Current Concepts on Pathogenic Mechanisms and Histopathology in Cutaneous Lupus Erythematosus

Psoriasis and Lupus Erythematosus-Similarities and Differences between Two Autoimmune Diseases

Systemic lupus erythematosus (SLE) and psoriasis (Ps) are two clinically distinct diseases with different pathogenesis. However, recent studies indicate some similarities in both clinical presentation and pathogenetic mechanisms. The coexistence of both entities is very uncommon and has not been fully elucidated. Thus, it remains a diagnostic and therapeutic challenge. In fact, drugs used in SLE can induce psoriatic lesions, whereas phototherapy effective in Ps is an important factor provoking skin lesions in patients with SLE. The aim of this work is to discuss in detail the common pathogenetic elements and the therapeutic options effective in both diseases.

Oral lupus erythematosus: Immunohistochemical evaluation of CD1a, CD21, CD123, and langerin expression in dendritic cells

BACKGROUND

Dendritic cells participate in the pathophysiology of lupus erythematosus (LE), which are studied in systemic and cutaneous forms; however, little is known about their oral manifestations.

METHODS

The expressions of dendritic cell markers (including CD1a, CD21, CD123, and langerin) were investigated by immunohistochemistry technique. Sixty intraoral and lower lip LE lesions, and additional 10 control samples were collected from 2003 to 2019. They were topographically analyzed in the epithelium (EP), lamina propria (LP), epithelial junction (JUN), and deep perivascular (PV) areas.

RESULTS

The expression of CD1a was decreased in the EP (p = 0.003) and increased in the deep PV area (p = 0.002). Langerin immunostaining showed no significant decrease in EP (p = 0.944); however, it increased in LP (p = 0.012) and JUN (p = 0.006). CD21 was expressed in only two specimens (EP, p = 0.012; LP, p < 0.001; deep PV area, p = 0.018). CD123 expression increased in all topographies (EP, p < 0.005; LP, p < 0.001, JUN, p < 0.001; deep PV, p < 0.001). The comparison between vermilion and intraoral mucosa LE lesions suggested that sun-exposed sites showed higher expression of CD123 (EP, p = 0.024; LP, p = 0.047; JUN, p = 0.001).

CONCLUSIONS

CD1a, langerin, and CD123 expressions were detected coincidently surrounding the inflammatory infiltrate in oral LE, suggesting that these cells may play an important role in immune response. Interestingly, plasmacytoid dendritic cells showed increased CD123 expression in sun-exposed site lesions, which point out a possible function in their pathogenesis. Further studies are needed to confirm this hypothesis.

The Spectrum of Cutaneous Manifestations in Lupus Erythematosus: A Comprehensive Review

Lupus erythematosus (LE) is an autoimmune inflammatory disease with complex etiology. LE may present as a systemic disorder affecting multiple organs or be limited solely to the skin. Cutaneous LE (CLE) manifests with a wide range of skin lesions divided into acute, subacute and chronic subtypes. Despite classic forms of CLE, such as malar rash or discoid LE, little-known variants may occur, for instance hypertrophic LE, chilblain LE and lupus panniculitis. There are also numerous non-specific manifestations including vascular abnormalities, alopecia, pigmentation and nail abnormalities or rheumatoid nodules. Particular cutaneous manifestations correlate with disease activity and thus have great diagnostic value. However, diversity of the clinical picture and resemblance to certain entities delay making an accurate diagnosis The aim of this review is to discuss the variety of cutaneous manifestations and indicate the clinical features of particular CLE types which facilitate differential diagnosis with other dermatoses. Although in diagnostically difficult cases histopathological examination plays a key role in the differential diagnosis of LE, quick and accurate diagnosis ensures adequate therapy implementation and high quality of life for patients. Cooperation between physicians of various specialties is therefore crucial in the management of patients with uncommon and photosensitive skin lesions.

Nano-encapsulated anandamide reduces inflammatory cytokines in vitro and lesion severity in a murine model of cutaneous lupus erythematosus

Cutaneous lupus erythematosus (CLE) is a heterogeneous autoimmune skin disease which occurs independently and in conjunction with systemic lupus erythematosus. Drug development for CLE is severely lacking. Anandamide (AEA) is a primary endocannabinoid which exhibits immunomodulatory effects through mixed cannabinoid receptor agonism. We evaluated AEA as topical treatment for CLE and assessed benefits of nanoparticle encapsulation (AEA-NP) on cutaneous drug penetration, delivery and biological activity. Compared to untreated controls, AEA-NP decreased IL-6 and MCP-1 in UVB-stimulated keratinocytes (p < 0.05) in vitro. In BALB/c mice, AEA-NP displayed improved cutaneous penetration, extended release and persistence of AEA in the follicular unit extending to the base after 24 h. Utilizing the MRL-lpr lupus murine model, twice weekly treatment of lesions with topical AEA-NP for 10 weeks led to decreased clinical and histologic lesion scores compared to unencapsulated AEA and untreated controls (p < 0.05). Prophylactic application of AEA-NP to commonly involved areas on MRL-lpr mice similarly resulted in decreased clinical and histologic scores when compared to controls (p < 0.05), and reduced C3 and IBA-1 in lesional tissue (p < 0.05). The demonstrated clinical and immunomodulatory effects of treatment with AEA support its potential as therapy for CLE. This work also suggests that encapsulation of AEA improves penetration and treatment efficacy. Future studies will be conducted to assess full therapeutic potential.

The differential panorama of clinical features of lupus erythematosus patients with different onset ages: a cross-sectional multicenter study from China

OBJECTIVES

This study aims to compare the differences among patients of different onset ages in various subtypes of lupus erythematosus (LE) and to draw a panorama of the clinical characteristics of patients with different onset ages.

METHOD

Subjects were recruited from the Lupus Erythematosus Multicenter Case-control Study in Chinese populations (LEMCSC), grouped by the age of onset (childhood-onset: onset < 18 years, adult-onset: onset 18-50 years, late-onset: onset > 50 years). The data collected included demographic characteristics, LE-related systemic involvement, LE-related mucocutaneous manifestations, and laboratory results. All included patients were assigned into three groups: systemic LE (SLE) group (with systemic involvement, with or without mucocutaneous lesions), cutaneous LE (CLE) group (patients who were accompanied by any type of LE-specific cutaneous manifestations), and isolated cutaneous LE (iCLE) group (patients who were in CLE group without systemic involvements). Data were analyzed using R version 4.0.3.

RESULTS

A total of 2097 patients were involved, including 1865 with SLE and 232 with iCLE. We also identified 1648 patients with CLE among them, as there was some overlap between the SLE population and CLE population (patients with SLE and LE-specific cutaneous manifestations). Later-onset lupus patients seemed to be less female predominance (p < 0.001) and have less systemic involvement (except arthritis), lower positive rates of autoimmune antibodies, less ACLE, and more DLE. Moreover, childhood-onset SLE patients presented a higher risk of LE family history (p = 0.002, vs adult-onset SLE). In contrast to other LE-nonspecific manifestations, the self-reported photosensitivity history decreased with the age of onset in SLE patients (51.8%, 43.4%, and 39.1%, respectively) but increased in iCLE patients (42.4%, 64.9%, and 89.2%, respectively). There was also a gradual increase in self-reported photosensitivity from SLE, CLE, to iCLE in both adult-onset and late-onset lupus patients.

CONCLUSIONS

A negative correlation was suggested between the age of onset and the likelihood of systemic involvement, except for arthritis. As the age of onset increases, patients have a greater propensity to exhibit DLE compared to ACLE. Moreover, the presence of rapid response photodermatitis (i.e., self-reported photosensitivity) was associated with a lower rate of systemic involvement.

TRIAL REGISTRATION

This study was registered with the Chinese Clinical Trial Registry (registration number: ChiCTR2100048939) on July 19, 2021, retrospectively registered. Key Points • We confirmed some phenomena that have been found in patients with SLE, such as the highest proportion of females of reproductive age, the higher risk of LE family history in childhood-onset SLE patients, and the less self-reported photosensitivity in the late-onset SLE group. We also compared the similarities and differences of these phenomena in patients with CLE or iCLE for the first time. • In patients with SLE, the proportion of females peaked in adult-onset patients, but this phenomenon disappeared in iCLE patients: the female-male ratio tends to decrease from childhood-onset iCLE, adult-onset iCLE, to late-onset iCLE. • Patients with early-onset lupus are more likely to have acute cutaneous lupus erythematosus (ACLE), and patients with late-onset lupus are more likely to have discoid lupus erythematosus (DLE). • In contrast to other LE-nonspecific manifestations, the incidence of rapid response photodermatitis (i.e., self-reported photosensitivity) decreased with the age of onset in SLE patients but increased with the age of onset in iCLE patients.

Cutaneous lupus erythematosus is associated with an increased risk of cardiac and vascular diseases: a large-scale, propensity-matched global retrospective cohort study

BACKGROUND

Autoimmune skin diseases can expedite various systemic sequelae involving other organs. Although limited to the skin, cutaneous lupus erythematosus (CLE) was noted to be associated with thromboembolic diseases. However, small cohort sizes, partially discrepant outcomes, missing data on CLE subtypes, and incomplete risk assessment limits these findings.

METHODS

The Global Collaborative Network of TriNetX provides access to medical records of more than 120 million patients worldwide. We used TriNetX to elucidate the risk for cardiac and vascular diseases after diagnosis of CLE, and its subtypes chronic discoid (DLE) and subacute cutaneous lupus erythematosus (SCLE). We included 30,315 CLE, 27,427 DLE, and 1613 SCLE patients. We performed propensity-matched cohort studies determining the risk to develop cardiac and vascular diseases (ICD10CM:I00-99) following diagnosis of CLE, DLE, or SCLE. Patients with systemic lupus erythematosus were excluded.

FINDINGS

We document that CLE and its subtype DLE but less so SCLE are associated with a higher risk for various cardiac and vascular diseases. This included predominantly thromboembolic events such as pulmonary embolism, cerebral infarction, and acute myocardial infarction, but also peripheral vascular disease and pericarditis. For example, the hazard ratio of arterial embolism and thrombosis was 1.399 (confidence interval: 1.230-1.591, p < 0.0001) following CLE diagnosis. The study is limited by retrospective data collection and reliance on ICD10-disease classification.

INTERPRETATION

CLE and its major subtype DLE are associated with an increased risk for the development of a wide range of cardiac and vascular diseases.

FUNDING

This research was funded by Deutsche Forschungsgemeinschaft (EXC 2167, CSSL/CS01-2022) and the Excellence-Chair Program of the State of Schleswig-Holstein.

Aberrant inflammasome activation as a driving force of human autoimmune skin disease

Autoimmune skin diseases are understood as conditions in which the adaptive immune system with autoantigen-specific T cells and autoantibody-producing B cells reacting against self-tissues plays a crucial pathogenic role. However, there is increasing evidence that inflammasomes, which are large multiprotein complexes that were first described 20 years ago, contribute to autoimmune disease progression. The inflammasome and its contribution to the bioactivation of interleukins IL-1β and IL-18 play an essential role in combating foreign pathogens or tissue damage, but may also act as a pathogenic driver of myriad chronic inflammatory diseases when dysfunctionally regulated. Inflammasomes containing the NOD-like receptor family members NLRP1 and NLRP3 as well as the AIM2-like receptor family member AIM2 have been increasingly investigated in inflammatory skin conditions. In addition to autoinflammatory diseases, which are often associated with skin involvement, the aberrant activation of the inflammasome has also been implied in autoimmune diseases that can either affect the skin besides other organs such as systemic lupus erythematosus and systemic sclerosis or are isolated to the skin in humans. The latter include, among others, the T-cell mediated disorders vitiligo, alopecia areata, lichen planus and cutaneous lupus erythematosus as well as the autoantibody-driven blistering skin disease bullous pemphigoid. Some diseases are characterized by both autoinflammatory and autoimmune responses such as the chronic inflammatory skin disease psoriasis. Further insights into inflammasome dysregulation and associated pathways as well as their role in forming adaptive immune responses in human autoimmune skin pathology could potentially offer a new field of therapeutic options in the future.

