Uraemic pruritus responsive to broadband ultraviolet (UV) B therapy does not readily respond to narrowband UVB therapy

Difelikefalin in the Treatment of Chronic Kidney Disease-Associated Pruritus: A Systematic Review

Chronic kidney disease-associated pruritus (CKD-aP) is a chronic condition that significantly reduces the quality of life of patients with end-stage renal disease. The etiology is not fully understood, but imbalance in the activity of the opioid pathways, including downregulation of the kappa-opioid receptor, may contribute to itching sensation. Difelikefalin is a selective, peripherally acting kappa-opioid receptor (KOR) agonist. Recently, difelikefalin has been approved as a first drug for the treatment of pruritus associated with chronic kidney disease (CKD) in adult hemodialysis patients. A systematic review of currently available clinical trials was performed to assess the efficacy and safety of difelikefalin in patients with uremic pruritus. A literature review was conducted in May 2022 based on the PRISMA 2020 guidelines. The analyzed clinical trials showed that difelikefalin was effective in reducing pruritus in patients as assessed by the Worst Itching Intensity Numerical Rating Scale. Improvement in quality of life assessed on the basis of the Skindex score and the 5-D itch scale was also noticed. The most commonly reported side effects were mild and included nausea, vomiting, dizziness, and diarrhea. Due to its proven efficacy and good safety profile, difelikefalin is a promising drug for the treatment of pruritus in patients with chronic kidney disease.

2020 guidelines for the diagnosis and treatment of cutaneous pruritus

The mechanisms underlying itch are not fully understood. Physicians usually encounter difficulty controlling itch in generalized pruritus. Since only a small percentage of patients with generalized pruritus respond to antihistamines (H₁ receptor antagonists), a variety of itch mediators and mechanisms other than histaminergic signals are considered to be involved in itch for these non-responsive patients. In 2012, we created guidelines for generalized pruritus. Those guidelines have been updated and revised to make some of the definitions, diagnostic terms, and classifications more applicable to daily clinical practice. Cutaneous pruritus as designated in these guidelines is a disease characterized by itch without an observable rash. Generalized pruritus (without skin inflammation) is defined as the presence of itch over a wide area, and not localized to a specific part of the body. This entity includes idiopathic pruritus, pruritus in the elderly, symptomatic pruritus, pregnancy-associated pruritus, drug-induced pruritus, and psychogenic pruritus. Localized pruritus (without skin inflammation) represents fixed itch localized to a specific part of the body, and includes anogenital pruritus, scalp pruritus, notalgia paresthetica, and brachioradial pruritus. These guidelines outline the current concepts and specify the diagnostic methods/treatments for cutaneous pruritus.

Chronic Kidney Disease-Associated Itch (CKD-aI) in Children-A Narrative Review

Chronic kidney disease (CKD) is a condition of widespread epidemiology and serious consequences affecting all organs of the organism and associated with significant mortality. The knowledge on CKD is rapidly evolving, especially concerning adults. Recently, more data is also appearing regarding CKD in children. Chronic itch (CI) is a common symptom appearing due to various underlying dermatological and systemic conditions. CI may also appear in association with CKD and is termed chronic kidney disease-associated itch (CKD-aI). CKD-aI is relatively well-described in the literature concerning adults, yet it also affects children. Unfortunately, the data on paediatric CKD-aI is particularly scarce. This narrative review aims to describe various aspects of CKD-aI with an emphasis on children, based on the available data in this population and the data extrapolated from adults. Its pathogenesis is described in details, focusing on the growing role of uraemic toxins (UTs), as well as immune dysfunction, altered opioid transmission, infectious agents, xerosis, neuropathy and dialysis-associated aspects. Moreover, epidemiological and clinical aspects are reviewed based on the few data on CKD-aI in children, whereas treatment recommendations are proposed as well, based on the literature on CKD-aI in adults and own experience in managing CI in children.

Itching as the onset of pain (part 3)

Itchy skin is an extremely unpleasant symptom that can provoke insomnia, depression, irritability, loss of appetite. There are several theories of itching. According to one of them, itching is a modified pain caused by a slight irritation of the nerve endings in the skin. According to the second, itching is an independent symptom, in the formation of which nervous, humoral and vascular mechanisms are involved. Other theories consider itching as a reaction of the autonomic nervous system or a hereditary pathological condition. According to recent studies, itchy skin is characterized by the absence of a universal peripheral mediator of itching. The trigger for itching is the action of pruritogen – a mechanical, chemical, thermal or electrical stimulant directly or indirectly through mediators. Free ends of type A delta fibers and type C fibers play a crucial role in itching and pain. If this was previously confirmed only by clinical observations, now there are neurophysiological studies that support the theory that itching and pain fibers are one with different activity thresholds. Today, it is unacceptable that there are separate specific receptors for different sensations. It is now assumed that there are mixed receptors for heat, cold, pain, itching and touch [95]. Systematic use of substances included in the list of drugs and manifested by mental and physical dependence on them – drug addiction, one of the diseases of society. But drug addiction is sometimes forced, according to medical indications, in cases of palliative conditions. Depending on the stage of the person after taking the drug or in the interval between drug use, one of the signs of use may be severe itching of the skin. And after excluding both the main diseases that cause itching and other secondary causes of itching, it can be assumed that a person has idiopathic generalized pruritus (itching) of unknown origin (GPOU). The itching of the elderly, which is quite common in the elderly, as a manifestation of concomitant, often combined, somatic pathology, but may also be due to physiological changes, both on the skin and on the physiological aging of nerve endings.

[Cutaneous manifestations in renal diseases]

In addition to general skin changes like pallor or dryness and the frequent, often excruciating nephrogenic pruritus, specific diseases in patients with renal failure may occur. Acquired perforating dermatoses are usually also highly pruritic. Calciphylaxis is a severe disease with poor prognosis. Nonhealing wounds with superinfection and progression to sepsis are characteristic. Bullous lesions can be caused by disturbances in porphyrin metabolism. Nephrogenic systemic fibrosis is a disease which was first described in 2000. Its incidence is already on the decline. Furthermore, this article provides an overview of systemic diseases which have both skin symptoms and kidney changes. These include connective tissue diseases, vasculitis or sarcoidosis and amyloidosis. After a kidney transplantation, particular attention must be paid to the development of skin tumors and infections. The last part of this article is dedicated to genodermatoses with skin and renal involvement, where numerous causative mutations have already been characterized. Knowing the correlations of characteristic skin symptoms and specific, potentially life-threatening kidney disease is important in order to initiate further investigations and steps such as referral to nephrologists at an early stage.

Pruritus in hemodialysis patients: Results from the Japanese Dialysis Outcomes and Practice Patterns Study (JDOPPS)

Pruritus affects many patients undergoing hemodialysis (HD). In this study, pruritus and its relationship to morbidity, quality of life (QoL), sleep quality, and patient laboratory measures were analyzed in a large sample of Japanese patients undergoing HD. Severity of patient-reported pruritus symptoms experienced during a 4-week period was collected from 6480 Japanese patients undergoing HD in three phases of the Dialysis Outcomes and Practice Patterns Study (DOPPS; 1996-2008; 60-65 study facilities/phase). Adjusted linear and logistic regressions were used to identify associations of pruritus with treatment parameters and QoL outcomes. Adjusted Cox regressions examined the influence of pruritus severity on mortality. Moderate to extreme pruritus was experienced by 44% of prevalent patients undergoing HD in the Japanese Dialysis Outcomes and Practice Patterns Study. Many patient characteristics were significantly associated with pruritus, but this did not explain the large differences in pruritus among facilities (20-70%). Pruritus was slightly less common in patients starting HD than in patients on dialysis >1 year. Patients with moderate to extreme pruritus were more likely to feel drained (adjusted odds ratio = 2.2-5.8, P < 0.0001), have poor sleep quality (adjusted odds ratio = 1.9-3.7, P < 0.0001), and have QoL mental and physical composite scores 2.3-6.7 points lower (P < 0.0001) than patients with no/mild pruritus. Pruritus in patients undergoing HD was associated with a 23% higher mortality risk (P = 0.09). The many poor outcomes associated with pruritus underscore the need for better therapeutic agents to provide relief for the 40-50% of prevalent patients undergoing HD substantially affected by pruritus. Pruritus in new patients with end-stage renal disease likely results from uremia or pre-existing conditions (not HD per se), indicating the need to understand development of pruritus before end-stage renal disease.

Narrowband ultraviolet B phototherapy for patients with refractory uraemic pruritus: a randomized controlled trial

BACKGROUND

Pruritus is very common in uraemic patients, but the treatment remains challenging. Studies regarding narrowband ultraviolet B (NB-UVB) phototherapy for uraemic pruritus are rare.

OBJECTIVES

To investigate whether or not NB-UVB phototherapy is an effective treatment for uraemic pruritus.

