Trachyonychia (or twenty-nail dystrophy) is an uncommon chronic disorder manifesting as thin, flattened, brittle nails with excessive longitudinal ridging and loss of luster creating a "sandpaper-like" texture that most commonly presents spontaneously in childhood as an isolated phenomenon; however, it has been historically associated with numerous dermatoses. Rarely, trachyonychia has been reported to occur in families, suggesting a potential hereditary predisposition. We report trachyonychia occurring simultaneously in dizygotic twins, further supporting a possible underlying genetic basis of this idiopathic nail disorder.

Trachyonychia, a rare inflammatory disease of the nail matrix, has a more chronic course in adults compared with that in children. However, the histopathologic features of the disease have not been sufficiently reported in the literature. We retrospectively reviewed the pathologic features of idiopathic trachyonychia in adult cases at our center. A total of 30 cases were included. The median age was 55.5 years (range, 27-77 years). Median disease duration was 84 months (range, 8-384 months). Histopathologic analysis showed upper dermal lymphocytic infiltrates (93.3%), acanthosis (86.7%), exocytosis (63.3%), spongiosis (63.3%), parakeratosis (46.7%), psoriasiform hyperplasia (40%), eosinophilic infiltrates (33.3%), vacuolar degeneration (33.3%), lichenoid pattern (13.3%), Civatte body (6.7%), and collection of neutrophils in the stratum corneum (3.3%). Statistical analysis among pathologic parameters revealed associations of spongiosis with exocytosis (P < 0.001) and lichenoid infiltration with vacuolar degeneration (P = 0.008). Three patients (10%) showed fungal co-infection. The majority of cases revealed inflammatory cell infiltration with epidermal changes. Given the inflammation and chronic course of idiopathic trachyonychia in adulthood, active treatment with anti-inflammatory agents should be considered. Additionally, mycological tests should be considered during initial evaluation as there are cases with fungal coinfection.

Two patients, one with nail lichen striatus and second with idiopathic trachyonychia were treated with intramatriceal injections of platelet-rich plasma. A total of 0.1 ml of the plasma solution was injected into the matrix of the involved nails at three weekly intervals. Follow-up was done at each sitting and thereafter at 16 and 20 weeks. Assessment was done both photographically and by dermoscopy. Case 1 showed marked improvement within 3 weeks and Case 2 showed improvement within 6 weeks. No relapses were seen at 16 and 20 weeks of follow up. Intramatricial PRP is a safe and effective therapeutic modality in nail lichen striatus and idiopathic trachyonychia refractory to other treatment options. Further studies with larger sample size and controls are required to validate the results.