Understanding Longitudinal Melanonychia: Causes, Symptoms, and Treatment

Posted on: May 23rd, 2025 by Our Team

In this week’s blog entry during Melanoma Awareness Month, we discuss longitudinal melanonychia. Longitudinal melanonychia is a medical condition characterized by a dark, pigmented stripe that runs along the nail plate and may be a sign of melanoma. This stripe can be either brown, black, or gray in color and can affect one or multiple nails. While longitudinal melanonychia can be a harmless cosmetic issue, it can also be a sign of a more serious underlying condition, such as melanoma. Understanding the causes, symptoms, and treatment of longitudinal melanonychia is important for maintaining good nail and overall health.

Causes of Longitudinal Melanonychia

There are several factors that can cause longitudinal melanonychia, including:

1. Genetics: Some people may have a genetic predisposition to the condition.
2. Trauma: Nail injury or trauma can cause the nail matrix to produce more pigment, leading to the formation of a dark stripe.
3. Melanoma: Melanoma is a type of skin cancer that can affect the nails. In some cases, it can present as a dark stripe running along the nail plate. Nail melanoma can affect individuals of any skin type and skin pigmentation.
4. Pigment-producing medications: Certain medications, such as hydroxyurea, certain antibiotics and some blood pressure medications, can cause the nails to produce more pigment, leading to longitudinal melanonychia.

Symptoms of Longitudinal Melanonychia

The most obvious symptom of longitudinal melanonychia is the appearance of a dark stripe along the nail plate. This stripe can range in size and can be either a single line or multiple lines. In some cases, the stripe may be wider or thicker in certain areas.

Diagnosis and Treatment of Longitudinal Melanonychia

Diagnosing longitudinal melanonychia usually involves a physical examination and a review of the patient’s medical history. In some cases, a biopsy of the affected nail may be necessary to determine the cause of the pigmentation. Board-certified dermatologist and board-certified, fellowship trained Mohs surgeon Dr. Thomas Knackstedt recommends evaluation of any isolated nail discoloration affecting a single finger and/or changing over time.

Treatment for longitudinal melanonychia will depend on the underlying cause. In most instances, the discoloration represents a benign freckle or pigmentation activation that requires no treatment. If the team at Apex Skin Center feels the pigmentation is due to a medication, discontinuing the medication may resolve the problem. If the pigmentation is due to a skin condition or possible melanoma, further treatment and/or biopsy will be necessary.