Mast cells, cortistatin, and its receptor, MRGPRX2, are linked to the pathogenesis of chronic prurigo.

BACKGROUND: Chronic prurigo (CPG) is characterized by intensive itch and interactions among nerves, neuropeptides, and mast cells (MCs). The role of some neuropeptides such as cortistatin (CST) and its receptor, Mas-related G protein-coupled receptor X2 (MRGPRX2), in CPG remains poorly investigated. OBJECTIVES: We evaluated first whether CST activates human skin MCs, and second whether CST and MRGPRX2 are expressed in the skin of CPG patients, and by which cells. METHODS: Skin prick tests and microdialysis with CST were performed in 6 and 1 healthy volunteers, respectively. Degranulation of human skin MCs was assessed using ß-hexosaminidase and histamine release assays. Skin samples from 10 patients with CPG and 10 control subjects were stained for CST, MCs, and MRGPRX2 (protein and mRNA) using immunohistochemistry, immunofluorescence, and/or in situ hybridization. Flow cytometry was used to assess CST in human skin MCs. MRGPRX2 levels were measured in serum by ELISA. RESULTS: CST induced concentration-dependent degranulation of human skin MCs in vivo and ex vivo. Skin lesions of CPG patients exhibited markedly higher numbers of CST-expressing cells, CST-expressing MCs, MRGPRX2-expressing cells, and MRGPRX2 mRNA-expressing cells than nonlesional skin. MCs were the main MRGPRX2 mRNA-expressing cells in the lesions of most CPG patients (70%). Stimulation of human skin MCs with anti-IgE led to a release of CST. The number of MRGPRX2-expressing cells correlated with disease severity (r = 0.649, P = .04). MRGPRX2 serum levels in CPG patients correlated with disease severity (r = 0.704, P = .023) and quality-of-life impairment (r = 0.687, P = .028). CONCLUSIONS: CST and MRGPRX2 may contribute to the pathogenesis of CPG and should be evaluated in further studies as potential biomarkers and novel therapeutic targets.

Non-Skin Related Symptoms Are Common in Chronic Spontaneous Urticaria and Linked to Active and Uncontrolled Disease: Results From the Chronic Urticaria Registry.

BACKGROUND: Chronic spontaneous urticaria (CSU) can present with non-skin related symptoms (NSRS), including recurrent unexplained fever, joint, bone, or muscle pain (JBMP), and malaise, which also occur in other conditions that manifest with wheals (eg, urticarial vasculitis or autoinflammatory disorders) or without wheals (eg, infection). OBJECTIVE: We sought to determine the rate of patients with CSU affected by fever, JBMP, and malaise, their trigger factors, links with clinical and laboratory characteristics, and their impact on everyday life and treatment responses. METHODS: We analyzed baseline data from the Chronic Urticaria Registry of 2,521 patients with CSU who were aged 16 years or older. RESULTS: One third of CSU patients (31.2%; 786 of 2,521) had one or more NSRS, including recurrent fever (5.3%), JBMP (19.1%), and/or malaise (18.6%). In a multivariable analysis, having one or more of these NSRS correlated with food and infection as trigger factors of urticaria (adjusted odds ratio [aOR] = 1.7 and 1.5), wheals of 24 hours or greater duration (aOR = 2.5), sleep disturbance (aOR = 2.4), anxiety (aOR = 2.8), comorbid atopic dermatitis (aOR = 2.1), gastrointestinal disease (aOR = 1.8), elevated leukocytes (aOR = 1.7) and erythrocyte sedimentation rate (aOR = 1.5). In a bivariate analysis, these NSRS were additionally associated with higher disease activity (weekly Urticaria Activity Score, median: 21 vs 14; P = .009), longer disease duration (years, median: 2 vs 1; P = .001), the presence of angioedema (74.6% vs 58.7%; P < .001), worse quality of life (Chronic Urticaria Quality of Life Questionnaire, median: 42 vs 29; P < .001) and more frequent poor control of CSU (78% vs 69%; P < .001). CONCLUSIONS: The presence of NSRS in a subpopulation of patients with CSU points to the need for better control of the disease, exclusion of comorbid conditions, and/or exclusion of urticarial vasculitis and urticarial autoinflammatory diseases.

Measuring Symptom Severity and Quality of Life in Mastocytosis.

