Proteus syndrome (PS) is a rare pathology characterized by mosaic and progressive hypertrophies, that can affect any organ or tissue of the body. A genetic mutation in the embryo is at the origin of the disease. Bones, fat, skin and connective tissue are the tissues most typically involved. The extent and severity of the abnormalities vary, giving different clinical presentations. The authors report two cases in two boys aged three and eight years respectively. In both, segmental and organ growth abnormalities, skin abnormalities and lipomas were present. The youngest patient was admitted for the management of severe malnutrition. He presented a major excrescence in the gluteal region, which required surgical management mainly because of its functional impact. In the second patient who was hospitalized following a viral meningoencephalitis, important vascular abnormalities were demonstrated, particularly at the cerebral and abdominal level. The clinical presentation was more severe in the latter, with the installation of an extended coma and a comitial state. PS is a pathology which could be incapacitating. It exposes to a high risk of benign tumours and deep venous thrombosis. The variability of abnormalities and the risks incurred required multidisciplinary management.