Exposure to silica and systemic sclerosis: A retrospective cohort study based on the Canadian Scleroderma Research Group

A scoping review of the epidemiology of systemic sclerosis and its organ manifestations: 2018-2024

PURPOSE OF REVIEW

Updates from large, observational cohorts and new statistical techniques have resulted in new data on the epidemiology of systemic sclerosis (SSc). This scoping review uses data from 2018 to 2024 to describe the current understanding of the epidemiology of SSc and several of its organ- manifestations.

RECENT FINDINGS

Our review identified new estimates for the global incidence and prevalence of SSc (1.4-8.6 per 100 000 person-years and 17.6-18.9 per 100 000 individuals, respectively). Mortality rates remain high, though mortality at younger ages has decreased. interstitial lung disease and pulmonary arterial hypertension remain the most common causes of death for patients with SSc. Literature on gastrointestinal (GI) manifestations of SSc was scarce, and we identified significant heterogeneity in results. Furthermore, data on the epidemiology of racial, ethnic and sex-based disparities was lacking.

SUMMARY

New techniques for the evaluation of the epidemiology of SSc highlight the high morbidity and mortality of SSc, and a growing prevalence rate compared with prior eras. Further research is needed to address notable heterogeneity in the reporting of epidemiological data and understudied disease manifestations, including GI disease and health disparities in disease outcomes.

Widespread mutagenesis and chromosomal instability shape somatic genomes in systemic sclerosis

Systemic sclerosis is a connective tissue disorder characterized by excessive fibrosis that primarily affects women, and can present as a multisystem pathology. Roughly 4-22% of patients with systemic sclerosis develop cancer, which drastically worsens prognosis. However, the mechanisms underlying systemic sclerosis initiation, propagation, and cancer development are poorly understood. We hypothesize that the inflammation and immune response associated with systemic sclerosis can trigger DNA damage, leading to elevated somatic mutagenesis, a hallmark of pre-cancerous tissues. To test our hypothesis, we culture clonal lineages of fibroblasts from the lung tissues of controls and systemic sclerosis patients and compare their mutation burdens and spectra. We find an overall increase in all major mutation types in systemic sclerosis samples compared to control lung samples, from small-scale events such as single base substitutions and insertions/deletions, to chromosome-level changes, including copy-number changes and structural variants. In the genomes of patients with systemic sclerosis, we find evidence of somatic hypermutation or kategis (typically only seen in cancer genomes), we identify mutation signatures closely resembling the error-prone translesion polymerase Polη activity, and observe an activation-induced deaminase-like mutation signature, which overlaps with genomic regions displaying kataegis.

Silica's silent threat: Contributing to skin fibrosis in systemic sclerosis by targeting the HDAC4/Smad2/3 pathway

Nowadays, silica products are widely used in daily life, especially in skin applications, which inevitably increases the risk of silica exposure in general population. However, inadequate awareness of silica's potential hazards and lack of self-protection are of concern. Systemic sclerosis (SSc) is characterized by progressive tissue fibrosis under environmental and genetic interactions. Silica exposure is considered an important causative factor for SSc, but its pathogenesis remains unclear. Within this study, we showed that lower doses of silica significantly promoted the proliferation, migration, and activation of human skin fibroblasts (HSFs) within 24 h. Silica injected subcutaneously into mice induced and exacerbated skin fibrosis. Notably, silica increased histone deacetylase-4 (HDAC4) expression by inducing its DNA hypomethylation in normal HSFs. The elevated HDAC4 expression was also confirmed in SSc HSFs. Furthermore, HDAC4 was positively correlated with Smad2/3 phosphorylation and COL1, α-SMA, and CTGF expression. The HDAC4 inhibitor LMK235 mitigated silica-induced upregulation of these factors and alleviated skin fibrosis in SSc mice. Taken together, silica induces and exacerbates skin fibrosis in SSc patients by targeting the HDAC4/Smad2/3 pathway. Our findings provide new insights for evaluating the health hazards of silica exposure and identify HDAC4 as a potential interventional target for silica-induced SSc skin fibrosis.

Systemic sclerosis, silica exposure and cellular therapies: The sand in the gears?

