Lupus recurring after numerous years of remission

Good Afternoon, All. I'm hoping for some validation. In 1973 I was given Azo Gantrisin for a UTI. I quite quickly developed a butterfly rash, joint pain and extremely fatigued. I was quickly pulled off this med yet it took me approximately a year to recover from joint pain and fatigue. (I was in my early 20's at the time) Doctors at that time did not treat me for any of the symptoms. I don't recall any flare ups until now at age 71. I have not taken any medications other than an anti-anxiety med which I have taken for years. Doctors are now questioning me and of course the doctor prescribing this med in 1973 has long since passed as are my records from way back then. Any suggestions? Has anyone else experienced this kind of scenario? Any and All suggestions would be greatly appreciated. Thank You, All. Sincerely, MelW