Positive ana 1:40 homogenous and speckled mixed pattern. what could cause this?

Autoimmune disorder: Lupus or other autoimmune disorder a possibility. Those titre numbers (1:40) are not extremely elevated so it may also be a normal variant. Also other connective tissue disorders possible: polymyositis, rheumatoid, sjogren's, etc. You probably need additional blood work and to possibly see a rheumatologist.

Not a significant: elevation. If you are having symptoms you can see a rheumitologist. You can have it repeated when you have symptoms and see if it is elevated more.