Nail psoriasis is a clinical diagnosis generally made in the context of existing psoriatic skin lesions [6]. Treatment of nail psoriasis is important given its association with decreased quality of life [7].
Treatment of nail psoriasis is challenging because of the anatomical properties of the nail unit that act as a barrier to active drug delivery and the naturally slow growth rate of the nail plate, which often delays noticeable clinical responses by months [6]. Although there have been many recent advances in the treatment of skin psoriasis, nail management is difficult, as no standardized therapeutic regimen currently exists [8]. Topical therapies such as corticosteroids, calcipotriol, retinoids, and calcineurin inhibitors are the first-line therapy in the management of skin psoriasis. The efficacy of these drugs in nail disease, however, is limited, mainly because of the difficulty in penetrating the nail bed and nail matrix and the lack of compliance [8,9,10]. Topical treatments are generally used for mild nail psoriasis, when disease is limited to one or two digits, or if nail involvement is the only manifestation of the disease [7]. Rigopoulos et al. found improvement in NAPSI symptoms from baseline with clobetasol cream [11].
Various local side effects have been described such as atrophy of the underlying phalanx known as disappearing digit due to chronic use of topical steroids [12, 13]. These reported side effects limited the usage of topical steroids [14].
Intralesional therapy was successfully used especially in isolated nail psoriasis. The most common therapy is the injection of triamcinolone acetonide into the nail matrix [15]. It appears to be an effective treatment [14]. However, various severe side effects such as injection site atrophy, disappearance of the phalanx under injection, or tendon rupture were described [16]. Phototherapy, photochemotherapy, and other forms of radiation therapy have shown some beneficial outcomes [17]. However, the problem of availability limits their use.
Systemic therapy, such as retinoids, cyclosporine, and methotrexate, is not the first choice for psoriatic nails because of known adverse effects [10, 14]. Biological agents have been recently used on nail psoriasis but their cost-effectiveness is questionable [8, 14]. As a result of a high baseline risk of infection, caution is required when administering these medications, especially in geriatric patients [10]. Besides, the long-term repercussions, mainly the risk of developing malignant tumors, is still controversial; some studies have suggested that these treatments do not seem to increase this risk [18]. Moreover, they are not available in many countries.
Few publications have been recently concerned intralesional injection of methotrexate in nail psoriasis. This therapy was documented for the first time in 2011. Saricaoglu et al. reported its use in a single nail of a patient. The injection was given into the proximal nail fold (2.5 mg into each side of the nail weekly for 6 weeks). Improvement of subungual hyperkeratosis and pitting were observed [14]. Similarly, Daulatabad et al. reported, in an open-label prospective study of four patients, that injections with methotrexate (five session of 2.5 mg of methotrexate in each affected nail at 3-weekly intervals) significantly reduced the mean NAPSI from baseline with only mild adverse events, such as pain with injection, subungual hemorrhage, pinpoint hemorrhage at the injection site, and hyperpigmentation, all of which resolved within 6 weeks [15]. Furthermore, Mittal and Mahajan concluded, through a very recent open-label study comparing intramatricial injections of triamcinolone acetonide (10 mg/ml), methotrexate (25 mg/ml), and cyclosporine (50 mg/ml) in psoriatic fingernails, that intramatricial methotrexate yielded the most improvement with minimum side effects [19].
In our case, the nail involvement was present for several months without any spontaneous improvement. Almost total healing of affected nails was achieved with 2.5 mg intralesional methotrexate for all affected nails once a month for 3 months, with tolerable pain and no clinical complications. The improvement was progressive given the slow growth of the nail.
Intramatricial injection of methotrexate is an interesting intralesional therapy as it provides a higher concentration of the drug at the site of action, while avoiding the complications seen with triamcinolone acetonide as cited above (injection site atrophy, disappearance of the phalanx under injection, or tendon rupture) [16] and the severe persisting pain noted with cyclosporine [19]. Moreover, it averts known adverse effects of systemic therapies that have disappointing results but expose the patient to multiple risks such as hypertension and renal dysfunction with cyclosporine, neutropenia and elevated liver function tests with methotrexate, hyperlipidemia with acitretin, and infections and malignancies with biologic therapies [7, 10]. Furthermore, this modality is a way of overcoming the problem of poor drug penetration encountered with topical treatment, essentially topical vitamin D3 [6], and of availability, high cost, and the significant number of visits required with phototherapy and excimer light/laser treatment.