Systemic sclerosis (SSc) is a chronic orphan autoimmune disease with the highest mortality rate among rheumatic diseases. SSc-related interstitial-lung disease (ILD) remains among the leading causes of SSc-related mortality with still few therapeutic effective strategies. In patients with crystallin silica exposure, SSc is recognized as an occupational disease according to the French social security system (Table 25A of the general insurance regimen). Lympho-ablative or myeloablative immunosuppression followed by autologous hematopoietic stem-cell transplantation (aHSCT) is the only therapeutic approach with demonstrated efficacy, improved survival with disease modifying effects on SSc-fibrotic manifestations (skin disease and ILD) and quality of life. A documented past and/or present occupational silica exposure, with extensive exposure and/or silica-related ILD and/or with persistent silica content in the broncho-alveolar lavage fluid are contra-indications to aHSCT in SSc patients, due to the risk of silica-related malignancy or of SSc relapse. This article aims to discuss alternative options in SSc patients with a history of silica exposure, and how innovative cellular therapies (mesenchymal stromal cells, CAR cells) could represent new therapeutic options for these patients.

Untangling the relationship between smoking and systemic sclerosis: an analysis of the EUSTAR cohort

OBJECTIVES

To untangle the association between smoking and systemic sclerosis (SSc).

METHODS

In the European Scleroderma Trials and Research cohort, the autoantibody status was compared between ever-smokers and never-smokers. Time until disease progression was assessed using Kaplan-Meier curves. Cox models were built to investigate the influence of smoking over 15 years of follow-up. All analyses were performed for the total cohort and stratified for sex and for positivity of anti-centromere (ACA) and anti-topoisomerase antibodies (ATA).

RESULTS

Overall, 12 314 patients were included in the study. Of these, 10 393 were women (84%), 4637 were ACA-positive (38%), 3919 were ATA-positive (32%) and 4271 (35%) were ever-smokers. In men, but not in women, smoking was associated with mortality (HR 1.63, 95% CI 1.23 to 2.16, p=0.001). Ever-smoking women were at higher risk for skin progression (HR 1.10, 95% CI 1.00 to 1.22, p=0.046) and for 'any organ progression' (HR 1.07, 95% CI 1.00 to 1.13, p=0.036). In women, 34% of never-smokers were ATA-positive compared with 21% of ever-smokers (p<0.001). In the group of ever-smokers, higher exposure rates, reflected by the number of pack-years (OR 0.98, 95% CI 0.97 to 0.99, p<0.001) and by smoking duration (OR 0.96, 95% CI 0.95 to 0.97, p<0.001), were associated with lower frequency of ATA. In ACA-positive patients, the risk of mortality (HR 1.29, 95% CI 1.02 to 1.63, p=0.033), cardiac involvement (HR 1.25, 95% CI 1.03 to 1.43, p=0.001), skin progression (HR 1.21, 95% CI 1.03 to 1.42, p=0.018) and 'any organ progression' (HR 1.14, 95% CI 1.05 to 1.24, p=0.002) was increased among smokers. In ATA-positive smoking patients, mortality (HR 1.40, 95% CI 1.10 to 1.78, p=0.006), skin progression (HR 1.19, 95% CI 1.03 to 1.37, p=0.020) digital ulcers (HR 1.17, 95% CI 1.02 to 1.34, p=0.029) and 'any organ progression' (HR 1.11, 95% CI 1.00 to 1.22, p=0.048) occurred more frequently.

CONCLUSIONS

Our stratified analysis demonstrates that smoking is associated with an increased risk for mortality in male SSc patients but not in women. Strikingly, smoking is associated with lower prevalence of ATA positivity, in particular in women. In both ATA-positive and ACA-positive patients, smoking is a risk factor for mortality, skin progression and 'any organ progression'.

Systemic Sclerosis in Individuals With Exposure to World Trade Center Ground Zero Rescue and Recovery Efforts: A Case Series

OBJECTIVE

The World Trade Center (WTC) attack in New York resulted in a dust plume containing silica, hydrocarbons, and asbestos. Autoimmune disorders have been reported among those with WTC site exposure. The characteristics of individuals developing systemic sclerosis (SSc) have not been previously described. The purpose of this study was to describe the features of patients with SSc with WTC exposure.

METHODS

Data were collected from 11 patients with SSc or SSc spectrum conditions who reported exposure to the WTC site. Seven patients completed an exposure assessment.

