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.

Green Nails

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.

Blue Nails

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.  

Black Nails

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.

White Nails

Also called leukonychia, white nails are seen in many settings. The causes can be classified as:

• True leukonychia due to disease of the nail matrix
• Apparent leukonychia caused by disease of the nail bed
• Pseudo-leukonychia caused by conditions that affect the nail plate, such as onychomycosis

Specific variants include:

• Mees lines: Most often caused by arsenic poisoning, they consist of narrow white lines running transversely across the nails. They may be single or multiple. They persist on blanching. Aside from arsenic toxicity, they may be caused by antimony poisoning, Hodgkin’s disease, mycobacterial diseases, herpes zoster and renal failure, among other conditions.
• Muehrcke’s lines: These consist of a double white transverse line that appears in hypoalbuminemic states, when the serum albumin level falls below 2g/dL, and vanishes when it normalizes. Thus they may be seen in kidney conditions such as nephrotic syndrome or glomerulonephritis, as well as in hepatic disease, and malnutrition. Chemotherapy may also bring it about.
• Lindsay’s nails (half and half nail): This refers to apparent leukonychia. The nail has a normally pink half proximally but the distal part is brownish. It is specific for uremic kidney failure.
• Terry’s nails are associated with congestive heart failure, hepatic failure, and peripheral vascular disease. Other conditions include:
  • • Malnutrition
    • Hyperthyroidism
    • Diabetes mellitus in adulthood
    • Hemodialysis
    • HIV
    • Peripheral vascular disease.

Yellow Nails

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:

• Bronchiectasis
• Rheumatoid arthritis
• Nephrotic syndrome
• Sinusitis
• Tuberculosis
• Raynaud’s disease
• Immunodeficiency

References

• http://www.ncbi.nlm.nih.gov/books/NBK8301/
• http://www.aafp.org/afp/2004/0315/p1417.html
• http://www.nhs.uk/conditions/nail-abnormalities/Pages/Introduction.aspx#Beaus
• http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4375768/
• http://www.aocd.org/?page=GreenNailSyndrome