A 59-year-old female with spontaneous painful ecchymoses developed ecchymoses after intracutaneous injection of washed autologous whole blood cells and calf thymus DNA. Immunofluorescent studies of the spontaneous lesions revealed granular deposits of IgM, C3, factor B and properdin at the dermal-epidermal junction but no deposits in her normal skin. T cells were decreased in number but responded normally to polyclonal mitogens and did not transform in response to DNA containing antigens. Repair of UV-damaged DNA by her lymphocytes appeared to be depressed. The findings presented here are the first immunologic abnormalities uncovered in this disorder and may help in understanding the pathogenesis of the inflammatory lesions seen in autosensitization to DNA.