The SNCA gene, encoding alpha-synuclein, is implicated in the pathogenesis of Parkinson’s disease (PD), with several single-nucleotide polymorphisms (SNPs) linked to increased risk. This study systematically evaluated the association between common SNCA polymorphisms and PD through a meta-analysis of cohort and case–control studies published before 20 November 2023. Eligible studies were identified via comprehensive searches of PubMed, Scopus, and Web of Science, and pooled odds ratios with 95% confidence intervals were calculated under allelic, dominant, and recessive models. Heterogeneity and publication bias were assessed, and subgroup and sensitivity analyses were performed. Twenty-seven studies were included. SNP rs11931074 showed consistent associations with PD across all models, with low heterogeneity and no evidence of publication bias. rs356219 and rs356165 were also significantly associated with PD, although regional differences contributed to heterogeneity. In contrast, rs2583988 showed marginal significance in the allelic model, which was lost after sensitivity analyses. No associations were found under dominant or recessive models for this SNP. These findings confirm rs11931074 as a robust PD risk variant and support the roles of rs356219 and rs356165 while suggesting weaker evidence for rs2583988. Large, multi-ethnic studies are warranted to elucidate underlying mechanisms and support precision medicine in PD.

Background: The clinical impact of hepatic steatosis (HS) among patients with autoimmune liver disease (AILD) remains unclear. We aim to determine the prevalence of HS and its clinical impact on treatment response and outcomes in patients with AILD. Methods: We systematically searched 3 electronic databases until 17 December 2025, including all studies that reported the prevalence, clinical impact, and treatment response of AILD patients with concomitant HS. The temporal trend of HS prevalence was analyzed using a quasi-Poisson regression model, with annual percent changes (APC, %) calculated. Results: Overall, 44 studies, comprising 19,898 patients with autoimmune hepatitis (AIH), primary biliary cholangitis (PBC), and primary sclerosing cholangitis (PSC) were included. The pooled prevalence of HS in patients with AIH, PBC, and PSC was 27.3%, 32.9%, and 21.6%, respectively. HS prevalence has significantly increased among PBC patients since 2010 (APC: +37.4%). While concomitant HS was associated with a higher risk of hepatic decompensation (OR: 1.6, 95% CI: 1.3–2.1, I ² =0%) and hepatocellular carcinoma (OR: 1.8, 95% CI: 1.3–2.6, I ² =0%) in patients with AIH, HS did not influence the clinical outcomes in patients with PBC. Treatment response in AIH and PBC was not influenced by concomitant HS. Available data on PSC with concomitant HS were insufficient to assess its association with clinical outcomes. Conclusions: AIH patients with concomitant HS had worse outcomes than those without HS; whereas HS did not influence the clinical outcomes in patients with PBC. Future research evaluating the impact of HS on PSC and overlap syndrome is much needed.

Background: Patients with primary biliary cholangitis (PBC) often suffer from debilitating symptoms, yet the overall symptom burden has not been systematically quantified. This study aims to systematically review the prevalence and severity of the symptom burden in PBC patients. Methods: We conducted a systematic search of 3 electronic databases to include studies that reported the prevalence and severity of PBC symptoms. Subgroup analyses were performed based on study type, publication year, risk of bias, study location, sex, and latitude. Results: A total of 25 studies involving 13,178 patients were included. Fatigue was the most common symptom, affecting 51% of patients, followed by pruritus at 33%. Severe fatigue and severe pruritus were reported in 23% and 10% of patients, respectively. The prevalence of fatigue was significantly higher in more recent studies, those with smaller sample sizes, and studies published as abstracts. Fatigue score was significantly higher in female patients compared with males. Severe fatigue was more prevalent in studies conducted in North America/Europe than those from Asia (26% vs. 8%, p =0.0005), and in studies with a higher proportion of patients with cirrhosis (28% vs. 8%, p =0.0005). Despite the high burden, only 36% of PBC patients with pruritus received anti-pruritic treatment, with antihistamines being the most frequently prescribed medication. Conclusions: Over half of PBC patients experience significant symptom burden, with substantial ethnic disparities identified. The proportion and quality of appropriate symptom management in PBC are suboptimal. There remains an unmet need for standardized assessment, consistent reporting, and improved management strategies for PBC-related symptoms in future research.