Longitudinal Melanonychia

Longitudinal melanonychia (LM) is a clinical term used to describe a pigmented longitudinal band that runs parallel to the nail plate and is present on the nail matrix or nail bed. LM is a common condition that affects the nails and is often benign, however, in some cases, it may be indicative of a more serious underlying condition. It is essential to have a comprehensive understanding of LM, its causes, diagnosis, and treatment options to manage this condition effectively.

Longitudinal melanonychia is a condition characterized by a brown or black pigmented streak or band that runs along the length of a nail. It can affect one or multiple nails and can occur in individuals of all ages and races. This condition can be caused by a number of different factors, including melanoma, a type of skin cancer that can affect the nails.

The nail matrix is the area at the base of the nail where the nail plate is produced, and the nail bed is the area beneath the nail plate that provides support and nourishment to the nail. The presence of LM on the nail matrix or nail bed can be due to various causes, including the following:

Melanocytic nevus: A melanocytic nevus is a type of mole that is formed due to an accumulation of melanocytes, the cells that produce pigment, in the skin. LM caused by a melanocytic nevus is known as a melanonychia striata.
Subungual melanoma: Subungual melanoma is a rare but aggressive form of skin cancer that affects the nails. LM caused by subungual melanoma is usually dark and can be accompanied by other symptoms, such as pain or bleeding.
Melanonychia due to systemic diseases: LM can also be a symptom of various systemic diseases, such as Addison’s disease, Peutz-Jeghers syndrome, and Hirschsprung’s disease.
Drug-induced LM: Certain medications, such as antimalarials, amiodarone, and some chemotherapy drugs, can cause LM.
Idiopathic LM: In some cases, the cause of LM is unknown and is referred to as idiopathic LM.

Causes

This condition can affect one or multiple nails, and can be a sign of various underlying conditions. In this article, we will discuss the main causes of longitudinal melanonychia and their underlying mechanisms.

Melanoma: Melanoma is the most dangerous cause of longitudinal melanonychia. It is a type of skin cancer that starts in the cells that produce melanin, the pigment that gives color to the skin, hair, and nails. Melanoma can spread to other parts of the body if left untreated, making it a serious condition. It typically presents as a dark streak that runs along the nail plate and may have irregular borders and uneven color.
Trauma: Trauma to the nail matrix (the area of the nail bed that produces the nail plate) can also cause longitudinal melanonychia. This is because the injury can stimulate the production of melanocytes (cells that produce melanin), leading to increased melanin deposition in the nail plate. The streak may be darker or lighter than the surrounding nail and may be accompanied by nail dystrophy (abnormal nail growth).
Subungual hematoma: A subungual hematoma is a collection of blood under the nail plate, usually as a result of trauma. It can cause longitudinal melanonychia by causing injury to the nail matrix, leading to an increase in melanin production. The streak may be dark or reddish in color, and the nail may be painful or tender.
Nail infections: Certain types of nail infections, such as onychomycosis (fungal nail infection) or paronychia (bacterial nail infection), can cause longitudinal melanonychia. The streaks may be darker or lighter than the surrounding nail, and the nail may be thickened, discolored, or brittle.
Hyperpigmentation disorders: Longitudinal melanonychia can also be caused by various hyperpigmentation disorders, such as Addison’s disease, Peutz-Jeghers syndrome, or iron deficiency anemia. These conditions can cause increased production of melanin, leading to dark streaks along the nail plate.
Drugs: Certain drugs, such as amiodarone, minocycline, and hydroxyurea, can cause longitudinal melanonychia as a side effect. This is because they can interfere with the normal functioning of the melanocytes, leading to increased melanin production. The streaks may be dark or lighter than the surrounding nail and may be accompanied by other nail changes, such as nail discoloration or dystrophy.

Symptoms

There are several symptoms associated with longitudinal melanonychia, which can range from mild to severe. Some of the most common symptoms include:

Dark Stripe or Streak on Nail: This is the most obvious symptom of longitudinal melanonychia, and is the primary reason why individuals seek medical attention. The dark stripe or streak can appear anywhere on the nail and can be either straight or slightly curved.
Change in Nail Texture: In some cases, individuals with longitudinal melanonychia may experience a change in the texture of their nail. This can include thickening, brittle nails, or even ridges.
Nail Deformation: In some cases, the nail may become deformed as a result of the dark stripe or streak. This can include changes in the shape of the nail, such as curling, bending, or even splitting.
Pain or Tenderness: In some cases, individuals with longitudinal melanonychia may experience pain or tenderness in the affected area. This can be due to the pressure placed on the nail by the dark stripe or streak, which can cause the nail to become deformed or thickened.
Nail Bed Discoloration: In some cases, individuals with longitudinal melanonychia may experience discoloration of the nail bed, which is the area under the nail. This discoloration can range from light brown to black, and can be due to the underlying medical issue causing the dark stripe or streak.
Nail Plate Discoloration: In some cases, individuals with longitudinal melanonychia may experience discoloration of the nail plate, which is the visible part of the nail. This discoloration can range from light brown to black, and can be due to the underlying medical issue causing the dark stripe or streak.
Nail Plate Thickening: In some cases, individuals with longitudinal melanonychia may experience thickening of the nail plate, which can make the nail more difficult to cut or file. This thickening can be due to the underlying medical issue causing the dark stripe or streak.
Nail Plate Fragility: In some cases, individuals with longitudinal melanonychia may experience fragility of the nail plate, which can cause the nail to break or split more easily. This fragility can be due to the underlying medical issue causing the dark stripe or streak.
Nail Bed Inflammation: In some cases, individuals with longitudinal melanonychia may experience inflammation of the nail bed, which can cause redness, swelling, and pain. This inflammation can be due to the underlying medical issue causing the dark stripe or streak.
Nail Plate Separation: In some cases, individuals with longitudinal melanonychia may experience separation of the nail plate from the nail bed, which can result in the nail lifting or becoming detached. This separation can be due to the underlying medical issue causing the dark stripe or streak.

