The term “melanonychia” comes from the Greek words “Melas,” meaning “black” or “brown,” and “Onyx,” meaning “nail.” It causes the nail plate to turn brownish-black, and the pigment that is usually meant is melanin. Lack of melanin, which pigments skin, makes nails semitransparent. Melanin is helpful in many ways, but it also contributes to melanonychia when it discolors the nails. It often affects a single nail or several nails on a finger or toe.
The nail mostly becomes dark brown or perhaps black as a result of Melanonychia. It predominantly affects fingernails and toenails. It manifests in a single nail, several nails, or every nail. There are numerous causes of melanonychia, ranging from benign to potentially lethal. If there are any dark streaks on the nails, it is recommended to consult a medical professional immediately.
Melanonychia appears to vary depending on the etiology. In most cases, it appears as:
- Melanonychia striata, also known as longitudinal melanonychia, is characterized by bands of brown, black, or grey color that extend from the nail bed to the tip of the nail.
- A darkening of the entire nail bed is known as diffuse or total melanonychia.
- A band that spans the nail from one side to the other is a sign of transverse melanonychia.
Melanonychia happens to people of any age, even children, and it affects both men and women equally. It is more common among those with a darker complexion, namely Fitzpatrick skin types V and VI.
Both fingernails and toenails are susceptible to melanonychia. It’s also possible for it to affect multiple nails simultaneously.
It mostly appears as:
- A black or brown vertical stripe across the length of the nail.
- A band of black or brown discoloration extends over the nail.
- Nail deformity or malformation.
Melanonychia’s complications range from mild to severe, depending on the etiology. For example, if melanonychia is malignant, it often spreads and harms other parts of the body, causing serious health problems. Nail deformities are a potential symptom of melanonychia and cause distress in certain patients.
Melanonychia is diagnosed after a series of examinations. The first step of any medical examination involves the doctor looking at the fingernails and toenails. This involves assessing whether the nail is distorted, the number of nails affected by melanonychia, and the color, shape, and size of the melanonychia. Melanonychia is also caused by several different illnesses, therefore the doctor also reviews the medical history of the patient.
The next stage of the diagnostic is a dermatoscopic examination, which makes use of a particular kind of microscope to acquire a close-up view of the discolored spots.
The nail plate is a keratin-based structure that is rigid and transparent. It is not generally pigmented. The proximal nail matrix, which is where the nail grows from, is often where dormant melanocytes are found. Longitudinal melanonychia is a pigmented band that forms when melanocytes are stimulated and deposit melanin into the growing nail.
There are two possible causes of melanin accumulation in the nail plate:
- Melanocytic hyperplasia: Melanocyte hyperplasia is a condition in which there are more melanocytes than usual in the nail. In some situations, it is non-cancerous or benign, while in others, it is cancerous and dangerous.
- Melanocytic activation: Activation of melanocytes does not alter the total amount of melanocytes, but rather stimulates these cells to increase melanin production and dispersion in the nail. Melanocytic activation mostly results from:
- Racial differences.
- Carpal tunnel syndrome.
- Biting of nails.
- A malformation of the foot that produces friction with footwear.
- Nail fungus.
- Warts caused by a virus.
- Skin cancer.
- Dysfunctional growth hormones.
Other possible causes of melanonychia include the following:
- A few bacteria.
- Silver nitrate.
- Hair dye.
Treatment for melanonychia depends on the underlying cause. Treatment is frequently not necessary if the source of the melanonychia is benign and noncancerous.
If the medicine is the source of melanonychia, the doctor modifies the medication or often suggests the patient stop taking it for a certain period, if possible.
Other therapeutic options, depending on the cause, include:
- Addressing the underlying disease or medical condition causing melanonychia with antibiotics or antifungal medicines if the infection is the cause.
- Full removal of the tumor or cancerous area is necessary if the melanonychia is malignant. This results in the whole or partial loss of the nail. In some circumstances, the tumor-bearing finger or toe needs to be removed.