Longitudinal melanonychia - Nail and Distal Digit
Alerts and Notices
SynopsisLongitudinal melanonychia describes a longitudinal band of pigment that extends from the nail matrix to the free edge of the nail. Melanonychia means "black nail." There are many causes of nail pigmentation (see Differential Diagnosis section) including skin diseases, systemic diseases, infections, trauma, medications, and pigmented lesions. While longitudinal melanonychia can have a benign etiology, it is critical to rule out acral lentiginous melanoma as a cause.
Melanocytes normally reside in the nail matrix and nail bed, though they are typically inactive in individuals of Northern European descent. In the nail matrix, if melanin production by melanocytes is greater than degradation by keratinocytes, the result is a longitudinal band. This phenomenon can be caused by melanocyte activation, melanocytic hyperplasia, lentigo simplex, melanocytic nevus, atypical melanocytic proliferations, and acral lentiginous melanoma.
Pediatric nail melanoma is extremely rare, particularly in individuals with Fitzpatrick phototypes I and II, but carries significant morbidity and mortality. The fingernails are more commonly involved than toenails. Evaluation of longitudinal melanonychia is more difficult in children than adults due to lack of clinical and histopathological guidelines. According to recent cohort studies from Asia, the majority of pediatric cases undergo regression or stagnation, and no incidence of melanoma was found in biopsied cases.
L60.8 – Other nail disorders
707196007 – Longitudinal melanonychia
Differential Diagnosis & PitfallsCauses of longitudinal melanonychia:
- Subungual melanoma / acral lentiginous melanoma – Most melanomas of the nail appear in adulthood, with a mean age of onset in the 50s-70s. Nail pigmentation is the presenting sign in two-thirds of cases, although melanoma may present with a mass lesion, invariably accompanied by nail dystrophy and nail plate ulceration. Rarely, lesions are amelanotic. Hutchinson sign, periungual pigmentation indicating the radial growth of subungual melanoma, is frequently seen. The thumb and hallux are most frequently affected.
- Longitudinal melanonychia is very common among those with darker skin colors, with up to 75% of Black individuals older than 20 years and nearly 100% of those older than 50 years showing longitudinal melanonychia. Nails of digits prone to trauma or those used for grasping (thumb, index, and middle fingers) are frequently affected.
- Congenital nevus / acquired nevus – Nevi cause approximately 12% of longitudinal melanonychia in adults and almost 50% of longitudinal melanonychia in children. Fingers are more commonly involved. Pseudo-Hutchinson sign (periungual pigmentation) is seen in one-third of cases.
- Subungual lentigo
- Benign nail tumors (onychopapilloma, onychomatricoma, subungual fibrous histiocytoma, verruca vulgaris, and subungual keratosis)
- Malignant nail tumors (squamous cell carcinoma, basal cell carcinoma)
- Chronic trauma-related injury (carpal tunnel syndrome, onychotillomania, onychophagia)
- Medication-induced longitudinal melanonychia (eg, zidovudine and hydroxyurea are both frequent causes of longitudinal pigment; minocycline, bleomycin, cyclophosphamide, and hydroxycarbamide have also been cited as causes of longitudinal melanonychia) (see drug-induced nail pigment)
- Infection (onychomycosis) – May present as diffuse or longitudinal melanonychia.
- Inflammatory skin diseases (psoriasis, lichen planus)
- Connective tissue diseases (systemic lupus erythematosus, localized scleroderma)
- Endocrine disorders (Addison disease, Cushing syndrome, Nelson syndrome, hyperthyroidism, acromegaly). Longitudinal melanonychia typically affects multiple fingernails and toenails. Individuals with Addison disease also show cutaneous and mucosal pigmentation.
- Nutritional disorders (protein energy malnutrition, vitamin D deficiency, vitamin B12 deficiency) and errors of metabolism (hyperbilirubinemia, alkaptonuria)
- Phototherapy, radiation (x-rays, electron beam therapy, occupational radiation exposure)
- Genetic syndromes including Laugier-Hunziker syndrome, Touraine syndrome, or Peutz-Jeghers syndrome
- Bacterial pigmentation, most commonly from Pseudomonas, Klebsiella, or Proteus, can have a greenish or grayish hue and is often located at the lateral edge of the nail.
- Subungual hematoma is often the result of trauma and is most commonly found on the medial aspect of the first toe.
- Exogenous nail pigmentation is most commonly caused by dirt, tobacco, potassium permanganate, and tar and typically does not cause a longitudinal streak. Most can easily be removed through physical means.
Drug Reaction DataBelow is a list of drugs with literature evidence indicating an adverse association with this diagnosis. The list is continually updated through ongoing research and new medication approvals. Click on Citations to sort by number of citations or click on Medication to sort the medications alphabetically.
Patient Information for Longitudinal melanonychia - Nail and Distal Digit
OverviewLongitudinal melanonychia, also known as melanonychia striata, is brown or black discoloration of the nail plate that appears as a line running lengthwise on the nail.
There are two causes of this condition:
- Melanocyte activation – Previously dormant melanin-forming cells (melanocytes) are stimulated to increase melanin (pigment) production in the skin under the nail; this can be triggered by trauma, infection, inflammatory disease, systemic disorders (affecting the whole body), and medications.
- Melanocyte hyperplasia – Refers to an increase in the number of melanocytes in the nail matrix; this can be related to benign (noncancerous) processes (eg, moles, pigmented spots) or malignant (cancerous) processes (eg, melanoma).
Longitudinal melanonychia is typically diagnosed clinically by the physician doing a physical examination and collecting a thorough history from the patient.
This condition can last for an extended period.
The onset of longitudinal melanonychia in childhood is more likely to be benign in nature.
Many nail melanomas (approximately two-thirds) present as longitudinal melanonychia.
Who’s At RiskLongitudinal melanonychia can present in any age group but more frequently occurs in adults. Men and women are affected equally, but it is more common in individuals with darker skin colors (ie, people of African, Hispanic, and Middle Eastern descent).
Signs & SymptomsLongitudinal melanonychia is typically characterized by a single pigmented longitudinal band that stretches the entire length of the nail.
It often presents as a single band, but multiple bands can also occur on one or several nails. In addition, the thickness and location of the melanonychia on the nail plate can vary.
- Avoid picking at the affected nail.
- Consult a dermatologist for further evaluation to determine if the nail pigmentation is due to a benign or more serious cause.
When to Seek Medical CareIf you have even one pigmented band on your nail, it should be evaluated by a doctor.
If you have many light-colored bands in more than one nail and one band that looks darker or different than the others, or if one is changing in width or color, seek medical care as a biopsy of the changing / different band may be indicated.
- Most cases of longitudinal melanonychia are benign, and treatment is often not needed. Some lesions fade on their own over time. Management of the underlying cause may help improve the discoloration (eg, discontinue offending medication, good control of systemic disease).
- If there is cause for concern, your doctor may recommend a biopsy of the nail matrix (where the nail grows at the base of the nail). Or if there are no features to warrant a biopsy, your doctor may want to schedule a follow-up visit to check for changes.
- If your longitudinal melanonychia is caused by melanoma, further testing and treatment, such as surgical removal, is required.
Longitudinal melanonychia - Nail and Distal Digit