Conditions › Melanonychia

Melanonychia (Dark Nail Stripe) Diagnosis in London

Melanonychia refers to dark brown or black pigmentation visible as a streak or band within the nail plate. It may be caused by benign conditions such as increased melanin production or more serious causes such as subungual melanoma. Early diagnosis is essential to rule out cancer and to guide management. At Skinhorizon Dermatology London, we offer expert assessment, dermoscopy, and nail biopsy when needed.

Call Us Book Consultation

Melanonychia at a Glance

What is melanonychia?	Melanonychia is dark pigmentation of the nail plate, often seen as a longitudinal brown or black band running along the nail.
What are the symptoms of melanonychia?	Dark streaks or bands on the nail, which may be single or multiple, stable or changing. Sometimes associated with nail thickening or irregularity.
Who is most likely to develop melanonychia?	More common in people with darker skin types, individuals with multiple moles, those with repeated nail trauma, or patients on certain medications.
Why is it important to assess melanonychia?	Because while many cases are harmless, melanonychia can sometimes indicate subungual melanoma, a rare but aggressive skin cancer.
How is melanonychia diagnosed?	Through clinical examination, dermoscopy, and if needed, nail matrix or nail bed biopsy to rule out melanoma or other pathology.
How is melanonychia treated?	Treatment depends on the cause: observation for benign cases, stopping causative drugs, managing trauma, or surgical removal if melanoma is found.
When should I see a doctor for melanonychia?	If the streak is new, changing, involves a single nail, widens, develops irregular borders, or is accompanied by pigment on surrounding skin.
What complications can melanonychia cause?	Most benign causes only affect appearance, but missing a diagnosis of melanoma can have life-threatening consequences if not detected early.

Understanding melanonychia

Melanonychia refers to dark streaks or bands in the nail, usually running lengthwise. The colour comes from melanin pigment, either due to activation of normal melanocytes or proliferation of abnormal ones. While often harmless, melanonychia can be a sign of subungual melanoma, making careful evaluation crucial.

Causes of melanonychia

Benign causes: Racial melanonychia in people with darker skin, trauma (e.g., repetitive nail injury), fungal infections, or medication-induced pigmentation.
Systemic causes: Addison’s disease, Laugier–Hunziker syndrome, or chemotherapy drugs.
Malignant causes: Subungual melanoma originating from the nail matrix.

Symptoms and clinical features of Melanonychia

Melanonychia usually appears as a pigmented streak. Warning features suggesting melanoma include:

A single dark band on one nail (rather than multiple nails)
Band that is wide (>3 mm) or increasing in size
Irregular colour or blurred borders
Pigment spreading into the surrounding cuticle or skin (Hutchinson’s sign)
Nail plate splitting, lifting, or destruction

Diagnosis of Melanonychia

Diagnosis of melanonychia involves:

History: Onset, changes, trauma, medications.
Examination: Dermoscopy of the nail band pattern.
Biopsy: If concerning features exist, a nail matrix biopsy is performed to confirm or exclude melanoma.

Treatment for Melanonychia

Treatment depends on the cause:

Benign melanonychia: Observation and reassurance.
Drug-related: Switching or stopping the medication.
Trauma-related: Protective measures to avoid further injury.
Melanoma: Urgent wide surgical excision of the nail and underlying tissue, possibly with further surgery depending on staging.

Prognosis of Melanonychia

Benign melanonychia carries no health risk but may be cosmetically concerning. However, early recognition of subungual melanoma is vital, as late diagnosis worsens survival outcomes.

Your first visit — what to expect

History: Detailed medical and family history plus review of symptoms.
Examination: Nail inspection and dermoscopy.
Investigations: Biopsy if the lesion is suspicious.
Discussion: Explanation of findings and reassurance or treatment planning.
Follow-up: Monitoring schedule if the lesion is benign, or referral to surgical oncology if melanoma is diagnosed.

Reviewed by: Dr Mohammad Ghazavi, Consultant Dermatologist
Skinhorizon Clinic, 4 Clarendon Terrace, Maida Vale, London W9 1BZ
Last reviewed: 22 August 2025

Concerned about a dark streak in your nail? Book a mole and nail check at Skinhorizon London for early detection and expert care.

Call Us Book Consultation

← Back to Skin Conditions

Melanonychia FAQs

Is melanonychia always cancer?

No. Most cases are benign, but some may indicate subungual melanoma. Medical assessment is essential for new or changing nail streaks.

Which nails are usually affected by melanonychia?

Melanonychia may affect one or several nails. Single-nail involvement, especially if irregular, is more concerning for melanoma.

Can children get melanonychia?

Yes, children can develop melanonychia, often from benign causes. However, any suspicious band should still be assessed by a dermatologist.

What does Hutchinson’s sign mean in melanonychia?

Hutchinson’s sign is pigmentation spreading to the skin around the nail. It is a warning sign for possible melanoma.

Do all melanonychia cases require biopsy?

No. Many benign cases do not need biopsy. Biopsy is performed if the band is irregular, enlarging, or concerning for melanoma.

Disclaimer: The information above is provided for general education only and should not be taken as medical advice for any individual case. A consultation with a qualified healthcare professional is required to assess suitability, risks, and expected outcomes.

Sources: