Total skin electron beam therapy for cutaneous T-cell lymphomas in the Netherlands: A retrospective analysis of treatment outcomes and selection for high or low dose schedule.

PURPOSE: Total skin electron beam therapy (TSEBT) is used mostly in the treatment of cutaneous T cell lymphoma. In this study we describe the results of TSEBT applied in the Netherlands using two different schedules, a conventional dose schedule of 35 Gy and a low-dose schedule of 12 Gy. We aimed to evaluate the treatment results in and compare treatment outcomes between the two treatment groups and to further define indications for both doses. METHODS: In the LUMC, Leiden, we performed a retrospective analysis of 51 patients treated with TSEBT between January 2008 and December 2018, with follow-up untill December 2019. Thirty one patients were treated with 35 Gy and twenty with 12 Gy. The dose was chosen based on the severity of skin involvement. Outcome measures were time to meaningful progression, survival, response rate and toxicity. RESULTS: Time to meaningful progression was 5.1 months with no significant differences between dose groups (P = 0.77). Overall survival was 27.4 months. Both time to progression and survival were significantly better for T2 vs T3 stage. Overall response rate was 80.4 %. Both dose groups showed improvement of symptoms. Treatment was generally well tolerated. CONCLUSIONS: Both high-dose and low-dose TSEBT offer similar results for TMP and OS. It remains unclear which patients benefit most from a high-dose schedule. We propose to use the low-dose schedule as a standard for TSEBT and use supplementary boosts or escalation to high-dose treatment for patients unresponsive to the low-dose schedule.

Quality of life in patients with Mycosis Fungoides and Sézary Syndrome: a systematic review of the literature.

Cutaneous T-cell Lymphoma's (CTCL) are a rare, heterogeneous group of T-cell lymphomas that primarily manifest in the skin. Mycosis fungoides (MF) and Sézary syndrome (SS) are considered the classic types of CTCL. The diverse manifestation of CTCL results in a wide range of symptoms with a possible mild to severe impact on Quality of Life (QoL) depending on the disease stage. Previous studies on QoL in CTCL patients report diverse patient populations and use many different QoL instruments. In the current literature, a clear overview on the influence of the different stages of disease (early MF, late-stage MF/SS or total group) on the QoL is lacking. Therefore, a systematic search of the literature was conducted using the PubMed, Embase, PsycINFO and Web of Science databases. Studies were included if they described QoL in patients with MF and SS retrieved by standardized instruments or qualitative interviews. In total, 24 studies were included using 18 different questionnaires to report on dermatology-specific, cancer-specific and generic QoL. The effect on QoL was found to be greater in patients with late-stage disease as compared to early stage disease, with significant impairments on functional, emotional and physical domains. Nonetheless, even in patients with limited disease, QoL was mildly to moderately affected. Overall, pruritus was the most frequent reported and most bothersome symptom. Significant influence of the disease on daily life activities were found, not only in patients but also on caregivers and family. This broad, structured overview on QoL in MF and SS patients underlines the influence of disease stage on QoL, and therefore, recommends future studies to distinguish between disease stages when reporting results. Furthermore, this overview can inform clinicians in clinical practice by creating awareness of QoL deficits according to disease stage.

Serum and cutaneous transcriptional expression levels of IL31 are minimal in cutaneous T cell lymphoma variants.

