Introduction

Although traditionally considered as only a skin problem, psoriasis is now best described as a complex, multifactorial and inflammatory disease. It is thought to affect between 2% to 4% of the population in Westernised countries.[1] While not life-threatening, psoriasis is associated with a significant impairment of quality of life, including work, family, sexual relations as well as physical and emotional well-being. Moreover, the visible nature of the condition has been reported as one of the most difficult aspects. Both sexes are affected equally, and for the majority of patients (75%)[2] psoriasis first presents between the ages of 15 and 5 with the remainder of those affected experiencing symptoms between the ages of 55 and 60.

 

Symptoms

Clinically, plaque psoriasis is characterised by well-defined erythematous, silvery/white hyperkeratotic scaling plaques that characteristically occur on extensor surfaces of the body, with scalp involvement in up to half of all sufferers. Abnormal nail plate growth leads to distinctive pitting, a build-up of keratinous material underneath the nail (subungual hyperkeratosis) and onycholysis (i.e. separation of the nail from the nail bed).

Psoriasis does occur, though less commonly, in children, where it can be misdiagnosed as atopic eczema, since the scaling is less prominent and lesions often affect the face.

 

Pathophysiology

The precise cause of psoriasis remains unclear and it is likely that a combination of genetic, environmental and immunological factors are responsible. Psoriasis clearly has a genetic component as witnessed by the presence of the condition in up to 30% of first degree relatives of those affected. The fact that the condition has an immunological component was realised in the late 1980s, when patients with psoriatic arthritis were treated with the biological agent, Etanercept.[4] The drug targets the pro-inflammatory cytokine, tumour necrosis factor alpha and investigators observed substantial improvements in a small number of patients with psoriasis. Subsequent work[5] has identified that psoriasis is associated with aberrations in several other interleukins (IL), such as IL23 and 17A, as witnessed by the efficacy of biologic agents that specifically block the action of these inflammatory mediators.

 

Impact of lifestyle factors

Several lifestyle factors are associated with psoriasis. In a case control Italian study,[6] it was found that cigarette smoking, body mass index and stress all appeared to be independently and positively correlated with psoriasis. Other studies[7-10] have shown an association between psoriasis and obesity, alcohol consumption and physical inactivity. Moreover, there is evidence to suggest that lifestyle modification such as weight loss and increased physical activity appear to reduce disease severity in those with psoriasis.[11] The vast majority of patients will report that exposure to sunlight improves their psoriasis and most patients experience a worsening of their symptoms during the colder, winter months. Patients may ask about the effect of dietary changes, and it appears that increased consumption of omega-3 as found in oily fish, improves the condition. There is some, limited evidence[12] to show that supplementing with oral vitamin D may also have some effect.

 

Co-morbidities

It is important that health professionals appreciate that psoriasis is more than just a skin problem. Two of the most common associated problems are:

  • Cardiovascular disease: Patients with severe disease are at a greater risk of cardiovascular disease. This is probably because both psoriasis and cardiovascular disease are associated with an increased level of inflammation in the body. However, it would seem prudent to undertake a cardiovascular risk assessment in all those with the condition, especially if they are overweight or a smoker.
  • Psoriatic arthritis (PsA): According to NICE, PsA affects up to 30% of those with psoriasis.[13] While joint pain is common in older patients, psoriasis patients presenting with dactylitis (sausage finger/toe) or enthesitis (especially at the Achilles insertion) should be referred to a rheumatologist. PsA can also be identified using a screening tool such as the psoriasis epidemiological screening tool (PEST) as shown in Table 2, which has a high degree of sensitivity and specificity.