RESULTS

Of the 11 patients, the majority (n = 8) were female. The median (range) for age at diagnosis was 46 (36-75) years, time between exposure and first non-Raynaud phenomenon SSc symptom was 8 (1-19) years, and time between exposure and diagnosis was 11 (2-18) years. Fifty-five percent had SSc onset > 5 years from WTC exposure. Five patients had limited cutaneous SSc, 3 patients had diffuse cutaneous SSc, 1 patient with SSc features met criteria for mixed connective tissue disease (CTD), and 2 patients had undifferentiated CTD with features of SSc. Four patients had overlapping features with other CTDs. Interstitial lung disease (ILD) was present in 10 patients. Five of 11 patients had a history of tobacco use. Seven of 7 patients who completed the questionnaire reported other hazardous exposures outside of WTC. Of these, only 2 patients reported personal protective equipment use.

CONCLUSION

A high frequency of ILD and overlap features were observed among patients with SSc with WTC exposure. Future studies are needed to characterize this association.

Autoantibodies Which Bind to and Activate Keratinocytes in Systemic Sclerosis

Systemic sclerosis (SSc) is a multisystem connective tissue disease characterised by pathological processes involving autoimmunity, vasculopathy and resultant extensive skin and organ fibrosis. Recent studies have demonstrated activation and aberrant wound healing responses in the epithelial layer of the skin in this disease, implicating the epithelial keratinocytes as a source of pro-fibrotic and inflammatory mediators. In this paper, we investigated the role of Immunoglobulin G (IgG) autoantibodies directed against epithelial cells, as potential initiators and propagators of pathological keratocyte activation and the ensuing SSc fibrotic cascade. A keratinocyte cell-based ELISA is used to evaluate the binding of SSc IgG. SSc skin biopsies were stained by immunofluorescence for the presence of IgG in the keratinocyte layer. Moreover, IgG purified from SSc sera was evaluated for the potential to activate keratinocytes in tissue culture and to induce TLR2 and 3 signalling in reporter cell lines. We demonstrate enhanced binding of SSc IgG to keratinocytes and the activation of these cells leading to the release of IL-1α, representing a potential initiating pathway in this disease.

Morphea, Eosinophilic Fasciitis and Cancer: A Scoping Review

Morphea is an autoimmune fibrotic skin disease. Eosinophilic fasciitis (EF) is considered to belong to the severe spectrum of morphea. We conducted a scoping review assessing the risk of secondary cancer among morphea/EF patients, paraneoplastic morphea/EF and morphea/EF developing secondary to cancer therapy. The search was conducted using MEDLINE, Embase, Cochrane databases for articles published from inception to September 2022 following the Preferred Reporting Items for Systematic reviews and Meta-Analyses for Scoping Reviews (PRISMA-ScR) guidelines with no language or date restrictions. Two hundred and one studies were included. Of these, 32 studies reported on secondary cancer in morphea/EF patients, 45 on paraneoplastic morphea/EF and 125 on cancer-treatment-induced morphea/EF. While the current evidence remains limited, data suggest an increased risk of secondary cutaneous and possibly pancreatic malignancy in morphea patients, particularly the generalized subtype. There were insufficient data for EF. On the other hand, paraneoplastic morphea was anecdotal, whereas several observational studies suggested that ~10% of EF cases may be paraneoplastic, primarily in the context of hematologic malignancies. Radiotherapy-induced morphea is rare, seen in ~0.2% of treated patients and is usually localized to the treatment site, except in patients with pre-existing autoimmunity. While chemotherapy-induced cases are reported, immunotherapy morphea/EF cases are emerging and are preferentially seen with PD-1 and not CTLA-4 inhibitors. This study is limited by the type of articles included (case reports, case series and observational studies), and hence, additional research on this important topic is needed.

Crystalline silica exposure in patients with rheumatoid arthritis and systemic sclerosis: a nationwide cross-sectional survey

OBJECTIVES

Develop and validate a thorough exposure questionnaire to comprehensively explore crystalline silica (SiO2) exposure in the general population (gender-specific, occupational and non-occupational) and in patients with autoimmune diseases (rheumatoid arthritis (RA), systemic sclerosis (SSc)).

METHODS

Lifetime exposures to SiO2 in occupational and non-occupational settings were assessed using a thorough exposure questionnaire. The questionnaire was applied to a general population panel (n = 2911) sampled from the French rolling census, and to unselected patients with SSc (n = 100) and RA (n = 97). Global (GES), occupational (OES) and non-occupational (NOES) exposure scores were assessed in SSc and RA patients, and compared with up to four controls from the general population, matched by age group, sex and tobacco consumption.

