Clinical analysis of Pseudomonas aeruginosa-positive and -negative green nail syndrome cases: A single center retrospective analysis.

Green nail syndrome (GNS) is a paronychial infection mainly due to Pseudomonas aeruginosa, characterized by green discoloration of the nail plate. Although the diagnosis of GNS may be straightforward with its distinctive color change, the clinical management of the disease can be sometimes confusing, especially when the bacterial culture result is inconsistent. There is, however, a paucity of comprehensive reviews regarding the treatment of GNS in the actual clinical setting. In this retrospective review of 34 patients, we found that GNS mostly occurs on a single digit (79.4%) on the big toe or thumb (85.3%) with frequent concurrent fungal infection (67.6%). The prevalence of inconsistent bacterial culture result with no evidence of P. aeruginosa was unexpectedly high (n = 22, 64.7%), in which case coagulase-negative staphylococci were most frequently detected. The P. aeruginosa-negative group did not demonstrate any statistically significant differences compared with the P. aeruginosa-positive group, and it still responded well to the typical topical and/or oral fluoroquinolone treatment. GNS without the evidence of P. aeruginosa may be a more common occurrence than reported in the literature, and it can be managed successfully with the same strategy employed to treat P. aeruginosa-positive cases. It may result from the low detection rate of P. aeruginosa due to the limited sensitivity of the test, or inadequate amount and/or contamination of the sample, warranting close scrutiny by clinicians.