Hypereosinophilia is a common biological finding in clinical practice, in some cases without an identifiable cause. We describe the case of a 59-year-old woman with recurrent attacks of facial angioedema, fever, pruritic cutaneous nodules, and eosinophilia that reached up to 12.7 x 10(9) cells/L during outbreaks. She had experienced 2 episodes every month for the last 12 years, and the episodes resolved with systemic corticosteroids. Other causes of eosinophilia were ruled out. The patient showed an aberrant T cell population with a CD3-CD4+ TCR- phenotype that accounted for up to 22% of circulating lymphocytes. Analysis of the T-cell receptor (TCR) gene showed evidence of clonal rearrangement. During the episodes, this cell population produced high levels of interleukin-5, which returned to normal levels between the outbreaks. However the aberrant T cell population remained unaffected after the treatment. We suggest that lymphocyte immunophenotyping analysis should be included in the diagnostic workup of patients with hypereosinophilic syndrome, including the variant type of episodic angioedema and eosinophilia (Gleich syndrome).