Chronic pruritus in the absence of specific skin disease: an update on pathophysiology, diagnosis, and therapy

[Rehabilitation for patients with chronic pruritus]

BACKGROUND

For a long time, chronic pruritus was considered difficult to treat. Modern therapy options and detailed guidelines have created new opportunities for patients to improve their quality of life. However, due to the complexity of the disease, the need for multimodal treatment remains.

OBJECTIVES

This article aims to investigate whether dermatological rehabilitation offers additional benefits to those affected and whether it should therefore be part of the treatment concept for chronic pruritus.

METHODS

After introduction of the pruritus program of a rehabilitation clinic, a prospective study is presented that focuses on the patient-relevant benefits of therapy. It used standardized questionnaires to record pruritus intensity, the presence of depression, anxiety, itch-related limitations, and quality of life in patients with chronic pruritus before and after rehabilitation.

RESULTS

Of the patients surveyed, 91.7% achieved a patient-relevant benefit through rehabilitation. Pruritus intensity, depression, anxiety, itch-related limitations, and restrictions on quality of life decreased significantly. Almost half of all participating patients had been initially diagnosed more than 10 years ago.

CONCLUSIONS

Dermatological rehabilitation with a multimodal concept for the treatment of chronic pruritus can help affected patients and should be part of the therapy concept. This should be done as early as possible before the disease progresses over a long period of time and makes treatment more difficult.

Evaluation and Management of Pruritus and Scabies in the Elderly Population

Pruritus is the most common dermatologic complaint in the geriatric population. Its growing prevalence coincides with the rapid growth of the elderly population (>65 years of age) in the United States. According to the US Census Bureau, 16.9% of the population, or more than 56 million adults 65 years and older, lived in the United States in 2022. Pruritus is a condition that accompanies a diverse array of underlying etiologic factors. The mechanism of normal itch impulse transmission has been recently elucidated. The itch sensation originates from epidermal/dermal receptors connected to unmyelinated, afferent C-fibers that transmit the impulse from the periphery.

Adherence to dermatologic treatment: A retrospective cross-sectional study on geriatric patients

OBJECTIVE

With the prolongation of the average life expectancy worldwide, diseases including dermatological disorders of the elderly are gaining importance. The presence of comorbidities in this age group may affect the treatment strategies; compliance with follow-up and adherence to medication can be poor. The aim of this study is to evaluate the dermatological disorders of patients aged 65 and over and determine their adherence to dermatologic treatment.

METHODS

A retrospective and cross-sectional study was conducted on patients aged 65 and over applied to a single tertiary dermatology clinic between April 2021 and April 2022. Diagnoses were that clinical and diagnostic tests were performed when only necessary.

RESULTS

A total of 207 admissions to the dermatology clinic by 135 patients were evaluated. Eczema (23.05%) and infections (25.2%) were the most common dermatological diagnoses. The percentage of patients with precancerous and cancerous lesions was 11.9%. Among 123 patients who need at least a follow-up visit, only 37 patients (30.1%) applied for follow-up as advised, and medicines were taken regularly by 23 of these patients (62.2%). Compliance with follow-up was lower among men (OR 0.365, 95% CI 0.160-0.834, and p=0.02) and patients who were treated only with local therapy agents (OR 0.345, 95% CI 0.138-0.863, and p=0.20).

CONCLUSION

Eczema and infections were the most common dermatological diagnoses among geriatric patients in the present study. The majority of geriatric patients with skin conditions were not applying for follow-up visits. Women and patients treated with systemic therapy agents were more compliant. The prevalence of basal cell carcinoma was not low, and this emphasizes the importance of a careful dermatological examination regardless of primary complaint in this age group.

Characterization of the effects on pruritus by novel treatments for atopic dermatitis

Chronic pruritus is a common and debilitating symptom in patients with atopic dermatitis and contributes to impairment of quality of life. Effective treatment of pruritus should therefore be one of the main treatment goals in patients with atopic dermatitis. Pathophysiologically, the histamine-independent pruritogens interleukin-31, interleukin-13, and interleukin-4, have been shown to play a major role in atopic dermatitis. All three cytokines can mediate chronic pruritus via Janus kinase 1/2 signaling pathways. Novel drugs target these pathways and have shown rapid and sustained reduction of pruritus in patients with atopic dermatitis in clinical use and in phase II and III clinical trials. Here we summarize the published data on the effects of these drugs on itch parameters such as overall reduction in pruritus intensity and percent of patients with atopic dermatitis achieving a relevant reduction in itch. Each of the novel drugs shows very good effects on pruritus. These data offer hope for an even better and possibly more specific treatment of pruritus in patients with atopic dermatitis in the future. In addition, the different pharmacological approaches give us the chance to learn more about the pathophysiology of pruritus in atopic dermatitis.

