Nevus Depigmentosus - Causes, Types, Diagnosis, and Treatment

Introduction:

The nevus depigmentosus is a rare birthmark and is also known as a non-pigmented nevus. There is a loss of skin pigmentation seen in the affected area. Age is not a significant factor in nevus depigmentosus, but most cases are discovered during delivery. The distribution (affected area) remains constant, so these hypopigmented patches are non-progressive. However, they may enlarge with the growth of the body. It is still unclear what causes nevus depigmentosus specifically. It is thought that the primary cause is a random abnormality in embryonic development. The condition has been incorrectly referred to as "localized albinism."

What Are the Types of Nevus Depigmentosus?

The three primary forms of nevus depigmentosus are whorled, segmental, and isolated.

• Whorled- Another name is linear or systematized type. Lesions are widespread in this type. These cutaneous (skin) lesions can overlap with HMI (hypomelanosis of Ito).

• Localized- The localized version is more prevalent than the others. It is a single lesion with sharp margins and a well-defined perimeter.

• Segmental- The segmental variety has a distinct midline marking, is more prominent in size and shape, and is also known as a "segmental de-pigmentation condition."

What Are the Causes of Nevus Depigmentosus?

It is currently unclear what causes nevus depigmentosus. However, it is thought that a defect in embryonic development is the leading cause of the condition. The cells responsible for the formation of skin pigments are melanocytes (pigment-forming cells) and melanosomes (melanin-storing cells present in melanocytes). They also help transfer these melanocytes to keratinocytes (skin cells). Most research shows the number of melanocytes and melanosomes as normal. However, the defect occurs during the transfer of melanosomes to keratinocytes. The transfer of melanosomes is necessary for pigment production in the area. Nevus depigmentosus occurs due to abnormal melanosome (melanin-containing granule) transfer that causes a decrease in keratinocytes. It also occurs due to a reduction in the number of melanosomes in melanocytes.

What Are the Symptoms of Nevus Depigmentosus?

Nevus depigmentosus shows certain specific features. The symptoms of the condition are the following:

• Nevus depigmentosus is typically diagnosed at birth or in the first few years of life. These small, localized white skin lesions can appear anywhere on the body.

• Lesions are typically hypo-pigmented and resemble splattered paint in most patients rather than being fully achromic.

• It can be seen anywhere on the body, but the trunk, neck, face, and proximal parts of the extremities are most frequently affected.

• Individual lesions are irreversible, and no proven treatments exist to re-pigment this nevus.

• If there is hair in the area, it is often white or colorless.

• The border of nevus depigmentosus is clearly defined but has an uneven, serrated, feathered, or geographic boundary.

• Individuals with light-colored skin may present lesions in middle childhood.

• Hypopigmentation is persistent and grows in size in proportion to the person's growth.

• Nevus depigmentosus appears before the age of three and has serrated irregular borders.

• It typically has a diameter of several centimeters. Size and shape can differ.

• The patient experiences social humiliation when the face is affected.

What Are the Extracutaneous Observations in Nevus Depigmentosus?

Patients with nevus depigmentosus rarely experience systemic symptoms. But reports show evidence in some cases, systematic involvement is seen with nevus depigmentosus. These include the following:

• Hemihypertrophy- Ipsilateral (half side of the body) extremity enlargement is sometimes seen.

• Neurologic abnormalities- These include seizures and mental disability.

• Sometimes, nevus depigmentosus is linked to other ocular, hair, musculoskeletal, and internal organ problems.

• Lentigines (darker lesions) may occasionally appear in the lesion, a phenomenon that occurs due to a mutation (alteration) in a pigmentation-related gene.

How to Make a Diagnosis of Nevus Depigmentosus?

1. Morphology of Lesion- The appearance of the lesion and location indicates nevus depigmentosus. The following are the most typical clinical diagnostic features that suggest a doctor the presence of nevus depigmentosus-

• A patch of pale skin (leukoderma) that appears at birth or very early in life.

• The patch stays in the exact location throughout life.

• The texture and sensation of the lesion do not change, either.

2. Biopsy- In some cases, a skin biopsy is helpful. A small amount of tissue is sectioned and observed under the microscope in a biopsy. Types of biopsies used in it are as follows:

• Shave Biopsy-. The outermost layers of the skin are taken with the help of using a razor.

• Puncture Biopsy- A sample of skin that includes both the top and deeper layers of skin is taken by a doctor using a specialized punch tool.

• Surgical Biopsy- The doctor removes the entire lesion and some of the surrounding skin with a knife.

3. Genetic Testing- All individuals with segmental or linear lesions and extracutaneous abnormalities (apart from skin) should go for genetic investigation, including screening of peripheral blood lymphocytes (type of blood cell) and skin fibroblasts (cells of the skin) to test for chromosomal abnormality.

What Is the Differential Diagnosis of Nevus Depigmentosus?

Hypopigmented lesions of tuberous sclerosis, nevus anemic, segmental vitiligo, hypomelanosis of Ito and other conditions are occasionally mistaken for nevus depigmentosus.

• Tuberous Sclerosis - This is a rare genetic disorder, noncancerous in nature, and results in hypopigmented skin lesions.

• Nevus Anemicus - It is an uncommon, congenital vascular malformation that causes hypopigmented skin lesions.

• Vitiligo - It occurs when pigment-producing cells die. It causes loss of skin color in patches.

• Hypomelanosis of Ito - A congenital disability that causes unusual patches of light-colored skin.

What Is the Treatment for Nevus Depigmentosus?

Nevus depigmentosus treatment is unnecessary other than for cosmetic purposes. The excimer laser, phototherapy, and skin grafting procedures have helped in the re-pigmentation of the skin. Nevus depigmentosus lesion can regain its original color after receiving 308-nm excimer laser treatment. However, surgery has a limited function in managing nevus depigmentosus as the degree of graft re-pigmentation depends on melanocyte migration, which is unpredictable under these circumstances.

Conclusion:

Nevus depigmentosus appear in various forms and sizes, but most are benign (non-cancerous). However, it is essential to monitor the growth because lesions may lead to an issue. Do not hesitate to let the doctor examine any moles that bother the patient. A biopsy can help rule out skin cancer.