The need to revisit the nosology of cutaneous lupus erythematosus

Clinical aspects of cutaneous lupus erythematosus

Lupus erythematosus (LE) is an autoimmune inflammatory disease with a wide clinical spectrum from life-threatening multi-organ inflammation in systemic lupus erythematosus (SLE) to limited skin disease in cutaneous LE (CLE). The etiology of CLE is still not fully understood but a multifactorial genesis with genetic predisposition and certain environmental factors as triggers for the development are generally accepted features. Lesions can be induced and aggravated by UV-irradiation and smoking is linked to more severe forms of skin disease and to co-morbidity. Drugs, including many common medicines like antihypertensives, are known to induce subacute CLE (SCLE). The mechanisms involved have recently been shown to be part of the IFN-I pathway and new, specific treatments are currently in clinical trials. CLE is currently classified in subtypes based on clinical presentation and duration into acute CLE (ACLE), SCLE, and chronic CLE (CCLE). Distinct subtypes can be seen in individual patients or coexist within the same patient. Because of the confluent and overlapping picture between these subsets, serology, and histopathology constitute an important role guiding towards correct diagnose and there is ongoing work to update the classification. The Cutaneous Lupus Area Severity Index (CLASI) is a validated tool to measure activity and damage both in clinical trials but also for the clinician to evaluate treatment and follow the course of the disease among patients. CLE is known to have substantial impact on the life of those affected. Several tools have been proposed to measure QoL in these patients, currently Skindex-29 is probably the most used. Patient education is an important part of prevention of flares, including UV-protection and smoking cessation. First-line treatment includes topical corticosteroids as well as topical calcineurin inhibitors with the addition of systemic treatment with antimalarials in more severe or therapy resistant cases. Treatment specifically targeting CLE has been lacking, however novel potential therapies are in later phase clinical trials. In this review we aim to describe the different subsets of the cutaneous form in LE with focus on clinical aspects.

Modulation of Immune Cells as a Therapy for Cutaneous Lupus Erythematosus

Cutaneous lupus erythematosus (CLE) is an autoimmune disorder like systemic lupus erythematosus (SLE). Both SLE and CLE characterize autoantibody secretion and immune cell recruitment. In particular, CLE can be divided into three more frequent types, varying in the severity of the skin lesions they present. The role of type I IFN was shown to be one of the leading causes of the development of this pathology in the skin. Different treatments have been developed and tested against these different variants of CLE to decrease the increasing levels of CLE in humans. In this article, a literature revision discussing the similarities between SLE and CLE is carried out. In addition, new advances in understanding the development of CLE and the leading treatments being evaluated in animal models and clinical trials are reviewed.

Current Concepts on Pathogenic Mechanisms and Histopathology in Cutaneous Lupus Erythematosus

Cutaneous lupus erythematosus (CLE) is an interferon (IFN)-driven autoimmune disease that may be limited to the skin or can be associated with systemic lupus erythematosus (SLE). CLE occurs in several morphologic subtypes ranging from isolated, disc-shaped plaques to disseminated skin lesions. The typical histopathologic pattern of skin lesions is named interface dermatitis and characterized by a lymphocytic infiltrate and necroptotic keratinocytes at the dermo-epidermal junction. Other histopathologic patterns primarily involve the dermis or subcutis, depending on the subtype. One critical mechanism in CLE is the chronic reactivation of innate and adaptive immune pathways. An important step in this process is the recognition of endogenous nucleic acids released from dying cells by various pattern recognition receptors (PRRs), including Toll-like receptors (TLRs) and other cytosolic receptors. Crucial cells in CLE pathogenesis comprise plasmacytoid dendritic cells (pDCs) as major producers of type I IFN, T cells exerting cytotoxic effects, and B cells, previously believed to contribute via secretion of autoantibodies. However, B cells are increasingly considered to have additional functions, supported by studies finding them to occur in highest numbers in chronic discoid lupus erythematosus (CDLE), a subtype in which autoantibodies are often absent. More precise knowledge of how CLE subtypes differ pathophysiologically may allow a tailored pharmacotherapy in the future, taking into account the specific molecular signature in relation to the morphologic subtype.

Prevalence and factors associated with long-term remission in cutaneous lupus: a longitudinal cohort study of 141 cases

BACKGROUND

Little is known about the prevalence and factors associated with long-term remission in cutaneous lupus erythematosus (CLE).

