HE hypereosinophilic syndrome comprises various idiopathic myeloproliferative disorders with sustained eosinophilia and damage to the heart, lungs, skin, and other organs by infiltrating eosinophils. 1 A single mechanism for this syndrome has not been identified, and multiple factors are likely to be involved. The serum level of interleukin-5, an eosinophilopoietic cytokine, is increased in some patients with the hypereosinophilic syndrome, 2 and a few have been found to have unusual T-cell abnormalities, including CD3¡CD4+CD8¡ T cells 3,4 and socalled double-negative CD3+CD4¡CD8¡ T cells. 5 CD3, a complex of five proteins associated with the T-cell receptor, is a distinctive feature of all normal T cells. CD4 and CD8 identify helper and cytotoxic T cells, respectively. Recently, Simon et al. described 16 patients with eosinophilia and unusual T cells, some of which secreted abnormal amounts of interleukin-5 when cultured in vitro. 6 The serum levels of interleukin-5 were not reported.We describe a patient with the hypereosinophilic syndrome who presented with a pericardial effusion, endobronchial lesions, and a population of activated T cells that expressed markers of natural killer cells (CD16 and CD56). Serum levels of interleukin-2 and interleukin-15, which are potent stimulators of the proliferation of T cells and natural killer cells, were elevated. After the initiation of therapy with hydroxyurea, the patient's condition improved markedly and the immunologic abnormalities resolved.
CASE REPORTA 34-year-old man was referred to the pulmonary clinic at the National Naval Medical Center in April 1997 after nine months T of worsening cough with dyspnea. He had no personal or family history of asthma, atopy, or serious illnesses. He had received antibiotics intermittently and short courses of oral glucocorticoids for presumed postinfectious bronchospasm, but he otherwise took no medications routinely and had never taken tryptophan or any type of antileukotriene therapy. He had no known drug allergies and did not smoke. A complete blood count obtained during a routine examination in 1989 showed an elevated absolute eosinophil count of 770 per cubic millimeter (normal value, <450). This measurement was not repeated until his presentation in 1997.The physical examination revealed a pulse of 115 beats per minute and diffuse wheezing in both lungs. There were no skin lesions or organomegaly, and the neurologic examination was normal. Initial laboratory studies were remarkable only for the presence of eosinophilia (23 percent eosinophils; absolute eosinophil count, 2074 per cubic millimeter). The serum IgE level was normal. A chest radiograph revealed an enlarged cardiac silhouette but no parenchymal abnormalities. Echocardiography demonstrated a large pericardial effusion.Pericardiocentesis yielded 600 ml of exudate, with 44 percent eosinophils, 6 percent neutrophils, and 50 percent monocytes. The eosinophils appeared to be morphologically mature. Drainage of the pericardial fluid transiently relieved the orthopnea, ...