Which is worse in psoriasis - skin or joints?

Abstract

Psoriasis (PsO) is a common disorder with its prevalence ranging from 1.5–3.0% among European and Scandinavian countries to just 0.15% in Chinese studies. Among those individuals with PsO, at least 10% are expected to have psoriatic arthritis (PsA). Both PsO and PsA impact on social, physical and psychological function, resulting in impairment of quality of life (QoL). This can be measured by a generic instruments such as Medical Outcomes Survey – Short Form 36 (SF36) or disease-specific QoL measures such as the Dermatology Life Quality Index (DLQI) as well as the PsAQoL assessment tool. SF36 has been validated and found reliable and responsive to change both in PsO and PsA.1, 2 The DLQI was developed and validated among PsO patients, and it is also responsive to change.3 PsAQoL, a 20-item questionnaire provides information about disease state; it is sensitive to change following therapy.4 It has also been translated and validated in various languages. Generic QoL measures such as SF36 have the additional strength and utility of allowing comparison of QoL in patients with other diseases in normal population.5 PsO results in debilitating psychiatric morbidity, stigmatization, embarrassment and impaired self-esteem.6-8 Female gender, duration of disease and treatment type has been shown to correlate with a poorer QoL.9 A systematic review of 17 studies showed that patients with PsO reported physical discomfort, impaired emotional functioning, negative body and self-image, limitations in daily activities, reduced social contacts, fewer activities involving skin exposure and reduced work.10 As the severity of PsO increases, so does the financial impact by way of health costs and impaired earnings, leading to impairment in global QoL.11 As a chronic psychological and physical disorder, it has been proposed that a measure of the cumulative QoL burden may have more utility. ‘Cumulative life course impairment’ considers overall physical, psychological and social damage while coping with psoriasis over a patient's lifetime.12 In support of this, it has been shown that life-time DLQI is a better predictor of patient outcomes related to weight, discrimination and depression than last-week DLQI.13 PsO has also been shown to be associated with symptoms of emotional distress, especially insomnia and general anxiety.14 Fortunately a number of therapies for PsO have also shown positive changes in QoL measures. Notably, biological therapies for PsO have been shown to result in better mental health than other systemic and topical treatments.15 PsA is a multifaceted disease, presenting with arthritis, enthesitis, dactylitis, skin and nail involvement. All of these manifestations have the potential to affect the assessment of QoL, thus confounding the assessment of QoL in these patients. Sleep disturbances have been reported in patients with PsO and PsA. Sleep disturbance was shown to be associated with generalized pain, anxiety, enthesitis and levels of C-reactive protein and erythrocyte sedimentation rate in patients with PsA.16 It has been shown that health-related QoL in patients with inflammatory arthritides, including PsA, improves with newer therapies like anti-tumor necrosis factor agents,17 and it has also been shown to worsen on withdrawal of therapy.18 While one study in 2012 showed greater impairment of QoL in PsA as compared to PsO,19 Tezel et al.20 in this issue of the Journal report a similar PsAQoL in both their groups, although the patients with PsA had worse functional state than those with PsO alone. As discussed by the authors in the current paper, their patients with PsO and PsA, on average, had similar degrees of skin disease. This may explain the similar impairment of QoL when measured by the PsAQoL instrument which otherwise seems to reflect predominantly the cutaneous facet rather than the arthritic facet of PsA. In spite of the modest sample size as a weakness of this study, the findings provide relevant information. In fact, survey data collected by the National Psoriasis Foundation, USA, from 2003 to 2011 also have shown significant impairment of QoL and work productivity in PsO.21 In that survey, 52.3% of patients with PsO and 45.5% of patients with PsA were dissatisfied with their treatment, thus highlighting significant impairment of QoL. In the current study as well, QoL was significantly impaired in both PsO and PsA as compared to controls. These observations emphasize the need for advocacy and education, so that these patients have access to effective treatment options.22 In conclusion, PsO alone leads to a poor QoL comparable to that in PsA, one of the most debilitating arthropathies. With the currently available highly effective treatment options like biologics and synthetic disease-modifying antirheumatic drugs, neither PsO nor PsA should go unnoticed and, as a consequence, left untreated.