Case report Harpoon nail: an unusual form of onychocryptosis

Onychocryptosis is a frequent nail disease, which most commonly affects the toes. It has some variants, including the little known "Harpoon Nail". The diagnosis is usually clinical, and the treatment is surgical, with different techniques described in the literature. We report the case of a 25-year-old man with a harpoon nail on the left hallux and the surgical method used for treatment with excellent results


INTRODUCTION
The ingrown nail, also called onychocryptosis, results from a conflict between the nail plate and adjacent soft tissues, causing an inflammatory reaction that can lead to the appearance of granulation tissue and hypertrophy of nail folds. 1 It most commonly affects the hallux in its distal lateral portion. 2,3 The literature describes some uncommon variants of onychocryptosis, such as the harpoon nail, where a sharp spike of the nail penetrates the periungual tissue forming a channel and emerging in the hyponychium. We report a case of this variant and its surgical treatment.

CASE REPORT
A 25-year-old man, student, sought medical care with a complaint of ingrown toenail of the left hallux for more than two years, accompanied by intermittent pain, more intense at the beginning of the condition. On physical examination, one of the lateral nail folds of the left hallux presented a marked increased volume, covering a good part of the nail plate and extending to the hyponychium. The end of the lateral nail fold had an erythematous papulo-nodular lesion covered by a small crust and surrounded by a keratotic collarette (Figure 1). In the contralateral fold, we identified a lesser degree of edema.
Due to the diagnosis of onychocryptosis in the two lateral nail folds and the formation of a harpoon nail in one of them, we referred the patient for surgery. We performed the resection of excess tissue from the lateral folds, which allowed the visualization of the sharp spike of the nail on the lateral portion of the nail plate ( Figure 2). Then, we followed with the avulsion of a lateral nail strip and finished with chemical cauterization (phenol 88%) of the lateral segment of the nail matrix and the portion of the nail lateral folds ( Figure 3). Healing occurred by secondary intention.
The patient evolved well in the postoperative period, with no signs of recurrence and a good aesthetic result after six months of progression ( Figure 4).

DISCUSSION
Nail ingrown results from constant pressure from the nail plate on adjacent soft tissues, 4 leading to a local inflammatory process. It is a frequent condition, with a prevalence of 2.5-5%, more common in men in the third and fourth decades of life, but the literature has already described congenital cases and in the elderly. 1 It most frequently affects the distal lateral portion of the nails of the halluces. 2,3 It can present pain, erythema, ede-    Onychocryptosis can be classified according to different stages described by Heifetz, Mozena, and Martinez Nova, with some modifications among them. In general, in stage I, there is mild erythema and edema of the nail bed with pain on digital pressure, not exceeding the limits of the nail plate. 3 In stage II, pain, swelling, and erythema are more intense, and abscess formation may occur in the lateral nail fold, exceeding the nail plate limits (in phase IIa, the fold measures <3 mm; in phase IIb, the fold measures >3 mm). In stage III, there is chronic hypertrophy of the lateral nail fold and the presence of granulation tissue. In stage IV, there is a chronic deformity, affecting the nail plate, the lateral nail folds, and the distal nail fold. 1, 3 We report the case of an uncommon variant of onychocryptosis described for the first time by Richert, Caucanas, and Di Chiacchio (2014): 4 the harpoon nail. This name is due to its resemblance to a marine hunting instrument that has a sharp tip and a wide base, the harpoon. 2 It is a specific variant of distal lateral ingrowing. It occurs when the patient manipulates the side of the nail blade to relieve the pain of an ingrown nail in the nail fold but is unable to cut the most external and deepest part of the nail plate. Thus, the remaining lateral nail fragment grows and creates a nail spicule, which crosses the periungual tissue and forms a fistulous path, emerging in the hyponychium. 2,4,5 Its diagnosis is clinical 1,5 and can be aided by exams such as high-frequency ultrasound (HFUS), which will show the ingrowing in the lateral nail fold associated with the nail spicule. 5 The harpoon nail treatment is surgical. If not performed, the condition may become chronic: the inflammation can disappear, and the canal containing the nail spicule can epithelialize. 5 The literature describes several surgical techniques, and the choice of any one of them depends on the stage and type of onychocryptosis and the surgeon's ability. The surgical approach that we used in this report was one of the most common techniques found in the literature. The procedure starts by opening the canal containing the nail spicule, removing the excess periungual tissue, then avulses the lateral nail band, and finishes by the chemical cauterization of the lateral spicule of the matrix with phenol 88%. 2,4,6 Alternatively, a wedge resection can be performed, containing the lateral nail fold with the nail spicule and its canal (Vandenbos procedure) or a Super U 7 , where all excess tissue is removed in a "U" shape. 1 The harpoon nail is a little-known clinical variant of onychocryptosis that affects the individual's quality of life. Through an appropriate surgical approach, it is possible to achieve resolution of the condition with good aesthetic results and without recurrence l