We describe a girl presenting with a childhood dermal mucinosis in which we had the unique opportunity to find all the transitional histological features of lichen myxoedematosus (papular mucinosis), from its early focal mucin deposition in the reticular dermis to its late findings of interstitial mucin deposition, dermal fibrosis and fibroblast proliferation. Her father reported having had similar lesions when he was a child, which completely disappeared during adolescence. This case, and a re-evaluation of the literature, suggests that cases of cutaneous mucinosis of infancy that are not hamartomatous conditions such as mucinous naevi are in fact the infantile presentation of lichen myxoedematosus (papular mucinosis) and, in addition to other cases in the literature, suggests a genetic and familial factor in lichen myxoedematosus (papular mucinosis).