Posttraumatic Retronychia of the Foot with Clinical and Ultrasound Correlation

Retronychia, the posterior embedding of the nail bed into the proximal nail fold, can be a complex clinical dermatologic diagnosis that may mimic other inflammatory ungual diseases or tumors of the nail. It has been related to a history of severe systemic conditions that secondarily affect the nail matrix and is commonly associated with onychomadesis. We present a case of retronychia of the foot with a purely traumatic origin, nonconcomitant with onychomadesis, that was diagnosed by color Doppler ultrasound in a long-time practitioner of martial arts who was otherwise healthy. Color Doppler ultrasound is an excellent imaging technique for supporting the diagnosis of retronychia. It provides information on the exact location and morphology of the nail plate as well as the presence of inflammatory signs in the ungual and proximal periungual regions. Additionally, this imaging technique can support the differential diagnosis with other nail conditions. Since there are many sports or activities that can potentially injure the toenails, retronychia may be an underestimated entity and the present case can raise the awareness of this condition and show the usefulness of color Doppler ultrasound.