Diagnosis

The accurate diagnosis of longitudinal melanonychia requires a comprehensive evaluation, including medical history, physical examination, and laboratory tests. In this article, we will discuss the main list of diagnosis and tests for longitudinal melanonychia.

Physical examination: The first step in diagnosing longitudinal melanonychia is a thorough physical examination of the affected nail. The physician will examine the color, shape, and size of the lesion, as well as the surrounding skin and nail. The physician may also look for any signs of trauma or infection, which can cause similar changes in the nail.
Dermatoscopy: Dermatoscopy is a non-invasive diagnostic tool that uses a magnifying lens and a light source to examine the skin and nails in detail. It can be used to differentiate between benign and malignant pigmented lesions and is often performed in conjunction with a physical examination.
Nail biopsy: A nail biopsy is a procedure in which a small sample of the affected nail is removed and examined under a microscope. This is the most reliable method for diagnosing the underlying cause of longitudinal melanonychia. The biopsy can be performed using a scalpel or a punch biopsy tool.
Histopathology: Histopathology is the microscopic examination of tissue samples. In the case of longitudinal melanonychia, a nail biopsy is examined under a microscope to determine the underlying cause of the pigmented lesion.
Dermoscopy-guided biopsy: Dermoscopy-guided biopsy is a newer diagnostic tool that combines dermatoscopy with a biopsy. This method allows the physician to identify the exact location of the pigmented lesion and to obtain a more accurate biopsy sample.
Blood tests: Blood tests may be performed to rule out systemic conditions that can cause longitudinal melanonychia, such as Addison’s disease or melanoma. The tests may include a complete blood count (CBC), electrolyte levels, liver function tests, and thyroid function tests.
Imaging studies: Imaging studies, such as X-rays, CT scans, and MRI, may be ordered to rule out underlying bone or systemic conditions that may be causing the longitudinal melanonychia.
Genetic testing: Genetic testing may be performed to determine if the patient has a genetic predisposition to melanoma or other pigmented skin lesions.

The diagnosis of longitudinal melanonychia requires a comprehensive evaluation that includes a physical examination, dermatoscopy, nail biopsy, histopathology, blood tests, imaging studies, and genetic testing. The specific tests that are performed will depend on the individual case and the suspected underlying cause of the pigmented lesion.

Treatment

The following is a list of treatments for longitudinal melanonychia:

Observation: In some cases, longitudinal melanonychia may be benign and require no treatment. Observation may be recommended if the streaks are not increasing in size, thickness or color and are not causing any discomfort or pain.
Nail Avulsion: This procedure involves removing the entire affected nail and the nail bed. Nail avulsion is typically performed if a biopsy is needed to determine the underlying cause of the streaks. The nail will grow back over time, but the streaks may persist or reappear in the new nail.
Topical Medications: Topical medications, such as topical corticosteroids, may be used to treat localized forms of longitudinal melanonychia caused by inflammation or other benign conditions. These medications are applied directly to the affected area and work by reducing inflammation and itching.
Systemic Medications: Systemic medications, such as oral corticosteroids, may be prescribed if the underlying cause of longitudinal melanonychia is an autoimmune or inflammatory condition. These medications work by suppressing the immune system and reducing inflammation throughout the body.
Nail Matrix Destruction: Nail matrix destruction is a procedure that involves destroying the cells in the nail matrix that produce the nail. This procedure is typically performed if the streaks are caused by a benign condition, such as a melanocytic nevus, and are not responding to other treatments. The nail will not grow back after this procedure.
Phototherapy: Phototherapy, also known as light therapy, may be used to treat some forms of longitudinal melanonychia caused by pigment-producing cells. This therapy involves exposing the affected area to specific wavelengths of light, which can destroy the pigment-producing cells and reduce the appearance of the streaks.
Surgical Excision: Surgical excision is a procedure that involves removing the affected tissue, including the nail and the underlying nail bed, if the streaks are caused by a malignant condition, such as melanoma. This procedure may be followed by additional treatments, such as radiation therapy or chemotherapy, to prevent the spread of the cancer.
Chemotherapy: Chemotherapy is a treatment that uses drugs to destroy cancer cells. This treatment may be used if the streaks are caused by a malignant condition, such as melanoma, and have spread to other parts of the body. Chemotherapy can have side effects, such as nausea, vomiting, and fatigue, and may cause hair loss and other changes in appearance.
Radiation Therapy: Radiation therapy is a treatment that uses high-energy rays to kill cancer cells. This treatment may be used if the streaks are caused by a malignant condition, such as melanoma, and have spread to other parts of the body. Radiation therapy can cause skin changes, such as redness, dryness, and itching, and may also cause fatigue.

In conclusion, the treatment of longitudinal melanonychia depends on the underlying cause of the streaks. Observation may be recommended if the streaks are benign, while more aggressive treatments, such as surgical excision and chemotherapy, may be required if the streaks are caused by a malignant condition.

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