Prurigo Simplex or "Itchy Red Bump" Disease: Review and Case Series

Prurigo simplex or “itchy red bump” disease is a controversial pruritic papular eruption. The objective of this study was to delineate the diagnostic criteria for this disease. A PubMed search was performed for: “prurigo simplex”, “prurigo simplex subacuta”, “subacute prurigo”, “chronic papular dermatitis in adults” and “itchy red bump disease”. Medical charts of patients with prurigo diagnoses in a university setting were analysed. The literature search revealed 32 relevant studies (431 patients) on different aspects of the disease. Out of 50 patients with prurigo diagnoses, 5 patients (4 women, mean age at onset 54 years) matched the description in literature. Small, severely itchy papules without secondary skin lesions continued to appear for years (mean 5.6 years). Skin biopsies revealed lymphocytic perivascular infiltrates, few eosinophils and occasionally spongiosis. Treatment with long-term methotrexate or cyclosporine cleared the symptoms. Some major and minor diagnostic criteria for prurigo simplex are proposed and compared with chronic prurigo.

Activation of Transient Receptor Potential Vanilloid-3 Channels in Keratinocytes Induces Pruritus in Humans

Carvacrol, a natural transient receptor potential vanilloid-3 activator, has been reported to cause pruritus in mice. This study aimed to evaluate the effects of carvacrol and various antipruritic agents in humans. A stimulation test with carvacrol, β-alanine, and histamine was performed. After application of the pruritic solutions, the skin was stimulated with pinpricks. In inhibition test A, Forsythia suspensa extract, containing forsythoside B (a transient receptor potential vanilloid-3 inhibitor), was applied by pricking prior to stimulation with pruritogens. In inhibition test B, olopatadine solution, tacrolimus ointment, and Scutellaria baicalensis root extract were applied, and carvacrol was applied to the same region. Carvacrol induces moderate pruritus in humans. The pruritus was relieved by Forsythia suspensa extract and olopatadine solution after 20 min of application and by tacrolimus ointment and Scutellaria baicalenis extract after 24 h of application. These results suggest that carvacrol is a pruritogen in humans, and that carvacrol-induced pruritus is inhibited by various antipruritic agents.

Chronic Nodular Prurigo: A European Cross-sectional Study of Patient Perspectives on Therapeutic Goals and Satisfaction

Chronic nodular prurigo is characterized by recalcitrant itch. Patient perspectives on therapeutic goals, satisfaction with therapy and efficacy of therapeutic regimens for this condition are unknown. This questionnaire study examined these issues in 406 patients with chronic nodular prurigo from 15 European dermatological centres. Improvements in itch, skin lesions and sleep were the most important goals. Emollients, topical corticosteroids and antihistamines were the most frequently used treatments, while a minority of patients were prescribed potent medications, such as systemic immunosuppressants and gabapentinoids. Most patients were not satisfied with their previous therapy (56.8%), while 9.8% did not receive any therapy despite having active disease. A substantial number of respondents (28.7%) considered none of the therapeutic options effective. Although chronic nodular prurigo is a severe disease, most patients were not treated with potent systemic drugs, which may contribute to the high levels of dissatisfaction and disbelief in available therapies. Specific guidelines for chronic nodular prurigo and the development of novel therapies are necessary to improve care.

Analysis of 325 Patients with Chronic Nodular Prurigo: Clinics, Burden of Disease and Course of Treatment

Chronic nodular prurigo presents with multiple pruriginous nodules and severe pruritus. This study aims to explore the treatment course and regimens in patients with chronic nodular prurigo and to analyse predictive factors contributing to therapeutic success. A total of 325 patients with chronic nodular prurigo (male 37.5%) were analysed concerning demographic data, pruritus intensity, medical history, psychological impairment, quality of life, treatment duration, regimens and outcome. These parameters were compared with 325 sex- and age-matched patients with chronic pruritus on non-lesional skin. Treatment success was dependent on duration and regime of treatment and independent of age, sex and initial itch intensity. Non-responders displayed a higher percentage of inflamed nodules, a higher portion of excoriated nodules and a higher impairment of quality of life and mood factors before initiation of treatment. Gabapentinoids and immunosuppressants proved to be the most successful therapeutic agents. Compared with patients with chronic pruritus, those with chronic nodular prurigo needed longer duration of therapy.

Attentional Bias Towards Visual Itch and Pain Stimuli in Itch- and Pain-free Individuals?

Itch and pain are important attention-demanding sensations that allow adaptive responses to potential bodily harm. An attentional bias towards itch and pain stimuli, i.e. preferential attention allocation towards itch- and pain-related information, has been found in healthy, as well as patient groups. However, it remains unclear whether attentional bias for itch and pain differs from a general bias towards negative information. Therefore, this study investigated attentional bias towards itch and pain in 70 itch- and pain-free individuals. In an attention task, itch- and pain-related stimuli, as well as negative stimuli, were presented alongside neutral stimuli. The results did not indicate an attentional bias towards itch-, pain-, and negative visual information. This finding suggests that people without itch and pain symptoms do not prioritize itch- and pain-related information above neutral information. Future research should investigate whether attention towards itch- and pain-related information might be biased in patients with chronic itch and pain.

