All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.
The diseases which prevent from enjoying sex completely or which prevent from full enjoyment, contagious diseases or dangerous ones which may be transmitted to the other spouse and / or the children, are the diseases which are not permissible to hide from the spouse. Therefore, if a husband conducts a marriage contract and he is not aware of one of the above diseases, he has the choice either to invalidate the contract or keep his wife.
As regards the diseases which do not prevent the spouses from enjoying each other and which do not make one resent from or hate the other because of them, it is not an obligation to inform the spouse about them. One such disease is diabetes, but informing about it is better so that the other party will know about the matter, as this would prevent disagreement and disputes and strengthens harmony and agreement between the spouses.
Finally, we ask Allaah to cure this woman very soon.
For more benefit, please refer to Fataawa 91297, 89168 and 84591.
Allaah Knows best.