Mastocytosis is a heterogeneous disease with a wide spectrum of signs, symptoms, and concomitant disorders, such as skin lesions, anaphylaxis, osteoporosis, gastrointestinal involvement, and organomegaly. Disease specificity for frequently reported symptoms, such as fatigue, headache, anxiety, and brain fog, is poorly defined and need to be addressed in further studies. Patients with CM and non-AdvSM are mostly affected by mast cell mediator-related symptoms, whereas in AdvSM symptoms also result from organ damage, which makes their assessment challenging. In this paper we discuss approaches currently used to measure symptom burden and QoL impairment in relation to the clinical phenotype.

The diagnostic workup for systemic mastocytosis differs from consensus recommendations: Results of a worldwide survey.

Objective: Mastocytosis is a complex disorder affecting various organs. The diagnostic workup can be challenging and requires a multidisciplinary approach including the use of uncommon tests. To assess mastocytosis management around the globe, we conducted the first worldwide online survey for physicians. Methods: A 21-item questionnaire was sent out to the members of the World Allergy Organization (WAO), the Global Allergy and Asthma European Network (GA2LEN), the Urticaria (UCARE) and Angioedema (ACARE) Centers of Reference and Excellence, the German Society of Allergology and Clinical Immunology (DGAKI), and the European Mast Cell and Basophil Research Network (EMBRN) in April-June 2021. Results: Across 628 respondents from 79 countries 87.7% and 9.7% of physicians were allergists/clinical immunologists and/or dermatologists. Participating physicians were from all regions of the world (Europe, EU: 41.6%; North America, NA: 24.8%; Latin America, LA: 14.5%; Asia-Pacific, AP: 12.6%; and Africa/Middle East, AME: 6.5%). Only 2.2% of respondents worked at Specialized Mastocytosis Centers (SMCs) in North America or European Union. Physicians reported caring for 4 patients with mastocytosis per year, with higher numbers in European Union and Asia Pacific (5/year) compared to Latin America (2/year). Dermatologists and physicians who work at SMCs reported higher patient numbers (15/year and 80/year, respectively). Suspicion of mastocytosis in the allergology and dermatology community is commonly driven by anaphylaxis (82.9%), mastocytosis skin lesions (82.1%), or elevated tryptase levels (76.6%). Osteoporosis and gastrointestinal symptoms less often prompted suspicion of mastocytosis (21.4% and 49.9%, respectively). World Health Organisation (WHO)-diagnostic criteria and classification, regardless of the region, are only used by about 50% of physicians, with higher rates for SMCs (83.3%). Serum tryptase, bone marrow biopsy, and KIT D816V mutation analysis are included in the diagnostic workup by 90.9%, 61.5%, and 58.4% of physicians, respectively. The biggest challenges for the management of mastocytosis are the lack of more effective treatment options (51.1%), missing multidisciplinary networks (47.1%), and the lack of experience of specialists from other disciplines (39.0%). Conclusions: The diagnostic workup for mastocytosis differs from consensus recommendations and varies between regions. This may be improved by establishing active multidisciplinary networks, increasing access to diagnostic procedures, consistently applying WHO criteria, and developing new Mastocytosis Centers of Reference and Excellence.

Positive Basophil Tests Are Linked to High Disease Activity and Other Features of Autoimmune Chronic Spontaneous Urticaria: A Systematic Review.

BACKGROUND: Chronic spontaneous urticaria (CSU) is believed to be Autoimmune (aiCSU) (type IIb CSU) in at least 8% of patients, associated with mast cell-activating IgG autoantibodies. Basophil tests such as the basophil activation test (BAT) and basophil histamine release assay (BHRA) are considered the best single tests for an aiCSU diagnosis. To date, the strength of associations among a positive BAT and/or BHRA (BAT/BHRA+) and CSU features, patient demographics, and response to treatment remains poorly characterized. OBJECTIVE: To evaluate the strength of current evidence on basophil tests as parameters for CSU characteristics. METHODS: We performed a systematic literature search and review to assess the relationship between BAT/BHRA+ and clinical and laboratory parameters of CSU. Of 1,058 records found in the search, 94 studies were reviewed by experts in urticaria and 42 were included in the analysis. RESULTS: In CSU patients, BAT/BHRA+ showed a strong level of evidence for an association with high disease activity and low levels of total IgE. A weak level of evidence was shown for the association of BAT/BHRA+ and the presence of angioedema, and basopenia. CONCLUSIONS: Our results suggest that aiCSU defined by BAT/BHRA+ is more active or severe and is linked to other aiCSU markers such as low total IgE/basopenia. Basophil tests should be standardized and implemented in routine clinical care to improve the diagnosis and treatment of patients with aiCSU.

