Double little toenails: Report of 4 familial cases

Abstract

Double little toenails, or accessory nails of the fifth toe, are a rare and particular deformity distinct from other nail dysplasias. We describe 4 cases of female patients, including a 6-year-old girl, experiencing this bilateral condition after birth. The nail anomaly shows an autosomal-dominant type of transmission that affects only female individuals. The subjects examined were from a family without marriages between blood relatives and without neuroectodermal hereditary diseases. The 4 patients had no bone alterations of the terminal phalanges of the fifth toe or alterations of the joints of the toes or hair. One patient had nail deformity associated with epilepsy; another patient, associated with an infection of an accessory nail.

Keywords: double little toenail; ectopic nail; hereditary accessory nail of the fifth toe; nail morphology; onychodysplasia; split nail.

Fig 1

Clinical presentation of double little toenail of the fifth toe in the proband (A, B). Clinical feature of the double little toenail of the fifth toe in the older sister of the proband (C, D).

Fig 2

A, Short pedigree of the affected family with double little toenail of the fifth toes. B, Dermoscopic features of the accessory nail of the fifth toe, resembling staves of a barrel (similar to the ectopic nail). C, Scanning electron microscopy image of the double little toenail, showing a stumpy nail with vertical groove, nail folds, and hyponychium. D to F, Echotomography of the nail of the fifth toe of the right foot of the proband. D, Coronal section below the eponychium, showing a hypoechoic area corresponding to the supernumerary nail matrix, 2 mm in diameter; this area seems separated from the main matrix of the nail by an isthmus. E, Longitudinal side section showing the accessory nail plate equipped with a nail bed above the bone phalanx, with a hypoechoic area of approximately 1.7 mm, which corresponds to its matrix. F, Coronal section in a distal position showing the 2.5-mm-wide accessory nail plate of the double little toenail, separated by a thin groove from the main plate.