A longtime friend of Anna Nicole Smith is claiming that the autoimmune disease lupus could have contributed to her tragic death.

Frank Rodriguez, who appeared with Smith on her reality TV show, says that he was one of the only people who knew about her battle wtih lupus. He is going public with the news now because he thinks that's what killed her.

Last night on Entertainment Tonight, Rodriguez said, " I just remember her telling me she didn't want her fans to remember her this way, that it couldn't get out."

He claims it was her battle with lupus that led to her sometimes strange behavior saying " Her whole body would ache. She would just shut down, basically...She'd black out a lot of the times...I don't want people to remember her for what they say - that she was a drug addict."

 Experts told Access Hollywood that two drugs Anna Nicole Smith is said to have been taking at the time of her death could have been prescribed to treat lupus.

The official cause of Smith's death has not been determined, but  reportedly she was usingTopamax, Dilaudid and Methadone at the time of her death.

Bob Lahita, a physician and professor of medicine at Mount Sinai Medical School told Access Hollywood that sleeping can be difficult when you have lupus because of severe pain. He states that Topamax and Dilaudid could have been used to help Smith sleep.

Anna Nicole Smith's companion, Howard K. Stern is insisting that the lupus report is untrue.