Re: What age
DeeDee, My understanding is the same as Shaymari's.
A famous British rheumatologist compiled a list of problems seen earlier in people who LATER ON go on to fulfill the ACR criteria. He calls his list "alternative criteria". Both the ACR criteria & the "alternative criteria" are in "sticky posts" ( = permanent info posts). See the top of the thread list.
Also, subacutes (no involvement of really major organs like kidney, CNS, heart, lung, etc.) may fly under the radar. I had multiple hospitalizations ages 3 thru 6, skin rashes at 8, a year of fever/ pain at 13, GI & urinary problems from mid-20's, next migraines, ETC. But the defining rashes that could ONLY be lupus arrived last, in my early 40's. I'll never even know whether I had lupus for years---or a long, slow trajectory.
Hope above helps. Is it YOU you're asking about, or someone close? Take good care, Vee