YNS (Yellow Nail Syndrome) is a rare disorder with unknown etiology and with chronic evolution. It is characterized by three fundamental clinical signs: yellow nails, primary (also called constitutional) lymphedema, and respiratory system dysfunctions. Nail anomalies, that are pathognomonic in YNS, are: decrease or total stop of nail growth, excessive nail curvature, lack of cuticle. These latter symptoms often are present much earlier (by months or years) than the other clinical signs. Systemic therapy with vitamin E has failed to prove effective in the long term, while therapy to control lymphedema is the same as the combined therapy employed in primary lymphedemas.