OBJECTIVES

To assess the prevalence, the factors associated with remission and long-term remission with and without treatment during CLE.

METHODS

Longitudinal cohort study including biopsy proven CLE patients seen between November 1st, 2019, and April 30th, 2021, with at least 6 months of follow-up after diagnosis. Demographic data, CLE subtypes, remission status and treatments were recorded. Remission was defined by a Cutaneous LE Disease Area and Severity Index activity (CLASI-A) score of 0. Long-term remission was defined by remission > 3 years.

RESULTS

Among 141 patients included (81% of women), 93 (66%) were in remission at last follow-up with a median duration since diagnosis of 11.4 years (IQR 4.2-24.7). Long-term remission was observed in 22 (19%) of 114 patients with at least 3 years of follow-up, including 5 (4.4%) with no systemic treatment. Active smoking (OR: 0.22 [95%CI: 0.05-0.97], p=0.04) and DLE lesions (OR: 0.14 [95%CI: 0.04-0.48], p=0.004) were associated with a lower risk of long-term remission.

LIMITATIONS

Partial retrospective data collection and tertiary center population.

CONCLUSION

Long-term remission is rare in CLE and negatively associated with active smoking and DLE.

Lupus erythematosus: correlation of clinical and histological findings and proposal for a modified disease classification

BACKGROUND

Classification of lupus erythematosus (LE) is conflicting as it is carried out from different starting points. Whereas dermatological classifications categorize LE morphologically based on specific cutaneous lesions, rheumatologic classifications are based on symptomatic aspects. Indeed, LE is a systemic autoimmune disease with variable acuity and organ involvement. All cutaneous disease patterns may occur in both limited-cutaneous and systemic LE.

PATIENTS AND METHODS

76 LE-patients with complete clinical data, clinical photographs and biopsy of cutaneous manifestations as well as paraclinical findings were retrospectively analyzed. Based on a published two-dimensional classification system that considers disease-specific skin manifestations and final disease diagnosis separately, patients' diagnoses were revised and compared with those in medical records. In addition, the extent to which patients could be clustered by diagnosis based on their LE-specific skin manifestations, corresponding histopathological changes, and paraclinical data was investigated.

RESULTS

After re-evaluation, the proportion of patients with limited-cutaneous LE decreased from 82% previously to 24%. More than two-thirds of patients indeed showed intermediate or systemic LE. Disease-specific skin manifestations, histologic characteristics and paraclinical data did not cluster with final diagnoses.

CONCLUSIONS

First, the work underlines the systemic character of the disease. Second, a two-dimensional approach can help overcome classification difficulties in LE, as skin-morphologic and symptomatic aspects can be considered separately.

Cutaneous manifestations of lupus erythematosus: A practical clinicopathologic review for pathologists

Accurate diagnosis of connective tissue diseases is often challenging and relies on careful correlation between clinical and histopathologic features, direct immunofluorescence studies, and laboratory workup. Lupus erythematosus (LE) is a prototype of connective tissue disease with a variety of cutaneous and systemic manifestations. Microscopically, cutaneous LE is classically characterized by an interface dermatitis, although other histopathologic patterns also exist depending on the clinical presentation, location, and chronicity of the skin lesions. In this article, we review the clinical, serologic, histopathologic, and direct immunofluorescence findings in LE-specific and LE-nonspecific skin lesions, with an emphasis on lesser known variants, newly described features, and helpful ancillary studies. This review will guide general pathologists and dermatopathologists in accurately diagnosing and subclassifying cutaneous LE.

Lupus erythematosus: Significance of dermatologic findings

Herein, the different skin manifestations in patients with lupus erythematosus are reviewed, and their diagnostic, pathogenic and prognostic relevance are discussed, as well as their impact on therapeutic choices. The so-called specific lesions of LE result from an autoimmune pathomechanism and they allow diagnosis of LE by simple clinicopathological correlation since the findings are characteristic. They include the classic acute, subacute and chronic variants, characterised microscopically by interface dermatitis; the dermal variants of lupus, such as tumid lupus, displaying dermal perivascular lymphocytic infiltrate with mucin deposition under the microscope, and lupus profundus, in which lymphocytic lobular panniculitis progressing to hyaline fibrosis is found. Antimalarials are the treatment of choice for patients with specific LE lesions. The presence of some dermatological signs is the result of thrombotic vasculopathy. Their recognition allows the identification of lupus patients at increased cardiovascular risk and with a worse overall prognosis. Those signs include reticulated erythema on the tip of the toes, splinter hemorrhages, atrophie blanche, pseudo-Degos lesions, racemosa-type livedo, anetoderma, ulceration and necrosis. Those clinical manifestations, often subtle, must be recognised, and if present, patients should be treated with antiplatelet drugs. Finally, neutrophilic cutaneous lupus erythematosus includes a few entities that suggest that autoinflammatory mechanisms might play a key role in certain lupus manifestations. Among those entities, it is very important to diagnose neutrophilic urticarial dermatosis, which can mimic a classic lupus flare, because it is characterised by rash with joint pain, but immunosuppressants are not helpful. Dapsone is the treatment of choice.

[Ungual lesions in lupus erythematosus: A retrospective study of 14 patients]

INTRODUCTION

There are few studies focusing on ungual lesions in patients with lupus erythematosus (LE). The aim of this study is to describe our experience with ungual lesions in LE patients.

MATERIALS AND METHODS

A multicentric retrospective descriptive study was performed at the dermatology departments of the university hospitals in Strasbourg and at the Tenon hospital in Paris and involved reviewing the medical records and photographs of patients with ungual lesions.

RESULTS

Fourteen patients were included: 12 (86 %) were women with a median age of 38 years (28-78 years). All patients had cutaneous LE presenting as follows: 3 isolated forms (21 %), and associated with systemic LE (LES) for remaining 11 patients (79 %). The most frequent ungual or peri-ungual lesions were longitudinal ridging (12 patients, 86 %), onycholysis and cuticular alterations (8 patients each, 57 %), pterygium (7 patients, 50 %), melanonychia, onychoschizia and subungual hyperkeratosis (5 patients with each, 36 %). Among patients with pterygium and onychoschizia, respectively 6 (86 %) and 5 (100 %) presented the discoid LE subtype, while respectively 6 (86 %) and 4 (80 %) had multisystemic involvement.

DISCUSSION

Ungual lesions do not appear specific and do not in themselves allow diagnosis of LE. They can in fact occur in other diseases such as connective tissue disorders. However, their diagnosis is important because certain of them, such as pterygium, can lead to severe ungual dystrophia, with functional consequences. In our study, pterygium and onychoschizia appeared to be associated with cutaneous discoid lupus erythematosus and multisystemic involvement. The coexistence of peri-ungual lesions related to cutaneous lupus erythematosus and/or multisystemic involvement does not out differentiation of lupus ungual lesions and post-inflammatory lesions.

Cutaneous lupus erythematosus: factors related to cutaneous activity and damage in a cohort of 260 patients from A Coruña, Spain

Background

Cutaneous lupus erythematosus is a chronic autoimmune disease that can leave important sequelae.

Objective

To determine the factors that predict the activity and damage of the skin disease, and the impact of tobacco on the efficacy of antimalarials using the Cutaneous Lupus Erythematosus Disease Area and Severity Index.

Materials and Methods

A consecutive case series was performed on 260 patients with cutaneous lupus erythematosus (α = 0.05; precision ± 6.5%). We carried out a descriptive analysis of the variables included, with a multivariate analysis to measure the association of variables with the Cutaneous Lupus Erythematosus Disease Area and Severity Index activity and damage ( p value < 0.05).

Results

The Cutaneous Lupus Erythematosus Disease Area and Severity Index activity was greater in smokers than non-smokers (4.0 ±5.3 vs 1.2 ±3.4, p = 0.006). No significant differences were observed in the Cutaneous Lupus Erythematosus Disease Area and Severity Index activity when the efficacy of antimalarials was analyzed between smokers and non-smokers. Cutaneous Lupus Erythematosus Disease Area and Severity Index damage was higher in smokers than in non-smokers (2.0 ± 3.6 vs 1.2 ± 2.6, p = 0.029). Cutaneous Lupus Erythematosus Disease Area and Severity Index activity was associated with: (a) being an active smoker (odds ratio 3.04, 95% confidence interval 1.68–5.51, p < 0.001; regression coefficient 2.05, 95% confidence interval 0.69–3.42, p = 0.003); (b) the chronic cutaneous lupus erythematosus subtype (odds ratio 1.98, 95% confidence interval 1.02–3.84, p = 0.044); and (c) C-reactive protein increase (≥0.5 mg/dL) (regression coefficient 2.56, 95% confidence interval 0.40–4.71, p = 0.020). Cutaneous Lupus Erythematosus Disease Area and Severity Index damage was associated with: (a) the activity (regression coefficient 0.11, 95% confidence interval 0.01–0.20, p = 0.024); (b) the chronic cutaneous lupus erythematosus subtype (regression coefficient 2.46, 95% confidence interval 1.37–3.56, p < 0.001); (c) the use of topical treatment (regression coefficient 1.31, 95% confidence interval 0.01–2.61, p = 0.049); and (d) systemic treatment (regression coefficient 1.44, 95% confidence interval 0.35–2.53, p < 0.010).

