In this issue of the Archives, Quimby et al1 discuss 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 I2,3 first 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
Dahl MV. Immunofluorescence, Necrobiosis Lipoidica, and Blood VesselsFluorescent Lights in the Tunnels. Arch Dermatol. 1988;124(9):1417-1419. doi:10.1001/archderm.1988.01670090073017