Nails are often referred to as a window on the body’s state of health or disease. They manifest with a variety of changes in shape and growth, due to systemic conditions which affect their normal growth.
Also known as chloronychia, green nail syndrome is the result of a fungal nail infection. The color may range from bluish-gray to dark green. Seen on either fingernails or toenails, the color is in the nail bed rather than on the nail plate, and so persists even after cleaning the nail. It usually affects one or two nails. It may be associated with paronychia.
The cause of the syndrome is a bacterial infection by Pseudomonas aeruginosa, which produces the green pigments pyocyanin and pyoverdin. It is picked up from wet environments, including a bath sponge or loofah, and the bathroom sink. The risk factors include working in a damp environment, and sustaining nail injury which lifts off the nail.
Bluish-purple peripheral cyanosis of the nails can occur in any condition which interferes with sufficient provision of oxygenated blood to the fingertips. Such conditions include hypothermia, congestive heart failure, disease of the peripheral vessels and cold exposure, all of which lead to a fall in the blood supply to the extremities.
An azure-blue color of the lunula is associated with quinacrine treatment, Wilson’s disease and silver toxicity.
Melanonychia is the term for blackish-brown discoloration of the nails. It is often seen as a normal association with a dark complexion. However, it is also seen with lichen planus. It could additionally indicate a subungual melanoma, or nevus, as well as an adverse effect of some drugs such as psoralens, phenytoin, sulfonamides and antimalarial drugs. Other conditions include malnutrition, thyroid disorders, smoking and hemochromatosis.
Trauma could cause a subungual hematoma to form, which leads to blackish discoloration of the nail bed.
Also called leukonychia, white nails are seen in many settings. The causes can be classified as:
Specific variants include:
Yellow nail syndrome is seen mostly in adults but occasionally occurs in children. The nails are thickened and yellowish-green. The lunula is no longer visible. The nail is excessively curved both transversely and longitudinally, and the cuticle is lost. This condition is associated with respiratory difficulty in pleural effusion, and with lymphedema.
Again, liver disease which results in jaundice may lead to yellow discoloration of the nails. Nicotine also stains the nails, which is a tell-tale sign of heavy smoking. Other conditions which produce yellow nails include: