Stroke-induced purpura in lesions of colloid milium.

We describe three patients with colloid milium whose lesions showed purpura upon stroking. Two of these patients had juvenile colloid milium and the third had adult colloid milium. Ultramicroscopic examination of purpuric colloid papules showed that the dermal blood vessel walls were infiltrated by colloid material. Traumatic purpura occurring in colloid milium may be analogous to that occurring in systemic amyloidosis. We suggest that the infiltrating colloid material decreases the elasticity of dermal blood vessel walls, accounting for the purpura following minor trauma.