of recurrent molecular abnormalities and secondary causes driving the eosinophilic manifestations in some patients with HES, as defined by Chusid et al,2 has led to controversy regarding the definition and classification of this rare syndrome. For the purposes of this review, HES will be defined according to a consensus definition developed by a multispecialty group of experts Hpt as (1) AEC 1500/L and clinical manifestations attributable to eosinophilia or (2) tissue hypereosinophilia with blood eosinophilia (AEC above the upper limit of normal for the reference laboratory).3-5 In contrast to the World Health Organization definition of HES,6 which excludes myeloid neoplasms associated with recurrent molecular abnormalities, the consensus definition includes at any time during their life, empiric ivermectin therapy (200 g/kg orally daily for 2 days) should be given concomitantly to prevent potentially fatal GC-associated hyperinfection syndrome.12 Intravenous administration of GC should be considered for patients who are acutely ill and/or have gastrointestinal involvement that may impair absorption. Cyclophosphamide should be added if EGPA is suspected based on clinical features, including but not restricted to asthma, sinus disease, and pulmonary infiltrates, and criteria for poor prognosis are met.13 Patients with known imatinib-sensitive mutations, including and translocations involving mutations are detected using currently available testing, and false negative results can occur, imatinib should also be considered as first-line therapy for patients who present with clinical features of this diagnosis (eg, male gender, splenomegaly, elevated serum B12 and/or tryptase levels, and a hypercellular marrow with dysplastic eosinophils and mast cells) and unknown or negative status.7 High-dose GCs should be added for the first few days if there is evidence of cardiac involvement (elevated serum troponin or echocardiographic abnormalities) to prevent myocardial necrosis, a rare complication of imatinib in this patient population.14 Although every attempt should be made to perform a limited diagnostic evaluation before the administration of GC, therapy should not be delayed for this purpose in the face of worsening signs and symptoms. More stable patients RI-2 with presumed HES should undergo comprehensive evaluation before initiation of treatment. Initial diagnostic testing should focus on identification of the etiology of the eosinophilia, classification by clinical variant, and delineation of end organ involvement (Table 2). In an acutely ill patient, tests that are affected by GC therapy should be prioritized. Table 2. Initial diagnostic testing in the patient with presumed HES and analysis by FISH or RT-PCRTesting of peripheral blood has comparable sensitivity to bone marrow; false negative results can occur, especially with FISH testing?T- and B-cell receptor rearrangement studiesClonal patterns are typical (but not diagnostic) of LHES?Lymphocyte phenotyping by flow cytometry*At a minimum, CD3, CD4, CD8, and CD19 or CD20 staining should RI-2 be performed to assess for aberrant CD3?CD4+, CD3+CD4+CD8+, and CD3+CD4?CD8? populations and B-cell lymphoproliferative disorders?Patients with features of MHES?Additional testing for mutations by PCR, FISH, or other methods as appropriateTesting should be guided by bone marrow findings?Myeloid mutation panel testingConsider if.