Yellow nail syndrome is a very rare disorder characterized by three features: yellow nail discoloration, respiratory problems, and lower limb swelling (lymphedema). In addition to being yellow, nails may lack a cuticle, grow very slowly, and become detached (onycholysis). Respiratory problems may include chronic cough, bronchiectasis, and pleural effusion. Chronic sinusitis may also occur. The cause of Yellow nail syndrome remains unknown. It usually occurs on its own, but is sometimes associated with autoimmune disease, lymphatic diseases, or cancers.