Differential Diagnosis for Green Colored Spot between Fourth and Fifth Toe

• Single most likely diagnosis
  • Chloronychia: A condition characterized by the discoloration of the nail, often green in color, due to the growth of bacteria such as Pseudomonas aeruginosa. This is a common condition in individuals with poor foot hygiene or those who frequently wear tight shoes, leading to moisture accumulation.
• Other Likely diagnoses
  • Fungal infection: Fungal infections like onychomycosis can cause nail discoloration, including greenish hues, especially if the infection is caused by specific fungi that produce pigments.
  • Bacterial infection: Bacterial infections other than Pseudomonas can also cause nail or skin discoloration, including greenish colors, especially in the context of an abscess or cellulitis.
  • Dyshidrotic eczema: Although less common, dyshidrotic eczema can lead to vesicles and crusts that might appear green due to secondary infection or the application of certain topical treatments.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Malignant melanoma: Although rare, a greenish discoloration could be a sign of a malignant melanoma, especially if there's a history of changing mole or new pigmented lesion. Early detection is crucial for treatment outcomes.
  • Gangrene: In diabetic patients or those with poor circulation, a greenish spot could be indicative of gangrene, which is a medical emergency requiring immediate attention.
• Rare diagnoses
  • Argyria: A condition caused by exposure to silver or silver compounds, leading to a bluish-gray pigmentation of the skin and mucous membranes. In rare cases, it might appear greenish.
  • Tinea nigra: A fungal infection caused by Hortaea werneckii, characterized by brown or black spots on the skin, but in some cases, it might appear green due to the production of pigments by the fungus.