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Longitudinal ridges -

Vertical nail ridges, also called longitudinal ridges, are generally a sign of aging. The clinical name for this condition is onychorrhexis.

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Longitudinal ridges -

Onychorrhexis can also be caused by iron, folic acid, or protein deficiency. As the nails age, their capacity to absorb nutrients diminishes, subsequently affecting their growth.

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Nail pitting -

Nail pitting is when small round depressions or notches appear on the nail surface. It can be a sign of psoriasis, eczema, or joint inflammation.

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Nail pitting -

Nail psoriasis is an autoimmune condition. Also known as psoriatic nail dystrophy, the condition is due to psoriasis involving the nail matrix or nail bed. It affects toenails and fingernails.

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Nail clubbing -

Nail clubbing, also known as digital clubbing, is a deformity of the finger or toe nails. It happens when the tips of the fingers get bigger and the nails curve around the fingertips.

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Nail clubbing -

Nail clubbing usually develops over several years and is associated with a number of diseases, mostly of the heart and lungs. But it can also be indicative of liver cirrhosis, gastrointestinal problems, or low oxygen levels in the blood.

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Terry's nails -

Terry's nails is a physical condition where the fingernail is minus a lunula (the crescent-shaped whitish area of the bed of a fingernail or toenail) and looks white except for a narrow red or pink band at the top.

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Terry's nails -

While Terry's nails sometimes develops because of aging, it may be a symptom of a serious medical condition; it frequently occurs in the setting of liver failure, cirrhosis, diabetes mellitus, congestive heart failure, hyperthyroidism, or malnutrition. Incidentally, the disorder is named after Richard Terry, who in 1954 described white nails in 82 of 100 consecutive patients with cirrhosis.

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Beau's lines -

Beau's lines are horizontal ridges or dents in one or more of your fingernails or toenails. They're a sign that an illness, injury, or skin condition has interrupted your nail growth.

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Beau's lines -

Beau's lines signal a range of medical disorders including infections and diabetes that is not well controlled. It's also indicative of measles, mumps, and pneumonia, among other illnesses. When Beau's line reaches its maximum depth, a condition known as onychomadesis may result.

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Onychomadesis -

The National Institutes of Health (NIH) defines onychomadesis as the proximal separation of the nail plate from the nail matrix due to a temporary cessation of nail growth. In other words, nail shredding.

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Onychomadesis -

Onychomadesis has been attributed to viral infections, autoimmune disorders, drug side effects, and physical trauma. One cause in children is hand, foot, and mouth disease. This condition usually gets better on its own in seven to 10 days.

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Paronychia -

Paronychia is a nail infection that occurs when bacteria gets under the skin around the nail.

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Paronychia -

If not treated promptly, paronychia may progress to a definite and painful abscess. The condition can be acute or chronic.

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Onycholysis -

Onycholysis is a common medical condition characterized by the spontaneous detachment of the nail from the nail bed.

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Onycholysis -

The separation of the nail plate is painless but unsightly and is caused by a nail injury, fungus, or skin diseases such as psoriasis.

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Leukonychia -

Leukonychia describes an either partially or completely whitish discoloration of the nail. There are several potential causes of this particular nail disorder.

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Leukonychia -

While not usually an alarming sign, leukonychia can sometimes be indicative of severe systemic disorders or congenital conditions. Heart disease, kidney failure, ulcerative colitis, and pneumonia have all been linked with the condition. Leukonychia has also been known to unmask arsenic and lead poisoning.

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Melanonychia -

Melanonychia is brown or black discoloration of a nail. It is characterized by brown-black discoloration of the nail plate, quite often appearing as a longitudinal band.

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Melanonychia -

A suspected case of melanonychia should never be ignored. Appearing in fingernails and toenails, the disorder occurs when the pigment cells, called melanocytes, deposit melanin—brown-colored pigment—into the nail. There are two primary processes: melanocytic activation, the causes of which can include pregnancy, lupus, and skin cancer; and melanocytic hyperplasia, the causes of which may include moles or birthmarks, and cancer of the nail.

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Rippled or pitted nails -

A nail that appears rippled or pitted, and is also discolored, with the skin under the nail a noticeable reddish brown, can be indicative of a number of disorders.

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Rippled or pitted nails -

In fact, rippled or pitted nails may be an early sign of psoriasis or inflammatory arthritis.

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Brittle nails -

Dry, brittle nails can occur due to environmental factors or underlying health conditions. The usual cause is repeated wetting and drying of the fingernails, or overexposure to detergents, household cleaners, and nail polish remover. What's more, age can affect the strength of a person's nails.

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Brittle nails -

Nutritional deficiencies, such as a lack of biotin (vitamin B7), zinc, and iron, can also promote brittle nails. More worryingly, anemia and diseases of the thyroid are associated with the condition.

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Absence of lunula -

The lunula is the white area at the base of the fingernail. Not being able to see a lunula, or half-moon, on the nails may be a sign of an underlying medical disorder (though some people only notice a lunula on their thumbs rather than all the fingers).

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Absence of lunula -

Absence of lunulae may indicate anemia, malnutrition, and, interestingly, depression. Findings reported by the National Center for Biotechnology Information also suggest absent lunula may indicate an underlying kidney disease.

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Nail fungus -

Nail fungus is a common infection of the nail. The condition usually affects toenails, but you can sometimes get them on your fingernails, too.

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Nail fungus -

Medically described as onychomycosis, nail fungus begins as a white or yellow-brown spot under the tip of the nail. If left untreated, it can easily spread to the rest of your body, causing itchy, red, and cracked skin.

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Nail biting -

Chronic biting of the nails, also known as onychophagy or onychophagia, may promote infection and can make the skin around your nails feel sore. In severe cases, the habit may damage the nail beds and cause the disappearing of nails.

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Nail biting -

Long-term damage from nail biting is rare. But it does happen, especially if you swallow the bitten nails, which can transport bacteria into your mouth and gut.

Sources: (American Academy of Dermatology) (DermNet) (WebMD) (NHS) (NIH) (National Center for Biotechnology Information) (ScienceDirect) 

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