In the skin lesions of patients with mycosis fungoides, the number of MRGPRX2-expressing cells is increased and correlates with mast cell numbers.

Background: Mycosis fungoides (MF) is an indolent T-cell lymphoma that mainly affects the skin and presents with itch in more than half of the patients. Recently, the expression of Mas-related G protein-coupled receptor X2 (MRGPRX2), a receptor of mast cell (MC) responsible for the IgE-independent non-histaminergic itch, has been shown in lesional skin of patients with pruritic skin diseases, including chronic urticaria, prurigo, and mastocytosis. As of yet, limited knowledge exists regarding the MRGPRX2 expression in the skin of patients with MF. Objectives: To investigate the number of MRGPRX2-expressing (MRGPRX2+) cells in the skin of patients with MF and its correlation with clinical and laboratory characteristics of the disease. Methods: MRGPRX2 was analyzed in lesional and non-lesional skin of MF patients and healthy skin tissues by immunohistochemistry. Co-localization of MRGPRX2 with the MC marker tryptase was assessed by immunofluorescence. Public single-cell RNAseq data was reanalyzed to identify the MRGPRX2 expression on the distinct cell types. Results: In lesional skin of MF patients, MRGPRX2+ cell number was higher than in non-lesional skin and healthy control skin (mean:15.12 vs. 6.84 vs. 5.51 cells/mm2, p=0.04), and correlated with MC numbers (r=0.73, p=0.02). MC was the primary cell type expressing MRGPRX2 in MF patients. The ratio of MRGPRX2+ MCs to MRGPRX2+ cells in lesional and non-lesional skin correlated with the severity of disease (r=0.71, p=0.02 and r=0.67, p=0.03, respectively). Conclusions: Our findings point to the role of MRGPRX2 and MC in the pathogenesis of MF that should be investigated in further studies.

Sarcoid Granulomas and Systemic Sarcoidosis Triggered by Cosmetic Tattoos.

Cosmetic tattooing of eyebrow and lips has become very popular and is expected to be paralleled by more frequent complications. We present 4 cases of granulomas in cosmetic tattoos complicated by regional or systemic manifestations of sarcoidosis including affection of the lungs in 2 cases, the activity triggered by the tattoo. Three cases of traditional decorative tattoos on extremities serve as reference. It is noteworthy that cosmetic tattoos despite small size and thereby low relative dose of pigment injected in the skin can trigger fully developed systemic sarcoidosis. It is hypothesized that iron oxide pigments popular in cosmetic tattoo inks of red or brown color may be prone to elicit sarcoid reactions and thus carry a special risk of granuloma. In decorative tattoos, carbon black is the commonest trigger. It is emphasized that the finding of granulomas in tattoos shall be followed by search of other manifestations of sarcoidosis through patient history and diagnostic examinations to exclude pulmonary, ocular, and other organ manifestations. Patients with granulomas in tattoos shall be informed that active sarcoidosis, if not already present, can become manifest later with a latency of months or years and often with abrupt debut when the triggering tattoo may be overlooked by the doctor who is unfamiliar with this less common type of sarcoidosis.

The Number of MRGPRX2-Expressing Cells Is Increased in Skin Lesions of Patients With Indolent Systemic Mastocytosis, But Is Not Linked to Symptom Severity.

