Anidiopathic disease is anydisease with an unknown cause or mechanism of apparentspontaneous origin.[1]
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 beidiopathic. With some other medical conditions, the root cause for a large percentage of all cases has not been established—for example,focal segmental glomerulosclerosis orankylosing spondylitis; the majority of these cases are deemed idiopathic.[2] Certain medical conditions, when idiopathic, notably some forms ofepilepsy andstroke, are preferentially described by the synonymous term ofcryptogenic.[3][4]
The term 'idiopathic' derives fromGreekἴδιοςidios "one's own" andπάθοςpathos "suffering", soidiopathy means approximately "a disease of its own kind".
Diseases where the cause is seen as wholly or partly idiopathic include:
Advances inmedical science improve the understanding of causes of diseases and the classification of diseases; thus, regarding any particular condition or disease, as more root causes are discovered and as events that seemed spontaneous have their origins revealed, the percentage of cases designated as idiopathic will decrease. Environmental and occupational risk factors are increasingly being associated with diseases classified asidiopathic. Emerging evidence indicates a complex relationship between intrinsic (genetic) and extrinsic (environmental and occupational risk factors) factors in disease physiopathology.[5]
The wordessential is sometimessynonymous withidiopathic (as inessential hypertension,essential thrombocythemia, andessential tremor) and the same is true ofprimary (as inprimary biliary cholangitis, orprimary amenorrhea), with the latter term being used in such cases to contrast withsecondary in the sense of "secondary to [i.e., caused by] some other condition." Another, less common synonym isagnogenic (agno-, "unknown" +-gen, "cause" +-ic).
The wordcryptogenic (crypto-, "hidden" +-gen, "cause" +-ic) has asense that is synonymous withidiopathic[6] and a sense that is contradistinguished from it. Some disease classifications prefer the use of the synonymous termcryptogenic disease as incryptogenic stroke,[4] and cryptogenicepilepsy.[3] The use of cryptogenic is also sometimes reserved for cases where it is presumed that the cause is simple and will be found in the future.
Somecongenital conditions are idiopathic, and sometimes the wordcongenital is used synonymously withidiopathic; but careful usage prefers to reserve the wordcongenital for conditions to which the literal sense of the word applies (that is, those whose pathophysiology has existed since theneonatal period).
The termsyndrome without a name(SWAN) is used "when a child or young adult is believed to have a genetic condition and testing has failed to identify its genetic cause". It is believed that "about half (50%) of children withlearning disabilities and approximately 60% of children with congenital disabilities (disabilities which are apparent from birth) do not have a definitive diagnosis to explain the cause of their difficulties".[7][8]
The dictionary definition ofidiopathic disease at Wiktionary