Disseminated microsporidiosis (Encephalitozoon hellem) and acquired immunodeficiency syndrome. Autopsy evidence for respiratory acquisition.

Microsporidia are obligate intracellular protozoal parasites that infect a variety of cell types in a broad range of invertebrates and vertebrates. They have recently come to medical attention due to the increased frequency with which members of two microsporidian genera, Enterocytozoon and Encephalitozoon, are being diagnosed in patients with the acquired immunodeficiency syndrome (AIDS). The majority of published reports of human microsporidiosis describe Enterocytozoon infection of small intestinal enterocytes. In addition, a growing number of AIDS patients have been identified with infection due to the two species of Encephalitozoon-Encephalitozoon cuniculi and Encephalitozoon hellem, observed in conjunctival, corneal, and, recently, sinonasal tissues. However, there are scant data regarding the systemic pathology and epidemiology of these infections. This article describes a patient with AIDS who died with systemic Encephalitozoon infection. The etiologic microsporidian was found to be E hellem by using antemortem biochemical and antigenic analyses. A complete autopsy, the first to be reported in a patient with this infection, revealed organisms in the eyes, urinary tract, and respiratory tract. A surprising observation was the occurrence of numerous organisms within the lining epithelium of almost the entire length of the tracheobronchial tree, suggestive of respiratory acquisition. Detailed light and electron microscopic findings and the biological and diagnostic features of microsporidiosis are discussed.