The nails often give an idea about a person’s health. Black or dark stripes on the fingernails and/or toenails may indicate a normal phenomenon, but sometimes also a serious problem such as melanoma. For nail changes such as a nail stripe, it is best for the patient to consult a doctor to be sure about the possible cause. This way, treatment is not delayed and the prognosis of any underlying medical condition is often better.

• Linear melanonychia and black lines on nails

• In African Americans
• Other causes

• Fungal infections and dark nail stripes
• Splinter hemorrhage and dark colored lines on fingernails
• Subungual melanoma and black line or lines on nail
• Nutritional deficiencies and nail stripes
• Diagnosis and examinations
• Alarm signals
• Prognosis of nail abnormality

Linear melanonychia and black lines on nails

In African Americans

Most often, dark streaks on the nail are the result of linear melanonychia. These stripes are common in people of African-American descent who are twenty years of age or older. About half of African Americans experience this nail disorder. Linear melanonychia is a normal variation in fingernail color. The nail disorder occurs when pigments (color cells) in the nail (melanocytes) produce excessive amounts of pigment. This gives the nail beds a darker color.

Other causes

Some less common causes of nail melanonychia include:

• an HIV infection
• the Laugier-Hunziker syndrome
• taking certain medications, such as chemotherapy, beta blockers (medications that lower heart rate and blood pressure), anti-malarial medications, or azidothymidine
• the Peutz-Jeghers syndrome (symptoms in the small intestine and skin)
• scleroderma (build-up of scar tissue in tissues and organs)
• systemic lupus erythematosus (autoimmune disorder)

The dark stripes on the nails have variable color shades in black, to deep brown and gray. These lines normally appear on two to five fingernails, but not necessarily on all ten.

Fungal infections and dark nail stripes

With most fungal infections of the fingernail and palm, abnormalities on the fingernails first appear, such as lines on the nails.

Splinter hemorrhage and dark colored lines on fingernails

Another cause of black or dark colored lines on the fingernails is splinter hemorrhage. The splinter hemorrhage manifests itself when small blood vessels under the nail beds of the fingernails are damaged, often as a result of injuries. Small black or deep red lines appear on the nails. They usually heal on their own within a few days. If a patient has multiple splinter hemorrhages on different nails, this sometimes indicates an underlying condition that requires medical treatment, such as:

• Raynaud’s disease (changes in skin color with cold and pain)
• a lung condition
• a kidney disease
• a circulation problem
• a fungal nail
• endocarditis (inflammation of the lining of the heart)
• infections
• lichen planus (symptoms of mouth, skin and genitals)
• psoriasis (chronic skin disease with dry skin and flakes)
• systemic lupus erythematosus
• vasculitis (blood vessel inflammation)

The use of chemotherapy or medications that alter blood clotting may also cause splinter hemorrhage, which causes black streaks on the nails.

Subungual melanoma and black line or lines on nail

A black line or lines on the nails sometimes indicate the presence of melanoma, a dangerous form of skin cancer. A melanoma under a fingernail is known in medical terms as a subungual melanoma. One of the types of melanoma is known as acral lentiginous melanoma. About half of all melanomas on the hands and feet are due to acral lentiginous melanoma. When a patient has a subungular melanoma, he often only has a stripe on one fingernail. Often a patient is unable to link the appearance of the stripe to an injury. The stripe often darkens or widens over time. Sometimes nail pain or nail bleeding occurs. The pigmentation sometimes extends to the cuticle, which represents the keratinized layer of skin on the nail wall. When the color spreads to this area, it is known as the Hutchinson sign, which is often an indicator of the presence of melanoma. It is located on the fingernails or toenails. The doctor first removes the melanoma area and the skin under the affected fingernail. He then performs a skin graft to improve the appearance of the finger after surgery. If the melanoma has spread to the bone, an amputation of the finger is necessary so that the melanoma can no longer spread further (metastasize).

Nutritional deficiencies and nail stripes

When the patient consumes a poor diet that causes mineral and vitamin deficiencies, dark lines sometimes appear on the fingernails. Consuming a healthy and balanced diet is necessary.

Diagnosis and examinations

The doctor asks the patient questions, for example how long the nail lines have been present, whether changes have occurred in the lines, whether the patient has had a nail trauma, whether the patient has nail pain. The doctor also wants information about medication use. The use of blood thinners (such as Warfarin or aspirin) in the past explains splinter hemorrhages. Sometimes a doctor takes a biopsy or tissue sample from the nail space and sends it to a pathologist. He then determines whether cancer cells are present, which confirms the presence of a subungual melanoma.

Alarm signals

It is especially important to see a doctor if a nail is bleeding or painful. Medical advice is also necessary for nail changes without a known cause. In addition, the patient visits the doctor for thinner nails, cracked nails or a changed nail shape.

Prognosis of nail abnormality

Most black lines on the fingernails and toenails are harmless. However, if a patient has melanoma, it is important to diagnose this condition in a timely manner, as this improves the prognosis. A melanoma in the foot or toenail usually has a worse prognosis than melanoma in other locations, because the doctor does not always diagnose it early.

read more

• Nails: Changes in color, strength and texture
• Acral lentinginous melanoma: Form of skin cancer
• Subungual melanoma: Form of skin cancer under the nail
• Splinter hemorrhage: Small, dark lines under nails
• Nail abnormalities: Common changes to nails