Treatment and Burden of Disease in a Cohort of Patients with Prurigo Nodularis: A Survey-based Study

Prurigo nodularis is a pruritic dermatosis with poor treatment options. To describe treatment patterns, comorbidities, pruritus, and quality of life a survey was administered to 92 patients with prurigo nodularis. A total of 52 patients completed the survey. The most frequently used treatments were topical corticosteroids, which were prescribed to 49/52 patients, with positive effect in 13/49. A total of 46/52 patients were treated with ultraviolet B, and 9/46 reported a positive effect. A positive effect was reported for topical corticosteroids under occlusion in 21/40, for zinc dressing treatment in 17/37, for steroid injection in 9/14, for methotrexate in 5/16, and for thalidomide in 4/12 of treated patients. Thirty-six patients reported a Pittsburgh Sleep Quality Index >5, indicating poor sleep. Patients with prurigo nodularis are severely bothered by pruritus negatively affecting quality of life. Various treatments are prescribed; most frequently topical corticosteroids and ultraviolet B. Surprisingly, patients reported topical corticosteroids under occlusion, zinc-dressing treatment and steroid injection as the most effective.

Prevalence of Pruritus in a Single Cohort of Long-term Kidney Transplant Recipients

is missing (Short communication).

Direct and Indirect Effects of Crisaborole Ointment on Quality of Life in Patients with Atopic Dermatitis: A Mediation Analysis

Crisaborole ointment is a nonsteroidal phosphodiesterase 4 inhibitor for the treatment of mild to moderate atopic dermatitis. Using pooled data from two phase 3 studies (NCT02118766/NCT02118792), mediation modeling determined the interrelationship among pruritus, quality of life (QoL), and treatment. Patients aged ≥ 2 years received crisaborole ointment 2% or vehicle twice daily for 28 days. QoL measures were Dermatology Life Quality Index (DLQI) (≥ 16 years) and Children's Dermatology Life Quality Index (CDLQI) (2-15 years). Pruritus was assessed by the Severity of Pruritus Scale (4-point scale from 0 to 3). The indirect effect of crisaborole on QoL mediated through its effect on pruritus was 51% (DLQI model, p < 0.05) and 72% (CDLQI model, p < 0.05). Direct effect (other effects) on QoL was 49% (DLQI model, p < 0.05) and 28% (CDLQI model, p > 0.05). Mediation modeling shows that crisaborole affects QoL mostly indirectly through pruritus severity reduction.

Characteristics of Pruritus in Relation to Self-assessed Severity of Atopic Dermatitis

The objective of this study was to explore characteristics of pruritus in atopic dermatitis (AD) in relation to the severity of AD. A web-questionnaire was used, which included the Patient-Oriented SCORing Atopic Dermatitis index, the 5-D itch scale and the Brest questionnaire. A total of 170 participants were included (86.5% women, mean age 30.9 years). Severity of AD was mild for 8.2% of patients, moderate for 38.2% and severe for 53.5%. Mean 5-D itch scale was 13.2. The mean intensity of pruritus was 5.8, and mean sleep loss was 4.7 (from 0 to 10). The participants frequently described burning (61.8%) and stinging (58.8%); these symptoms suggest a neuropathic component. Pruritus was worse in severe AD compared with moderate AD, exhibiting a higher impact on sleep and more associated symptoms. The majority of participants reported sleep disturbance as a result of pruritus. The characteristics of pruritus varied depending on the severity of AD.

Effects of Short-term Temperature Change in the Innocuous Range on Histaminergic and Non-histaminergic Acute Itch

While temperatures in the noxious range are well-known to inhibit acute itch, the impact of temperature in the innocuous temperature range is less well understood. We investigated the effect of alternating short-term temperature changes in the innocuous range on histamine and cowhage-induced acute itch, taking into account individual differences in baseline skin temperature and sensory thresholds. Results indicate that cooling the skin to the cold threshold causes a temporary increase in the intensity of histamine-induced itch, in line with previous findings. Skin warming increased cowhage-induced itch intensity. Potential mecha-nisms of this interaction between thermosensation and pruritoception could involve cold-sensitive channels such as TRPM8, TREK-1 or TRPC5 in the case of histamine. The rapid modulation of cowhage induced itch - but not histamine-induced itch - by transient skin warming could be related to the lower temperature threshold of pruriceptive polymodal C-fibres (cowhage) as compared to the higher temperature threshold of the mechanoinsensitive C-fibres conveying histaminergic itch.