Itching in Psoriasis: Impact on Quality of Life and Treatment Options
For many years, psoriasis was classified as a chronic, non-itchy skin disease. However, an increasing number of clinical studies have demonstrated an association between psoriasis and chronic itching (Latin: pruritus) [1, 2]. Itching occurs in 60–90% of patients with psoriasis [1–13]. The intensity of itching in psoriasis has been found to correlate with disease severity and poorer quality of life [4–6]. Specific treatment for itching in psoriasis is still lacking. Its management largely depends on rational psoriasis treatment aimed at reducing psoriatic lesions, usually assessed using the Psoriasis Area and Severity Index (PASI), thereby reducing itching [10].
Pathogenesis
The pathogenesis of itching in patients with psoriasis has been evaluated in numerous studies. However, no specific mechanism has been identified to fully explain it. Itching, like pain, arises from a signal transmitted by C tactile fibers to the dorsal horn of the spinal cord and from there through the spinothalamic tract to the cerebral cortex, where the signal is perceived. The nerve plexus of C fibers terminates close to skin cells (fibroblasts, keratinocytes, mast cells, and Langerhans cells). Nerve endings release neuropeptides that act directly and indirectly on receptors of keratinocytes and Langerhans cells, stimulating nerve endings and causing itching [1].
An increasing number of studies have investigated the secretion of neuropeptides (substance P and neurokinins) in psoriasis-affected skin. The greater the amount of these substances, the more immune cells (dendritic cells, lymphocytes, mast cells, neutrophils, and macrophages) are activated, accelerating keratinocyte proliferation and mast cell degranulation. All of this promotes angiogenesis and causes chronic itching [1–3, 7–10]. According to research data, higher expression of substance P and neurokinin-containing nerve fibers has been detected in psoriasis-affected skin compared with unaffected skin. A significant correlation has been found between the intensity of itching, substance P-containing nerve fibers, and neurokinin receptors in psoriasis-affected skin [7]. Another important marker in the development of neurogenic inflammation is impaired innervation. Immunofluorescence study data showed a greater number of epidermal nerve fibers in psoriasis-affected, non-itchy scalp skin compared with unaffected skin [8]. Another mechanism of itching is associated with immune inflammation. Higher levels of GABA and GABAA receptors depend on the number of immune cells and significantly correlate with the intensity of itching in psoriasis-affected skin [9]. In summary, increased expression of substance P-containing nerve fibers, neurokinins, and GABA system receptors is significant in the pathogenesis of itching in patients with psoriasis.
Quality of Life
Itching of psoriatic lesions is one of the most common and distressing symptoms of the disease. It is most commonly experienced in the lower extremities and scalp. Many patients (80%) with scalp psoriasis suffer from intense scalp itching [4]. The scalp has more nerve endings than other areas of the body. The intensity of itching is assessed using the Visual Analog Scale (VAS). In patients with scalp psoriasis, the VAS itching score correlates with the PASI score [8]. An increasing number of studies have examined the impact of itching on the quality of life of patients with psoriasis. According to these data, half of respondents report a significant change in their quality of life (Table 1). The intensity of itching, the severity of psoriasis, and changes in quality of life are interrelated.
Table 1. Effect of Psoriasis and Itching on Patients’ Quality of Life [4, 8]
| % (n = number of respondents) | Variable | % (n = number of respondents) |
|---|---|---|
| 56.5 (n = 131) | ↓ Quality of life | 52.2 (n = 42) |
| 52.2 (n = 96) | ↓ Mood | 32.5 (n = 26) |
| 21.2 (n = 39) | ↓ Sleep duration | 5 (n = 4) |
| 13 (n = 24) | ↓ Sexual desire | 22 (n = 27.5) |
| 39.1 (n = 72) | ↓ Concentration | 48.8 (n = 39) |
| 9.2 (n = 17) | ↓ Appetite | 5 (n = 4) |
Study participants with generalized psoriasis (n = 230).
Study participants with scalp psoriasis (n = 80).
Figure. Prevalence of Itching Among Patients With Psoriasis (%) [10]
| Study | Prevalence (%) |
|---|---|
| Mrowietz et al. 1977 | 93 |
| Gupta et al. 1988 | 67 |
| Yosipovitch et al. 2000 | 86 |
| Krueger et al. 2001 | 80 |
| Szepietowski et al. 2002 | 80 |
| Reich et al. 2005 | 93 |
| Chang et al. 2007 | 75 |
| Reich et al. 2007 | 75 |
| Amatya et al. 2008 | 92 |
| Prignano et al. 2009 | 83 |
| Bilac et al. 2009 | 99 |
| Reich et al. 2010 | 90 |
| Gupta et al. 2014 | 81 |
| Janowski et al. 2014 | 99 |
Table 2. Effect of Daily Environmental Factors on Itch Management in Patients With Psoriasis [4]
| Factor | Positive Effect (%) | Negative Effect (%) |
|---|---|---|
| Sleep | 15 | 8 |
| Rest | 16 | 12 |
| Clothing | 38 | 51 |
| Poor mood | 34 | 52 |
| Cold environment (°C) | 30 | 58 |
| Hot water | 25 | 65 |
| Sweating | 29 | 62 |
| Dryness | 12 | 78 |
| Stress | 15 | 84 |
Table 3. Review of Studies on the Results of Itch Treatment in Patients With Psoriasis [1, 2, 10, 12]
| Emollients (20% reduction in itching) | Szepietowski et al. 2002; Dawn and Yosipovitch 2006 |
|---|---|
| In individual cases, antidepressants (mirtazapine or paroxetine) may be used | Dawn and Yosipovitch 2006 |
| Endocannabinoids | Kupczyk et al. 2009; Tóth et al. 2011 |
| Antiepileptic drugs (pregabalin or gabapentin) | Kumagai et al. 2012; Reich and Szepietowski 2012 |
| Antihistamines (used by 45% of all study participants) – 34.5% experienced a short-term reduction in itching; 65.5% experienced no effect. Emollients (used by 53% of all study participants) – 35% experienced a short-term reduction in itching; 65% experienced no effect. | Giuseppe et al. 2014 |
| Glucocorticoids (used by 48% of all study participants) – 55% experienced a short-term reduction in itching; 45% experienced no effect. | Giuseppe et al. 2014 |
Itch Management
Daily environmental factors play a significant role in the course of eczema and itching. An overview of these factors is presented in Table 2 [8]. Conservative measures such as avoiding stress, improving mood, getting adequate rest, choosing appropriate and looser clothing, and soothing the skin with cold water can alleviate itching and eczema symptoms [4]. Research findings on the effectiveness of treatments for reducing itching in patients with eczema are presented in Table 3. Treatment of itching in patients with eczema should focus on treating eczema-affected skin with emollients, UVB phototherapy, topical keratolytics, vitamin D analogs and, when necessary, systemic medications and biological therapy.
According to one study, the use of emollients reduced itching in patients with eczema by 20% [12]. In a study in which 45% of patients with eczema used antihistamines, only 34.5% experienced a temporary reduction in itching, while 65.5% experienced no effect. Among patients using emollients, 35% experienced a temporary reduction in itching, while 65% experienced no effect. Among participants using topical corticosteroids, 55% experienced a temporary reduction in itching, while 45% experienced no effect. All of these studies indicate that specific treatment for itching is not yet available. Its management depends largely on rational eczema treatment aimed at reducing PASI. Therefore, itching is another significant clinical marker for evaluating the course of eczema.
Source: Lithuanian Doctor's Journal, No. 9, 2015