Approach to the Patient with Chronic Pruritus

Chronic pruritus (itch lasting ≥6 weeks) is a bothersome chief complaint that may present in a broad variety of diseases. Most itch-causing diagnoses fit into 1 of 5 categories (inflammatory, secondary to systemic disease, neuropathic, chronic pruritus of undetermined origin, and psychogenic itch) and this broad differential can be narrowed using key findings in the history and physical. In this article, we discuss which key findings are most pertinent for narrowing this differential and guiding further workup and treatment, as well as how to treat many itchy conditions.

Itching as the onset of pain (part 2)

Itching of the skin is a particularly unpleasant subjective sensation that causes the need to scratch. Physiological itching occurs in response to environmental irritants (friction, insect crawling, temperature changes, etc.) and disappears after elimination of the cause. Pathological itching is caused by changes in the skin or throughout the body and causes a strong need to get rid of itching by combing or any other method. Itching is a common symptom of local (dermatological) or general (systemic) disease. It can be limited (localized) or diffuse (generalized).One of the causes of itching is often noted endocrine diseases and metabolic disorders: hyper- and hypofunction of the thyroid gland, diabetes mellitus and hyperparathyroidism. In thyroid hyperfunction, generalized (inconstant and little-pronounced) itching of the skin is observed in the clinical picture only in 10 % of patients. It is accepted that itching of the skin in thyrotoxicosis syndrome is due to increased activity of kinin in combination with an increase in major metabolism and an increase in body and skin temperature (123).Itching caused by impaired bile secretion is characteristic of many diseases of the liver: primary biliary cirrhosis, sclerosing cholangitis, viral hepatitis caused by cholestasis medications and other causes of obstructive jaundice. It is in these cases that prurigo is usually generalized, but in some typical cases it is more pronounced on the feet and palms. With this pathology, itching is caused by obstruction of the biliary tract, however, and to this day, no close correlation has been found between serum bilirubin and the severity of itching.If it was previously thought that itching in pathology of the peripheral or central nervous system, such as multiple sclerosis, neuropathy, compression or irritation of nerves (e.g., paraesthetic dorsalgia, brachioradial itching) is also a significant symptom, then modern studies prove that in more cases, itching is not characteristic of most pathologies of the nervous system, so after a detailed anamnesis, examination and initial research, the patient should be referred to a related specialist, except in cases of about obvious postherpetic neuropathy, painless paresthesia, or brachioradial itching, which can often be guided in the provision of primary care.Instead, there are some psychological conditions and a number of psychiatric illnesses (obsessive-compulsive disorders, depression, and parasite illusions) that are most commonly diagnosed with the exclusion method. Neurotic squabbles are scattered on the body of the excorii, covered with scales that may occur in any area of the body that the patient may reach, but are often limited by limbs.

Case series of reports of pruritus and sipuleucel-T submitted to the Food and Drug Administration Adverse Event Reporting System

Sipuleucel-T, an autologous active cellular immunotherapy, is indicated for the treatment of asymptomatic or minimally symptomatic castration-resistant prostate cancer. The U.S. Food and Drug Administration Adverse Event Reporting System (FAERS) received a report of pruritus without rash following the second dose of sipuleucel-T in a patient who had otherwise not started any new medications concurrent with the first and second doses of sipuleucel-T. No further sipuleucel-T was administered, but symptoms persisted for at least 6 weeks despite treatment with several medications aimed at symptomatic relief of pruritus. Rash is the only dermatologic adverse event included in the sipuleucel-T U.S. package insert. A search of the FAERS database yielded seven additional U.S. reports of pruritus and sipuleucel-T identified as the primary suspect medication; two of these occurred prior to the administration of sipuleucel-T (following leukapheresis). In data mining analyses, pruritus following sipuleucel-T was not reported more frequently than expected when compared to all other adverse event-drug/biologic combinations in FAERS. Thus, pruritus following sipuleucel-T administration was rarely, but not disproportionately, reported to FAERS. Although we cannot exclude the possibility that diabetes, malignancy, or other conditions may have contributed to pruritus in our index patient, in view of the timing of sipuleucel-T therapy and onset of symptoms, a drug/biologic-related reaction is plausible. In the appropriate clinical scenario, sipuleucel-T (or its components) should not be overlooked as a potential etiological agent in pruritus.

