Rizzo, who had been working in Brussels for several months for the European Research Council Executive Agency (ERCEA), was killed in the metro during Tuesday's attacks.
Rome confirmed her death and her cousin Massimo Leone paid tribute to her on Facebook, posting photos and the message: "Patricia, I miss you, we all miss you."
Rizzo was reported missing after the explosion at the city's Maelbeek metro station.
Three other Italians were among over 100 people injured in the metro station explosion, the Italian embassy said on Tuesday.
The process of identifying the victims is painstakingly slow, complicated by the violence of the explosions and because many of the victims were from overseas.
"The number of non-identified people is very, very exceptional," federal
police spokesman Michael Jonnois told AFP earlier this week.
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"It was an 'open' catastrophe, there was no list of who was in the train or at the airport terminal -- there was no passenger list like when there's a plane crash," he said.
Italy on Tuesday raised its security level to 2, the highest possible in the absence of a direct attack.