An otherwise healthy 60-year-old dishwasher presents with asymptomatic green discoloration of his right middle fingernail over a period of 2 months. The discoloration began from the distal margin. He denies wearing gloves while working and reports a tendency to pick at his nails when nervous. On examination, distal onycholysis and green discoloration are present exclusively on the right middle nail plate starting from the distal edge without signs of paronychia. Dermoscopy reveals pigment localization under the nail plate.
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Green nail syndrome, also known as chloronychia, is caused by secondary Pseudomonas aeruginosa infection in the setting of nail damage and is characterized by green discoloration of the nail plate.1-3 P aeruginosa is an opportunistic gram-negative bacterium that infects the lungs, urinary tract, soft tissues, skin, and nails, in both immunocompetent and immunocompromised patients.4
Although it is not a component of normal skin flora, P aeruginosa is prevalent in soil and water, and it can colonize moist regions of the skin, axillae, anogenital regions, and retroauricular areas.4 The most common predisposing factors for P aeruginosa nail infection are distolateral onycholysis and proximal chronic paronychia.3
Onycholysis refers to separation of the nail plate from the nail bed in the fingers and toes and most commonly occurs due to constant local trauma, especially in the elderly.1 Secondary infection of the onycholytic space occurs when the nails are exposed to warm, moist environments.4 Chronic paronychia refers to nail matrix damage producing an irregular and friable nail plate, which is easily colonized.2 Chloronychia is most common in homemakers, barbers, dishwashers, and medical personnel, and it can be considered an occupationally triggered disease.4
Chloronychia is diagnosed clinically and confirmed by gram stain and culture of the exudate and ungual fragments from the affected nail.1,5 Usually, infection is restricted to one or two nails, and it causes a sudden green or brown appearance of the damaged nail.2 In the setting of onycholysis, P aeruginosa colonizes the subungual space, causing discoloration of one side of the nail.2 Dermoscopy reveals green pigment and localization under the nail plate.2 In the setting of chronic paronychia, pigmentation occurs above the nail plate, typically on one side, and may resemble a band to the naked eye.2 Dermoscopy reveals a bright green color that fades to yellow.2 Gram stain of cuttings of the affected nail results in randomly arranged gram-negative rods.4 Cultures on cetrimide agar result in flat, large, oval colonies that produce the blue-green exopigment, pyocyanin, and the characteristic fruity smell due to production of trimethylamine.4,5 Alternatively, clinicians may collect scrapings from under the affected nail and culture for fungus.5 When fungal culture results are negative, patients are treated empirically for P aeruginosa.5
In summary, green or black discoloration of the nail in the setting of nail trauma should raise suspicion for P aeruginosa infection.3 Other conditions that can produce discoloration include subungual hematomas, which are associated with repetitive trauma and present with extreme pain, malignant melanoma, which often presents as a pigment band along the length of the nail plate, and glomus tumors, which present as bluish discolorations under the fingernails and are associated with pain, especially with cold exposure.5
Patients with chloronychia are treated with removal of the detached nail plate, application of a topical antiseptic solution, and use of antibiotics. First, the damaged nail plate should be clipped every 2 weeks until the nail plate grows in normally.6 Occasionally, removal of the entire nail may be indicated.5 Second, topical antiseptic solutions, such as 2% to 4% thymol in chloroform, or 2% sodium hypochlorite solution, should be applied twice daily on the exposed nail bed to prevent infection.4,6 Topical therapies, including silver sulfadiazine, ciprofloxacin, gentamicin, polymyxin B, and bacitracin, are initially applied up to four times daily for up to 4 months.4 If topical therapies fail or are not preferred by the patient, oral ciprofloxacin is prescribed for 2 to 3 weeks.4 In addition, patients must be counseled to avoid trauma to the affected digits, including avoiding aggressive cleaning under the nail plate, wet and irritating environments, and nail cosmetics and artificial nails until 3 months after the onycholysis has resolved.6,7 Treatment is important to prevent transmission of P aeruginosa to wounds or surgical sites, which can result in local and systemic complications in immunocompromised invidiuals.3
The patient described in this case was treated with oral ciprofloxacin and topical application of 2% sodium hypochlorite, and he was counseled to wear cotton gloves under rubber gloves during dishwashing responsibilities. Bacterial infection was cured after 6 weeks of therapy.
Melinda Liu, BA, is a medical student and Maura Holcomb, MD, is a dermatology resident at Baylor College of Medicine in Houston.
- Zaias N, Escovar SX, Zaiac MN. Finger and toenail onycholysis. J Eur Acad Dermatol Venereol. 2015;29(5):848-853.
- Piraccini BM, Dika E, Fanti PA. Tips for diagnosis and treatment of nail pigmentation with practical algorithm. Dermatol Clin. 2015;33(2):185-195.
- Müller S, Ebnöther M, Itin P. Green nail syndrome (Pseudomonas aeruginosa nail infection): two cases successfully treated with topical nadifloxacin, an acne medication. Case Rep Dermatol. 2014;6(2):180-184.
- Chiriac A, Brzezinski P, Foia L, Marincu I. Chloronychia: green nail syndrome caused by Pseudomonas aeruginosa in elderly persons. Clin Interv Aging. 2015;10:265-267.
- Barankin B, Levy J. Dermacase. Can you identify this condition? Pseudomonas aeruginosa infection. Can Fam Physician. 2012;58(10):1103-1104.
- Iorizzo M. Tips to treat the 5 most common nail disorders: brittle nails, onycholysis, paronychia, psoriasis, onychomycosis. Dermatol Clin. 2015;33(2):175-183.
- Bae Y, Lee GM, Sim JH, et al. Green nail syndrome treated with the application of tobramycin eye drop. Ann Dermatol. 2014;26(4):514-516.