Cutaneous immunoglobulin G4-related systemic disease

Assessment of specificity of dermatopathologic criteria for IgG4-related skin disease

BACKGROUND

IgG4-related disease (IgG4-RD) represents a recently characterized multisystemic fibroinflammatory condition that can manifest a spectrum of skin findings (IgG4-related skin disease; IgG4-RSD). Histopathologic and immunohistochemical criteria have been proposed; however, the specificity of these criteria merits scrutiny given the potential histopathologic overlap of IgG4-RSD and both neoplastic and inflammatory skin conditions featuring lymphoplasmacytic infiltrates (IgG4-RSD mimics). This study sought to assess the specificity of the criteria by quantifying the frequency by which an expanded spectrum of IgG4-RSD mimics meet proposed thresholds.

METHODS

Following IRB approval, a total of 69 cases of IgG4-RD mimics, representing 14 different diagnoses featuring plasma cells, were reviewed and analyzed for the following histopathologic and immunohistochemical features: (i) maximum IgG4+ count/high-powered field (hpf) >200; (ii) IgG4/IgG ratio >0.4 averaged over 3 hpfs; (iii) IgG4+ count >10 per hpf.

RESULTS

Screening for IgG4-RSD by histopathologic criteria demonstrated the high frequency of lymphoplasmacytic infiltrates, contrasted with the rarity of storiform fibrosis (only one case of erythema elevatum diutinum [EED]) and obliterative phlebitis (0 cases). By immunohistochemical criteria, the analysis revealed that no cases exceeded 200 IgG4+ cells; 13% (9/69) cases demonstrated an IgG4/IgG ratio of >0.4 averaged over 3 hpfs; and 23% (16/69) cases demonstrated a mean IgG4+ count of >10 per hpf.

CONCLUSION

Application of proposed IgG4-RSD histopathologic criteria to an expanded spectrum of potential IgG4-RSD mimics (to include cutaneous marginal zone lymphoma, syphilis, necrobiosis lipoidica, lichen sclerosus, ALHE, psoriasis, lymphoplasmacytic plaque, EED, and erosive pustular dermatosis), highlights the relative nonspecificity of lymphoplasmacytic infiltrates contrasted with the stringency of storiform fibrosis and obliterative fibrosis. Furthermore, an IgG4+ cell count of >10 per hpf and an IgG4/IgG ratio of >0.4 are not specific to IgG4-RSD alone. In the appropriate clinical context for IgG4-RSD, histopathologic features still represent the entry threshold for diagnosis consideration, which then allows for further screening by immunohistochemical criteria.

Management of IgG4-related disease

IgG4-related disease was unrecognised as a unified disease entity until this century, yet in a short period of time the disease has been appreciated to have a worldwide distribution, and its clinical, pathological, and radiological features have been described in considerable detail. The disease has strong organ predilections, and many of the clinical presentations of disease are increasingly familiar to both generalists and specialists. Early recognition of IgG4-related disease is crucial because although the disease is highly treatable, it can lead to serious organ damage and even death if undiagnosed until advanced stages. Its indolent nature often makes diagnosis challenging, and IgG4-related disease is one of the great mimickers of other diseases in the current era. Glucocorticoids are an effective treatment for IgG4-related disease, but their long-term use is problematic in a disease that frequently affects middle-aged to elderly individuals and often leads to pancreatic dysfunction. Our understanding of the pathophysiology of the disease is surprisingly advanced given the relatively recent recognition of this condition. Insights into disease pathophysiology offer the possibility of a variety of targeted treatment approaches. Looking ahead, biological therapies could profoundly alter the way in which IgG4-related disease is managed, permitting the use of specific therapies that are tailored to patients' clinical phenotypes.

