Key points are not available for this paper at this time.
Prurigo nodularis (PN), as a subtype of chronic prurigo (CPG), is characterized by nodular lesions and severe pruritus, which significantly affect patients' quality of life.1 It has been observed that patients with PN often have comorbidities, including physical and mental diseases.2 However, information on comorbidities in Chinese PN patients is lacking. This study aims to fill this gap by using a representative patient population to provide comprehensive data on comorbidities in Chinese patients with PN. This study is based on the China Type II Inflammatory Skin Disease Clinical Research and Standardized Diagnosis and Treatment Project (https://clinicaltrials.gov/, ClinicalTrials.gov, NCT05316805) conducted by the National Clinical Research Center for Skin and Immune Diseases. More than 100 centers participated in this project from June 2021 to October 2022. This study was approved by Clinical Research Ethics Committee of Peking University First Hospital (No. 2021/223). All patients gave consent with the understanding that this information may be publicly available. The diagnosis of PN was based on objective criteria, including chronic pruritus for more than 6 weeks, persistent scratching, and the presence of localized or generalized nodular lesions.3 Additional data collected for further analysis included the patients' general condition, comorbidities, PN characteristics, and clinical scores, such as Investigator Global Assessment (IGA), Peak-Numerical Rating Scale (Peak-NRS), Dermatology Life Quality Index (DLQI), and Hospital Anxiety and Depression Scale (HADS). Based on previous research, we selected 18 distinct diseases to investigate, including common systemic diseases in the Chinese community, dermatologic diseases, allergic diseases, and mental health disorders potentially associated with PN. Identification of comorbidities was performed by thorough physical examination and detailed review of medical records. Patients who were unable to understand or cooperate with the project were excluded. All statistical analyses were performed using SPSS 24.0 (IBM Corp, Armonk, USA). A total of 759 patients diagnosed with PN were enrolled in this study. The mean age at the time of diagnosis was 44.3 ± 19.7 years, and 44% were female. A total of 2892 questionnaires were finally collected, including 752 IGA, 717 Peak-NRS, 725 DLQI, and 698 HADS. In the IGA, 427 (56.8%) individuals scored above 2 points. In addition, 596 (79.8%) patients reported pruritus exceeding 4 points on the Peak-NRS. DLQI scores greater than 6 points were observed in 372 (51.3%) patients, and the HADS indicated anxiety or depression symptoms in 207 (29.7%) patients Figure 1A; further, out of the 759 enrolled patients, 316 (41.6%) had at least one comorbid condition. Allergic rhinitis was the most common comorbidity (167, 22.0%), followed by atopic dermatitis (93, 12.3%) and food allergy (40, 5.3%). The corresponding prevalences in the general population were 17.6%, 2.5%, and 8.0%, respectively. No gender differences were observed. Hypertension was the most common systemic comorbidity (28, 3.7%). No significant differences were found between adolescents and adults regarding the presence or absence of comorbidities. However, the DLQI scores were significantly lower in the adolescent group (P = 0.042). And adolescents demonstrated a lower risk of comorbid coronary heart disease (odds ratio OR, 0.127, 95% confidence interval CI, 0.025–0.641), and a higher risk of comorbid atopic stigmata (OR, 4.110, 95% CI, 1.271–13.290). Data for all comorbidities are shown in Figure 1B.Figure 1: (A) The stacked bar chart of clinical scores. (B) The funnel plot of the number of different comorbidities. (C–E) The forest plots of multivariate binary logistic regression analysis of (C) allergic rhinitis, (D) atopic dermatitis, and (E) food allergy. CI: Confidence interval; DLQI: Dermatology Life Quality Index; HADS: Hospital Anxiety and Depression Scale; IGA: Investigator Global Assessment; OR: Odds ratio; Peak-NRS: Peak-Numerical Rating Scale.Gender was identified as an independent risk factor for comorbidity based on the logistic regression analysis. Male patients were more likely to have comorbidities (OR, 