Yours  citizenship  Italian to be finished  in Italy depends on a document called:  Mancata Rinuncia  or popularized as Non Rinuncia and is a process between the comune where the practice is being carried out among the Brazilian consulates. 
This means that the comune where the process is being carried out will send a request to all the consulates where your ancestors were born.  of the citizenship process in order to issue a document stating that none of those people renounced Italian citizenship.   

You can't give up something you don't have, in this case, truly,  the only one who could resign would be the Italian, but for that he would need to have become a naturalized Brazilian. If we have a negative certificate this will never have happened, and it is nothing more than a mere formality that no one can explain its existence. 

This would be justified if the Italian had become a Brazilian citizen, or if any of the people in your straight line process had already obtained Italian citizenship and had formally resigned as follows: 

To renounce Italian nationality.  

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The declaration of renunciation of citizenship is made before the civil registry of the municipality where the applicant resides, or, in the case of residence abroad, the competent diplomatic or consular authority. It must be accompanied by the following documentation: 

The)  Birth certificate issued by the municipality for which this act is written or transcribed. 
B)  Certificate of Italian Citizenship. 
ç)  Documents relating to the possession of foreign nationality. 
d)  Documentation relating to residency abroad, if required.

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Therefore, 99.9% of applicants for Italian citizenship have nothing to worry about in this regard,  She will be  always Non Rinnuncia.