IgG4-related skin disease may have distinct systemic manifestations: a systematic review

IgG4-related disease (IgG4-RD) is an increasingly prevalent protean multisystem disorder characterized by single or multi-organ infiltration of IgG4-bearing plasma cells. Skin involvement has been recognized and is relevant to proper diagnosis. A systematic literature review of 50 cases involving the skin reveals that patients with IgG4-related skin disease show predominant involvement of the head and neck and have a distinct pattern of systemic involvement, also favoring the head and neck - lymphatics, orbit, salivary, and lacrimal glands - but generally lacking pancreaticobiliary involvement (16% of cases), which by contrast is a predominant manifestation in systemic IgG4-RD (60% with pancreaticobiliary involvement). We summarize clinical and pathologic descriptive data from this systematic review. We review differential diagnosis and propose a diagnostic scheme for stratifying probability of disease based upon comprehensive integration of clinical, histopathologic, and laboratory data. Plasmacyte infiltration and storiform fibrosis are prominent in IgG4-related skin disease, but obliterative venulitis is less common than in the prototypical IgG4-related disease manifestation of autoimmune pancreatitis. IgG4 tissue and serum values, with a mean (±95% CI) in the reviewed cases of 132.8 ± 32.6 IgG4-positive plasma cells per high-power field and 580 ± 183.8 mg/dl, respectively, are incorporated into the suggested criteria. The distinct set of manifestations identified by this systematic review and the proposed diagnostic considerations, while requiring further validation in prospective studies, highlight the need to consider that IgG4-related skin disease defines a unique systemic disease complex along the spectrum of IgG4-RD.

Diagnostic sensitivity of cutoff values of IgG4-positive plasma cell number and IgG4-positive/CD138-positive cell ratio in typical multiple lesions of patients with IgG4-related disease

OBJECTIVES

This study aimed to investigate the diagnostic sensitivity of the cutoff values of IgG4-positive plasma cell (PC) number and IgG4-positive/CD138-positive cell ratio proposed by the International consensus statement (ICS) on the pathology of IgG4-related disease (IgG4-RD) in typical multiple lesions of patients with IgG4-RD.

METHODS

We evaluated IgG4-positive PC number and IgG4-positive/CD138-positive cell ratio in 39 samples from 18 IgG4-RD patients having more than two typical lesions of IgG4-RD.

RESULTS

We evaluated 12 submandibular, 12 ophthalmic, six skin, five kidney, two pancreatic, and one bronchus and prostate lesion each in 18 patients with typical clinical, serological, and radiographic features. Concerning IgG4 + PC number per high-power field, most ophthalmic (11/12), kidney (5/5), pancreatic (2/2), and bronchial lesions (1/1) fulfilled the cutoff value of ICS, whereas many of the submandibular (6/12) and skin lesions (0/6) did not. In contrast to the absolute number, all lesions fulfilled the cutoff value of IgG4+/CD138 + cell ratio. In eight cases, only one or two lesions in the same patient fulfilled the cutoff value of ICS, while the others did not.

CONCLUSIONS

These results suggest that ICS criteria have different sensitivities among the affected organs for the diagnosis of IgG4-RD.

A Solid Pseudopapillary Neoplasm of the Pancreas Associated With IgG4-Related Pancreatitis: A Case Report

A solid and cystic pancreatic lesion was incidentally found in a 62-year-old woman on abdominal computed tomography. The lesion was diagnosed as a solid pseudopapillary neoplasm by using endoscopic ultrasound-guided fine needle aspiration, and the tumor was resected. Histologically, the tumor cells had relatively small, round nuclei and papillary-like architecture in a hemorrhagic background. On immunohistochemical examination, the tumor cells were diffusely positive for nuclear β-catenin and cytoplasmic CD10. In addition, typical histological findings of IgG4-related pancreatitis (obstructive phlebitis, storiform-type fibrosis, and abundant IgG4-positive plasma cell infiltration) were found in the surrounding stroma of the solid pseudopapillary neoplasm. Postoperative workup failed to detect any other sclerotic lesions or serum IgG4 elevation, suggesting that the patient had no evidence of IgG4-related disease. To avoid misdiagnosis of a combined pancreatic neoplasm and fibro-inflammatory lesion, pathologists should consider such situations and make a definitive diagnosis after careful observation of all pancreatic lesions.

Granuloma Faciale and Erythema Elevatum Diutinum in Relation to Immunoglobulin G4-Related Disease: An Appraisal of 32 Cases

OBJECTIVES

To elucidate whether granuloma faciale (GF) and erythema elevatum diutinum (EED), two inflammatory skin dermatoses, meet the consensus histopathologic diagnostic criteria for immunoglobulin G4-related disease (IgG4-RD).

METHODS

With institutional review board approval, we assessed the clinical, microscopic, and immunophenotypic features of skin specimens of patients with GF and EED. We compared these findings with previously published consensus diagnostic criteria for IgG4-RD.

RESULTS

Thirty-two patients (GF, n = 25; EED, n = 7) met study inclusion criteria. Histopathologic findings of small-vessel vasculitis, dermal fibrosis, and plasma cell infiltrates were uniformly present, and eosinophilic inflammation was frequent. No specimen met diagnostic criteria for IgG4-RD.

CONCLUSIONS

Our results indicate that despite some histopathologic similarities between GF/EED and IgG4-RD, the cases did not meet the consensus immunohistochemical diagnostic criteria for IgG4-RD.

Rituximab for the Treatment of IgG4-Related Tubulointerstitial Nephritis: Case Report and Review of the Literature

Immunoglobulin type gamma 4 (IgG4)-related disease is a relatively newly described clinical entity characterized by a distinctive histopathological appearance, increased numbers of IgG4 positive plasma cells and often, but not always, elevated serum IgG4 concentrations. The most common renal manifestation of IgG4-related disease is tubulointerstitial nephritis marked with proteinuria, hematuria, decreased kidney function, hypocomplementemia, and radiologic abnormalities. Renal biopsy characteristics include dense lymphoplasmacytic tubulointerstitial nephritis that stains for IgG4, storiform fibrosis, and immune complex deposition in the interstitium and along tubule basement membranes. Treatment traditionally consists of prolonged glucocorticoids but cases refractory to glucocorticoids have been reported.We report a case of a 58-year-old Caucasian man who presented with fatigue, 50 pound weight loss, dyspnea, lymphadenopathy, and nephromegaly. The patient was first misdiagnosed as chronic interstitial nephritis secondary to renal sarcoid and was treated with repeated doses of prednisone. On his third relapse, he underwent a repeat renal biopsy and a diagnosis of IgG4-tubulointerstitial nephritis was confirmed. He was refractory to treatment with prednisone. The patient received Rituximab and had prompt sustained improvement in renal function. At 1 year post Rituximab treatment, his serum creatinine remains at baseline and imaging study revealed reduction in his kidney size.This is the first case report using Rituximab as a steroid sparing option for refractory IgG4-tubulointerstitial nephritis. More information is needed on the long-term effects of using of B-cell depleting agents for glucocorticoid resistant IgG4-tubulointerstitial nephritis.

Immunoglobulin G4-related diseases in the head and neck: a systematic review

BACKGROUND

Immunoglobulin G4 related disease (IgG4-RD) is a poorly understood chronic inflammatory disorder affecting the middle-aged and elderly that can present to the otolaryngologist. We aim to summarize the current literature regarding the manifestations and management of IgG4-RD in the head and neck.

METHODS

Pubmed and EMBASE were searched using the term relevant search algorithm utilizing keywords such as: IgG4 related disease, head and neck, orbit, salivary glands, sialadenitis, Kuttner, angiocentric eosinophilic fibrosis, submandibular, lacrimal, thyroid, dacryoadenitis, nasal, sinus, and Mikulicz's. Reference lists were searched for identification of relevant studies. Case reports, original research and review articles published in English from 1964 to 2014 whose major topic was IgG4-RD affecting the head and neck were included. Data regarding patient demographics, presentation, histopathology, management and treatment outcomes of IgG4-RD were extracted. Level of evidence was also assessed and data were pooled where possible. Three independent reviewers screened eligible studies; extracted relevant data and discrepancies were resolved by consensus, where applicable. Descriptive and comparative statistics were performed.

