Retronychia in children: A case series.

Background: Retronychia is characterized by proximal ingrowing of the nail plate into the proximal nail fold. It is always associated with the presence of two or more overlapping nail plates under the proximal nail fold, clinical signs of chronic proximal paronychia refractory to antimicrobial treatment, and a yellowish nail that does not grow. It mainly affects young female adults, with less than 30 pediatric cases described in the literature so far.

Methods: Retrospective and observational study of patients between 0 and 18 years with a clinical and/or ultrasound diagnosis of retronychia attending a pediatric dermatology service between December 2020 and January 2022.

Results: We identified 9 patients with retronychia, 7 girls and 2 boys. In all cases, the hallux nails were affected with 5 unilateral and 4 bilateral cases. On physical examination we observed the following signs: thickened and opaque nail plate (one patient), yellowish nail plate (7 patients), double nail plate (6 patients), and erythema with edema, pain, and suppuration of the proximal nail fold (7 patients). Ultrasound was performed in 7 patients and specific findings of retronychia were found in 5 of them. All patients received topical treatment and were referred for the appropriate surgical treatment. To date, only one patient underwent nail avulsion, which was followed by complete recovery.

Conclusions: Retronychia is underdiagnosed, particularly in the pediatric population. We present a series of 9 cases of retronychia in children, with clinical and ultrasonographic findings consistent with those of adults. We emphasize the importance of recognizing this entity, which will allow early and adequate treatment.