Nail Discoloration in a 55-Year-Old Female - Clinical Assessment

What the Image Shows

Differential Diagnosis (Painless Nail Blackening/Darkening)

1. Subungual Melanoma / Acral Lentiginous Melanoma (ALM) - ⚠️ Must Rule Out

• Subungual melanoma arises from the nail matrix, most commonly on the thumb or great toe
• It presents as brown-to-black discoloration or a widening, dark longitudinal streak (melanonychia striata)
• Hutchinson sign - pigmentation spreading to the proximal or lateral nail fold - is a red-flag warning sign of subungual melanoma
• ALM is the most common form of melanoma in darker-skinned individuals (60-72% in African Americans, 29-46% in Asians), and is diagnosed more often in older patients (median age 65)
• It is often initially misdiagnosed as a plantar wart, hematoma, or fungal infection, leading to delayed diagnosis and poorer outcomes
• Single-digit melanonychia in an adult requires a biopsy (Fitzpatrick's Dermatology)

The lateral nail fold pigmentation seen in this image could represent a Hutchinson sign, which makes melanoma evaluation a priority.

2. Onychomycosis (Fungal Nail Infection)

• Some fungi (especially non-dermatophyte molds) can cause dark/black discoloration
• Usually associated with nail thickening, brittleness, crumbling, or subungual debris
• Can mimic melanoma
• The roughness/thickening at the nail fold in the image is compatible

3. Subungual Hematoma

• Caused by trauma (can be forgotten minor trauma)
• Typically dark red-brown or black, grows out with the nail
• Usually presents under the nail plate, not at the lateral fold
• No pain now is possible if the hematoma is old

4. Benign Melanonychia / Lentigo / Nevus

• Common in individuals with darker skin types
• A benign longitudinal pigmented band that can widen with age
• Important to distinguish from melanoma

5. Periungual Wart (HPV)

• Can cause thickening, discoloration, and roughness at the nail fold
• The rough, thickened lateral fold tissue in this image is a possible feature

6. Systemic/Drug Causes

• Addison disease, B12 deficiency, HIV, certain medications (hydroxyurea, chemotherapy), and Laugier-Hunziker syndrome can all cause nail pigmentation
• Usually affect multiple nails

Red Flags Present in This Case

Recommended Action

This patient needs urgent dermatology referral.

1. Dermoscopy/Onychoscopy - first-line assessment to evaluate the pigmentation pattern (parallel ridged pattern, irregular bands, blurred borders all raise suspicion)
2. Nail biopsy - if any features suggest melanoma, biopsy of the nail matrix/nail fold is required to confirm
3. KOH preparation and nail culture - to rule out fungal infection concurrently
4. Hutchinson sign assessment - careful inspection of all nail folds under good lighting/dermoscopy

Bottom Line

Disclaimer: This is an AI-assisted clinical discussion and does not replace an in-person medical evaluation. Please refer this patient to a dermatologist promptly.