Background/Aims: The term trachyonychia, also known as twenty-nail dystrophy, is used to describe thin, brittle nails with excessive longitudinal ridging. The term twenty-nail dystrophy has been incorrectly applied to other conditions that can affect all twenty nails. Therefore, we have conducted a comprehensive review of the clinical features of trachyonychia and have included a discussion regarding the diagnostic accuracy of this condition in the literature. Methods: In November and December 2015, we conducted a thorough literature search using the following search terms: ‘trachyonychia', ‘twenty nail dystrophy', and ‘sandpaper nails'. Articles that reported the epidemiology, disease associations, clinical presentation, histopathology, and treatment options for trachyonychia were included. Particular attention was given to case reports to identify misdiagnosed cases of twenty-nail dystrophy. Results: Our preliminary search yielded 184 results with 72 unique articles ultimately selected for review. Excluded articles included 27 articles in languages other than English, 18 commentaries or reviews, and 67 irrelevant articles. Twelve additional articles described nail abnormalities clinically different from trachyonychia. Conclusion: Many other conditions can cause widespread nail dystrophy. The specific characteristics of trachyonychia need to be considered to make the diagnosis of twenty-nail dystrophy.

Trachyonychia is also known as twenty-nail dystrophy and describes rough, sandpapered nails that are brittle and thin. Alkiewicz [1] first used the term trachyonychia in 1950, but the condition was later identified as twenty-nail dystrophy by Hazelrigg et al. [2 ]in 1977. However, the term twenty-nail dystrophy is misleading as in trachyonychia any number of nails can be affected and on the other hand widespread nail dystrophy is often incorrectly diagnosed as twenty-nail dystrophy even when the clinical signs of trachyonychia are not evident. It is for this reason that we have conducted a comprehensive review of the clinical features of trachyonychia in addition to a discussion regarding diagnostic accuracy of this condition.

We conducted a thorough search of PubMed, Cochrane Central Register of Controlled Trials (CENTRAL), clinicaltrials.gov, and Embase. The search was performed in November and December 2015 using the following search terms: ‘trachyonychia', ‘twenty nail dystrophy', and ‘sandpaper nails'. Inclusion criteria required articles to report or investigate the epidemiology, disease associations, clinical presentation, histopathology, and treatment options for trachyonychia. Clinical trials, case series, and case reports were included. Reviews were excluded but accessed as a reference for the topic. Articles published in a language other than English were excluded. Titles and abstracts were reviewed for relevance; full-text review was conducted in the event of inconclusive titles and abstracts. References of selected articles were also screened for completeness. Case reports suggesting novel disease associations were reviewed in full text, with particular attention to clinical photographs to verify if the nail abnormalities were consistent with a diagnosis of trachyonychia.

The preliminary search yielded 184 results. A total of 72 unique articles were initially identified for inclusion in our review. Of the remaining 112 articles, 27 were in languages other than English, 18 were commentaries or reviews, and 67 were deemed irrelevant. Of the 72 articles identified for inclusion, 12 articles were considered to report nail abnormalities that were different from trachyonychia (table 1). Figure 1 depicts the article selection process in detail.

Epidemiology

Trachyonychia follows an insidious disease course and is most common in the pediatric population [2]. In children, all twenty nails are usually affected and trachyonychia is more commonly idiopathic. The most common associated disease is alopecia areata where trachyonychia is estimated to affect 3.65% of patients [3]. The prevalence of idiopathic trachyonychia is not known [4].

A number of other cutaneous and systemic diseases have been associated with trachyonychia including the following: amyloidosis [5], atopic dermatitis [6], treatment with chemotherapeutic agents [7,8], hematologic abnormalities (i.e. idiopathic thrombocytopenia) [9], ichthyosis vulgaris [10,11], immune dysregulation polyendocrinopathy enteropathy X-linked syndrome (IPEX) [12], immunoglobulin A deficiency [13], incontinentia pigmenti (Bloch-Sulzberger syndrome) [14], pemphigus vulgaris [15], primary biliary cirrhosis [16], reflex sympathetic dystrophy [17], and sarcoidosis [18,19]. However, for some of these cases, the clinical pictures show nail abnormalities that are different from trachyonychia (table 1). Vitiligo has also been associated with trachyonychia [20,21,22], but this probably reflects the fact that trachyonychia is commonly associated with alopecia areata.

We believe that it is important for clinicians to make the diagnosis of trachyonychia carefully, especially when it is thought to be concomitant with one of the above-listed disease associations. For example, although trachyonychia has been associated with amyloidosis, the pictures illustrating the case reports with this association show lichen planus-like changes with severe onychorrhexis but not trachyonychia [5,23].

Lichen planus and psoriasis can also cause trachyonychia [24], and in a retrospective study of 15 children with nail lichen planus, 2 exhibited trachyonychia [25].

Clinical Presentation and Histopathology

To aid the clinician in making an accurate diagnosis of trachyonychia, we will describe the clinical presentation in detail. First, we want to emphasize again that any number of nails can be affected. The degree of severity can also vary from nail to nail [4]. Two clinical varieties, opaque and shiny, have been described by Baran et al. [26], where the opaque form represents a more severe condition. Table 2 describes these two varieties. In both forms, fingernails are affected more often than toenails and koilonychia is common.

