Lethal infection by a previously unrecognised metazoan parasite.

Abstract

BACKGROUND: New microbial pathogens or variant clinical manifestations of known organisms may be first found in immunodeficient patients. An HIV-infected man developed a rapidly-enlarging abdominal mass, suggestive of a neoplasm, that subsequently invaded his liver and caused death. Initial studies showed unusual tissue morphology that could not be matched with any known disease process. METHODS: Tissues obtained from biopsy at laparotomy and necropsy were studied by light microscopy, immunohistochemistry, electron microscopy, and broad-range ribosomal DNA-amplification and sequence analysis. FINDINGS: Tissue lesions were characterised by peculiar cytoplasmic sacs containing minute cells with very prominent nucleoli. The pathological process was recognised as a parasitic infection, although its features were different from those of any known eukaryotic pathogen. Phylogenetic analysis of a 357 bp 18S rDNA sequence amplified directly from the involved tissue indicated that the causative agent was a previously-uncharacterised cestode. INTERPRETATION: Fatal disease produced by this newly recognised cestode may not be limited to immunodeficient hosts. Awareness of this metazoan infection may allow early diagnosis-by morphology and DNA sequence analysis--and perhaps successful treatment of subsequent cases.