Grade 1 Mild; asymptomatic or mild symptoms; clinical or diagnostic observations only; intervention not indicated. Grade 2 Moderate; minimal, local or noninvasive intervention indicated; limiting ageappropriate instrumental ADL*. Grade 3 Severe or medically significant but not immediately life-threatening; hospitalization or prolongation of hospitalization indicated; disabling; limiting self care ADL**. Grade 4 Life-threatening consequences; urgent intervention indicated. Grade 5 Death related to AE. A Semicolon indicates 'or' within the description of the grade. A single dash (-) indicates a Grade is not available. Not all Grades are appropriate for all AEs. Therefore, some AEs are listed with fewer than five options for Grade selection. Grade 5 Grade 5 (Death) is not appropriate for some AEs and therefore is not an option. Definitions A brief Definition is provided to clarify the meaning of each AE term. A single dash (-) indicates a Definition is not available. Navigational Notes A Navigational Note is used to assist the reporter in choosing a correct AE. It may list other AEs that should be considered in addition to or in place of the AE in question. A single dash (-) indicates a Navigational Note has not been defined for the AE term. Activities of Daily Living (ADL) *Instrumental ADL refer to preparing meals, shopping for groceries or clothes, using the telephone, managing money, etc. **Self care ADL refer to bathing, dressing and undressing, feeding self, using the toilet, taking medications, and not bedridden. Table of Contents Blood and lymphatic system disorders .

Key Points An international panel established the first ever diagnostic criteria for iMCD based on review of 244 clinical cases and 88 tissue samples. The criteria require multicentric lymphadenopathy with defined histopathology, ≥2 clinical/laboratory changes, and exclusion of iMCD mimics.

Castleman disease (CD) describes a group of at least 4 disorders that share a spectrum of characteristic histopathological features but have a wide range of etiologies, presentations, treatments, and outcomes. CD includes unicentric CD (UCD) and multicentric CD (MCD), the latter of which is divided into idiopathic MCD (iMCD), human herpes virus-8 (HHV8)-associated MCD (HHV8-MCD), and polyneuropathy, organomegaly, endocrinopathy, monoclonal plasma cell disorder, skin changes (POEMS)-associated MCD (POEMS-MCD). iMCD can be further subclassified into iMCD–thrombocytopenia, ascites, reticulin fibrosis, renal dysfunction, organomegaly (iMCD-TAFRO) or iMCD–not otherwise specified (iMCD-NOS). Advances in diagnosis, classification, pathogenesis, and therapy are substantial since the original description of UCD by Benjamin Castleman in 1954. The advent of effective retroviral therapy and use of rituximab in HHV8-MCD have improved outcomes in HHV8-MCD. Anti–interleukin-6–directed therapies are highly effective in many iMCD patients, but additional therapies are required for refractory cases. Much of the recent progress has been coordinated by the Castleman Disease Collaborative Network (CDCN), and further progress will be made by continued engagement of physicians, scientists, and patients. Progress can also be facilitated by encouraging patients to self-enroll in the CDCN’s ACCELERATE natural history registry (#NCT02817997; www.CDCN.org/ACCELERATE).

Abstract Castleman disease (CD) describes a group of heterogeneous hematologic disorders with characteristic histopathological features. CD can present with unicentric or multicentric (MCD) regions of lymph node enlargement. Some cases of MCD are caused by human herpesvirus-8 (HHV-8), whereas others are HHV-8–negative/idiopathic (iMCD). Treatment of iMCD is challenging, and outcomes can be poor because no uniform treatment guidelines exist, few systematic studies have been conducted, and no agreed upon response criteria have been described. The purpose of this paper is to establish consensus, evidence-based treatment guidelines based on the severity of iMCD to improve outcomes. An international Working Group of 42 experts from 10 countries was convened by the Castleman Disease Collaborative Network to establish consensus guidelines for the management of iMCD based on published literature, review of treatment effectiveness for 344 cases, and expert opinion. The anti–interleukin-6 monoclonal antibody siltuximab (or tocilizumab, if siltuximab is not available) with or without corticosteroids is the preferred first-line therapy for iMCD. In the most severe cases, adjuvant combination chemotherapy is recommended. Additional agents are recommended, tailored by disease severity, as second- and third-line therapies for treatment failures. Response criteria were formulated to facilitate the evaluation of treatment failure or success. These guidelines should help treating physicians to stratify patients based on disease severity in order to select the best available therapeutic option. An international registry for patients with CD (ACCELERATE, #NCT02817997) was established in October 2016 to collect patient outcomes to increase the evidence base for selection of therapies in the future.

Multicentric Castleman disease (MCD) describes a heterogeneous group of disorders involving systemic inflammation, characteristic lymph node histopathology, and multi-organ dysfunction because of pathologic hypercytokinemia. Whereas Human Herpes Virus-8 (HHV-8) drives the hypercytokinemia in a cohort of immunocompromised patients, the etiology of HHV-8-negative MCD is idiopathic (iMCD). Recently, a limited series of iMCD cases in Japan sharing a constellation of clinical features, including thrombocytopenia (T), anasarca (A), fever (F), reticulin fibrosis (R), and organomegaly (O) has been described as TAFRO syndrome. Herein, we report clinicopathological findings on 25 patients (14 males and 11 females; 23 Japanese-born and two US-born), the largest TAFRO syndrome case series, including the first report of cases from the USA. The median age of onset was 50 years old (range: 23-72). The frequency of each feature was as follows: thrombocytopenia (21/25), anasarca (24/25), fever (21/25), organomegaly (25/25), and reticulin fibrosis (13/16). These patients frequently demonstrated abdominal pain, elevated serum alkaline phosphatase levels, and acute kidney failure. Surprisingly, none of the cases demonstrated marked hypergammoglobulinemia, which is frequently reported in iMCD. Lymph node biopsies revealed atrophic germinal centers with enlarged nuclei of endothelial cells and proliferation of endothelial venules in interfollicular zone. 23 of 25 cases were treated initially with corticosteroids; 12 patients responded poorly and required further therapy. Three patients died during the observation period (median: 9 months) because of disease progression or infections. TAFRO syndrome is a unique subtype of iMCD that demonstrates characteristic clinicopathological findings. Further study to clarify prognosis, pathophysiology, and appropriate treatment is needed.