Pseudomonas Green Nail Syndrome Presenting as Refractory Diabetic Foot Cellulitis in an Elderly Patient

Background: Green nail syndrome (GNS) is a bacterial nail disorder most commonly associated with Pseudomonas aeruginosa and is often regarded as a benign or cosmetic condition.In vulnerable patient populations, however, it may serve as an overlooked reservoir for persistent soft tissue infection.Case Presentation: This is a case report of an 82-year-old female with a past medical history significant for diabetes mellitus, post-traumatic arthritis of the left foot, mild cognitive impairment, and chronic venous stasis who developed dorsal foot erythema, edema, and pain that was refractory to multiple courses of empiric oral antibiotics.Physical exam revealed asymmetric distribution of green discoloration of the toenails of the left foot, with associated interdigital skin breakdown but no deep probing wounds, purulence, or fluctuance.Fungal testing of the nail plate was negative, but bacterial culture revealed Pseudomonas aeruginosa with polymicrobial anaerobic growth.The patient demonstrated clinical improvement in her symptoms after antimicrobial therapy was escalated to include anti-Pseudomonas coverage. Conclusion:This case highlights the importance of a careful nail examination and targeted microbiological intervention.In patients presenting with atypical or empirically antibiotic-resistant foot cellulitis, especially in those patient populations with diabetes and structural foot deformities, green nails should be recognized as a potential source of occult gram-negative SSTI in this population.