AIM: Recent studies suggested a role for IL31 in the pathogenesis of pruritus and disease severity in patients with cutaneous T cell lymphomas (CTCL). However, discrepant results were reported for IL31 serum levels, transcriptional expression levels or immunohistochemistry studies and its relation to pruritus intensity and/or disease severity in CTCL. Most studies did not distinguish between different CTCL variants. We investigated IL31 serum levels in different subtypes of CTCL, including Mycosis Fungoides (MF) (typically not pruritic), Folliculotropic Mycosis Fungoides (FMF) and Sézary syndrome (SS) (both often pruritic). METHODS: From 54 CTCL patients (17 SS, 21 FMF and 16 classic MF) serum samples were analyzed with a high sensitivity V-PLEX immunoassay for IL31. The study group included 35/54 (65%) patients with complaints of pruritus. Thirty-five patients had advanced stage disease (≥stage IIB). A visual analog scale score (VAS score) for pruritus was available in 29 CTCL patients (7 SS, 9 FMF and 13 classic MF) and in other cases complaints of pruritus were retrieved from medical records. qPCR analyses for IL31 expression were performed in lesional skin biopsies from 8 CTCL patients. Serum samples from 4 healthy individuals without pruritus and from 5 atopic dermatitis (AD) patients with severe pruritus were included as controls. RESULTS: In 11/54 (20%) of CTCL patients low serum levels of IL31 were detected (mean 0.48 pg/mL, range 0.20-1.39 pg/mL) including 6/17 (35%) SS patients (mean 0.57 pg/mL) and 5/21 (24%) FMF patients (mean 0.33 pg/mL). All 11 patients with detectable levels of IL31 reported complaints of moderate to severe pruritus and 9/11 patients presented with advanced stage disease (≥IIB). qPCR analyses resulted in lowly expressed IL31 expression levels in 4 of 8 patients; these patients all suffered from pruritus and advanced stage disease. CONCLUSIONS: Translational and transcriptional expression levels of IL31 were very low or undetectable in CTCL patients. Detectable low IL31 serum levels were exclusively observed in SS and FMF patients and not in patients with classic MF. However, these marginal IL31 levels in a small proportion of CTCL patients do not support an essential role for IL31 in CTCL patients.

Primary cutaneous peripheral T-cell lymphoma, not otherwise specified: results of a multicentre European Organization for Research and Treatment of Cancer (EORTC) cutaneous lymphoma taskforce study on the clinico-pathological and prognostic features.

BACKGROUND: Cutaneous peripheral T-cell lymphoma, not otherwise specified (PTL NOS) is an aggressive, but poorly characterized neoplasm. OBJECTIVES: The European Organization for Research and Treatment of Cancer cutaneous lymphoma taskforce (EORTC CLTF) investigated 33 biopsies of 30 patients with primary cutaneous PTL NOS to analyse their clinical, histological, immunophenotypic features and outcome. METHODS: Retrospective analysis of clinical data and histopathological features by an expert panel. RESULTS: Cutaneous PTL NOS manifested clinically either with solitary or disseminated rapidly grown ulcerated tumours or disseminated papulo-nodular lesions. Histologically, a mostly diffuse or nodular infiltrate in the dermis and often extending into the subcutis was found. Epidermotropism was rarely present and only mild and focal. Unusual phenotypes were frequent, e.g. CD3+ /CD4- /CD8- and CD3+ /CD4+ /CD8+ . Moreover, 18% of the cases exhibited an aberrant expression of the B-cell marker CD20 by the tumour cells. All solitary tumours were located on the limbs and presented a high expression of GATA-3 but this did not correlate with outcome and therefore could not serve as a prognostic factor. The prognosis was shown to be generally poor with 10 of 30 patients (33%) dying of lymphoma within the follow-up of 36 months (mean value; range 3-144). The survival rates were 61% after 3 years (CI, 43-85%) and 54% after 5 years (CI, 36-81%). Small to medium-sized morphology of tumour cells was associated with a better outcome than medium to large or large tumour cells. Age, gender, clinical stage, CD4/CD8 phenotype and GATA-3 expression were not associated with prognosis. Chemotherapy was the most common treatment modality, but surgical excision and/or radiotherapy may represent an appropriate first-line treatment for solitary lesions. CONCLUSIONS: Cutaneous PTL NOS shows an aggressive course in most patients independent of initial presentation, age and phenotype. Cytomorphology was identified as a prognostic factor. The data indicate a need for more effective treatment modalities in PTL NOS.

The importance of assessing blood tumour burden in cutaneous T-cell lymphoma.

Mycosis fungoides (MF) and Sézary syndrome (SS) are the best-studied subtypes of cutaneous T-cell lymphoma. The level of blood tumour burden in patients is important for diagnosis, disease staging, prognosis and management, as well as assessing treatment response. Until recently, the assessment of blood involvement was made using manual counts of morphologically atypical T cells (Sézary cells), but this approach may be subjective, and is affected by interobserver variability. Objective and consistent approaches to accurately quantifying blood involvement are required to ensure appropriate stage-related management of patients and to improve our understanding of the prognostic implications of blood tumour burden in these diseases. While assessment of blood involvement is common in SS and advanced-stage MF, an improved understanding of the implications of blood involvement at early disease stages could help identify patients more likely to progress to late-stage disease, and hence guide treatment decisions and frequency of follow-up assessment, ultimately improving patient outcomes. This concise review discusses the development of flow cytometry-based classifications for assessing blood involvement in MF and SS, and summarizes current recommendations for blood classification and assessment of blood response to treatment.

Clinical and pathogenic aspects of the severe cutaneous adverse reaction epidermal necrolysis (EN).

The severe cutaneous adverse reaction epidermal necrolysis (EN) which includes toxic epidermal necrolysis and the milder Stevens-Johnson syndrome is characterized by epidermal loss due to massive keratinocyte apoptosis and/or necroptosis. EN is often caused by a drug mediating a specific TCR-HLA interaction via the (pro)hapten, pharmacological interaction or altered peptide loading mechanism involving a self-peptide presented by keratinocytes. (Memory) CD8 + T cells are activated and exhibit cytotoxicity against keratinocytes via the perforin/granzyme B and granulysin pathway and Fas/FasL interaction. Alternatively drug-induced annexin release by CD14 + monocytes can induce formyl peptide receptor 1 death of keratinocytes by necroptosis. Subsequent keratinocyte death stimulates local inflammation, activating other immune cells producing pro-inflammatory molecules and downregulating regulatory T cells. Widespread epidermal necrolysis and inflammation can induce life-threatening systemic effects, leading to high mortality rates. Research into genetic susceptibility aims to identify risk factors for eventual prevention of EN. Specific HLA class I alleles show the strongest association with EN, but risk variants have also been identified in genes involved in drug metabolism, cellular drug uptake, peptide presentation and function of CD8 + T cells and other immune cells involved in cytotoxic responses. After the acute phase of EN, long-term symptoms can remain or arise mainly affecting the skin and eyes. Mucosal sequelae are characterized by occlusions and strictures due to adherence of denuded surfaces and fibrosis following mucosal inflammation. In addition, systemic pathology can cause acute and chronic hepatic and renal symptoms. EN has a large psychological impact and strongly affects health-related quality of life among EN survivors.

Frequency and prognosis of associated malignancies in 504 patients with lymphomatoid papulosis.

BACKGROUND: Lymphomatoid papulosis (LyP) can be associated with other haematological malignancies (HM), but reported percentages vary from 20% to over 50%. OBJECTIVE: To evaluate the frequency and prognostic significance of associated HM and non-HM in LyP patients. METHODS: In this multicentre cohort study, the complete Dutch LyP population was included from the Dutch Cutaneous Lymphoma Registry between 1985 and 2018. Clinical and histopathological information was retrieved from every individual patient. RESULTS: After a median follow-up of 120 months (range, 6-585), an associated HM was observed in 78/504 (15.5%) patients. Most common associated HM were mycosis fungoides (MF; n = 31) and anaplastic large-cell lymphoma (ALCL; n = 29), while 19 patients had another HM of B-cell (n = 14) or myeloid origin (n = 5). Even after a 25-year follow-up period, percentages of associated HM did not exceed 20%. Thirty-nine of 465 patients (8.4%) without a prior or concurrent associated HM developed an associated HM during follow-up, after a median of 68 months (range of 3-286 months). Nine of 78 patients died of associated HM, including 6/22 patients developing extracutaneous ALCL, while all patients with associated MF or skin-limited ALCL had an excellent prognosis. Compared with the general population, LyP patients showed an increased risk (relative risk, 2.8; 95% confidence intervals, 2.4-3.3) for non-HM, in particular cutaneous squamous cell carcinoma, melanoma and intestinal/lung/bladder cancer. CONCLUSIONS: An associated HM was reported in 15.5% of the LyP patients, particularly MF and ALCL. Although the frequency of associated HM is lower than suggested and the prognosis of most patients with associated HM is excellent, a small subgroup will develop aggressive disease, in particular extracutaneous ALCL. Furthermore, LyP patients have a higher risk of developing other malignancies. Clinicians should be aware of these risks, and LyP patients require close monitoring.

Evaluation of treatment results in multifocal primary cutaneous anaplastic large cell lymphoma: report of the Dutch Cutaneous Lymphoma Group.

