An unusual onychocryptosis
A 17-year-old Caucasian man presents with a four-month history of a painful, swollen hallux around the base of the nail. Prior to presentation he had received two courses of oral antibiotics via the GP for persistent pain and swelling around the nail base with a diagnosis of acute IGTN. Further history failed to identify any specific precipitating event rather an insidious onset of pain to the base of the nail plate over several weeks prior to GP consultation. Despite two seven-day courses of oral antibiotics the infection failed to fully resolve and pain persisted. Persistent weeping and bleeding from the eponychium was noted.
Clinical history and examination confirmed a fit and healthy male with normal neurovascular status. Significant inflammation was noted to along the eponychium with lifting of the nail plate. Extensive granulation tissue was noted immediately ahead of the eponychium consistent with chronic inflammation.
A total nail avulsion was undertaken (without phenolisation), and the following picture was taken intra-operatively revealing a second nail growing beneath the main nail plate (figure 1).
What is the diagnosis?
Retronychia. First described by de Berker in 1999 (1), retronychia is a condition where the nail plate embeds in a retrograde direction into the proximal nail fold (PNF). In the early stage it usually begins following an acute trauma which forcibly pushes the nail backwards and upwards into the PNF. Simultaneously, the nail undergoes a proximal detachment of the nail plate (onychomadesis). The loosening of the nail plate within the matrix, creates a space under which a new nail can grow. Visually the nail may appear to have stopped growing and show a proximal yellowing.
At the Intermediate Stage mild to moderate paronychia may ensue with elevation or bulging of the proximal nail fold as a new nail grows beneath creating pressure within the matrix. The toe maybe painful at this stage.
In the late stage intense pain and paronychia, hypergranulation emerging from the proximal nailfold (Figure 2). In addition, Beaus lines may be seen along with leukonychia (whitening) of the nail or sub-ungual haemorrhage. Occasionally the proximal nail edge becomes elevated (figure 2).
Figure 2: Late stage retronychia showing paronychia with hypergranulation, haematoma and leukonychia of the nail plate (2)
The diagnosis is generally made on clinical grounds owing to its unique clinical presentation although high frequency ultrasound of the PNF can image multiple nail plates in situ. Surgical avulsion allows for full visualisation of the multiple nail plates to confirm the diagnosis. Avulsion of the nail plates releases pressure on the PNF and allows healing to ensue and a new nail to grow through. Phenolisation is not necessary. Recurrence is possible, particularly if the source of the original trauma is not removed. For most, this arises from impaction of the hallux nail into a steel toe cap or end on trauma to the free edge of the nail.
1. De Berker DAR, Renall JRS. Retronychia-proximal ingrowing nail. J Eur Acad Dermatol Venerol. 1999;12(supp 2):126S.
2. Bristow I, Boyle A. Retronychia - a different kind of ingrowing toenail. Dermatological Nursing. 2021;20(1):21-4.