Differential Diagnosis for Nail Discoloration
Single Most Likely Diagnosis
- Fungal infection (onychomycosis): This is the most common cause of nail discoloration, often resulting in yellow, brown, or black discoloration due to fungal invasion of the nail plate.
Other Likely Diagnoses
- Bacterial infection: Certain bacteria can cause nail discoloration, typically presenting with greenish or blackish discoloration.
- Trauma: Injury to the nail can lead to discoloration due to bleeding under the nail plate, often appearing as a black or purple color.
- Nail polish staining: Prolonged use of nail polish can cause yellow or brown discoloration of the nails.
- Smoking: Smoking can cause yellow or brown discoloration of the nails due to nicotine staining.
Do Not Miss Diagnoses
- Melanoma: Although rare, subungual melanoma can present with nail discoloration, often appearing as a black or brown streak under the nail. Early detection is crucial for treatment and survival.
- Psoriasis: Nail psoriasis can cause discoloration, pitting, and thickening of the nails, and is often associated with skin psoriasis.
- Lupus: Systemic lupus erythematosus can cause nail discoloration, typically presenting with blue or purple discoloration due to vasculitis.
Rare Diagnoses
- Wilson's disease: A rare genetic disorder that can cause blue or green discoloration of the nails due to copper accumulation.
- Arsenic poisoning: Chronic exposure to arsenic can cause white or yellow discoloration of the nails.
- Hemochromatosis: A genetic disorder that can cause bronze or gray discoloration of the skin and nails due to iron overload.
- Sarcoidosis: A rare autoimmune disorder that can cause nail discoloration, typically presenting with yellow or brown discoloration due to granulomatous inflammation.