BACKGROUND: There is no consensus on the treatment of multifocal primary cutaneous anaplastic large cell lymphoma (C-ALCL). Radiotherapy (RT) and methotrexate (MTX) are the current treatment options, but their efficacy is unknown. Recently, targeted therapies showed promising results in C-ALCL, and may therefore be an attractive first choice of treatment. OBJECTIVES: To assess the efficacy of conventional treatment strategies for patients with multifocal C-ALCL, and to define which patients may require novel targeted therapies. METHODS: In this multicentre study, treatment was evaluated in patients initially presenting (n = 24) or relapsing with multifocal C-ALCL (n = 17; 23 relapses). Distinction was made between patients with five or less lesions (n = 36) and more than five lesions (n = 11). RESULTS: Treatments most commonly used were RT (n = 21), systemic chemotherapy (n = 9) and low-dose MTX (n = 7) with complete response rates of 100%, 78% and 43%, respectively, and an overall response rate of 100%, 100% and 57%, respectively. Four patients showed complete spontaneous regression. In total, 16 of 24 patients (67%) first presenting with multifocal C-ALCL relapsed, including all five patients initially treated with CHOP (cyclophosphamide, hydroxydaunorubicin, oncovin and prednisone). Compared with patients presenting with two to five skin lesions, patients presenting with more than five lesions had a higher chance of developing extracutaneous relapse (56% vs. 20%) and more often died of lymphoma (44% vs. 7%). CONCLUSIONS: Patients with five or less lesions should be treated with low-dose RT (2 × 4 Gy). Maintenance low-dose MTX (20 mg weekly) is a suitable option in patients with more than five lesions. Targeted therapies may be considered in rare patients who are refractory to MTX or patients developing extracutaneous disease.

Recommendations for treatment in folliculotropic mycosis fungoides: report of the Dutch Cutaneous Lymphoma Group.

BACKGROUND: Folliculotropic mycosis fungoides (FMF) is an aggressive variant of mycosis fungoides (MF) and generally less responsive to standard skin-directed therapies (SDTs). Recent studies distinguished indolent (early-stage FMF) and more aggressive (advanced-stage FMF) subgroups. The optimal treatment for both subgroups remains to be defined. OBJECTIVES: To evaluate initial treatment results in patients with early- and advanced-stage FMF. METHODS: A study was undertaken of 203 patients (84 early-stage, 102 advanced-stage, 17 extracutaneous FMF) included in the Dutch Cutaneous Lymphoma Registry between 1985 and 2014. Type and results of initial treatment were retrieved from the Dutch Registry. Main outcomes were complete remission (CR); sustained complete remission; partial remission (PR), > 50% improvement; and overall response (OR; CR + PR). RESULTS: Patients with early-stage FMF were treated with nonaggressive SDTs in 67 of 84 cases resulting, respectively, in CR and OR of 28% and 83% for monotherapy topical steroids, 0% and 83% for ultraviolet B (UVB), and 30% and 88% for psoralen plus ultraviolet A (PUVA). In patients with advanced-stage FMF these SDTs were less effective (combined CR and OR 10% and 52%, respectively). In patients with advanced-stage FMF local radiotherapy (CR 63%; OR 100%), total skin electron beam irradiation (CR 59%; OR 100%) and PUVA combined with local radiotherapy (CR 5%, OR 75%) were most effective. CONCLUSIONS: The results of the present study demonstrate that not all patients with FMF should be treated aggressively. Patients with early-stage FMF may benefit very well from standard SDTs also used in early-stage classic MF and have an excellent prognosis.

Histopathological and immunophenotypical criteria for the diagnosis of Sézary syndrome in differentiation from other erythrodermic skin diseases: a European Organisation for Research and Treatment of Cancer (EORTC) Cutaneous Lymphoma Task Force Study of 97 cases.

BACKGROUND: Patients with erythrodermic disease are a diagnostic challenge regarding the clinical and histological differential diagnosis. OBJECTIVES: To evaluate histopathological and immunohistochemical diagnostic markers for Sézary syndrome. METHODS: Ninety-seven erythrodermic cases [Sézary syndrome (SS), n = 57; erythrodermic inflammatory dermatoses (EIDs), n = 40] were collected by the EORTC Cutaneous Lymphoma Task Force histopathology group. Evaluation criteria were (i) epidermal and dermal changes; (ii) morphology of the infiltrate; (iii) immunohistochemical analysis of marker loss (CD2, CD3, CD4, CD5 and CD7); (iv) bystander infiltrate by staining for CD8, FOXP3 and CD25; and (v) expression of Ki-67, CD30, PD-1 and MUM-1. RESULTS: The workshop panel made a correct diagnosis of SS in 51% of cases (cutaneous T-cell lymphoma 81%) and of EID in 80% without clinical or laboratory data. Histology revealed a significantly increased degree of epidermotropism (P < 0.001) and more intraepidermal atypical lymphocytes (P = 0.0014) in SS biopsies compared with EID. Pautrier microabscesses were seen only in SS (23%) and not in EID (P = 0.0012). SS showed significantly more dermal cerebriform and blastic lymphocytes than EID. Immunohistochemistry revealed a significant loss of CD7 expression (< 50%) in 33 of 51 (65%) cases of SS compared with two of 35 (6%) EID (P < 0.001). The lymphocytic infiltrate in SS skin samples was found significantly to express PD-1 (P = 0.0053), MUM-1 (P = 0.0017) and Ki-67 (P < 0.001), and showed less infiltration of CD8(+) lymphocytes (P < 0.001). A multivariate analysis identified CD7 loss, increased numbers of small cerebriform lymphocytes, low numbers of CD8(+) lymphocytes and increased proliferation (Ki-67(+) lymphocytes) as the strongest indicators for the diagnosis of SS. CONCLUSIONS: A number of different histological and immunophenotypical criteria are required to differentiate between SS and EIDs.