Investigating endogenous µ-opioid receptors in human keratinocytes as pharmacological targets using novel fluorescent ligand

Opioids in skin function during stress response, regeneration, ageing and, particularly in regulating sensation. In chronic pruritus, topical treatment with Naltrexone changes μ-opioid receptor (μ-OR) localization to relieve itch. The molecular mechanisms behind the effects of Naltrexone on μ-OR function in reduction of itching behavior has not been studied. There is an immediate need to understand the endogenous complexity of μ-OR dynamics in normal and pathological skin conditions. Here we evaluate real-time behavior of μ-OR-Endomorphine complexes in the presence of agonist and antagonists. The μ-OR ligand Endomorphine-1 (EM) was conjugated to the fluorescent dye Tetramethylrhodamine (TAMRA) to investigate the effects of agonist and antagonists in N/TERT-1 keratinocytes. The cellular localization of the EM-TAMRA was followed through time resolved confocal microscopy and population analysis was performed by flow cytometry. The in vitro analyses demonstrate fast internalization and trafficking of the endogenous EM-TAMRA-μ-OR interactions in a qualitative manner. Competition with Endomorphine-1, Naltrexone and CTOP show both canonical and non-canonical effects in basal and differentiated keratinocytes. Acute and chronic treatment with Naltrexone and Endomorphine-1 increases EM-TAMRA binding to skin cells. Although Naltrexone is clinically effective in relieving itch, the mechanisms behind re-distribution of μ-ORs during clinical treatments are not known. Our study has given insight into cellular mechanisms of μ-OR ligand-receptor interactions after opioid agonist and antagonist treatments in vitro. These findings potentially offer opportunities in using novel treatment strategies for skin and peripheral sensory disorders.

Sensory TRP channels contribute differentially to skin inflammation and persistent itch

Although both persistent itch and inflammation are commonly associated with allergic contact dermatitis (ACD), it is not known if they are mediated by shared or distinct signaling pathways. Here we show that both TRPA1 and TRPV1 channels are required for generating spontaneous scratching in a mouse model of ACD induced by squaric acid dibutylester (SADBE), a small molecule hapten, through directly promoting the excitability of pruriceptors. TRPV1 but not TRPA1 channels protect the skin inflammation, as genetic ablation of TRPV1 function or pharmacological ablation of TRPV1-positive sensory nerves promotes cutaneous inflammation in the SADBE-induced ACD. Our results demonstrate that persistent itch and inflammation are mediated by distinct cellular and molecular mechanisms in a mouse model of ACD. Identification of distinct roles of TRPA1 and TRPV1 in regulating itch and inflammation may provide new insights into the pathophysiology and treatment of chronic itch and inflammation in ACD patients.

Allergic contact dermatitis is associated both with persistent itch and inflammation, but it is not known if these are mediated by shared signaling pathways. The authors show that persistent itch requires both TRPA1 and TRPV1, while TRPV1 has a protective role against skin inflammation in mice.

Clinical, epidemiological and therapeutic profile of patients with brachioradial pruritus in a reference service in dermatology

This is a cross-sectional study, conducted from May to November/2014, in a dermatology reference unit, through review of medical records and interviews. In a sample of 49 patients with brachioradial pruritus, we observed higher prevalence of Caucasian (81.6%) and women (73.5 %), with a mean age of 56.1 years. Pruritus occurred in the topography of brachioradialis muscle in 87.8% of cases; 59.2% of the sample reported worsening of pruritus with sun exposure; the mean intensity of this symptom before treatment was 8.63. Therapy effectiveness was described as "very good/good" in 79.2% of cases, and for 55.3% relapses were categorized as "uncommon".

Maternal serum but not breast milk IL-5, IL-6, and IL-13 immune markers are associated with scratching among infants

BACKGROUND

Scratching in infants is considered to be related to early development of eczema. Little is known about the effects of maternal immune markers on scratching among infants. The objective is to compare the risks related to maternal serum immune markers (IMs) during pregnancy and IMs in breast milk for the occurrence of scratching in infants at 6 and 12 months of age.