Other co-morbidities include atrial fibrillation (20% increased risk)[14], uveitis (affecting up to 40% of patients, with an increased prevalence associated with greater disease severity),[15] depression and anxiety (affecting between 28 and 67% of patients).[16]

 

Assessment of disease severity

There is no universally accepted definition of disease severity. The psoriasis area and severity index (PASI) is used in clinical trials and some secondary care units. According to the National Psoriasis Foundation in the US, severity can be defined in terms of the total body surface area (BSA) affected.[17] The surface area of a single hand (i.e., flat palm and 5 fingers) of the affected person, represents about 1% of the skin. Using this measure, mild psoriasis affects less than 3% BSA, moderate, between 3 and 10% BSA, and severe more than 10% BSA. Though less accurate than a PASI score, the BSA assessment offers a pragmatic guide to disease severity. In addition, it is important to enquire about the impact of the disease on quality of life and whether patients adapt their lives (e.g. avoiding going swimming or to a gym) because of their condition.

 

Management of psoriasis in primary care

Fortunately, the majority of patients with plaque psoriasis (roughly 80%) have mild to moderate disease[18] that is amenable to treatment in primary care with topical therapies. The range of available treatments are described in Table 1.

 

Emollients

Although generally not covered in clinical guidelines, emollients have an important effect in psoriasis, helping to reduce the scale and potentially helping with symptoms such as itch. Emollients are effective adjunctive treatments and should be offered to all patients. In practice, it seems that in many patients, application of an emollient 30 minutes or so before active treatments seem to enhance the effect of treatments.

Combination therapy

To date, the only commercial combination topical therapy is calcipotriol (a vitamin D analogue) and the potent topical steroid, betamethasone, launched in the UK in 2002 under the brand name Dovobet. The product was originally an ointment, but has since been available as a gel formulation, either alone or applied via an applicator device. More recently, a foam formulation (Enstilar) has been introduced. Several systematic reviews have shown that the combination is more effective than either of the separate components used alone.

 

Treatment guidelines

In 2012, NICE produced guidelines13 on the assessment and management of plaque psoriasis. However, other guidelines produced in the UK are inconsistent with the advice from NICE, which is potentially confusing for healthcare professionals.

As an initial therapy, NICE recommended that practitioners:

“Offer a potent corticosteroid applied once daily plus vitamin D or a vitamin D analogue applied once daily (applied separately, one in the morning and the other in the evening) for up to 4 weeks as initial treatment for adults with trunk or limb psoriasis.”

Additionally, given the risks of using potent topical steroids long term, the guideline advises that patients are reviewed after 4 weeks of treatment. If the combination appears to be effective, then the topical steroid should not be used at the same site for longer than 8 weeks and treatment can be continued with the vitamin D analogue, allowing for a 4-week “steroid free” interval.

Guidance from the Scottish Intercollegiate Guideline Network (SIGN) produced in 2010 is slightly different and states that for initial treatment:

“Short term intermittent use of a potent topical corticosteroid or a combined potent corticosteroid plus calcipotriol ointment [i.e. Dovobet™] is recommended to gain rapid improvement in plaque psoriasis.” [19]

The primary care dermatology society advice is more aligned with that of SIGN rather than NICE, stating that:

“Many GPs and GPSI use calcipotriol and betamethasone combination products first-line to encourage a rapid improvement and hence adherence in chronic plaque psoriasis: NB here our advice differs from the NICE psoriasis guideline which suggests starting with its individual components” [20]

This latter recommendation has clearly taken route in primary care. The latest prescribing data for England and Wales in 2016[21] shows that 55% of all topical psoriasis treatments issued were for the various formulations (e.g. gel, ointment and foam) of the combination product.

Treatment adherence

Adherence to topical regimes in psoriasis is generally poor. For example, in one study 44% of patients failed to redeem their initial prescription,[22] while in another, 39% were non-compliant[23] with their recommended treatment regime. Knowledge of the most important factors associated with adherence may help healthcare professionals to adapt their approach with patients to help facilitate improved adherence. However, the evidence from reviews of the literature[24,25] suggest that adherence is a complex issue with one systematic review concluding that the current evidence makes it difficult to ascertain the most important determinants of adherence. NICE did recommend that the combination product (i.e. Dovobet) could be used when adherence was identified as a problem, though, as highlighted in a systematic review of treatment; as patients become expert at managing their condition, they may alter the medication regime to suit themselves so that while disease severity may not be optimally improved, the strategy may improve their quality of life. For example, if itch is a prominent symptom, patients may use treatment in order to minimize the severity of itch, rather than aiming for complete clearing of a plaque.

