Clinical features of fifteen patients with the hypereosinophilic syndrome.

Fifteen patients with the hypereosinophilic syndrome were studied during a period of 6.5 years. The mean age at onset was 36 years. Two were female. The commonest presenting symptoms were nocturnal sweating with or without severe coughing attacks, symptoms of cardiovascular disease, anorexia and weight loss, neurological and gastrointestinal symptoms and itching with or without skin lesions. The mean blood eosinophil counts at presentation were 20.1 X 10(9)/l. Eight patients had previous allergic or parasitic disease which could have predisposed them to the development of hypereosinophilia. Eight patients had raised serum immunoglobulin levels: IgM in five, IgE in four and IgG in one. Five of nine patients had raised serum eosinophil cationic protein levels. Episodes of clinical relapse occurred with increased white blood counts and were treated with prednisolone and cytotoxic drugs. Thrombotic and embolic complications developed in 10 patients, despite treatment with anticoagulants and inhibitors of platelet function, and were the cause of death in three. Two patients with severe endomyocardial fibrosis responded well to cardiac surgery, and a third required emergency mitral valve replacement. The 12 surviving patients have lived 0.8-11.5 years (mean 4.4), since the onset of their illness. It is concluded that the hypereosinophilic syndrome has distinctive features with an episodic course. The principal complications affect the cardiovascular system, especially endomyocardial fibrosis and thromboembolic occlusion of large and small blood vessels in many organs. Although treatment is usually effective in overcoming relapses, the underlying disease process appears to be unaffected. Despite this, patients can have prolonged periods of remission and may survive for many years.