Gleich syndrome, sometimes referred to as episodic angioedema with eosinophilia (EAE), is an extremely rare disorder, classified as a subgroup of idiopathic hypereosinophilic syndromes (HES). It is characterized by hypereosinophilia, recurrent nonallergic angioedema, and increased immunoglobulin M (IgM) levels. Angioedema may present as facial or limb edema, and other clinical manifestations of EAE include urticaria, fever, and weight gain.

Reported cases suggest a slight female predilection, with the mean age of onset in the fourth decade. While most cases have occurred in adults, there have been some reports of EAE in childhood. Most reported cases are in the United States, Europe, and Japan. There does not appear to be any genetic or hereditary predisposition.

The exact pathophysiology remains unclear. It is hypothesized that the stimulation of T helper cells with subsequent production of interleukin-5 (IL-5) and IL-6 leads to migration and activation of eosinophils and the production of cationic eosinophilic protein. This propagates an inflammatory reaction, increasing serum viscosity due to vascular wall injury, causing angioedema and weight gain. IgM has been shown to enhance capillary permeability or adherence of eosinophils to capillary walls.

Atypical presentations of Gleich syndrome, including accounts of arthralgia as well as cardiovascular and neurologic involvement, are uncommonly reported, and the disease typically follows a benign course. There have also been reports of a nonepisodic form of the disease where IgM is not increased.

Some of the most commonly reported associated diseases include allergic rhinitis, atopic dermatitis, eczema, uveitis, episcleritis, and asthma. A recent systematic review suggested a relationship between prior asthma and other allergic conditions and disease incidence, with almost 25% of the sample population reporting either allergies, asthma, or both.