“What are these blue spots?” A mother had brought in her three-year-old daughter. Her story was astonishing. Her daughter had diabetes and she had developed pinpoint blue spots on her thighs, buttocks, and arms, each at the site of certain insulin injections. The spots did not itch and were not tender, but had not faded over a period of months. The mother had also noticed blue-black spots on the top of the rubber stopper of each insulin bottle as it was used, including both regular and protamine insulin. Puzzled by the pigment on the rubber caps, they switched from silicone-treated needles to polymer-coated needles. Both types were standard disposable sterile 28-gauge hypodermic needles. They made no change in the insulin brand. Once this was done, neither their child nor the rubber stoppers got any more blue spots. But why? What caused the blue spots?

Examination revealed about twenty blue to blue-black punctate spots on each upper arm with a scattering of these same points of pigment on the thighs and buttocks. They looked like tattoo spots, and a skin biopsy of one showed a streak of fine black particles extending down into the skin. Obviously, they were along the path of a needle insertion. They did not reflect light as seen with talcum powder. A special stain showed they were not iron, and x-ray spectrometer studies proved they were not of metabolic origin.

Examination of the silicone-treated needles and syringes showed no pigment on flushing with either saline or insulin.