Melanonychia refers to a brown or black discoloration of the nail plate due to melanin pigment deposition. It can appear as a single longitudinal stripe or affect the entire nail.
🔍 Types of Melanonychia
Type
Description
Longitudinal melanonychia
A pigmented stripe running from nail base to tip, often benign but may require evaluation
Diffuse melanonychia
Darkening of the entire nail plate, can be due to systemic causes or medications
Melanoma of the nail
Malignant melanoma presenting as a pigmented band, often widening and irregular
⚠️ Causes
Category
Examples
Benign causes
Ethnic pigmentation (common in darker skin), trauma, melanocytic nevus
Systemic diseases
Addison’s disease, Laugier-Hunziker syndrome
Medications
Chemotherapy drugs, antimalarials
Infections
Fungal infections (sometimes)
Malignant
Subungual melanoma (requires urgent evaluation)
🔍 Signs to Watch For (Concerning for Melanoma)
Pigmented band wider than 3 mm
Irregular borders or color variation
Hutchinson’s sign: pigmentation extending onto the surrounding skin
Rapid progression or change in appearance
Nail dystrophy or bleeding
🛠️ Diagnosis
Clinical examination
Dermoscopy of the nail
Nail matrix biopsy (if melanoma suspected)
Patient history (duration, changes, trauma, medications)
🛡️ Management
Benign cases may require no treatment, just monitoring
Address underlying causes if systemic or medication-related
Prompt referral and biopsy for suspicious lesions to rule out melanoma