1.539; 95% CI, 1.136–2.084). To explore potential interactions among different comorbidities, we performed multivariate binary logistic regression analysis. Several risk factors for comorbid allergic rhinitis were found in PN patients, including being male (OR, 1.625; 95% CI, 1.11–2.378), having a food allergy (OR, 3.461; 95% CI, 1.094–10.954), and having allergic conjunctivitis (OR, 19.366; 95% CI, 4.072–92.089) Figure 1C. In addition, PN patients with atopic stigmata (OR, 2.365; 95% CI, 1.305–4.286) and those with a family history of atopic disease (OR, 3.977; 95% CI, 2.279–6.939) demonstrated an increased likelihood of developing atopic dermatitis Figure 1D. Patients with asthma (OR, 4.742; 95% CI, 1.615–13.920), allergic conjunctivitis (OR, 5.055; 95% CI, 1.122–22.777), and ichthyosis vulgaris (OR, 5.653; 95% CI, 1.075–29.727) showed an increased likelihood of having food allergies Figure 1E. Conversely, no statistically significant risk factors were found for other comorbidities. Clinical scores were compared between the two cohorts based on the presence of comorbidities. Individuals with comorbidities generally experienced higher level of pruritus (P = 0.014). And there were no significant differences between the cohorts in IGA (P = 0.358), HADS (P = 0.778), and DLQI (P = 0.967) scores. Female accounted for 44% in this study, in line with previous studies on Asian PN patients.4 Patients were diagnosed at a mean age of 44.3 years, lower than that in other studies, possibly due to the inclusion of 101 minors.1 Most participants presented with moderate to severe skin lesions and pruritus. PN significantly impacted the quality of life of nearly half of the patients and approximately 25% of patients suffered from anxiety or depression symptoms. Multiple comorbidities, including atopic dermatitis, exhibit higher prevalence in PN, aligning with prior research. Nevertheless, a lower occurrence rate of systemic, mental, and certain allergic disorders was observed, such as hypertension in adults (3.4% in Chinese PN, 31.61% in German PN, and 25.2% in Chinese general population), which indicates a noteworthy gap in the data collection efforts. Based on our research, allergic rhinitis, atopic dermatitis, and food allergies are the most prevalent comorbidities associated with PN. It appears that male PN patients exhibit a greater vulnerability to developing comorbidities, and those who suffer from comorbidities are more prone to experiencing severe pruritus, potentially linked to their specific comorbidities. Moreover, there are distinct relations between different comorbidities. Individuals diagnosed with allergic conjunctivitis have a higher risk of developing allergic rhinitis. Patients presenting with allergic conjunctivitis, ichthyosis vulgaris, and bronchial asthma are more likely to develop food allergies. Furthermore, a family history of atopy or an atopic stigmata may further increase the risk of developing atopic dermatitis. Previous researches have demonstrated that these diseases are connected through a shared Th2 inflammatory pathway, potentially resulting in the higher occurrence of comorbidity and complex internal interactions.5 However, this study has some limitations. Notably, the incidence of particular comorbidities was lower than others and the range of 95% CI was significantly broad; it is thus essential to validate our findings with a more comprehensive collection of comorbidity medical histories and a larger sample size. Acknowledgments The authors would like to thank the 101 collaborating hospitals of the "China Type II Inflammatory Skin Disease Clinical Research and Standardized Diagnosis and Treatment Project" for their collaboration and allocation of data Supplementary Table 1, https://links.lww.com/CM9/B992. Funding This study was supported by grants from the National Natural Science Foundation of China (No. 81972930), the Shenzhen Natural Sciences Foundation (No. JCYJ20210324105411030), the Scientific Research Foundation of Peking University Shenzhen Hospital (No. KYQD2021016), the Shenzhen Key Medical Discipline Construction Fund (No. SZXK040), and the Guangdong Basic and Applied Basic Research Foundation (No. 2021A1515111009). Conflicts of interest None.
Yin et al. (Tue,) studied this question.