RESULTS

Fourty-three articles met our inclusion criteria. IgG4-RD most often presents as a mass lesion in the head and neck region. Common diagnostic features include: (1) elevated serum IgG4 level, (2) marked infiltration of exocrine glands by IgG4-positive plasma cells with fibrosis, and (3) marked improvement with corticosteroid therapy and additional immunosuppressive therapy in corticosteroid refractory cases. Early diagnosis and involvement of rheumatology is important in management.

CONCLUSIONS

IgG4-RD is a challenging non-surgical disease that has multiple manifestations in the head and neck. It must be distinguished from various mimics including malignancy, systemic diseases, and infectious. Otolaryngology-Head and Neck surgeons should be aware of this condition and its management.

Dermatologic disorders in 118 patients with autoimmune (immunoglobulin G4-related) pancreatitis: a retrospective cohort analysis

BACKGROUND

Autoimmune pancreatitis is the prototypical manifestation of immunoglobulin G4-related disease, a fibroinflammatory syndrome that can affect virtually any organ. Rarely, skin involvement has been reported in immunoglobulin G4-related disease. Isolated case reports have described other distinct associated dermatoses.

OBJECTIVE

Our objective was to determine the frequency and nature of dermatologic manifestations of immunoglobulin G4-related disease in patients with autoimmune pancreatitis.

METHODS

Retrospective analysis of dermatologic conditions of patients with autoimmune pancreatitis.

RESULTS

Among the 118 identified patients, 31 (26.3%) had a dermatologic diagnosis [mean (standard deviation; SD) follow-up 5.9 (4.6) years]. Two patients (1.7%) had necrobiotic xanthogranuloma; three (2.5%) had another xanthomatous or xanthogranulomatous process. One patient (0.8%) had pemphigus erythematosus. No patient had immunoglobulin G4-related skin disease.

CONCLUSION

Skin involvement in immunoglobulin G4-related disease appears to be rare. A disproportionately high number of patients had xanthomatous or xanthogranulomatous processes, including necrobiotic xanthogranuloma. It remains unclear whether the association between immunoglobulin G4-related disease and necrobiotic xanthogranuloma or other xantho(granulo)matous processes represents shared pathophysiology, a mutual underlying driver, or coincidence, though the results of this study cast doubt on the latter. Although pemphigus was not reported in immunoglobulin G4-related disease previously, the prominent role of the immunoglobulin G4 subclass in each condition makes this association intriguing.

IgG4 immunostaining and its implications in orbital inflammatory disease

Objective

IgG4-related disease is an emerging clinical entity which frequently involves tissue within the orbit. In order to appreciate the implications of IgG4 immunostaining, we analyzed gene expression and the prevalence of IgG4- immunostaining among subjects with orbital inflammatory diseases.

Methods

We organized an international consortium to collect orbital biopsies from 108 subjects including 22 with no known orbital disease, 42 with nonspecific orbital inflammatory disease (NSOI), 26 with thyroid eye disease (TED), 12 with sarcoidosis, and 6 with granulomatosis with polyangiitis (GPA). Lacrimal gland and orbital adipose tissue biopsies were immunostained for IgG4 or IgG secreting plasma cells. RNA transcripts were quantified by Affymetrix arrays.

Results

None of the healthy controls or subjects with TED had substantial IgG4 staining. Among the 63 others, the prevalence of significant IgG4-immunostaining ranged from 11 to 39% depending on the definition for significant. IgG4 staining was detectable in the majority of tissues from subjects with GPA and less commonly in tissue from subjects with sarcoidosis or NSOI. The detection of IgG4+ cells correlated with inflammation in the lacrimal gland based on histology. IgG4 staining tissue expressed an increase in transcripts associated with inflammation, especially B cell-related genes. Functional annotation analysis confirmed this.

