Summary Erdheim–Chester disease (ECD), a type of systemic non‐Langerhans cell histiocytosis, is uncommon and characterized by the accumulation of CD68+CD1a− foamy histiocytes. It is extremely rare in children. The skin lesions of paediatric ECD have not been systemically described before. We report a case of ECD in a 3·5‐year‐old Chinese boy. The patient presented with generalized skin and bone involvement of 3 years’ duration. Marked generalized annular maculopapular lesions with central atrophy were seen. These differed from previously reported adult xanthoma‐like papules or periorbital xanthelasma‐like lesions. Computed tomography revealed diffuse pulmonary fibrosis and generalized skeletal involvement, including osteolysis and osteosclerosis. The presence of CD68+CD1a− histiocytes allowed the diagnosis of ECD. According to our review of the literature, this is the paediatric case of ECD with the youngest age of onset. The generalized skin involvement made our case unique in comparison with those previously reported. What's already known about this topic? Erdheim–Chester disease (ECD) is extremely rare in children, and skin lesions have not been described systemically before. What does this study add? The patient presented with generalized annular maculopapular lesions with central atrophy, which differed from previously reported xanthoma‐like papules or periorbital xanthelasma‐like lesions. Computed tomography and the presence of CD68+CD1a− histiocytes allowed the diagnosis of ECD to be made. The case described here has the youngest age of onset reported, and the generalized skin involvement makes it unique in comparison with previous reports. Linked Comment: Chasset and Haroche. Br J Dermatol 2018; 178:31–32.