METHODS

Pregnant women were recruited in Columbia and Charleston, South Carolina. Blood (median 3 weeks prepartum) and breast milk (3 weeks postpartum) samples were collected. The concentrations of interferon (IFN)-γ, IFN gamma-induced protein 10 (IP-10) (or CXCL10), CCL11, interleukin (IL) 1β, IL-4, IL-5, IL-6, IL-8 (CXCL8), IL-10, IL-12 (p70), IL-13, transforming growth factor (TGF)-β1, and immunoglobulin (Ig) A in both maternal serum and whey were assayed using optimized immunoassays. Scratching and skin manifestations were ascertained at 6 and 12 months. Generalized estimating equations were used to estimate relative risks (RRs) of IMs for repeated measurements of scratching, considering intra-individual correlations and adjusting for confounders.

RESULTS

Of 178 women, 161 provided blood and 115 breast milk samples. IL-1β, IL-4, IL-10, IL-12, and CCL11 in maternal serum and whey were not analyzed due to a large proportion of non-detectable values. Infants in the highest tertile of IL-6 and IL-13 in maternal serum were at higher risk of scratching (RR 1.73 and 1.84, respectively; p ≤ 0.002) compared to infants in the first tertile; similarly, infants born to mothers with high (versus low) levels of serum IL-5 were also at increased risk (RR 1.60, p = 0.002). None of the breast milk IMs studied were associated with scratching.

CONCLUSIONS

Scratching but not doctors diagnosed eczema was associated with higher levels of maternal IL-5, IL-6, and IL-13 during pregnancy. Further investigations are necessary to determine how maternal serum IMs influence infants scratching.

Pruritus epidemiology and quality of life

The burden of chronic pruritus is increasingly recognized as significant worldwide. As wet-laboratory researchers investigate the pathophysiology of chronic pruritus, epidemiologists and health services researchers are quantifying the impact of pruritus by incidence, prevalence, and quality of life measures. Outcomes researchers are also investigating factors that may predict chronic pruritus incidence and severity. Such efforts will direct resources for research, public health intervention, and clinical care.

Itch control by Toll-like receptors

Toll-like receptors (TLRs) are cellular sensors designed to recognize molecular danger signals associated with exogenous or endogenous threats. Their activation leads to initiation of the host's immune responses in order to remove or contain the danger. However, one of the most effective methods of defense against invading pathogens and parasites is itch. The perception of itch elicits the rapid defensive action to scratch, which can remove the offending pathogen or parasite before infection can occur. Recent findings show that TLRs such as TLR3, TLR4, and TLR7 are expressed in a subset of pruriceptive/nociceptive neurons in the dorsal root and trigeminal ganglion providing a direct link between TLR activation and itch. Activation of neuronal TLRs can initiate itch sensation by coupling with ion channels. Furthermore, TLRs are expressed in skin cells and glial cells in the spinal cord to regulate inflammation and neuroinflammation in chronic itch. Thus, identification of the role of TLRs in neurons, skin cells, and glial cells may provide new targets for the treatment of chronic itch, a common clinical problem associated with skin diseases, systemic diseases, and metabolic disorders, for which current treatments are far from sufficient.

Advanced aging skin and itch: addressing an unmet need

Itch is the most common skin disorder in the elderly and frequently diminishes quality of life in this population. The high prevalence of pruritus in elderly patients is attributed in part to the decline in the normal physiology of the advanced aging skin, and reflects poor hydration, impaired skin barrier, and altered neural function, all ultimately contributing to inflammation and pruritus. As the elderly population continues to grow, practitioners need to be aware of how to evaluate and manage pruritus, recognizing the common conditions contributing to itch in elderly patients as well as the challenges of treatment in this group. Ultimately, management of pruritus will require an individually tailored approach that is guided by a patient's general health, severity of symptoms, and the potential adverse effects of itch therapies.

Prurigo nodularis: an update on etiopathogenesis and therapy

Prurigo nodularis (PN) is a chronic, highly pruritic condition characterized by the presence of hyperkeratotic, excoriated, pruritic papules and nodules, with a tendency to symmetrical distribution. No reliable data exist about incidence and prevalence of PN in the general population, but it seems to be more frequent and more intense in females. PN may be associated with many dermatological and non-dermatological comorbidities, including psychiatric disease. Recent findings suggest a neuropathic origin of PN, with alterations in the dermal and epidermal small diameter nerve fibers. PN may have a tremendous impact on the quality of life, and few effective treatment options are available. Few randomized controlled trials (RCT) on the therapy of PN are available, demonstrating the efficacy of phototherapy alone or with psoralen, and of topical calcipotriol and topical steroids in occlusive medications. Thalidomide may be effective, but no RCT are available and its use is impractical due to the unfavorable safety profile. Gabapentin, pregabalin and the neurokinin receptor 1 antagonist, aprepitant, seem also to be effective in the therapy of PN, but RCTs are still lacking.