Conclusion

IgG4+ plasma cells are common in orbital tissue from patients with sarcoidosis, GPA, or NSOI. Even using the low threshold of 10 IgG4+ cells/high powered field, IgG4 staining correlates with increased inflammation in the lacrimal gland based on histology and gene expression.

IgG4-related skin lesions: case report and review of the literature

IgG4-related disease (IgG4-RD) is a systemic disease, mostly affecting the pancreas. It presents as accumulation of IgG4-producing plasma cells in various tissues. Other possible affected organs include the lacrimal glands, salivary glands, lungs, kidneys, liver, bile duct, retroperitoneum, breast, aorta, pituitary gland and prostate. A cutaneous presentation has also been described in the literature, and might be the initial presenting feature of IgG4-RD. We describe a 73-year-old white man who presented with two infiltrated, erythematous nodules on his abdomen. The histopathological characteristics were highly suggestive of IgG4-related cutaneous disease. Immunohistochemical stains were positive for IgG4. In the past, the patient's other organs had also been affected by IgG4-RD. Cutaneous presentation of IgG4-RD has been described previously in the literature but only in Asian patients (both East and South Asian). We also provide an overview of previously reported cutaneous manifestations of IgG4-RD.

Increased immunoglobulin (Ig) G4-positive plasma cell density and IgG4/IgG ratio are not specific for IgG4-related disease in the skin

OBJECTIVES

Immunoglobulin (Ig) G4-related disease (IgG4-RD), a fibroinflammatory condition that can affect multiple organs, is suggested by lymphoplasmacytic inflammation, fibrosis, phlebitis, and increased IgG4+ plasma cell (PC) tissue density. In patients with suspected IgG4-RD and skin changes, skin biopsy may serve as a diagnostic screen or to supplement nondiagnostic visceral biopsy specimens. We aimed to determine whether increased cutaneous IgG4+ PCs or IgG4/IgG ratio is specific for IgG4-RD.

METHODS

We examined 50 mucocutaneous specimens representing seven PC-rich dermatoses and reactive PC-rich infiltrates with IgG and IgG4 immunohistochemical stains.

RESULTS

IgG4+ density exceeded 10 cells per high-power field in 22 (44%) of 50 specimens, representing six of seven diagnoses and reactive infiltrates. In five specimens (10%), the IgG4/IgG ratio exceeded 0.40.

CONCLUSIONS

Moderately elevated IgG4+ PC density or IgG4/IgG ratio is a nonspecific finding in the skin. In cutaneous biopsy specimens showing increased IgG4+ PCs, careful consideration should be given to clinical, serologic, and other histopathologic features before attributing clinical changes to IgG4-RD.

Primary cutaneous marginal zone lymphomas with plasmacytic differentiation show frequent IgG4 expression

The expression of IgG4 in malignant B-cell lymphomas has only partially been studied. Recent reports described single cases of marginal zone lymphomas arising in the ocular adnexae that express IgG4. Moreover, a subset of dura-associated marginal zone lymphomas appear to express IgG4 as well. We investigated IgG4 expression in a more systematic manner in a large cohort of marginal zone lymphoma specimens derived from the archive of our institute. Overall, we examined 169 marginal zone lymphomas of various primary sites that displayed a distinct plasmacytic differentiation and light chain restriction, allowing for a detailed investigation of the immunoglobulin heavy chain expression in these tumors by immunohistochemistry. Unexpectedly, primary cutaneous marginal zone lymphomas showed frequent IgG4 expression. Although only 1 out of 120 noncutaneous marginal zone lymphomas, located in the ocular adnexae, expressed IgG4, 19 of 49 (39%) primary cutaneous marginal zone lymphomas showed this feature, constituting the highest expression rate of IgG4 reported to date in any B-cell lymphoma. None of the IgG4-positive cutaneous marginal zone lymphomas with available clinical data showed evidence of a preexisting systemic IgG4-related disease, suggesting a localized immunologic IgG4-driven pathogenetic process at early stages of the disease. IgG4-positive and IgG4-negative primary cutaneous marginal zone lymphomas did not significantly differ in architectural features of the infiltrate or the composition of the reactive T-cell infiltrate as determined by analysis of T-cell content, CD4/CD8 ratio, and content of FOXP3- and PD1-positive T cells. Although the pathogenetic role of IgG4 expression in a significant subset of primary cutaneous marginal zone lymphomas with plasmacytic differentiation remains unclear at present, the demonstration of IgG4 expression in a marginal zone lymphoma involving the skin might be a helpful clue in the routine diagnostic setting, as these tumors will almost invariably be of primary cutaneous origin with an extremely low risk of spread to noncutaneous sites and an excellent prognosis.

