Discussion
We experienced a case of subungual abscess with paronychia that improved
with manual drainage without antibiotics. Among the numerous reviews on
subungual tumors using US and MRI,1–4 the most
comprehensive is that of Mundada et al..1 This review
broadly divided subungual tumors into nail tumors and nail tumor-like
lesions (e.g., mucoid cyst and epidermoid cyst). Nail tumors are divided
into benign (e.g., glomus tumors and subungual exostosis, etc.) and
malignant tumors (e.g., squamous cell carcinoma and malignant melanoma).
They also stated that high-resolution MRI can identify subungual tumors
better than X-ray or US although not in a perfect manner. However, four
studies, including this one, did not include subungual abscesses.
Subungual abscesses are mainly reported in case
reports,5–7 and no reports included US or MRI images
as far as we have examined. All these three cases were improved through
CO2 laser drainage of the abscess and antibiotic
treatment; however, the current case was improved through manual
drainage without antibiotics. No studies have reported the organisms
responsible for subungual abscesses; however, a study reported the
organisms responsible for paronychia, with the Enterobacteriaceae
family being the most common, followed by the Staphylococci
genus .8 The causative organism in our case wasS. aureus , which is the most common member of theStaphylococci genus . Paronychia has been reported to be more
common in occupations that involve frequent handling of water, such as
bartenders, housekeepers, housemakers, dishwashers, and
swimmers.8 The patient in the present case was a
healthcare worker who frequently washed his hands because of the
COVID-19 pandemic, which may have caused the subungual abscess.
Anticancer agents, such as taxanes and anthracyclines, have also been
reported as a cause of subungual abscesses, but no drugs were used in
the present case.9
Ávila de Almeida et al. reported one subungual tumor, a glomus tumor,
using a 33 MHz transducer with very sophisticated US images while
previous US studies of subungual tumors were reported using a 15–18 MHz
transducer.10 We clearly delineated a subungual
abscess before and after treatment using a high-frequency transducer of
2–22 MHz in the present case, similar to that reported by Ávila de
Almeida et al.
Abscesses should also be listed in the differential diagnosis of
subungual tumors, and this is the first report of a subungual abscess
that included US and MRI images.