Immunofluorescence, Necrobiosis Lipoidica, and Blood Vessels

In this issue of theArchives, Quimby et al1discuss the cutaneous immunopathology of necrobiosis lipoidica diabeticorum (NLD). They studied biopsy specimens obtained from 12 patients with NLD by direct immunofluorescence and found the following fluorescing immunoreactants in involved skin of 11 patients: IgM (six patients), C3 (nine patients), IgG (one patient), and IgA (two patients). Even in uninvolved skin, vessels contained deposits. IgM was deposited in vessels in three patients, C3 in four, and IgA in one. Ullman and I2,3first examined blood vessels of patients with NLD for the presence of immune deposits a decade ago because the histologic features suggested a vasculopathy. Nonetheless, we were a bit surprised to find them. Immune complexes in vessels are frequently associated with a vasculitis. Yet, the indolent plaques of necrobiosis do not reek with the clinical signs of vasculitis—purpura, edema, and necrosis. Furthermore, the inflammation around blood vessels