Prognostic factors, prognostic indices and staging in mycosis fungoides and Sézary syndrome: where are we now?

Mycosis fungoides is the most prevalent form of primary cutaneous T-cell lymphoma. Patients frequently present with early-stage disease typically associated with a favourable prognosis and survival of 10-35 years, but over 25% may progress to advanced disease with a median survival < 4 years, and just 13 months in those with nodal involvement. Sézary syndrome presents in advanced disease with erythroderma, blood involvement and lymphadenopathy. The Bunn and Lamberg staging system (1979) includes stages IA-IIA (early-stage disease) and IIB-IVB (advanced-stage disease) and provides prognostic information, but some patients with tumour-stage disease (IIB) have a worse prognosis than those with erythrodermic-stage (III). Conversely, patients with plaque-stage (IB) folliculotropic mycosis fungoides may have a worse outcome than those with tumour-stage (IIB). The more recent staging system of the European Organisation for the Research and Treatment of Cancer/International Society for Cutaneous Lymphoma has been designed to reflect tumour burden at different sites. However, this staging system has not been validated prospectively for prognosis. Furthermore, this staging system does not include a detailed measurement of skin tumour burden, as indicated by the modified skin weighted severity assessment tool. This assessment measures body surface area of disease and is weighted to record patch, plaque and tumour to produce a numerical value from 0·5 to 400 and is an established endpoint for clinical studies. Nor does this staging include clinicopathological features associated with a poor prognosis such as folliculotropism. Here we review the clinical, haematological, pathological and genotypic parameters outside the staging system, which may affect survival in mycosis fungoides and Sézary syndrome. Most studies are retrospective and single centre. The identification of poor prognostic factors may be used to develop a prognostic index to use alongside staging, which may be of benefit in mycosis fungoides/Sézary syndrome to identify patients with a potentially poor prognosis.

Quantitation of tumour development correlates with prognosis in tumour stage (stage IIB) mycosis fungoides.

BACKGROUND: Patients with mycosis fungoides (MF) tumour stage IIB disease show considerable variation in the number of tumours and time interval between each tumour occasion. OBJECTIVES: To quantify the extent of tumour formation in patients with stage IIB MF and correlation with survival. METHODS: The variability in tumour development of 46 patients with stage IIB MF was quantified by calculating a frailty score with the use of a statistical frailty model, based on both the number of tumours developed during follow-up and the time interval between each tumour occasion. The prognostic value of the frailty scores and the number of tumours at 6 and 12 months after first tumour development were studied. RESULTS: Frailty scores varied between 0·05 and 6·94. Patients with high frailties (> 1·0, n = 14) had the worst disease-specific survival (DSS) and overall survival (OS), compared with patients in the low frailty group (0-0·35, n = 17) and medium frailty group (0·35-1·0, n = 15). Differences in DSS and OS between the three frailty groups were highly significant (both P < 0·001). The number of tumours that developed within 6 months after the diagnosis of MF stage IIB was prognostic for subsequent DSS and OS (P < 0·001 and P = 0·021, respectively). CONCLUSIONS: The number of tumours and time interval between tumour formation differs greatly among patients with stage IIB MF and these differences correlate with survival. Patients with an adverse prognosis can be identified by quantifying the number of tumours that develop within 6 months after diagnosis of MF stage IIB.

Langerhans cell histiocytosis first presenting in the skin in adults: frequent association with a second haematological malignancy.

