In medicine, a forme fruste (French, "crude, or unfinished, form"; pl., formes frustes) is an atypical or attenuated manifestation of a disease or syndrome, with the implications of incompleteness, partial presence or aborted state. The context is usually one of a well defined clinical or pathological entity, which the case at hand almost — but not quite — fits.
An opposite term in medicine, forme pleine — seldom used by English-speaking physicians — means the complete, or full-blown, form of a disease.
According to gastroenterologist William Haubrich:
A patient may exhibit sudden, intense, epigastric pain and a rigid abdomen. He is thought to have a perforated peptic ulcer. But at operation, only a penetrating ulcer is found, sealed off by adhesion to the omentum or anterior abdominal wall. Such a patient is said to have a forme fruste of acute free perforation as a complication of his peptic ulcer disease.[1]
The Latin phrase frustra esse means "to be mistaken" or "to be confused". As a technical term in French, the cognate fruste has been used in two related ways. First, as an antiquarian’s term it refers to a coin, medal or ancient stone on which figures and characters can no longer be recognized due to wear. Secondly, it was employed in natural history to denote mollusk shells whose striations, grooves or tips were worn down. By extension, this sense could be applied to sculpture, pottery, or other objects of great antiquity.
It was in this sense of "indistinctness due to wear or through long use" that the French internist Armand Trousseau (1801–67) first employed the term in connection with an obscured form of Graves' disease, which he described as a "…maladie dite fruste par l’absence du goitre et de l’exophthalmie" ("…disease said to be crude [i.e., indistinct] for its absence of goiter and exophthalmia")[2]
The sense of the term in medicine has slightly evolved to mean a "not fully developed form of an illness", rather than simply an obscure form. Sigmund Freud (1856–1939) often used the term forme fruste in connection with incomplete or obscured cases of neuroses and psychoses and thus the literature of psychoanalysis is replete with it. (An equivalent term in German is minimalvariante, but Freud used the French version.)
Forme fruste bipolar disorder (cyclothymia) - a variant of bipolar disorder characterised by regularly alternating periods of both heightened and depressed mood, neither of which meet the full criteria for mania, hypomania or depression.
Forme fruste schizophrenia forms (paranoid and schizotypal personality disorders) - Cluster A personality disorders which represent an accentuated variant of the whole schizophrenic process (schizotypal personality disorder) or the paranoid subtype specifically (paranoid personality disorder). Schizoid personality disorder, the third Cluster A personality disorder, is often also considered a "schizophrenia spectrum disorder."
. Huda Zoghbi. The Story of Rett Syndrome: From Clinic to Neurobiology. 2007. Cell Press. https://archive.today/20120707043040/http://ac.els-cdn.com/S0896627307007568/1-s2.0-S0896627307007568-main.pdf?_tid=f8e8d8b47fae7d2941b9b3f05edf1553&acdnat=1335101224_91c30fe7a68f3633df00258c94c0c142. dead. 2012-07-07.