Alexis Arquette's Cause of Death Revealed, Actress Battled HIV for 29 Years

The actress and transgender advocate died on Sept. 11. She was 47.

More than a week after Alexis Arquette died, her cause of death has been revealed.

The transgender actress' immediate cause of death was cardiac arrest, according to a death certificate obtained by ET. However, she was also battling HIV.

WATCH: Actress and Transgender Advocate Alexis Arquette Dead at 47

According to the document, Arquette was living with the disease -- the underlying cause of her death -- for 29 years. She suffered a bacterial infection of the heart three weeks before she died of a heart attack on Sept. 11 at the age of 47.

While Arquette transitioned to a woman in the early 2000s, her death certificate interestingly uses her full name, Robert Alexis Arquette, and lists male under sex.

Arquette's brother, Richmond, was the first to share the news of his sister's death.

"Our brother Robert, who became our sister Alexis, who became our brother Alexis, passed this morning September 11, at 12:32 am," he wrote on Facebook. "He was surrounded by all of his brothers and sisters, one of his nieces and several other loved ones."

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Sister Patricia Arquette also took to social media to pay tribute to her late sibling.

"To My first best friend - Cosmic Dancer," she posted to Twitter, alongside a YouTube clip of the T. Rex song.

"Thank you all for your love and kind words about Alexis. My hero for eternity," brother David Arquette tweeted shortly after.

RELATED: David Arquette Says Sister Alexis Does Not Identify as Transgender Anymore