1. De Quervain's syndrome may be considered an occupational disease in many cases.
2. Its cure is very frequently accompanied by a predisposition to rheumatoid arthritis. De Quervain's disease may be an integral part of the clinical picture of rheumatoid arthritis or the collagen diseases.
3. The anatomical findings suggest that the existence of more than two tendons in the radial osteofibrous groove should not be considered abnormal.
4. The phylogenic development of the thumb also forms a plausible motive for the modification of the classic concept of de Quervain's disease.