The classic triad occurs only in about one-third of patients, and involvement of the nails only is observed in about 10% of cases. Lymphedema and respiratory tract involvement may develop before, during, or after the nail dystrophy.
YNS affects men and women equally. It usually presents in the fourth to sixth decade of life.
The pathophysiology is not well understood, but microangiopathy and titanium have both been implicated as being responsible for the disease.
- Microangiopathy as the cause of the nail changes is proposed because dermoscopy of the nail fold capillaries in some patients with YNS showed dilated and tortuous capillary loops.
- Reports have implicated titanium in the development of YNS. Elevated levels of titanium have been found in patients with YNS, and this exposure may be from medications and dental implants. It is thought that the interaction between amalgam and gold leads to the yellow nail color.