An idiopathy is any disease with unknown pathogenesis or spontaneous origin.
From Greek ἴδιος idios “one's own” and πάθος pathos “suffering”, idiopathy means approximately “a disease of its own kind”. For some medical conditions, one or more causes are somewhat understood, but in a certain percentage of people with the condition, the cause may not be readily apparent or characterized. In these cases, the origin of the condition is said to be idiopathic. With some other medical conditions, the root cause for a large percentage of all cases has not been established.
The etiology (cause) of idiopathic normal pressure hydrocephalus (INPH) is not well understood, as the term “idiopathic” indicates that the cause is unknown.