Rethinking Ormond's disease: "idiopathic" retroperitoneal fibrosis in the era of IgG4-related disease

Idiopathic retroperitoneal fibrosis (RPF) is a periaortic sclerotic disease that encases adjacent retroperitoneal structures, particularly the ureters. A subset of idiopathic RPF cases can be associated with IgG4-related disease, but the frequency of this association is not clear. We selected 23 cases of idiopathic RPF and identified IgG4-related RPF cases based on the presence of IgG4+ plasma cells in the tissue, using an IgG4/IgG ratio cutoff of >40%. We then compared the IgG4-related RPF patients and the non-IgG4-related RPF patients in terms of both the presence of histopathologic features typical of IgG4-related disease and the simultaneous occurrence (or history) of other organ manifestations typical of IgG4-related disease. The IgG4-related RPF and non-IgG4-related RPF groups were also analyzed in terms of clinical, laboratory, and radiologic features and treatment review. We identified 13 cases of IgG4-related RPF (57% of the total cohort). The distinguishing features of IgG4-related RPF were histopathologic and extra-organ manifestations of IgG4-related disease. The IgG4-related RPF patients were statistically more likely than non-IgG4-related RPF patients to have retroperitoneal biopsies showing lymphoplasmacytic infiltrate (p = 0.006), storiform fibrosis (p = 0.006), or tissue eosinophilia (p = 0.0002). Demographics of the 2 groups, including a middle-aged, male predominance (mean age, 58 yr; 73% male), were similar. IgG4-related disease accounts for a substantial percentage of patients with "idiopathic" RPF. Histopathologic features such as storiform fibrosis, obliterative phlebitis, and tissue eosinophilia are critical to identifying this disease association. Extraretroperitoneal manifestations of IgG4-related disease are also often present among patients with IgG4-related RPF. Elevated IgG4/total IgG ratios in tissue biopsies are more useful than the number of IgG4+ plasma cells per high-power field in cases of RPF that are highly fibrotic.

IgG4-related disease: nomenclature, clinical features, and treatment

Concepts about IgG4-related disease (IgG4-RD) are now emerging swiftly. The condition has been identified in virtually every organ system, and its features are often excellent mimickers of malignancies, infections, and other immune-mediated disorders. Recommendations for nomenclature were proposed by the Organizing Committee of the 2011 International IgG4-related disease Symposium, and guidelines for the pathologic diagnosis of this condition have been published by an international group of experts. Experience with treatment regimens is growing. Glucocorticoids and B-cell depletion strategies both appear to be effective and are the subject of ongoing studies. This article reviews the current thought and understanding of this disease with regard to nomenclature, organ system involvement, and approaches to therapy.

Investigations of IgG4-related disease involving the skin

OBJECTIVES

IgG4-related skin disease is not widely recognized. This prompted us to investigate the clinical and pathological features of five patients we encountered with IgG4-related disease (IgG4-RD) affecting the skin.

METHODS

We investigated the clinical and pathological features of these five patients, including the distribution, onset, and morphology of eruptions, their pathological and immunohistochemical characteristics, and the occurrence of disease in other organs.

