The fingernails (its shape, color, and texture) reflect our general health status. As such certain diseases and other disturbances in the body may impact on the fingernails and even the toenails in different ways. This may be seen as a change in the shape, color and/or texture of the nails. The usual color of healthy fingernails is a shade of whitish-pink to a very light brown color. The blood flow underneath the nail (in the nail bed) gives it a pinkish tinge.
Not every person has the exact same shade of fingernail color. Some variation in the white shade of fingernails is considered normal. However, excessive discoloration may point to an underlying health problem. A brownish discoloration of fingernails (technically called melanonychia) is one such condition that could result from a variety of health abnormalities. The brownish discoloration may either affect the entire area of a fingernail or be localized to only a specific part of it. The discoloration my appear as spots, streaks or bands on the nail surface.
However, not all discolorations of nails are due to diseases. Melanonychia may also be observed in some normal health conditions. For example, brownish fingernails may be present in certain races with a darker skin pigmentation. This is known as racial melanonychia, and is not abnormal. Melanonychia may also occur in pregnancy. However, this is a temporary condition and resolves on its own after childbirth.
Causes of Brown Fingernails
Brown fingernails are caused by a variety of conditions. Some of the causes are external factors that are not associated with any internal disorders or diseases. Others include diseases that cause widespread systemic abnormalities, including on the fingernails.
Following are some of the common causes of brown fingernail discoloration:
Cigarette smoking affects the body in many adverse ways. Yellow to brown discoloration of teeth and fingernails is a common occurrence in long-term smokers. However, these stains are not permanent. They tend to fade away after a person quits smoking.
Contact with chemicals such as paints, inks, dyes, nail polishes, varnishes, and nail polish removers could also lead to brownish discoloration of nails. This type of discoloration is also reversible, and goes away once contact with the offending chemical agent is removed.
Damage to fingernails is another external cause of fingernail discoloration. Nail damage is frequently caused by some kind of mechanical trauma. Nail biting is a common example. Presence of a foreign body under the nail could also lead to discolored fingernails. Fingernail damage can also be caused by heat.
Exposure to radiation and intense sunlight for prolonged periods of time can lead to fingernail discoloration.
Fungal infections of the nails (technically called onychomycosis) can lead to brownish discoloration of the fingernails. Fungal nail infections are most commonly caused by a group of fungi known as dermatophytes. These dermatophytes are also responsible for fungal skin infections in other parts of the body (such as ringworm, tinea pedis, and tinea cruris).
Psoriasis is an autoimmune disease that is characterized by skin abnormalities such as thick, rough, itchy and silvery patches. These skin conditions are caused by abnormalities in turnover of skin cells. Both finger and toe nails may also be affected in psoriasis, causing their discoloration.
Like psoriasis, lichen planus is an autoimmune disorder that affects the skin and the mucus membranes. It is a rare disease, and skin discoloration is a common feature of this condition. Both fingernails and toenails may be affected. Brown discoloration and other nail abnormalities may occur. There is no cure for lichen planus. However, the symptoms of the condition tend to resolve on their own with time.
Nevus refers to circular brown moles on the skin. They are commonly called “birthmarks” or “beauty marks”. Although they are benign, some skin cancers do arise from pre-existing nevi. Nevi could also cause brown spots on the fingernails.
Scleroderma, also known as systemic sclerosis, is a rare condition that mostly affects women. It is characterized by hardening of the skin. The fingernails may show a rough surface and discoloration.
Macronutrient and micronutrient deficiencies can cause nail discoloration. Examples include vitamin B12 deficiency, zinc deficiency, and malnutrition. Both fingernail and toenails may show yellow, brown or gray discoloration in these deficiency conditions.
Fingernail discoloration is also caused by toxicity or excessive intake of certain elements. The culprits include arsenic, iodine, fluoride, mercury and thallium.
Brown discoloration of fingernails is also associated with intake of certain medicines. Some of the drugs associated with brown fingernails include tetracycline (an antibiotic), lamivudine (an antiretroviral drug), chemotherapeutic agents, corticosteroids, salts of gold, phenythoin, psoralens, and chlomipramine (a tricyclic antidepressant).
Genetics also plays a role in the coloration of the fingernails. Brown discoloration of fingernails is a common occurrence in two different genetic conditions – acrodermatitis enteropathica, and keratosis follicularis. Both are rare genetic diseases. In acrodermatitis enteropathica, there is a defect in a gene called ZIP4. The ZIP4 gene encodes a zinc transporter protein. ZIP4 mutation compromises the ability of intestinal cells to absorb zinc from food, resulting in zinc deficiency. On the other hand, keratosis follicularis (also known as Darier disease) affects calcium transport into cells. This genetic disease leads to various abnormal skin conditions.
Various hormonal disorders (technically known as endocrine disorders) could also result in brown fingernails. Hormonal disorders refer to conditions in which the quantity or quality of hormones produced is adversely affected. Examples include Addison disease, Cushing syndrome, hyperthyroidism, and diabetes mellitus.
Certain skin cancers, such as malignant melanoma and basal cell carcinoma, can also cause brown fingernails. However, this is a rare event. Also, the brown discoloration of fingernails in these cancers may actually be due to an effect of cancer on the nail bed, rather than on the nail itself.
Apart from the conditions mentioned above, there are a variety of other causes for skin and fingernail discoloration. These conditions affect many different organs of the body. Examples include infective endocarditis, hemosiderosis, hyperbilirubinemia, kidney failure, liver disease, Peutz-Jeghers syndrome, porphyria, systemic lupus erythematosis (SLE), and acquired immunodeficiency syndrome (AIDS).