If someone is suspectd to get lupus in later stages i.e 30s-40s.will his blood test for ana & antidns b +iv in 10s-20s without disease symtoms.

Need big picture: I understand that you have mouth ulcers, unexplained weight loss, and are taking azathioprine and Plaquenil / hydroxychloroquine; you have a positive ANA at some titer and anti-dsdna. I suspect you have lupus though no one really knows what lupus is and it's defined by criteria; the burning question is whether to treat this aggressively. You deserve a 2nd opinion beyond what we can do. Best 2u.

Possibly: This is impossible to answer. Most people don't have ANA tests performed unless they are symptomatic so it is impossible to foretell your answer. Relatives of persons with lupus may have a positive ANA test but it does not mean they will definitely develop the disease.