Differential Diagnosis for Greenish Discoloration of Nail of Right Thumb

• Single Most Likely Diagnosis
  • Pseudomonas infection: This is a common cause of greenish discoloration of the nail, often resulting from bacterial infection, particularly in individuals with exposure to water or who have compromised nail integrity. The green color is due to the production of pyocyanin, a pigment produced by Pseudomonas aeruginosa.
• Other Likely Diagnoses
  • Fungal infection: Onychomycosis can cause nail discoloration, including greenish hues, although it's more commonly associated with yellow, brown, or black discoloration. The green color could be due to secondary bacterial infection.
  • Trauma: Physical injury to the nail can lead to hematoma formation under the nail plate, which may appear greenish due to the breakdown of blood products over time.
  • Nail polish or dye: Certain chemicals in nail polish or dyes can cause greenish discoloration of the nail, especially if used improperly or in excessive amounts.
• Do Not Miss Diagnoses
  • Squamous cell carcinoma: Although rare, this type of skin cancer can present with nail changes, including discoloration. It's crucial to consider this diagnosis to avoid delayed treatment.
  • Melanoma: Nail melanoma can cause pigmentation changes, including greenish discoloration, especially if there is bleeding or secondary infection involved.
• Rare Diagnoses
  • Arsenic poisoning: Chronic exposure to arsenic can lead to various nail changes, including discoloration, which might appear greenish in some cases.
  • Wilson's disease: This genetic disorder leads to copper accumulation in the body and can cause nail changes, including blue or green discoloration due to copper deposition.
  • Argyria: Silver or gold accumulation in the body can lead to bluish or greenish discoloration of the skin and nails, although this is extremely rare and usually associated with more widespread skin changes.