Diagnosis of Eumycetoma via Bedside Ultrasound

Abstract

Background

Mycetoma is a chronic infection of skin and soft tissues that results from vulnerable skin contact with fungi (eumycetomas) or bacteria (actinomycetomas) in soil, commonly involving feet and hands. Mycetomas are gradually progressive over months to years and can invade bone if untreated or misdiagnosed, leading to deformity, disability, and/or amputation. The ‘dot-in-circle’ sign on bedside ultrasound has been reported as a specific finding for mycetomas, potentially expediting diagnosis. In this case, we describe a patient diagnosed with mycetoma, which was first seen on bedside ultrasound.

Description

A 74-year old immunocompromised male presented to clinic with subcutaneous masses on the right lateral ankle and knee. Ultrasound of the masses showed a small, oval-shaped hyperechoic ‘dot’ surrounded by hypoechoic tissue. Due to mycetoma’s rarity in Minnesota, it was not initially recognized. Months later, the patient returned with a new left thumb mass and enlarged leg masses. He was referred to the Emergency Department for drainage, where cultures later grew Dematiaceous mold. Given the ultrasound findings and the fungus growing on the culture, he was hospitalized for workup of mycetoma and concern for disseminated fungal infection.

Lessons Learned and Conclusions

Mycetoma is an underdiagnosed tropical disease that can progress to significant morbidity and/or mortality. Delays in diagnosis of mycetomas can have limb- and life-threatening consequences. In Tanzania, mycetomas are endemic, though data is unavailable on prevalence.

In this case, bedside ultrasound was used to assist in the early recognition and diagnosis of mycetoma, likely preventing involvement of the bone. Ultrasounds should be performed on unknown soft-tissue masses. A ‘dot-in-circle’ sign should prompt workup for mycetoma including drainage with fungal and bacterial cultures. Further research is needed to evaluate the sensitivity and specificity of ultrasound evaluation of mycetomas, which may yield improved data on the prevalence of the disease process.