Psoriasis is a long-term condition and deserves as much attention as other chronic problems such as asthma and hypertension. Unfortunately, the lack of financial remuneration for dermatological conditions in QOF has resulted in much dissatisfaction among those with skin diseases. However, screening for co-morbidities such as cardiovascular disease and depression, which are remunerated, will highlight the fact that psoriasis is more than just a skin condition and will improve the care and well-being of this patient group.

 

References

  1. Parisi R, Symmons DPM, Griffiths CEM et al. J Invest Dermatol. 2013; 133: 377-385
  2. Griffiths CEM, Barker JNWN, Chalmers RJG et al. Br J Dermatol. 2007; 156: 258-262
  3. Weigle N, McBane S. Psoriasis. Am Fam Physician. 2013; 87(9): 626-633
  4. Mease PJ, Goffe BS, Metz J et al. 2000; 356: 385 – 390
  5. Jinna S, Strober B. Anti-interleukin-17 treatment of psoriasis. J Dermatol. Treat. 2016; 27(4): 311-315
  6. Naldi L, Chatenoud L, Linder D et al. J Invest Dermatol. 2005; 125: 61-67
  7. Armstrong AW, Harskamp CT, Armstrong EJ. Nutrition and Diabetes. 2012; 2:e54
  8. Kirby B, Richards HL, Mason DL et al. Br J Dermatol. 2007; 158(1): 138-140
  9. Frankel HC, Han J, Li T et al. Arch Dermatol. 2012; 148(8): 918- 924
  10. Upala S, Sanguankeo A. Int J Obes. 2015: 39(8): 1197-2002
  11. Naldi L, Conti A, Cazzaniga S et al. Br J Dermatol. 2014: 170(3): 634-42
  12. Millsop JW, Bhavnit K, Debbaneh BA et al. J Am Acad Dermatol 2014; 71(3): 561 – 569
  13. Psoriasis: assessment  and management. National Institute for Healthcare Excellence https://www.nice.org.uk/guidance/cg153/chapter/1-Guidance#principles-of-care [Accessed December 2017]
  14. Ungpreasert P, Srivali N, Kittanamongkolchai W. Indian J Dermatol Venereol Leprol. 2016; 82(5): 489-497
  15. Egeberg A, Khalid U, Gislason GH et al. JAMA Dermatol. 2015; 151(11): 1200-1205
  16. Lakshmy S, Balasundaram S, Sarkar S et al. Indian J Psychol Med. 2015; 37(4): 434-440
  17. About psoriasis. National Psoriasis Foundation. Available on-line at: https://www.psoriasis.org/about-psoriasis [Accessed December 2017]
  18. Menter A, Koman NJ, Fledman SR et al. J Am Acad Dermatol. 2009; 60:643-59
  19. Diagnosis and management of psoriasis and psoriatic arthritis. SIGN. Available on-line at: http://sign.ac.uk/guidelines/fulltext/121/index.html [Accessed December 2017]
  20. Chronic plaque psoriasis. Primary Care Dermatology Society guideline. Available on-line at: http://www.pcds.org.uk/clinical-guidance/psoriasis-an-overview#management [Accessed December 2017]
  21. Prescription cost analysis, 2016. NHS Digital. Available on-line at https://digital.nhs.uk/catalogue/PUB23631 [Accessed December 2017]
  22. Storm A, Andersen ES, Benfeldt E et al. J Am Acad Dermatol. 2008; 59: 27-33
  23. Richards HL, Fortune DG, O’Sullivan TM et al. J Am Acad Dermatol. 1999; 41(4): 581-583
  24. Devaux S, Castela A, Archier E et al. J Eur Acad Dermatol Venereol. 2012;26(S3): 61-67
  25. Thorneloe RJ, Bundy C, Griffiths CEM et al. Br J Dermatol. 2013; 168: 20-31.

Dr Rod Tucker

Community pharmacist, Researcher with a special interest in dermatology, East Yorkshire