@DonielF in a comment here seem to clame that (by the end of Ketubot) it is written that a marriage can be annuled (as a mekach tous) if the bride (I guess or her father) withheld information about her medical condition (but did reveal her vows, mumim (phisical deformaties) and her virgin status)
If this true?
(If yes is it all medical conditions?
(If not which ones?))
Where is this written?
Thank You
Yes this is true. Part of the discussion can be found in kesuvos 73b. However, it is not necessarily a simple case. In fact, many cases will have a get issued in order to avoid the complexities, though this causes problems if the woman wants to marry a kohen.
As an example, Rabbi Hershel Shachter writes Making a Farce of the Halacha discusses the situation in which someone attempts to use the concept of mekach taus to free an agunah.
It is important to keep in mind that Rav Moshe Feinstein clearly states that the negative condition must be preexisting and so severe that no reasonable person would tolerate it - and the spouse must leave immediately upon discovering it. In addition a psak of mekach taus based entirely upon negative reports from the wife - without the husband being directly evaulated by a neutral expert therapist - is clearly invalid and indicative of biased poskim.
He states
Furthermore, kiddushin (entering into a marriage) apparently requires a level of da'as even higher than mekach u'memkar (see the famous comment of the Ran to Nedarim 87a. See also Beis Yitzchak 5748, pg. 241). In order to nullify a marriage by reason of kiddushei ta'us (because of lack of da'as), one would presumably require an even more obvious ta'us than what might be sufficient to invalidate a purchase of stocks or a sale of real estate. Indeed, the Talmud (Kesubos 73b) describes certain cases that based on the general principles of ta'us would qualify as kiddushei ta'us and as such would be invalid and should not need a get. Nevertheless, the gemara declares that a get is required- either as a chumra d'rabanan (rabbinical stringency), or perhaps even because of a safek d'oraysa (legal doubt on the biblical level). It is plain from this source that we are more reluctant to invalidate a wedding on ta'us grounds than to declare a mekach taus on a business transaction.
To declare a marriage a kiddushei ta'us because the wife didn't realize that the husband would be unsuccessful in holding down a job and earning a living is simply unacceptable. To invalidate a kiddushin due to ta'us the halacha requires an extraordinary mum gadol (very significant defect), with a very obvious umdana d'muchach (compelling assumption) that no reasonable woman would agree to marry such a man (see Teshuvos Beis Halevi, vol. 3, pg. 23).
There is an analysis of some classic cases at Classic Cases: Mekach Ta'ut, Get and Annulment
