De Quervain’s tendinitis is a condition that affects the base of the thumb. Any limitation in the use of your thumb would limit the number of jobs available to you. I cannot think of a job where you would not need to use your thumb. However, this condition is typically highly treatable with splints, injections and physical therapy. Sometimes surgery is required, but it is typically successful. If you have this condition it would most certainly contribute to the limitations that would prevent you from being able to work, but it is unlikely that you would be able to get disability benefits on the basis of this problem alone. It is very important that you are compliant with your doctor’s prescribed treatment to the extent that you finances will allow.
However, there are a few situations in which you have so many other problems that the loss of dexterity in a hand pushes you over the edge into disability. For example, if you cannot walk, you cannot handle stand up work. If you also cannot read, you cannot handle clerical work. That leaves benchwork assembly, which requires rapid, dexterous manipulation with both hands — which is impossible if you also have Dequervain’s disease.