CAT-SCRATCH DISEASE AND ACQUIRED IMMUNODEFICIENCY DISEASE - DIAGNOSISBY TRANSMISSION ELECTRON-MICROSCOPY

A 33-year-old, homosexual, cat-owning, African-American man with human immunodeficiency virus infection by positive serologic tests and acqu ired immunodeficiency syndrome by CD4 lymphocyte count alone (39 cells /mL) presented with a one-year history of intermittent fever, weight l oss, and generalized lymphadenopathy. A malignant lymphoma was suspect ed clinically. Light microscopic study of a left inguinal lymph node b iopsy specimen revealed effacement of the lymph node architecture by a diffuse infiltrate of large, atypical reticulum cells, loose, patchy granulomatous inflammation, diffuse hyaline fibrosis, diffusely prolif erated blood vessels, and multifocal degeneration and necrosis. Lymph follicles were absent and lymphocytes were moderately depleted. Microo rganisms were not seen in lymph node sections stained with special his tochemical stains (including the War-thin-Starry stain). These light m icroscopic changes were considered suggestive of a malignant lymphoma, especially Hodgkin's disease. The diagnosis of cat scratch disease (C SD) became apparent only after transmission electron microscopic study of the lymph node revealed clusters of small, pleomorphic bacteria in degenerated collagenous tissue and in blood vessel walls. This case i llustrates the value of transmission electron microscopy in making the diagnosis of CSD, especially when light microscopic changes are super imposed on those of late human immunodeficiency virus infection of the lymph node.