In the more severe or opaque form, the nails have a ‘sandpaper-like' appearance. These nails present excessive longitudinal ridging due to fine parallel oriented superficial striations. They look thin, rough, and fragile with frequent onychoschizia. The cuticle is hyperkeratotic and irregular. However, they do not show longitudinal fissures (onychorrhexis), distal splitting, or crumbling (fig. 2). In mild or shiny trachyonychia, the nails retain their luster as they present with multiple small geometric pits arranged to form longitudinal ridges. These reflect light and the nails are not as thin and fragile as in opaque trachyonychia (fig. 3). A differential diagnosis of trachyonychia is presented in table 3.

The extent of inflammation in the nail matrix is thought to contribute to the wide range of severity observed in trachyonychia. Tosti et al. [27 ]have hypothesized that when inflammation is severe and persistent, diffuse damage causes an opaque variety. In contrast, mild and intermittent inflammation results in multifocal damage, with nails that retain their luster as a result [4]. This hypothesis is supported by the variable location of histopathologic changes observed in trachyonychia, which are more prominent in the proximal nail matrix and ventral proximal nail fold; this nonuniform inflammatory activity results in a spectrum of disease severity [28].

Trachyonychia is a clinical diagnosis and there is no indication for a nail biopsy in these patients. Trachyonychia never causes permanent nail damage or pterygium, including cases of trachyonychia caused by lichen planus, and for this reason, there is no necessity for a nail matrix punch or longitudinal nail biopsy, which is invasive and can cause scarring. Pathological studies of trachyonychia showed that the most common features are spongiosis and exocytosis of inflammatory cells into the nail epithelia [3,27,29,30]. Histopathology can also show the features of nail matrix lichen planus or nail matrix psoriasis. Further, trachyonychia due to nail lichen planus has been reported to occur in patients with alopecia areata [3,31], suggesting that these two diseases can occur simultaneously [28].

Treatment

Trachyonychia is a chronic condition. However, it is important to keep in mind that it is neither scarring nor painful, so treatment is often prescribed only for cosmetic reasons and patients may often improve without any treatment. In a case series, 50% of patients (n = 12) experienced resolution or considerable improvement in 6 years regardless of treatment [32] (fig. 4). In patients with idiopathic trachyonychia as well as in those with childhood onset with symptoms lasting more than 6 years, spontaneous improvement is less common [32].

For patients who desire cosmetic improvement and patients with very severe varieties who have difficulty with daily manual functions [33], there are many treatment modalities reported in the literature but no standard evidence-based approaches. Conservative approaches include mild emollients and camouflage with nail polish. An emollient may improve the nail surface texture in opaque trachyonychia, while nail polish can help improve appearance in shiny trachyonychia [4].

Topical options include corticosteroids, tazarotene gel [34], and 5% 5-fluorouracil [35]. However, use of topical tazarotene gel and 5-fluorouracil has only been reported in the literature in one case each. A more recent study of 36 patients with 432 affected nails has found significant improvement in 98.6% of nails after 6 months of treatment with calcipotriol/betamethasone dipropionate ointment [36].

Procedure-based options reported in the literature include nail plate dressings (ultra-thin adhesive bandage applied once a week with lactic acid, silicon dioxide, aluminum acetylacetonate, copolymer of vinyl acetate with acrylic acid, and azelaic acid) [37], intralesional injection of triamcinolone into the proximal nail fold [38,39,40], and topical psoralen UVA [41]. The once weekly nail plate dressings were found to improve symptoms after 3 months in a pediatric patient [37]. Intralesional triamcinolone improved symptoms in 17 of 25 reported cases [38,39,40]. This option, while appearing efficacious, is uncomfortable and may not be an appropriate selection for some pediatric patients.

Systemic treatments include biotin 2.5 mg/day [42], cyclosporine 2-3.5 mg/kg/day [43,44], retinoids [33], systemic corticosteroids [45,46], and tofacitinib citrate [47]. In cases of trachyonychia due to psoriasis, acitretin is an effective option [33]. As treatment for trachyonychia is primarily for cosmetic reasons, the decision to treat systemically should be made carefully in regard to risk factors and patient preference.

As we presented above, the diagnosis of twenty-nail dystrophy should be carefully considered, as there are other conditions that can cause widespread nail dystrophy such as inflammatory and systemic diseases, ectodermal disorders, and infection. We found that trachyonychia and twenty-nail dystrophy have been misdiagnosed in the literature in several cases [5,35,41,48,49,50,51,52](table 1). The diagnosis is often incorrectly based on the presence of dystrophic nail changes on all twenty nails, despite the fact that the nails do not show specific signs of trachyonychia.

We also want to emphasize that the diagnosis of trachyonychia is based on a specific morphology and the presence of fissures and splitting is not consistent with this diagnosis. Additionally, it is important to avoid the statement that trachyonychia is characterized by dystrophy of all twenty nails [51] which, as we demonstrate in this review, is not accurate.

In conclusion, trachyonychia is a chronic condition that can be idiopathic or associated with a variety of cutaneous and systemic conditions. The diagnosis should be made carefully, with consideration of the key clinical features including brittle, thin nails with excessive longitudinal ridging in severe forms or superficial ridging with geometric pitting and retention of nail luster in less severe forms.

A.A.J. has no disclosures to report. A.T. is an advisor for Meiji, Valeant Pharmaceuticals, Viamet Pharmaceuticals, Pharmaderm, Polichem, and a speaker for Pharmaderm.

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