METHODS

We conducted a single-blind, randomized, controlled trial for patients with refractory uraemic pruritus. The treatment group received NB-UVB phototherapy three times per week for 6 weeks. The dose of NB-UVB started from 210 mJ cm(-2) and was increased by 10% each time. The control group received time-matched exposures to long-wave UVA radiation. A visual analogue scale (VAS) score was evaluated weekly for pruritus intensity for 12 weeks. The characteristics of pruritus were also assessed by a questionnaire at baseline and after 6 weeks of phototherapy.

RESULTS

Both the NB-UVB and control groups had significant and comparable improvement in the pruritus intensity VAS scores during the period of phototherapy and follow-up. Compared with the control group, the NB-UVB group showed a significant improvement in the involved body surface area affected by pruritus (P = 0·006), but not in sleep quality. More detailed regression and estimating analysis revealed that the patients in the NB-UVB group had lower pruritus intensity scores at week 6, week 10 and week 12. This may indicate a beneficial difference at certain time points, but the effect seems marginal.

CONCLUSIONS

NB-UVB phototherapy does not show a significant effect in reducing pruritus intensity compared with a control group for refractory uraemic pruritus. Further studies are warranted.

Pruritus and renal failure

Patients with renal failure, usually end-stage renal disease (ESRD), commonly are afflicted by severe pruritus. The pathogenesis of ESRD pruritus is unknown, but improving the quality of dialysis can reduce the prevalence and severity of ESRD pruritus. Topical and systemic agents as well as broadband ultraviolet phototherapy can be extremely beneficial. Gabapentin has been recently discovered as an effective agent for the patient with ESRD pruritus. Kappa opiate agonists are promising new therapeutic options.

Pruritus: management algorithms and experimental therapies

Pruritus (itch) is a major symptom in many dermatologic as well as systemic diseases and has a dramatic impact on the quality of life in these patients. The symptom of itch has to be treated on the basis of its pathophysiology and its underlying disease. In daily practice, a "quick" diagnosis of the underlying disease is often difficult, although a rapid relief of the itch is desired. We often treat patients on the basis of the symptomatology. A rational therapeutic ladder for a symptomatic therapy is useful until the final diagnosis has been confirmed. There are probably many subtypes of pruritus, just as there are many diseases that cause itch. The pathophysiology in many subtypes of pruritus is still poorly understood, hindering a rapid and targeted treatment strategy. An extensive diagnostic workup is often required to determine the final cause(s) of the itch. Thus, in daily life, physicians often start with a more or less rational therapeutic strategy to combat the debilitating itch. We present possible therapeutic ladders that form the basis for effective therapeutic itch strategies in various diseases. On the basis of our current knowledge about the different pathophysiologies of itch, on clinical trials or case reports, and our own clinical experience, we aim to present therapeutic ladders for the rapid as well as long-term management of itch. Finally, we summarize current exciting developments of experimental strategies in itch research and in clinical development for itch therapy.

Chronic pruritus--pathogenesis, clinical aspects and treatment

Chronic pruritus is a major symptom in numerous dermatological and systemic diseases. Similar to chronic pain, chronic pruritus can have a dramatic impact on the quality of life and can worsen the general condition of the patient considerably. The pathogenesis of itch is diverse and involves a complex network of cutaneous and neuronal cells. In recent years, more and more itch-specific mediators and receptors, such as interleukin-31, gastrin-releasing peptide receptor or histamine H4 receptor have been identified and the concept of itch-specific neurons has been further characterized. Understanding of the basic principles is important for development of target-specific treatment of patients with chronic pruritus. In this review, we summarize the current knowledge about the pathophysiological principles of itch and provide an overview about current and future treatment options.

Innovative management of pruritus

Pruritus remains a significant problem facing dermatologists and can be associated with various dermatoses and systemic derangements. At times, one can treat the underlying cutaneous or systemic process to alleviate itch. However, it is frequently challenging to identify the cause of a patient's itch and, in this situation, even more difficult to manage the symptom effectively. In this article, the authors discuss the approach to a patient with generalized pruritus without clinically obvious dermatoses. They also addresses mechanisms and management modalities of itch in common systemic diseases, including cholestasis, uremia, and neuropathic dysfunction.

Treatment of uremic pruritus with narrowband ultraviolet B phototherapy: an open pilot study

We report the results of a pilot study of narrowband ultraviolet B phototherapy for the treatment of 20 patients with uremic pruritus. Ten patients completed the 6-week study period. A total of 8 patients were found to be responders. Of the remaining 10 patients who left the study before 6 weeks, 6 were satisfied with the response. In the follow-up period, 7 responders could be examined, and 3 were in remission 6 months after completing treatment. However, pruritus recurred in the remaining 4 responders. Narrowband ultraviolet B phototherapy may be an effective treatment for patients with uremic pruritus. Recurrence of pruritus, however, is a frequent problem.

