In delusional disorder, patients have false, unshakeable beliefs. They may start doubting the intentions of others or doubt spouse's fidelity or have any other belief about which they are convinced firmly inspite of contrary evidence. It responds to psychotropic medications. It can be treated with medication & kept under control but it can't be cured as it is a chronic illness similar to
diabetes & high bp ( which can be treated but not cured completely).
Since he had responded to medicine before, the dosages need to be adjusted or changed depending upon the response.