Francesca Cheung, MD CCFP, is a family physician with a special interest in dermatology. She received the Diploma in Practical Dermatology from the Department of Dermatology at Cardiff University in Wales, UK. She is practising at the Lynde Centre for Dermatology in Markham, Ontario and works closely with Dr. Charles Lynde, MD FRCPC, an experienced dermatologist. In addition to providing direct patient care, she acts as a sub-investigator in multiple clinical studies involving psoriasis, onychomycosis, and acne.

Abstract
Green nail syndrome is a paronychia caused by Pseudomonas aeruginosa. The affected toenail may show discoloration that ranges from greenish-yellow, greenish-brown, and greenish-black. Differential diagnosis includes other conditions causing nail plate discolouration such as subungual hematoma, malignant melanoma or infections by other pathogens including Aspergillus, Candida, and Proteus. Gram stain and culture of the subungual scrapings confirm the diagnosis of suspected pseudomonas aeruginoa infection. Topical antibiotics, such as bacitracin, silver sulfadiazine, or gentamicin, applied 2 to 4 times daily will treat most patients within 1 to 4 months. Oral ciprofloxacin for 2 to 3 weeks has been successful in treating patents who fail topical therapies.