Green Nail_0813 Derm Dx
A 40-year-old patient complains of a discolored fingernail. She has no other medical problems. She used to wear acrylic gel nails, and is employed as a dishwasher.
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Pseudomonas green nail syndrome is caused when pyocyanin, a greenish-blue pigment produced by Pseudomonas aeruginosa, accumulates. The clinical presentation of green nail syndrome is usually that of a patient who has frequent exposure to water, detergents and soaps, and develops a green/blue or dark green hue underneath the nail plate.
Green nail syndrome is not painful unless the skin around the nail is affected. It is usually confined to only one or two nails. Barbers, dishwashers, bakers and medical personnel are frequently affected. If infected, medical staff can transmit pseudomonas infection to debilitated patients.
Green nail syndrome often develops in the setting of an onycholytic nail — a nail that has become detached from the nail bed due to trauma, fungal infection or a variety of other causes — which creates better access for microorganisms such as pseudomonas to thrive. Since P. aeruginosa favors damp environments, exposure to water is another important risk factor for developing green nail syndrome.
P. aeurginosa is a common bacteria that is nearly ubiquitous in the environment. It thrives in soil, water, on the skin and on most surfaces. Because it can be found on medical equipment, it may be the cause of opportunistic infections in the hospital.
Infection commonly manifests as P. aeurginosa folliculitis (also called hot tub folliculitis), a pruritic follicular eruption, usually occurring one to four days after bathing in a hot tub. It can appear as an acute onset of tender plantar nodules (pseudomonas hot-foot syndrome) after exposure to water containing high concentrations of the bacteria.
It may also manifest as external otitis media, especially in swimmers (swimmer’s ear). A more severe infection of the ear, malignant otitis externa can occur in diabetic and immunocompromised patients.
Other manifestations of P. aeruginosa include ecthyma gangrenosum, which is an opportunistic infection in debilitated patients. This presents as vesicles or pustules that quickly become hemorrhagic and rupture to form ulcers with necrotic black centers.
Diagnosis & Treatment
Green nail syndrome diagnosis can be made clinically based on the characteristic green color of the affected nail in the setting of onycholysis. Performing a gram stain and culture of exudate and nail fragments can confirm the diagnosis.
Treatment involves clipping back the nails and applying topical fluoroquinolones or acetic acid. Oral fluoroquinolones may also be used.
James Wu, BS, is a senior medical student at Chicago Medical School at Rosalind Franklin University in Illinois.
Adam Rees, MD, is a graduate of the University of California Los Angeles School of Medicine and a resident in the Department of Dermatology at Baylor College of Medicine in Houston.
- Bolognia J, Jorizzo JL, Schaffer JV. “Chapter 70: Nail Disorders.” Dermatology. St. Louis: Mosby/Elsevier, 2008.
- James WD, Berger TD, Elston DM et al. “Chapter 14: Bacterial Infections.” ndrews’ Diseases of the Skin: Clinical Dermatology. London: Saunders Elsevier, 2011.