Background: Recently, the expression of the mast cell (MC) receptor Mas-related G protein-coupled receptor X2 (MRGPRX2) has been detected in lesional skin of adult patients with cutaneous mastocytosis. As of yet, little is known about the clinical relevance of MRGPRX2 and its agonists in patients with mastocytosis, including indolent systemic mastocytosis (ISM). Methods: MRGPRX2 and MRGPRX2 agonists, cortistatin (CST), and major basic protein (MBP) were analyzed in lesional and non-lesional skin of patients with ISM and skin of healthy controls by immunohistochemistry. Co-localization of MRGPRX2 and MRGPRX2-mRNA with the MC marker tryptase was assessed by immunofluorescence microscopy and in situ hybridization, respectively. We assessed clinical, demographic, and laboratory data, including mastocytosis activity score (MAS), serum tryptase, and KIT D816V allele burden. Results: The number of MRGPRX2-expressing (MRGPRX2+) cells, MRGPRX2-mRNA+ MCs, and CST-expressing (CST+) and MBP-expressing (MBP+) cells was significantly higher in lesional skin as compared to non-lesional skin and/or skin of healthy controls (all p < 0.05). Increased numbers of MRGPRX2+ cells, MRGPRX2-mRNA+ MCs, and CST+ and MBP+ cells were not associated with clinical and laboratory features of ISM, including disease burden, symptom severity, evidence of anaphylaxis, and tryptase levels. Conclusions: Skin lesions of patients with ISM showed high numbers of MRGPRX2+ cells, although they were not linked to symptom severity. Clinical relevance of the MRGPRX2-mediated pathway of MC activation in ISM remains unclear and should be investigated in further studies.

Refined Treatment Response Criteria for Indolent Systemic Mastocytosis Proposed by the ECNM-AIM Consortium.

Indolent systemic mastocytosis (ISM) has a favorable prognosis and normal life expectancy. However, many patients suffer from mast cell (MC) mediator-related symptoms, which significantly affect quality of life (QoL). Cutaneous, gastrointestinal, and neurological complaints, musculoskeletal pain, and the presence of skin lesions, anaphylaxis, and osteoporosis are the main symptoms and signs in ISM and must be assessed in all patients before and during treatment. Validated mastocytosis-specific patient-reported outcome measures (PROMs) should be used for this purpose. Serum tryptase and KIT D816V allele burden are recommended as secondary outcome parameters, noting that they do not reflect the severity of signs, symptoms, and related QoL impairment, but indirectly express MC burden. Changes from baseline of 90%, 60%, and 30% indicate complete response >90%, major response 60% to 90%, partial response 30% to 60%, and no response <30% to treatment. To conclude, we recommend the use of PROMs as primary outcome parameters to define treatment response in patients with ISM in clinical trials and in everyday clinical practice.

Total IgE as a Marker for Chronic Spontaneous Urticaria.

OBJECTIVE: Immunoglobulin E (IgE) and its receptor, FcɛRI, importantly contribute to the pathophysiology of chronic spontaneous urticaria (CSU). Recent findings point to a possible role of total IgE as a marker of CSU disease activity, endotypes, and responses to treatment. The evidence in support of total IgE included in the diagnostic workup of patients with CSU has not yet been reviewed. METHODS: Publications were searched via PubMed. The search terms used were "chronic urticaria" and "total IgE." Studies were screened by titles and abstracts, and 141 were used in the review. RESULTS: CSU patients frequently had elevated total IgE serum levels (up to 50%), but normal or very low total IgE levels also occurred. High total IgE may represent high disease activity, longer disease duration, high chance of responding to omalizumab treatment, quick relapse after stopping omalizumab, and lower chance of responding to cyclosporine. Low IgE, in contrast, may suggest Type IIb autoimmune CSU, poor response to treatment with omalizumab and a better chance to benefits from cyclosporine treatment. Furthermore, IgE in different CSU cohorts may have different physicochemical properties that could explain differences in treatment responses to IgE-directed therapies. CONCLUSION: The results of our review suggest that total IgE is a valuable marker for CSU, and we recommend its assessment in the routine diagnostic workup of CSU patients.

The Diagnostic Workup in Chronic Spontaneous Urticaria-What to Test and Why.

BACKGROUND: In chronic spontaneous urticaria (CSU), the guidelines recommend very limited diagnostic procedures during the routine workup, although additional investigations might be indicated in some patients with CSU. For physicians treating patients with CSU, it is often difficult to decide which diagnostic tests are useful. OBJECTIVE: To provide recommendations on what diagnostic tests should be performed on which patients with CSU. METHODS: We performed an extensive literature search on the respective topics and identified relevant questions that should prompt diagnostic procedures based on the published evidence and expert consensus among all authors. RESULTS: We provide questions, diagnostic testing, where appropriate, and recommendation that should be included when assessing the history of a patient with CSU, to explore and rule out differential diagnoses, to assess patients for underlying causes and modifying conditions, to explore patients for comorbid diseases and consequences of having CSU, and to assess patients for CSU components that can help to predict their disease course and response to treatment. CONCLUSIONS: Here, we provide physicians treating patients with CSU with information about which clues should lead to which tests and why.