We report a case of naevus mucinosus, a recently described condition. Clinically, the lesions presented as unilateral, multiple, firm, 3–5-mm-diameter, coalescent papules in a linear arrangement on the back of a 23-year-old man. Histologically, large amounts of acid mucoploysaccharides (proteoglycans) were demonstrated in the superficial dermis. As far as we are aware, this is the first report of the onset of naevus mucinosus in an adult. Naevus mucinosus appears to be a distinct type of connective tissue naevus which is characterized by an increase in proteoglycans.