Ultraviolet phototherapy for pruritus

Ultraviolet-based therapy has been used to treat various pruritic conditions including pruritus in chronic renal failure, atopic dermatitis, HIV, aquagenic pruritus and urticaria, solar, chronic, and idiopathic urticaria, urticaria pigmentosa, polycythemia vera, pruritic folliculitis of pregnancy, breast carcinoma skin infiltration, Hodgkin's lymphoma, chronic liver disease, and acquired perforating dermatosis, among others. Various mechanisms of action for phototherapy have been posited. Treatment limitations, side effects, and common dosing protocols are reviewed.

Willan's itch and other causes of pruritus in the elderly

Itch in the elderly presents a diagnostic and therapeutic challenge. A thorough history, review of systems, and physical examination are critical to determining its cause. Examination of the skin may be misleading. There are frequently only secondary lesions, eczematous changes, lichenification, and excoriation, which may be misdiagnosed as a primary dermatitis. Xerosis may be the cause, but it is sometimes merely coincidental. If primary lesions are present, a skin biopsy can enable a diagnosis to be made. Systemic causes of itch, such as cholestasis, uremia, hyperthyroidism, medications, or lymphoma, must be considered. If the cause remains elusive, idiopathic itching of the elderly or so-called "senile pruritus" may be considered. However, we propose to discard the term "senile pruritus", which can be offensive and frightening. We propose to replace it with "Willan's itch". Robert Willan (1757-1812) is honored as one of the founders of modern dermatology thanks to his book, On Cutaneous Diseases, and its morphological approach to skin disease. He was probably the first to give a good clinical description of itching in the elderly. The diagnosis of Willan's itch should be reserved for generalized pruritus in the absence of xerosis or other recognizable cause. The pathophysiology of this form of pruritus is poorly understood, but it is likely that age-related changes of the skin, cutaneous nerves, and other parts of the nervous system play a role. Anecdotal and limited data suggest that gabapentin, cutaneous field stimulation, serotonin antagonists, and ultraviolet B phototherapy may attenuate itch in some of these patients.

[New and established indications for phototherapy with narrowband UVB]

Phototherapy with ultraviolet (UV) irradiation of wavelengths between 280 and 320 nm (UV-B) is a safe and effective treatment for a variety of inflammatory skin diseases. In addition to standard broad band UVB, narrow band phototherapy with fluorescent bulbs emitting near monochromatic UV between 310-315 nm has become an important treatment for diseases such as psoriasis, atopic dermatitis or vitiligo. Other diseases respond favorably to narrow band UV-B phototherapy, the number of potential indications for such phototherapy is continuously growing. The differential effects of narrow band UV-B phototherapy in comparison to other UV phototherapies, as well as new and established indications for this treatment modality are reviewed.

Itch in systemic disease: therapeutic options

A new pathophysiologically based classification of itch is proposed, which should help the clinician adopt a rational approach to diagnosis and management of generalized itch. Focusing on neurogenic itch (itch without visible rash), common causes are reviewed and guidelines for laboratory and radiologic investigation are proposed. A stepwise approach to the management of generalized itch resulting from systemic disease is recommended. Specifically, the relative merits of broad versus narrowband ultraviolet B (UVB) are discussed and the pros and cons of doxepin, opioid antagonists, and selective serotonin reuptake inhibitors (SSRIs) such as paroxetine are considered. Attention is drawn to some novel approaches, including bright-light phototherapy and molecular adsorbent recirculating system (MARS) for selected patients with intractable itch caused by hepatic failure, and mirtazapine for nocturnal itch.

Phototherapy with narrowband vs broadband UVB

Phototherapy with ultraviolet (UV) radiation of wavelengths between 280 and 320 nm (UVB) is a safe and effective treatment for a variety of diseases. In addition to standard broadband UVB (bUVB), narrowband phototherapy with fluorescent bulbs emitting near monochromatic UV around 311 nm (nUVB) has become an important treatment for diseases such as psoriasis, atopic dermatitis and vitiligo. In addition to these indications, the number of diseases for which nUVB phototherapy is reported to be effective is continuously growing. The differential effects of nUVB phototherapy in comparison to other UV wavelengths as well as established and new indications for this treatment modality are reviewed.