RESULTS

The skin lesions were typically erythematous nodules and papules and brown papules like prurigo nodularis, which developed on the face or in the head and neck areas in four patients. Skin lesions were the first clinical manifestation in three patients. All five patients had sialadenitis and/or dacryoadenitis. The mean serum IgG4 concentration was 665.6 ± 410.0 mg/dl. Infiltrations of IgG4-positive plasma cells were observed in both the dermis and subcutaneous tissue. Germinal center formations were seen in three patients. Mild to moderate fibrosis was observed in all patients, and focal obliterative phlebitis in one. The average count of IgG4-positive cells was 67.3/high-power field (23.0-128.6). Wide variation in the numbers of infiltrating IgG4-positive cells was noted.

CONCLUSION

IgG4-RD appears to have a distinctive clinicopathological presentation in the skin, differentiating it from other cutaneous disorders.

Cutaneous multicentric Castleman's disease mimicking IgG4-related disease

Castleman's disease, an uncommon lymphoproliferative disorder, can be difficult to differentiate from immunoglobulin (Ig) G4-related disease. The latter is typically characterized by elevated serum IgG4 levels and abundant IgG4-positive cells. However, multicentric Castleman's disease can also have elevated serum IgG4 levels and even fulfill the histological diagnostic criteria for IgG4-related disease. We present a case of cutaneous multicentric Castleman's disease mimicking IgG4-related disease. A 55-year-old Japanese woman developed erythematous and brown plaques on her back. Skin biopsy revealed regressive follicles with interfollicular plasmacytosis, and many plasma cells were positive for IgG4 (mean 263.67±79.19, range 214-355 per high power field). The IgG4-/IgG-positive cell ratios were 35.6%, 36.2%, and 48.4%, respectively, with an average of 40.6%, thus fulfilling the histological diagnostic criteria for IgG4-related disease. Furthermore, serum IgG4 level was significantly elevated (1490 mg/dl; normal range: 4.8-105 mg/dl). However, laboratory findings of anemia, hypoalbuminemia, polyclonal gammaglobulinemia, high C-reactive protein level, and elevated serum interleukin-6 level were consistent with hyper-IL-6 syndrome. Hence, the diagnosis of cutaneous multicentric Castleman's disease was made. In conclusion, IgG4-related disease cannot be differentiated from hyper-IL-6 syndromes on histology alone. Instead, laboratory analyses are necessary to distinguish between the two diseases.

Consensus statement on the pathology of IgG4-related disease

IgG4-related disease is a newly recognized fibro-inflammatory condition characterized by several features: a tendency to form tumefactive lesions in multiple sites; a characteristic histopathological appearance; and-often but not always-elevated serum IgG4 concentrations. An international symposium on IgG4-related disease was held in Boston, MA, on 4-7 October 2011. The organizing committee comprising 35 IgG4-related disease experts from Japan, Korea, Hong Kong, the United Kingdom, Germany, Italy, Holland, Canada, and the United States, including the clinicians, pathologists, radiologists, and basic scientists. This group represents broad subspecialty expertise in pathology, rheumatology, gastroenterology, allergy, immunology, nephrology, pulmonary medicine, oncology, ophthalmology, and surgery. The histopathology of IgG4-related disease was a specific focus of the international symposium. The primary purpose of this statement is to provide practicing pathologists with a set of guidelines for the diagnosis of IgG4-related disease. The diagnosis of IgG4-related disease rests on the combined presence of the characteristic histopathological appearance and increased numbers of IgG4⁺ plasma cells. The critical histopathological features are a dense lymphoplasmacytic infiltrate, a storiform pattern of fibrosis, and obliterative phlebitis. We propose a terminology scheme for the diagnosis of IgG4-related disease that is based primarily on the morphological appearance on biopsy. Tissue IgG4 counts and IgG4:IgG ratios are secondary in importance. The guidelines proposed in this statement do not supplant careful clinicopathological correlation and sound clinical judgment. As the spectrum of this disease continues to expand, we advocate the use of strict criteria for accepting newly proposed entities or sites as components of the IgG4-related disease spectrum.