The acquired immunodeficiency syndrome and other causes of immunosuppr
ession have ushered in a variety of opportunistic infections. One of t
hese is bacillary angiomatosis, a vasoproliferative lesion whose princ
ipal causative agent is Rochalimaea henselae. Bacillary angiomatosis,
while preponderantly a cutaneous affliction, can be systemic, includin
g involvement of the head and neck mucous membranes. Molecular technol
ogy and epidemiologic studies used to identify the bacterial agent of
bacillary angiomatosis have also uncovered R henselae as the organism
responsible for most cases of cat-scratch disease. Why the same organi
sm promotes two different histopathologic lesions, as seen in bacillar
y angiomatosis and cat-scratch disease, is unknown.