Conclusion

Smoking is related to an increase risk and a greater activity of cutaneous lupus erythematosus. The chronic cutaneous lupus erythematosus subtype and an increased C-reactive protein level were also associated with a higher disease activity. The sequelae were related to the activity, the chronic cutaneous lupus erythematosus subtype, and the use of topical and systemic treatment. The impact of tobacco on the efficacy of antimalarials may be caused by an increase in the severity of the disease more than by resistance in smokers.

Cutaneous lupus erythematosus: new insights into pathogenesis and therapeutic strategies

Cutaneous lupus erythematosus (CLE) is an autoimmune disease that can present as an isolated skin disease or as a manifestation within the spectrum of systemic lupus erythematosus. The clinical spectrum of CLE is broad, ranging from isolated discoid plaques to widespread skin lesions. Histologically, skin lesions present as interface dermatitis (inflammation of the skin mediated by anti-epidermal responses), which is orchestrated by type I and type III interferon-regulated cytokines and chemokines. Both innate and adaptive immune pathways are strongly activated in the formation of skin lesions owing to continuous re-activation of innate pathways via pattern recognition receptors (PRRs). These insights into the molecular pathogenesis of skin lesions in CLE have improved our understanding of the mechanisms underlying established therapies and have triggered the development of targeted treatment strategies that focus on immune cells (for example, B cells, T cells or plasmacytoid dendritic cells), as well as immune response pathways (for example, PRR signalling, Janus kinase (JAK)-signal transducer and activator of transcription (STAT) signalling and nuclear factor-κB signalling) and their cytokines and chemokines (for example, type I interferons, CXC-chemokine ligand 10 (CXCL10), IL-6 and IL-12).

Heterogeneous lupus-specific lesions and treatment outcome, in a single patient, over a period of time

The report highlights the importance of strict clinico-histological correlations when skin biopsies are performed in diagnostic doubt in systemic lupus erythematosus. Furthermore, PUVA is never indicated in autoimmune conditions involving photosensitivity, due to high potential for internal and cutaneous aggravation of the disease, as the authors observed in this case.

The Cutaneous Spectrum of Lupus Erythematosus

Systemic lupus erythematosus is a complex autoimmune disease with a wide spectrum of clinical and immunopathological features. Cutaneous and articular manifestations are the most common signs in patients with systemic lupus erythematosus. We here review the pathogenesis and the new classification of cutaneous lupus erythemathosus with a discussion of the significance of the various cutaneous signs. The lesions are classified according to the level of the cellular infiltrate and tissue damage in the epidermis, dermis, and/or subcutis. Furthermore, cutaneous lesions pointing to the presence of a thrombotic vasculopathy and those due to a distinct inflammatory, neutrophilic-mediated reaction pattern are highlighted. Particular attention will be given in describing the histology of skin manifestation. Treatment options for cutaneous lupus erythemathosus have increased with the introduction of new biological therapies. However, the majority of the patients still benefit from antimalarials, which remain the cornerstone of treatment. The evaluation and management of cutaneous lupus erythemathosus patients depend on the clinical findings and associated symptoms.

[Cell-mediated immunity: Lupus and connective tissue diseases]

Lupus can present itself in a multitude of clinical and histopathological manifestations. Cutaneous lesions can be very variable either from the clinical point of view or at the microscopic scale. Signs can be specific, concerning the dermo-epidermal stage, the dermal stage or the hypodermal stage. Conversely, some manifestations can be not specific but associated to the lupus. Finally, the question of the differential diagnosis can be tricky and often requires a beam of clinical, biological and histopathological arguments.

[Cutaneous panniculitis]

Panniculitis is an inflammation of the subcutaneous fat. Skin biopsy plays a critical role in the differential diagnosis of panniculitis. The most common approach to diagnosis relies on the differentiation between predominantly septal or lobular panniculitis, followed by the distinction between lesions with and without vasculitis. It is also very important to submit a part of the skin biopsy for microbiological analysis and for T-cell clonal expansion if T-cell lymphoma is suspected. Erythema nodosum, the most frequent septal panniculitis, has many causes and in its typical clinical presentation, does not require skin biopsy. In other panniculitis, diagnosis is based on the integration of the clinical and histological data, which renders a deep cutaneous biopsy necessary. Periarteritis nodosa, a septal panniculitis with vasculitis characterized by subcutaneous nodules and livedo racemosa, can be associated with systemic involvement. Nodular thrombophlebitis needs search for associated coagulopathy, Behçet's disease, periarteritis nodosa or Buerger's disease. Lobular panniculitis are classified according to the nature of cells present in the inflammatory infiltrate. If there is a lymphocytic infiltration, lupus panniculitis is difficult to differentiate from subcutaneous panniculitis-like T-cell lymphoma. If there are histiocytes, it can be a sarcoidosis, a cytophagic histiocytic panniculitis or, in newborn, a subcutaneous fat necrosis. Neutrophilic panniculitis needs careful clinic-pathologic correlation. Treatment of panniculitis can be challenging and is based on the histopathological findings. Frequently, the precise cause of panniculitis cannot be established from the outset, so it is important to follow-up patients and not hesitate to repeat the skin biopsy.

A study of the influence of ethnicity on serology and clinical features in lupus

OBJECTIVE

The objective of this study was to review the links between ethnicity, serology and clinical expression in systemic lupus erythematosus (SLE) in a single cohort that was followed over a 36-year period.

PATIENTS AND METHODS

Patients with SLE treated at the University College London Hospitals (UCLHs) between January 1978 and December 2013 formed the cohort. We assessed the demographic, clinical and serological data. Standard methods were used for laboratory testing. The Student t test and Mann-Whitney U test were used for the continuous variables; the Fisher's exact test was used for the categorical variables.

RESULTS

We studied 624 SLE patients: There were 571 women (91.5%), with a mean age at diagnosis of 29.0 ± 6.5 years; and 53 men (8.5%), with a mean age at diagnosis of 29.4 ± 15.3 years. Ethnically, 369 of the patients were European, 100 were Afro-Caribbean, 77 were East Asian, 56 were South Asian and 21 were of mixed ethnicity. The East Asian patients developed the disease at a younger age than the other ethnic groups (p < 0.0001). The Afro-Caribbean patients were less frequently associated with the presence of rash and photosensitivity, and the non-European patients were more likely to have alopecia and renal involvement. The South Asian patients were significantly associated with musculoskeletal and neurological involvement, serositis, Sicca syndrome and hematological features. The Afro-Caribbean patients had the highest prevalence of anti-Smith, anti-RNP, anti-Ro and anti-La antibodies. Anti-IgG anticardiolipin (aCL) antibodies were significantly associated with the non-East Asian groups; and hypocomplementemia was common in the East Asians. Rash, alopecia, mouth ulcers, serositis, neurological, joint and renal involvement were significantly associated with the presence of anti-Smith and anti-RNP antibodies in the Afro-Caribbean group. We also observed an association of joint involvement and the presence of anti-Ro and anti-La antibodies in this group.

CONCLUSIONS

The East Asian patients developed their SLE disease at a younger age than the other ethnic groups. Cutaneous involvement was more frequent in those who were not Afro-Caribbean. Serositis, joint and neurological involvement were more frequently diagnosed in the South Asian patients. Anti-ENA antibodies were frequently associated with the Afro-Caribbean patients.

Lupus erythematosus and neutrophilic urticarial dermatosis: a retrospective study of 7 patients

Neutrophilic urticarial dermatosis (NUD) resembles urticaria clinically but is a neutrophilic dermatosis histopathologically. The majority of patients with NUD have an underlying systemic condition, mainly, autoinflammatory disorders such as cryopyrin-associated periodic syndromes, Schnitzler syndrome, and adult-onset Still disease, but a few also have systemic lupus erythematosus (LE). Here, we confirm these data and we report relevant clinical and histopathological data of 7 patients with LE and NUD. We retrospectively retrieved the medical records of all patients with LE in whom skin biopsy showed NUD in registers of Strasbourg and Montpellier University hospitals since 2000. All were female and aged between 13 and 45 years. Skin lesions were typically rose or red macules or slightly elevated papules occurring in a wide distribution. Individual lesions resolved within 24 hours and were not or only slightly itchy. Every patient had associated signs, most of the time polyarthritis and/or fever. NUD was the presenting mode of LE in 2 patients. NUD was misdiagnosed as a classic lupus flare and led to therapeutic intensification with the introduction of immunosuppressive drugs in 4 patients. Histopathological findings consisted of intense neutrophilic interstitial and perivascular infiltrate with leukocytoclasia and without fibrinoid necrosis of vessel walls. Direct immunofluorescence testing showed a lupus band in 4 patients. Antinuclear antibodies were always positive, anti-dsDNA antibodies were positive in 5 patients, and anti-Ro/SSA antibodies in 6 patients. Immunosuppressive drugs such as prednisone, hydroxychloroquine, mycophenolate mofetil, and methotrexate were never effective to treat NUD. Antihistamines were effective in 1 patient and dapsone or colchicine was effective in 5 patients. NUD is not exceptional in patients with systemic LE and is easily misdiagnosed as an acute LE flare. Furthermore, we show that conventional immunosuppressive LE treatments are not efficient and we underline the major interest of dapsone and colchicine, classic neutrophil migration inhibitors, in those patients.

Neutrophilic skin lesions in autoimmune connective tissue diseases: nine cases and a literature review

The pathophysiology of neutrophilic dermatoses (NDs) and autoimmune connective tissue diseases (AICTDs) is incompletely understood. The association between NDs and AICTDs is rare; recently, however, a distinctive subset of cutaneous lupus erythematosus (LE, the prototypical AICTD) with neutrophilic histological features has been proposed to be included in the spectrum of lupus. The aim of our study was to test the validity of such a classification. We conducted a monocentric retrospective study of 7028 AICTDs patients. Among these 7028 patients, a skin biopsy was performed in 932 cases with mainly neutrophilic infiltrate on histology in 9 cases. Combining our 9 cases and an exhaustive literature review, pyoderma gangrenosum, Sweet syndrome (n = 49), Sweet-like ND (n = 13), neutrophilic urticarial dermatosis (n = 6), palisaded neutrophilic granulomatous dermatitis (n = 12), and histiocytoid neutrophilic dermatitis (n = 2) were likely to occur both in AICTDs and autoinflammatory diseases. Other NDs were specifically encountered in AICTDs: bullous LE (n = 71), amicrobial pustulosis of the folds (n = 28), autoimmunity-related ND (n = 24), ND resembling erythema gyratum repens (n = 1), and neutrophilic annular erythema (n = 1). The improvement of AICTDS neutrophilic lesions under neutrophil targeting therapy suggests possible common physiopathological pathways between NDs and AICTDs.

Photoprovocation in cutaneous lupus erythematosus: a multicenter study evaluating a standardized protocol

Photosensitivity is an important and distinguishing sign in various subtypes of cutaneous lupus erythematosus (CLE); however, it remains poorly defined. The purpose of this study was to evaluate whether standardized photoprovocation is a reproducible method to assess photosensitivity in subjects with CLE. A total of 47 subjects with CLE (subacute cutaneous lupus erythematosus (SCLE), n=14; discoid lupus erythematosus (DLE), n=20; lupus erythematosus tumidus (LET), n=13) and 13 healthy volunteers underwent photoprovocation at seven European sites. Of these, 22 (47%) subjects (57% SCLE, 35% DLE, and 54% LET) and none of the healthy volunteers developed photoprovoked lesions according to clinical analysis. Of these 22 subjects, 19 (86%) developed lesions that were histopathologically confirmed as specific for lupus erythematosus (LE). In CLE subjects who developed UV-induced lesions, 86% had Fitzpatrick's phototypes I or II, and the mean minimal erythema dose (MED) was significantly lower compared with subjects without UV-induced lesions (P=0.004). No significant differences in photoprovocation results were observed between study sites. Safety parameters showed no clinically meaningful differences between CLE subjects and healthy volunteers after photoprovocation. In conclusion, a standardized, safe, and reproducible protocol for photoprovocation using UVA and UVB radiation induced skin lesions in approximately half of all CLE subjects and showed comparable results across multiple sites. This method may therefore be used for future diagnostic testing and clinical trials.