Table of Content


Spring 2015, Vol. 23 No. 1

Hong Kong J. Dermatol. Venereol. (2015) 23, 3-4


Nail psoriasis: an orphan disease?

KH Yeung 楊國鴻

Orphan disease is a disease that has not been "adopted" by the pharmaceutical industry because it provides little financial incentive for the private sector to raise funding to investigate its causes; and manufacture and market new medications to treat or prevent it. An orphan disease may be a rare disease (according to the United States criteria, a disease that affects fewer than 200,000 people) or a common disease that has been ignored by the physicians and/or pharmaceutical companies because of its low prevalence.

Nail psoriasis in some way is similar to an orphan disease. Firstly, although psoriasis is not a rare disease, nail psoriasis is treated more as a diagnostic sign by physicians and often neglected during treatment. As it is difficult to treat, and with no international clear consensus in its measurement of severity, there are few studies that focus on nail psoriasis alone. However, the impact of nail psoriasis on the quality of life of patients is unimaginable. Apart from the face; the nails, especially the finger nails, are the most conspicuous part of our body because they are exposed during our daily activities. It is a norm that the nails reflect one's health. Deformed nails are usually considered to be a sign of poor personal hygiene and ill health. Moreover, deformed fingernails can make fine manual activities difficult and even painful, while psoriatic toenails are often secondarily infected with dermatophytes, which may complicate treatment assessment. Immunosuppressive medications for more severe skin psoriasis or nail psoriasis may even contribute to the development of onychomycosis in patients with toenail psoriasis. For these reasons, most studies evaluate fingernail psoriasis alone. This leads to incomplete research for nail psoriasis.

A unified approach such as the Nail Psoriasis Severity Index (NAPSI) can help in nail psoriasis assessment so that different studies can be compared on the same basis.1 Nevertheless, this scale measures the extent of nail disease but not the severity of nail involvement, so a modified NAPSI has been proposed that assigns a severity score for both nail bed and matrix involvement.2 However, some studies used a single target nail while others used an overall severity score. The wide variety of objective measures used in nail psoriasis studies makes comparison of treatment outcomes for various interventions difficult.

On the other hand, nail psoriasis is not that rare. Although the incidence of nail psoriasis as the sole clinical feature is rare, 40%3 to 78%4 of psoriatic patients' nails can be affected. As there is a strong correlation of nail psoriasis with psoriatic arthritis, nail psoriasis may be a predictor of joint disease developing later in life. It is also associated with more severe psoriasis and a longer disease duration.5 In this issue, a review of nail psoriasis by CT Chau highlights the difficulties in assessment and treatment of nail psoriasis. Some evidence-based recommendations on treatment modalities are discussed. With more understanding and attention from the dermatologists, one would expect that nail psoriasis will not be so "lonely". Future trials need to be meticulous in design, with adequate reporting. Trials should correctly describe the patients' characteristics and diagnostic features, be long enough to report the safety and efficacy of treatment, use standard validated nail scores and patient-reported outcomes, and include details of effects on nail psoriasis.

KH Yeung


1. Rich P, Scher RK. Nail Psoriasis Severity Index: a useful tool for evaluation of nail psoriasis. J Am Acad Dermatol 2003;49:206-12.

2. Cassell SE, Bieber JD, Rich P, Tutuncu ZN, Lee SJ, Kalunian KC, et al. The modified Nail Psoriasis Severity Index: validation of an instrument to assess psoriatic nail involvement in patients with psoriatic arthritis. J Rheumatol 2007;34:123-9.

3. van de Kerkhof PC, de Hoop D, de Korte J, Kuipers MV. Scalp psoriasis, clinical presentations and therapeutic management. Dermatology 1998;197:326-34.

4. Salomon J, Szepietowski JC, Proniewicz A. Psoriatic nails: a prospective clinical study. J Cutan Med Surg 2003;7:317-21.

5. Armesto S, Esteve A, Coto-Segura P, Drake M, Galache C, Martínez-Borra J, et al. Nail psoriasis in individuals with psoriasis vulgaris: a study of 661 patients [in Spanish]. Actas Dermosifiliogr 2011;102:365-72.