Lymphocytic variant of hypereosinophilic syndrome.

Hypereosinophilia may be associated with any of several underlying diseases. Atopy or allergic drug reactions are the most common causes, but infections with bacteria and parasites should also be considered in the differential diagnosis. When thorough evaluation of a patient with chronic hypereosinophilia fails to reveal an underlying disease, the diagnosis of idiopathic hypereosinophilic syndrome (HES) should be considered. We report a patient with unexplained persistent hypereosinophilia associated with a chronic pruritic rash and an underlying diagnosis of HES (lymphocytic variant).