Fibrous long-spacing collagen in bacillary angiomatosis.

Fibrous long-spacing (FLS) collagen is a distinct ultrastructural form of collagen present in normal tissue, various tumors, and tissues degraded by bacterial collagenases in vivo and in vitro. An association between FLS collagen and bacillary angiomatosis has not been previously described. Six cases of bacillary angiomatosis, including one autopsy case with disseminated disease, were examined ultrastructurally. In addition, Kaposi sarcoma (3), pyogenic granuloma (3), capillary hemangioma (3), and cavernous hemangioma (2) were examined for comparison. A vascular proliferation in a lymph node from a patient with AIDS (1) and a case of pulmonary capillary hemangiomatosis (1), also in an AIDS patient, were studied. Abundant FLS collagen was identified in 4 of 6 cases of bacillary angiomatosis, in close association with the organisms. FLS collagen was not seen beyond the immediate vicinity of the organisms. The FLS collagen in bacillary angiomatosis was seen in skin biopsies and in lung and skeletal muscle in the autopsy case; in the latter case, as well as in the two AIDS-associated, nonbacillary angiomatosis, non-Kaposi sarcoma vascular proliferations, there was a striking distribution of FLS collagen around small blood vessels. Occasional FLS collagen was observed in all three pyogenic granuloma. When present in pyogenic granuloma, FLS collagen was intermixed with subendothelial collagen. Abundant FLS collagen was identified in close association with the organisms of bacillary angiomatosis in four cases; this morphologic alteration was seen in skin as well as lung and skeletal muscle. An association between FLS collagen and endothelial cells in normal tissue (Descemet's membrane) and in certain vascular proliferations appears to exist.