Brachioradial pruritus -- descriptive analysis of Brazilian case series

BACKGROUND

The epidemiology and clinical features of brachioradial pruritus are variably described in the literature. We sought to analyze these features in a large group of Brazilian patients.

PATIENTS AND METHODS

In a descriptive, observational study, we identified all patients with a final diagnosis of brachioradial pruritus seen over a one-year period and re-trospectively reviewed their records. The diagnosis was made after clinical-laboratory investigation had ruled out other causes of chronic pruritus. Demographic and clinical variables were collected along with pruritus characteristics, and analyzed using des-criptive statistics.

RESULTS

Forty-three patients were identified; their mean age was 55.9 years, with predominance of women (81.4%) and Caucasians (86%). In 52%, the pruritus worsened with heat and sun exposure; 58.1% had intermittent complaints; the ice-pack sign was present only in 20.9%. The arms involving dermatomes C5-C6-C7-C8 (62.8%) were the most affected sites, while psychoactive drugs were the most frequently prescribed therapy.

CONCLUSIONS

Although uncommon, brachioradial pruritus should not be neglected in dermatological diagnosis. This case series analysis indicated that Brazilian patients from a tropical climate show characteristics similar to those described in other series from more temperate regions.

Emerging role of Toll-like receptors in the control of pain and itch

Toll-like receptors (TLRs) are germline-encoded pattern-recognition receptors that initiate innate immune responses by recognizing molecular structures shared by a wide range of pathogens, known as pathogen-associated molecular patterns (PAMPs). After tissue injury or cellular stress, TLRs also detect endogenous ligands known as danger-associated molecular patterns (DAMPs). TLRs are expressed in both non-neuronal and neuronal cell types in the central nervous system (CNS) and contribute to both infectious and non-infectious disorders in the CNS. Following tissue insult and nerve injury, TLRs (such as TLR2, TLR3, and TLR4) induce the activation of microglia and astrocytes and the production of the proinflammatory cytokines in the spinal cord, leading to the development and maintenance of inflammatory pain and neuropathic pain. In particular, primary sensory neurons, such as nociceptors, express TLRs (e.g., TLR4 and TLR7) to sense exogenous PAMPs and endogenous DAMPs released after tissue injury and cellular stress. These neuronal TLRs are new players in the processing of pain and itch by increasing the excitability of primary sensory neurons. Given the prevalence of chronic pain and itch and the suffering of affected people, insights into TLR signaling in the nervous system will open a new avenue for the management of clinical pain and itch.

Oxidative stress induces itch via activation of transient receptor potential subtype ankyrin 1 in mice

OBJECTIVE

To investigate the role of oxidative stress in itch-indicative scratching behavior in mice, and furthermore, to define the cellular and molecular mechanisms underlying oxidative stress-mediated itch.

METHODS

Scratching behavior was induced by intradermal injection of the oxidants hydrogen peroxide (H₂O₂) or tert-butylhydroperoxide (tBHP) into the nape of the neck in mice. The mice were observed for 30 min.

RESULTS

Intradermal H₂O₂ (0.03%-1%) or tBHP (1-30 μmol) elicited robust scratching behavior, displaying an inverted U-shaped dose-response curve. Naloxone, an opioid receptor antagonist, but not morphine, largely suppressed the oxidant-induced scratching. Chlorpheniramine, a histamine H1 receptor antagonist, blocked histamine- but not oxidant-induced scratching, indicating the involvement of a histamine-independent mechanism in oxidant-evoked itch. Further, resiniferatoxin treatment abolished oxidant-induced scratching, suggesting an essential role of C-fibers. Notably, blockade of transient receptor potential subtype ankyrin 1 (TRPA1) with the selective TRPA1 antagonist HC-030031, or genetic deletion of Trpa1 but not Trpv1 (subfamily V, member 1) resulted in a profound reduction in H₂O₂-evoked scratching. Finally, systemic administration of the antioxidant N-acetyl-L-cysteine or trolox (a water-soluble vitamin E analog) attenuated scratching induced by the oxidants.

CONCLUSION

Oxidative stress by different oxidants induces profound scratching behavior, which is largely histamine- and TRPV1-independent but TRPA1-dependent. Antioxidants and TRPA1 antagonists may be used to treat human itch conditions associated with oxidative stress.