To review the clinical and diagnostic aspects of mucopolysaccharidosis type II (Hunter syndrome).The different phenotypes are described and the multisystem clinical symptoms are considered, with special emphasis on skeletal deformities and cardiorespiratory and neurological complications.Paediatricians and certain specialists (in neurology, ORL, rheumatology and cardiology) must be aware of the need to increase the clinical suspicion of this condition, which can nowadays be treated using enzyme replacement therapy.