Cutaneous Lupus Erythematosus: An Update on Pathogenesis and Future Therapeutic Directions

Lupus erythematosus comprises a spectrum of autoimmune diseases that may affect various organs (systemic lupus erythematosus [SLE]) or the skin only (cutaneous lupus erythematosus [CLE]). Typical combinations of clinical, histological and serological findings define clinical subtypes of CLE, yet there is high interindividual variation. Skin lesions arise in the course of triggers such as ultraviolet (UV) light exposure, smoking or drugs; keratinocytes, cytotoxic T cells and plasmacytoid dendritic cells (pDCs) establish a self-perpetuating interplay between the innate and adaptive immune system that is pivotal for the pathogenesis of CLE. Therefore, treatment relies on avoidance of triggers and UV protection, topical therapies (glucocorticosteroids, calcineurin inhibitors) and rather unspecific immunosuppressive or immunomodulatory drugs. Yet, the advent of licensed targeted therapies for SLE might also open new perspectives in the management of CLE. The heterogeneity of CLE might be attributable to individual variables and we speculate that the prevailing inflammatory signature defined by either T cells, B cells, pDCs, a strong lesional type I interferon (IFN) response, or combinations of the above might be suitable to predict therapeutic response to targeted treatment. Therefore, pretherapeutic histological assessment of the inflammatory infiltrate could stratify patients with refractory CLE for T-cell-directed therapies (e.g. dapirolizumab pegol), B-cell-directed therapies (e.g. belimumab), pDC-directed therapies (e.g. litifilimab) or IFN-directed therapies (e.g. anifrolumab). Moreover, Janus kinase (JAK) and spleen tyrosine kinase (SYK) inhibitors might broaden the therapeutic armamentarium in the near future. A close interdisciplinary exchange with rheumatologists and nephrologists is mandatory for optimal treatment of lupus patients to define the best therapeutic strategy.

Characterization of B cells in lupus erythematosus skin biopsies in the context of different immune cell infiltration patterns

Cutaneous lesions in lupus erythematosus (LE) subtypes are heterogenous. In line with the heterogeneity of the clinical presentation, the underlying lesional inflammation in LE skin samples is defined by different immune cell infiltrates. Pathophysiologically, lesional inflammation is driven by autoreactive cytotoxic T cells, targeting keratinocytes; plasmacytoid dendritic cells (pDCs), producing large amounts of interferon (IFN); and B cells, whose function in cutaneous LE is still unclear. This study aims to (a) classify inflammatory patterns with regard to the dominating cell type or cytokine expression and (b) investigating the specific role of B cells in LE skin lesions. Therefore, the immunohistological expression of inflammatory surrogates (CD20, CD123, MXA) in skin samples of n = 119 LE (subtypes: subacute cutaneous LE, chronic discoid LE, chilblain LE, LE tumidus, other LE) and n = 17 patients with inflammatory skin diseases (atopic dermatitis, psoriasis) were assessed. Samples were classified with regard to inflammatory groups. In addition multiplex-immunohistochemical analyses of n = 17 LE skin samples focusing on lesional B cells were conducted. In this study, we show that cutaneous lesions present with eight different inflammatory groups dominated by B cells, pDCs, a strong IFN expression, or overlapping patterns. Altogether, LE subtypes show heterogenous infiltration regardless of LE subtype, certain subtypes display a preference for infiltration groups. Furthermore, lesional B cells either form diffuse infiltrates or pseudofollicular structures, wherein they show antigen-presenting and T cell-activating properties. Altogether, in the light of emerging targeted therapeutic options, we suggest histological assessment in regard to B-cell or pDC preponderance to allow tailored treatment decisions.