Photo Rounds

Green thumbnail

A 34-year-old woman presented to the clinic with concerns about her thumbnail, which had turned green. Although her finger didn’t hurt, its appearance bothered her. Several months earlier, the woman had sought care at a different clinic because the same nail had become brittle and came loose from the nail bed, which was spongy. The physician diagnosed onychomycosis and prescribed ciclopirox lacquer, but it didn’t help. Over the next 3 weeks, the patient noticed a faint green hue developing at the tip of the nail, which expanded and intensified in color. The patient’s medical history was significant for type 1 diabetes mellitus and Hashimoto’s thyroiditis.

What’s your diagnosis?


Green thumbnail

The patient was given a diagnosis of green nail syndrome (GNS), an infection of the nail bed caused by Pseudomonas aeruginosa. These bacteria produce pyocyanin, a blue-green pigment that discolors the nail. GNS often occurs in patients with prior nail problems, such as onychomycosis, onycholysis, trauma, chronic paronychia, or psoriasis.

Nail disease disrupts the integumentary barrier and allows a portal of entry for bacteria. Scanning electron microscopy of patients with GNS has shown that fungal infections create tunnel-like structures in the nail keratin, and P aeruginosa can grow in these spaces. Nails with prior nail disease that are chronically exposed to moisture are at greatest risk of developing GNS, and it is typical for only one nail to be involved.

It’s likely that this patient’s earlier nail problem had been a case of onycholysis, based on her description of a “spongy” nail bed and loose nail. This created a favorable environment for an infection by allowing moisture and bacteria to infiltrate the space. The patient also acknowledged that she washed dishes by hand and bathed her young children. This frequent soaking of her hands likely helped to provide a moist environment in which P aeruginosa could thrive. In addition, onycholysis is associated with hypothyroidism, which the patient also had.

GNS can be diagnosed by clinical observation and characteristic pigmentation along with an appropriate patient history. Nail discoloration, or chromonychia, can present in a variety of colors. Nail findings may represent an isolated disease or provide an important clinical clue to other systemic diseases. The specific shade of discoloration helps to differentiate the underlying pathology. Culture of the nail bed may be helpful if bacterial resistance or co-infection with fungal organisms is suspected. GNS is often painless, but may be accompanied by mild tenderness of the nail.

The patient was prescribed ciprofloxacin 500 mg twice a day for 10 days, plus bleach soaks (1 part bleach to 4 parts water) twice a day. She also was advised to wear gloves for household tasks that involved immersing her hands in water, and to dry her finger with a hair dryer after bathing.

This case was adapted from: Gish D, Romero BJ. Green fingernail. J Fam Pract. 2017;66:E7-E9.

Next Article: