Pain is a common overlapping factor between psoriasis and psoriatic arthritis (PsA).1 According to a 2021 review by Kodumudi and Rajput, painful psoriasis and psoriatic arthropathy may be underreported in practice, resulting in substantial undertreatment of the pain.1

Plaque psoriasis, with primary symptoms of itching and flaking skin lesions, affects an estimated 7.4% of the general population.1 These lesions cause significant discomfort due to cracking, scaling skin, which is often accompanied by burning. Approximately 40% of patients with psoriasis report superficial skin pain that is neuropathic in nature.1,2 Psoriatic arthritis is  frequently associated with cutaneous manifestations, such as pitting nail disease and onycholysis.1,3 Pain in PsA can affect any joints, as well as muscles, tendons, and ligaments in the body, and may be nociceptive and neuropathic in nature.1

What Are the Challenges in the Diagnosis of Psoriatic Disease?

The overlap between psoriasis and psoriatic arthritis has been recognized in research and clinical practice; however, there is a lack of a cohesive approach with regard to pain management in these diseases on a systemic level.  


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Depending on the definitions of psoriasis used, research has indicated that between 10% and 40% of cases will evolve into PsA, with extracutaneous manifestations at multiple sites in the body.2-4 Not all patients with psoriasis go on to develop PsA, but there are multiple patterns of symptomatic emergence among those who do. Although most common signs of PsA often lag behind a diagnosis of psoriasis by up to 10 years, in at least 20% of cases, they will appear before the cutaneous manifestations of psoriasis. Approximately 15% of cases present with both skin and joint symptoms simultaneously.2,4 The wide spectrum of comorbid conditions, including osteoporosis, uveitis, subclinical bowel inflammation, and cardiovascular disease, also complicates accurate diagnosis.3,4

There is a lack of reliable biomarkers to identify which patients are likely to progress from psoriasis to PsA. Acute phase reactant tests that measure inflammatory responses in erythrocyte sedimentation rates (ESR) and C-reactive proteins (CRP) often yield negative results even in the presence of active PsA.4,5 Because these tests lack both sensitivity and specificity, they cannot be used to determine disease probability enough to support treatment decisions.5

The tremendous heterogeneity of pain in psoriasis also complicates therapeutic decisions, and specific guidelines for each of the subtypes is lacking. The more superficial pain symptoms of psoriasis are usually experienced as burning, tenderness, cramping, or even intense itching. Some patients also describe sensations of throbbing, stabbing or piercing pain. Moreover, the many presentations of pain in psoriasis occur at various sites throughout the body, including the ears, scalp, palms, hands, elbows, and the legs, knees, feet and toes. The nails may also be a source of pain, but the most predominant regions are those with skin folds and genital areas.5

What Is the Impact of Diagnosis on Treatment Decisions?

The most recent European Alliance of Associations for Rheumatology (EULAR) recommendations for management of pain associated with inflammatory forms of arthritis suggest that therapeutic choices are “not only determined by effects on pain but also by effects on functioning, social participation and well-being.”6 However, these domains have been perceived differently in different specialties.

A 2015 study including physicians’ perspectives showed that 62.6% of dermatologists who treated psoriasis as an isolated condition recognized the significant impact of the disease on patients’ activities of daily living (ADL); 79.3% observed that their patients were affected socially and/or emotionally by psoriasis; and 92.1% believed the burden of the disease was widely underreported.7

Dermatologists included in the study reported that a high percentage of patients with PsA experienced negative effects of their condition on ADL, as well as a social and emotional impact (73.7% and 76.8%, respectively).7 Conversely, rheumatologists treating patients with PsA were far less likely to recognize the impact of the disease on patients’ daily lives or the social and emotional impact. However, rheumatologists were more likely to initiate discussions with patients about the potential consequences of undertreatment of their disease.7  

Because psoriasis and PsA are diagnosed in different clinical settings, subsequent treatment approaches and outcomes have been shown to vary.

What Are the Various Treatment Approaches?

Pain is not a specific treatment target in psoriasis.2,5 Kodomudi and colleagues state that “Pain control in psoriasis is closely interwoven with control of the burden of psoriatic disease.”5 They also point out that while pain from psoriasis is localized to the affected areas of skin, “Painful psoriatic arthropathy is not a homogenous disease clinically or therapeutically. It has different manifestations as well as different response to treatments.”5

Although the pathogenic associations between psoriasis and PsA are becoming more evident, they are regarded as separate entities, which may limit the effectiveness of the therapies chosen.Topical agents are the first-line therapies for mild to moderate forms of psoriasis, and are recommended for all patients with psoriasis to reduce skin discomfort. However, patients first diagnosed with psoriasis may be likely to receive topical treatments for cutaneous symptoms only, without consideration of possible axial and/or peripheral joint involvement.4 Early diagnosis of PsA is a significant factor in achieving good outcomes in pain management and joint preservation, as irreversible joint erosion has been demonstrated after even a 6-month delay in treatment from the time of initial joint symptoms.4 

For more severe cases of psoriatic disease, advanced targeted biologic drugs have become available during the last 2 decades, which include oral agents such as methotrexate, which is the most commonly prescribed biologic, as well as ciclosporin, acitretin, fumarates and apremilast.2 Four classes of biologic therapies are currently used to treat moderate to severe psoriasis along immunomodulatory pathways: anti-tumor necrosis factor (TNF) α, anti-interleukin (IL)-17, anti-IL-12p40 and IL-23p40. These agents, and others currently in development, target the full spectrum of psoriatic disease and their direct effects as pain reduction have not been measured.

In their study, Griffiths et al concluded that, “A cure for psoriasis, or even a preventive strategy, is unlikely to be delivered in the near future, but an approach that allows matching the best treatment plan to each individual is achievable.”2

Treatments for PsA start with systemic therapies that target disease modification of the joint decay process. This involves an array of traditional disease-modifying antirheumatic therapies (DMARDs) and the biologics already in use for psoriasis, as well as newer oral agents, including a phosphodiesterase-4 inhibitor and a Janus kinase (JAK)/signal transducer and activator of transcription (STAT) inhibitor (tofacitinib).3

While novel therapies offer a range of options for patients with PsA and psoriasis, the heterogeneity of these diseases makes it difficult to know which therapies are appropriate. Researchers continue to develop biomarkers of disease activity and prognostic indicators that will help with optimal therapeutic decisions.

References

  1. Kodumudi V, Rajput K. Pain management in painful psoriasis and psoriatic arthropathy: challenging and intricately intertwined issues involving several systems. Curr Pain Headache Rep. 2021;25(6):36. doi:10.1007/s11916-021-00952-5
  2. Griffiths CEM, Armstrong AW, Gudjonsson JE, Barker JNWN. Psoriasis. Lancet. Seminar. 2021;397(10281):1301-1315. doi:10.1016/S0140-6736(20)32549-6
  3. Ogdie A, Coates LC, Gladman DD. Treatment guidelines in psoriatic arthritis. Rheumatology (Oxford). 2020;59(1):i37-i46. doi:10.1093/rheumatology/kez383
  4. Rida MA, Chandran V. Challenges in the clinical diagnosis of psoriatic arthritis. Clin Immunol. 2020;214:108390. doi:10.1016/j.clim.2020.108390
  5. Bray C, Bell LN, Liang H, et al. Erythrocyte sedimentation rate and C-reactive protein measurements and their relevance in clinical medicine. WMJ. 2016;115(6):317-321.
  6. Geenen R, Overman CL, Christensen R, et al. EULAR recommendations for the health professional’s approach to pain management in inflammatory arthritis and osteoarthritis. Ann Rheum Dis. 2018;77(6):797-807. doi:10.1136/annrheumdis-2017-212662
  7. van de Kerkhof PCM, Reich K, Kavanaugh A. Physician perspectives in the management of psoriasis and psoriatic arthritis: results from the population-based Multinational Assessment of Psoriasis and Psoriatic Arthritis survey. J Eur Acad Dermatol Venereol. 2015;29(10):2002-2010. doi:10.1111/jdv.13150