Idiopathic & Cryptogenic Disease

An idiopathic disease is any disease with an unknown cause or mechanism that appears prima facia of apparent spontaneous origin.[1] 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 have not been established—for example, focal segmental glomerulosclerosis or ankylosing spondylitis; the majority of these cases are deemed idiopathic.[2] With other conditions, idiopathic cases account for only a small percentage (for example, pulmonary fibrosis).[3]

Advances in medical science improve the study 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 decreases.

The word essential is sometimes synonymous with idiopathic (as in essential hypertension, essential thrombocythemia, and essential tremor) and the same is true of primary (as in primary biliary cholangitis, or primary amenorrhea), with the latter term being used in such cases to contrast with secondary in the sense of “secondary to [i.e., caused by] some other condition.” Another, less common synonym is agnogenic (agno-, “unknown” + -gen, “cause” + -ic). The word cryptogenic (crypto-, “hidden” + -gen, “cause” + -ic) has a sense that is synonymous with idiopathic[4] and a sense that is contradistinguished from it.

Some disease classifications prefer the use of the synonymous term cryptogenic disease as in cryptogenic stroke,[5] and some forms of epilepsy. The use of cryptogenic is also sometimes reserved for cases where the cause is presumed to be simple and which will be found in the future.

Some congenital conditions are idiopathic, and sometimes the word congenital is used synonymously with idiopathic; but careful usage prefers to reserve the word congenital for conditions to which the literal sense of the word applies (that is, those whose pathophysiology has existed since the neonatal period).

 Not to confuse with a Diagnosis of Exclusion

A diagnosis of exclusion (per exclusionem) is a diagnosis of a medical condition reached by a process of elimination, which may be necessary if presence cannot be established with complete confidence from history, examination or testing. Such elimination of other reasonable possibilities is a major component in performing a differential diagnosis.

The largest category of diagnosis by exclusion is seen among psychiatric disorders where the presence of physical or organic disease must be excluded as a prerequisite for making a functional diagnosis. Diagnosis by exclusion tends to occur where scientific knowledge is scarce, specifically where the means to verify a diagnosis by an objective method is absent. As a specific diagnosis cannot be confirmed, a fall back position is to exclude that group of known causes that may cause a similar clinical presentation.

An example of such a diagnosis is “fever of unknown origin”: to explain the cause of elevated temperature the most common causes of unexplained fever (infection, neoplasm, or collagen vascular disease) must be ruled out.

Reference

  1.  “Idiopathic”. Concise Medical Dictionary (8th ed.). doi:10.1093/acref/9780199557141.001.0001
  2. Daskalakis N, Winn M (2006). “Focal and segmental glomerulosclerosis”. Cell Mol Life Sci. 63 (21): 2506–11. doi:10.1007/s00018-006-6171-y
  3. “Medical Encyclopedia: Idiopathic pulmonary fibrosis”. MedlinePlus. Retrieved 2007-02-13.
  4.  “cryptogenic”. Dorland’s Illustrated Medical Dictionary. Elsevier. (Subscription required (help)).
  5.  Ahmad, Y; Howard, JP; Arnold, A; Shin, MS; Cook, C; Petraco, R; Demir, O; Williams, L; Iglesias, JF; Sutaria, N; Malik, I; Davies, J; Mayet, J; Francis, D; Sen, S (24 March 2018). “Patent foramen ovale closure vs. medical therapy for cryptogenic stroke: a meta-analysis of randomized controlled trials”. European Heart Journal. 39 (18): 1638–1649. doi:10.1093/eurheartj/ehy121

 

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