Genetic conditions are increasingly recognised as a cause of multisystem diseases in children. We report a 6-year-old boy with hypohidrotic ectodermal dysplasia, immunodeficiency, osteopetrosis and lymphoedema, associated with a novel mutation in the NF–κβ essential modulator (NEMO) gene. He is the longest surviving of three reported boys with these clinical features. Hypohidrotic ectodermal dysplasia, a congenital disorder of teeth, hair and eccrine sweat glands is most commonly inherited as an X-linked recessive trait. Associated immunodeficiency (HED-ID) may give rise to serious infections in early life. Mutations in the NEMO gene give rise to a heterogeneous group of disorders, including the X-linked dominant disorder incontinentia pigmenti. This is characterised by typical skin changes leading to linear pigmentary change and variable associated features; in males, prenatal death usually occurs. Our patient, like one if the previous cases and all of their mothers, demonstrates features of incontinentia pigmenti.