BACKGROUND: Langerhans cell histiocytosis (LCH) in adults first presenting in the skin is rare. Guidelines for staging, treatment and follow-up are lacking. OBJECTIVES: To better define staging procedures, treatment results and clinical course in adult patients with LCH first presenting in the skin. METHODS: Eighteen adult patients with LCH first presenting in the skin were collected from five centres collaborating in the Dutch Cutaneous Lymphoma Group. Clinical records and (skin) biopsy specimens were reviewed and follow-up data were obtained. A literature search on adult patients with LCH presenting in the skin was performed. RESULTS: Staging procedures showed extracutaneous disease in three of 16 patients who were adequately staged. One patient had a histologically confirmed lytic LCH bone lesion, while two patients had a myelodysplastic syndrome. During follow-up two of 18 patients developed extracutaneous localizations of LCH. Five patients developed a second haematological malignancy, including (myelo)monocytic leukaemia (two cases), histiocytic sarcoma (one case), diffuse large B-cell lymphoma (one case) and peripheral T-cell lymphoma (one case). Review of the literature revealed six other adult patients with a second haematological malignancy preceding or following a diagnosis of LCH. CONCLUSIONS: The results of the present study suggest an increased risk of a second haematological malignancy in adult patients with LCH presenting in the skin. Extensive staging at presentation and long-term follow-up are therefore warranted in such patients.

A restricted clonal T-cell receptor αß repertoire in Sézary syndrome is indicative of superantigenic stimulation.

BACKGROUND: Sézary syndrome (SS) is a cutaneous T-cell lymphoma characterized by erythroderma, lymphadenopathy and malignant clonal T cells in the skin, lymph nodes and peripheral blood. A role for superantigens in the pathogenesis of SS has been postulated before. OBJECTIVES: To investigate a putative involvement of chronic (super-)antigenic stimulation in driving T-cell expansion in SS. METHODS: Antigenic specificity of the T-cell receptor (TCR) was assayed by molecular analysis of the TCRA (n=11) and TCRB (n=28) genes, followed by detailed in silico analysis. RESULTS: Sequence analysis of clonally rearranged TCRB genes showed over-representation of Vß8, Vß13, Vß17, Vß21 and Vß22, and under-representation of Vß2 and Jß1.1 when compared with healthy controls. No similarity was detected in amino acid motifs of the complementarity determining region 3 (CDR3). Analysis of TCRA rearrangements showed that there was no common Vα or Jα gene usage, and that TCRA CDR3 amino acid motifs were not highly similar. CONCLUSIONS: The lack of clear stereotypic TCRA and TCRB CDR3 amino acid motifs would argue against involvement of a single common antigen in the pathogenesis of SS. Nevertheless, the skewing of Vß and Jß gene usage does seem to point to a restricted TCR repertoire, possibly as a result of superantigenic selection prior to neoplastic transformation.

Antiplectin autoantibodies in subepidermal blistering diseases.

BACKGROUND: Hemidesmosomal proteins may become targets of autoimmunity in subepidermal blistering diseases. Well-known recognized autoantigens are the intracellular plaque protein BP230, the transmembrane BP180 and its shed ectodomain LAD-1. OBJECTIVES: To establish the prevalence of autoimmunity against plectin, another intracellular plaque protein, and to investigate its antigenic sites. METHODS: Two hundred and eighty-two patients with subepidermal blistering diseases, investigated by routine immunoblot analysis for possible antiplectin antibodies, were included in the study. Epitope mapping was performed using recombinantly produced overlapping plectin domains from the actin-binding domain to the rod domain. The COOH-terminal region of plectin was not included in the study. RESULTS: In 11 of 282 (3.9%) patients an immunoblot staining pattern identical to that of antiplectin monoclonal antibody HD121 was found. Affinity-purified antibodies bound back to normal human skin in a pattern typical for plectin, i.e. to the epidermal basement membrane zone as well as to keratinocytes in the epidermis, and to myocytes. No binding was seen to plectin-deficient skin of a patient with epidermolysis bullosa simplex with muscular dystrophy. Epitope mapping of the plectin molecule showed that the central coiled-coil rod domain is an immunodominant hotspot as 92% of the sera with antiplectin antibodies reacted with it. Most patients with antiplectin antibodies also had antibodies to other pemphigoid antigens. CONCLUSIONS: Plectin is a minor pemphigoid antigen with an immunodominant epitope located on the central rod domain.