There are many. Catatonia is a syndrome that most often occurs when someone is having a major depressive or manic episode. It can occur with other psychiatric or neurological illnesses. There are abnormal signs on a neurological exam, blood pressure/temperature/heart rate swings, either severe psychomotor slowing or nonspecific agitation, decreased ability to communicate with language and odd posturing behaviors.
Catatonia is not an. Illness, but a symptom involving changes in muscle tone/activity. Catatonic stupor involves a lack of movement while catatonic excitement involves violent movement towards oneself or others.