Nail abnormalities refer to abnormal color, shape, texture, or thickness of the fingernails or toenails.

Just like the skin, the fingernails tell a lot about a person's state of health.

Pitting (the presence of small depressions on the nail surface) is often accompanied with crumbling of the nail. Detachment of the nail can also occur (the nail becomes loose and sometimes even comes off).

Ridges (linear elevations) can develop along the nail occurring in a lengthwise or crosswise direction.

Beau's lines are linear depressions that occur crosswise (transverse) in the fingernail. They can occur after illness, trauma to the nail, and with malnutrition.

Leukonychia describes white streaks or spots on the nails.

Koilonychia is an abnormal shape of the fingernail where the nail has raised ridges and is thin and concave. This disorder is associated with iron deficiency anemia.

Trauma:

• A crush injury to base of the nail or the nail bed may produce a permanent deformity
• Nail biting can be a sign of anxiety, chronic tension or uncontrollable compulsion
• Chronic picking or rubbing of the skin behind the visible portion of the nail can produce a washboard nail
• Chronic exposure to moisture or to nail polish can produce brittle nails with peeling of the edge of the nail

Infection:

• Fungus or yeast produce changes in the color, texture, and shape of the nails
• Bacterial infection may cause a change in color (green nails with pseudomonas) or painful pockets of infection under the nail or in skin surrounding the nail -- severe infections may cause loss of the nail plate
• Viral warts may cause a change in the shape of the nail or ingrown skin under the nail

Internal diseases:

• Disorders that affect the amount of oxygen in the blood (such as abnormal heart anatomy and lung diseases including cancer or infection) may produceclubbing , in which the nail looks like the back of a teaspoon
• Kidney disease that causes a build-up of nitrogen waste products in the blood
• Liver disease including chronic liver failure
• Thyroid diseases including hyperthyroidism or hypothyroidism may produce brittle nails or splitting of the nail bed from the nail plate (onycholysis)
• Infection (especially of the heart valve) may produce splinter hemorrhages (red streaks in the nail bed)
• Systemic amyloidosis
• Severe illness or surgery may produce horizontal depressions in the nails (Beau's lines)
• Vitamin deficiency can cause a loss of luster or brittle nails
• Malnutrition of any sort can affect the appearance of the nails

Skin diseases:

• Psoriasis may produce pitting, splitting of nail plate from nail bed (onycholysis), and chronic destruction of the nail plate (nail dystrophy)
• Lichen planus

Heavy metal ingestion:

• Arsenic poisoning may produce white lines and horizontal ridges
• Silver intake can produce a blue nail