RESULTS

Patients had higher GES than their matched controls (SSc: P = 0.001; RA: P < 0.0001) due to higher OES (P < 0.0001 for SSc and RA). Men had higher GES than women (SSc: P < 0.0001; RA: P = 0.002) due to higher OES (P < 0.0001 for SSc and RA). The NOES did not differ between men and women. In SSc patients: Men had higher GES than controls (P < 0.0001). Men and women with SSc had higher OES than controls (P < 0.0001). In RA patients: GES and OES were higher in both men (P = 0.00521; P < 0.0001) and women (P < 0.0001; P < 0.0001) than in their respective controls. Women had higher NOES than controls (P = 0.045).

CONCLUSION

The lifetime SiO2 exposure gap between RA and SSc patients and controls was substantially due to occupational exposure. In both diseases, men had higher exposure scores than women.

The Role of Sex and Gender in Dermatology - From Pathogenesis to Clinical Implications

BACKGROUND

Sex and gender have increasingly been recognized as significant risk factors for many diseases, including dermatological conditions. Historically, sex and gender have often been grouped together as a single risk factor in the scientific literature. However, both may have a distinct impact on disease incidence, prevalence, clinical presentation, severity, therapeutic response, and associated psychological distress.

OBJECTIVES AND PROJECT DESCRIPTION

The mechanisms that underlie differences in skin diseases between males, females, men, and women remain largely unknown. The specific objectives of this review paper are:To highlight the biological differences between males and females (sex), as well as the sociocultural differences between men and women (gender) and how they impact the integumentary system.To perform a literature review to identify important sex- and gender-related epidemiological and clinical differences for various skin conditions belonging to a range of disease categories and to discuss possible biological and sociocultural factors that could explain the observed differences.To discuss dermatological skin conditions and gender-affirming treatments within the transgender community, a population of individuals who have a gender identity which is different than the gender identity they were assigned at birth.

FUTURE IMPACT

With the rising number of individuals that identify as non-binary or transgender within our increasingly diverse communities, it is imperative to recognize gender identity, gender, and sex as distinct entities. By doing so, clinicians will be able to better risk-stratify their patients and select treatments that are most aligned with their values. To our knowledge, very few studies have separated sex and gender as two distinct risk factors within the dermatology literature. Our article also has the potential to help guide future prevention strategies that are patient-tailored rather than using a universal approach.

Silica-associated lung disease in developing countries

PURPOSE OF REVIEW

There is a considerable burden of silica-associated lung diseases in the developing world. This review summarizes the epidemiology of these diseases, especially silicosis and silico-tuberculosis, mitigative efforts and treatment, especially in the context of developing countries.

RECENT FINDINGS

In 2017, the highest incidence of silicosis was in China, India and Brazil among the developing countries. The prevalence of silicosis amongst exposed workers may vary from 4 to 55%; there is a risk of underestimation because of the 'healthy worker effect'. The permissible exposure limit for respirable silica adopted by governments in developing countries remains higher than the proposed 0.025 mg/m3. Silica exposure in informal or unorganized industries is challenging, as it falls outside statutory controls. Recent efforts on regulation and compensation by various governments in developing countries are encouraging but need proper implementation on the ground. Biomarkers such as club cell protein 16 and imaging methods such as computed tomography may offer earlier and easier detection of silicosis. Advanced silicosis remains incurable; novel treatments such as antifibrotics agents may be potentially effective.

SUMMARY

Silica-associated lung diseases are prevalent in developing countries. Efforts directed at preventing or minimizing exposure to respirable crystalline silica are required for mitigation.

Silica associated systemic sclerosis: an occupational health hazard

A middle-aged male working in the sandblasting and stone-cutting industry was brought to the medicine department with skin tightness, dysphagia and discolouration of the skin for the last 1 year. On examination, he had skin thickening over the face and the extremities with restricted mouth opening. His hands were cold and showed peripheral cyanosis. Systemic examination was suggestive of diffuse cutaneous systemic sclerosis, further confirmed by the antinuclear antibody testing. Further, CT of the chest showed mediastinal lymphadenopathy with eggshell calcification and interstitial fibrosis consistent with silicosis and fibrotic non-specific interstitial pneumonitis. The patient was started on pulse monthly cyclophosphamide for six cycles, and steroids were given for 4 weeks and tapered. Tadalafil and amlodipine were given for his pulmonary artery hypertension and Raynaud's phenomenon, respectively. This case also highlights the importance of periodic screening of the workers exposed to silica dust to prevent silicosis.