Lymphocytic variant of hypereosinophilic syndrome: A report of seven cases from a single institution

Background: Lymphocytic variant of hypereosinophilic syndrome (L-HES) is a subtype of HES driven by cytokines produced by clonal T-cells. Due to the rarity of its occurrence and challenges in diagnosis, this subtype of HES is under recognized. Methods and Results: We report seven patients with L-HES, diagnosed from a group of 136 patients who were referred to our institution for the work-up of hypereosinophilia. The clinical presentation, symptoms and signs were heterogeneous and uncharacteristic; indistinguishable from idiopathic HES. Flow cytometry immunophenotypic analysis revealed aberrant T-cells in all patients, with a Th2 immunophenotype, CD2 + CD3−CD4 + CD5 + CD7dim+/−CD8− in six of seven (86%) cases. CD10 was partially expressed in one of seven (14%) cases, and clonal TCR gene rearrangement was detected by PCR in five of seven (71%) patients. All patients were treated with corticosteroids and two of seven (29%) patients received anti-IL5 antibody therapy. With a median follow-up time of 7.5 years (2.3–14.1 years), one (11%) patient developed peripheral T-cell lymphoma 6.1 years after the initial diagnosis of L-HES and responded well to chemotherapy. All patients were alive at the last follow-up. Conclusion: In conclusion, a combination of flow cytometry immunophenotyping and molecular analysis allows the identification of aberrant T-cells, facilitating a diagnosis of L-HES in patients with eosinophilia. A correct diagnosis is essential for the proper management of these patients.