Are You Confident of the Diagnosis?
Retronychia is caused by an ingrown nail plate at the proximal nail fold.
Characteristic findings on physical examination
Characteristic features include a yellow discoloration of the nail plate, detachment of the nail plate from the nail bed (onycholysis), inflammation of the proximal nail fold. An inflammatory exudate and granulation tissue is often present. The toes are more commonly affected than the fingers, and the great toenails are the nail units most likely to be affected on the feet (Figure 1).
A preliminary diagnosis can be made by recognizing the clinical appearance of an affected nail unit, and can be confirmed with visualization of the presence of multiple layers of proximal nail noted during a therapeutic nail avulsion.
Who is at Risk for Developing this Disease?
An important risk factor for developing retronychia includes trauma to the nails. Cases have been described which have been associated with the repetitive trauma of jogging, hiking, and the use of high heeled shoes.
What is the Cause of the Disease?
Retronychia is caused by pressure from the proximal nail plate on the proximal nail fold. This can be precipitated by trauma.
The proximal nail plate will lose its connection to the matrix. The nail plate is often firmly adhered to the distal nail bed, and is not able to be pushed out by the newly formed nail plate. New proximal nail plate will be formed, and will push the old nail plate further into the proximal nail fold, and exacerbate the inflammatory response.
Subsequent formation of granulation tissue and serum exudate can occur. Multiple layers of proximal nail plate will form beneath the proximal nail fold.
Systemic Implications and Complications
Retronychia itself is a localized process which does not have systemic effects. However, cases have been reported to be associated with Beau’s lines, and a systemic illness resulting in Beau’s lines might predispose a susceptible individual to the development of retronychia. If an area of retronychia became infected, there could be systemic complications from infection.
Retronychia is treated by nail plate avulsion. In a series of 19 patient cases with retronychia described by de Berker et al, all of the patients who were treated with nail avulsion had a resolution of symptoms.
Optimal Therapeutic Approach for this Disease
Nail avulsion should be curative, as opposed to other forms of ingrown nails.
After a nail avulsion, the patient with retronychia should be followed to ensure healing of the treated site. As opposed to other forms or ingrown nails, recurrences of the problem are not expected.
Unusual Clinical Scenarios to Consider in Patient Management
Other causes of xanthonychia (yellow nails) should be considered in the differential diagnosis, such as the yellow nail syndrome, congenital malalignment of the nails, and onychomycosis.
However, retronychia will demonstrate some different features (yellow discoloration of the nail plate, detachment of the nail plate from the nail bed [onycholysis], inflammation of the proximal nail fold, an inflammatory exudate and granulation tissue) which will help differentiate it from other entities.
What is the Evidence?
de Berker, D, Richert, B, Duhard, E, Piraccini, B, Andre, J, Baran, R. “Retronychia: Proximal ingrowing of the nail plate”. Journal of the American Academy of Dermatology. vol. 58. 2008. pp. 978-83. (This study describes cases collected by a European Nail Society expert group. In this series, 19 patients were described, which were collected over an 8-year-period, and were managed in five different dermatology units in Europe. The mean age of the patients was 39 years, and 84% of the patients were women. All of the patients had resolution of retronychia, 17 of which were treated with nail avulsion. The article includes a comprehensive description and diagrams of the mechanism of the evolution and features of retronychia.)
Baumgartner, M, Haneke, E. “Retronychia: Diagnosis and Treatmen”. Dermatol Surgery. vol. 36. 2010. pp. 1-5. (The authors describe five cases of retronychia, and treatment outcomes. Nail avulsions performed on these patients relieved the symptoms.)
Dahdah, M, Kibbi, A, Ghosn, S. “Retronychia: Report of two cases”. Journal of the American Academy of Dermatology. vol. 58. 2008. pp. 1051-3. (A descriptive article that includes two patients with retronychia and describes the mechanism of how retronychia occurs.)
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