The narrow charmonium state near 3872 MeV reported by the Belle Collaboration and confirmed by CDF lies almost exactly at the D 0 D * 0 threshold. As was predicted many years ago it can be a DD * deuteronlike meson-meson state called a deuson. If so, its spin-parity should be 1 + + , or possibly 0 - + , and its isospin predominantly 0. An important decay mode should be via D 0 D * 0 to D 0 D 0 π 0 . Large isospin breaking is expected because of the isospin mass splitting between the neutral and charged D (D * ) mesons. Because of this large isospin breaking the decay X(3872)->J/ψρ would be allowed, while J/ψσ would be forbidden by C-parity, as indicated by the present data.