When the Quest for a Cure Is Personal.

We asked three researchers how their personal connection to disease has affected them and what lessons it has taught them along the way.

Sequencing of Kaposi's Sarcoma Herpesvirus (KSHV) genomes from persons of diverse ethnicities and provenances with KSHV-associated diseases demonstrate multiple infections, novel polymorphisms, and low intra-host variance.

Recently published near full-length KSHV genomes from a Cameroon Kaposi sarcoma case-control study showed strong evidence of viral recombination and mixed infections, but no sequence variations associated with disease. Using the same methodology, an additional 102 KSHV genomes from 76 individuals with KSHV-associated diseases have been sequenced. Diagnoses comprise all KSHV-associated diseases (KAD): Kaposi sarcoma (KS), primary effusion lymphoma (PEL), KSHV-associated large cell lymphoma (KSHV-LCL), a type of multicentric Castleman disease (KSHV-MCD), and KSHV inflammatory cytokine syndrome (KICS). Participants originated from 22 different countries, providing the opportunity to obtain new near full-length sequences of a wide diversity of KSHV genomes. These include near full-length sequence of genomes with KSHV K1 subtypes A, B, C, and F as well as subtype E, for which no full sequence was previously available. High levels of recombination were observed. Fourteen individuals (18%) showed evidence of infection with multiple KSHV variants (from two to four unique genomes). Twenty-six comparisons of sequences, obtained from various sampling sites including PBMC, tissue biopsies, oral fluids, and effusions in the same participants, identified near complete genome conservation between different biological compartments. Polymorphisms were identified in coding and non-coding regions, including indels in the K3 and K15 genes and sequence inversions here reported for the first time. One such polymorphism in KSHV ORF46, specific to the KSHV K1 subtype E2, encoded a mutation in the leucine loop extension of the uracil DNA glycosylase that results in alteration of biochemical functions of this protein. This confirms that KSHV sequence variations can have functional consequences warranting further investigation. This study represents the largest and most diverse analysis of KSHV genome sequences to date among individuals with KAD and provides important new information on global KSHV genomics.

Single-cell landscape of idiopathic multicentric Castleman disease in identical twins.

ABSTRACT: Idiopathic multicentric Castleman disease (iMCD) is a rare cytokine-driven disorder characterized by systemic inflammation, generalized lymphadenopathy, and organ dysfunction. Here, we present an unusual occurrence of iMCD in identical twins and examined the immune milieu within the affected lymphoid organs and the host circulation using multiomic high-dimensional profiling. Using spatial enhanced resolution omics sequencing (Stereo-seq) transcriptomic profiling, we performed unsupervised spatially constrained clustering to identify different anatomic structures, mapping the follicles and interfollicular regions. After a cell segmentation approach, interleukin 6 (IL-6) pathway genes significantly colocalized with endothelial cells and fibroblastic reticular cells, confirming observations using a single-cell sequencing approach (10× Chromium). Furthermore, single-cell sequencing of peripheral blood mononuclear cells revealed an "inflammatory" peripheral monocytosis enriched for the expression of S100A family genes in both twins. In summary, we provided evidence of the putative cell-of-origin of IL-6 signals in iMCD and described a distinct monocytic host immune response phenotype through a unique identical twin model.

Inflammasome activation in patients with Kaposi sarcoma herpesvirus-associated diseases.

ABSTRACT: Kaposi sarcoma herpesvirus (KSHV)-associated diseases include Kaposi sarcoma (KS), primary effusion lymphoma (PEL), KSHV-associated multicentric Castleman disease (MCD), and KS inflammatory cytokine syndrome (KICS). PEL, MCD, and KICS are associated with elevated circulating inflammatory cytokines. However, activation of the inflammasome, which generates interleukin-1ß (IL-1ß) and IL-18 via active caspase-1/4/5, has not been evaluated in patients with KSHV-associated diseases (KADs). Herein we report that patients with HIV and ≥1 KAD present with higher plasma levels of IL-18 and increased caspase-1/4/5 activity in circulating monocytes compared with HIV-negative healthy volunteers (HVs) or people with HIV (PWH) without KAD. Within KAD subtypes, KICS and MCD shared enhanced caspase-1/4/5 activity and IL-18 production compared with HVs and PWH, whereas patients with PEL showed remarkably high levels of inflammasome complex formation (known as apoptosis-associated speck-like protein containing a caspase recruitment domain). Moreover, caspase-1/4/5 activity and IL-18 plasma levels correlated with KSHV viral load, indicating KSHV-driven inflammasome activation in KAD. Accordingly, factors released by cells latently infected with KSHV triggered inflammasome activation and cytokine production in bystander monocytes in vitro. Finally, both supervised and unsupervised analyses with inflammasome measurements and other inflammatory biomarkers demonstrate a unique inflammatory profile in patients with PEL, MCD, and KICS as compared with KS. Our data indicate that detrimental inflammation in patients with KAD is at least partially driven by KSHV-induced inflammasome activation in monocytes, thus offering novel approaches to diagnose and treat these complex disorders. These trials were registered at www.ClinicalTrials.gov as #NCT01419561, NCT00092222, NCT00006518, and NCT02147405.

Kaposi sarcoma-associated herpesvirus complement control protein (KCP) and glycoprotein K8.1 are not required for viral infection in vitro or in vivo.

Kaposi sarcoma-associated herpesvirus (KSHV), also known as human herpesvirus-8, is the causal agent of Kaposi sarcoma, a cancer that appears as tumors on the skin or mucosal surfaces, as well as primary effusion lymphoma and KSHV-associated multicentric Castleman disease, which are B-cell lymphoproliferative disorders. Effective prophylactic and therapeutic strategies against KSHV infection and its associated diseases are needed. To develop these strategies, it is crucial to identify and target viral glycoproteins involved in KSHV infection of host cells. Multiple KSHV glycoproteins expressed on the viral envelope are thought to play a pivotal role in viral infection, but the infection mechanisms involving these glycoproteins remain largely unknown. We investigated the role of two KSHV envelope glycoproteins, KSHV complement control protein (KCP) and K8.1, in viral infection in various cell types in vitro and in vivo. Using our newly generated anti-KCP antibodies, previously characterized anti-K8.1 antibodies, and recombinant mutant KSHV viruses lacking KCP, K8.1, or both, we demonstrated the presence of KCP and K8.1 on the surface of both virions and KSHV-infected cells. We showed that KSHV lacking KCP and/or K8.1 remained infectious in KSHV-susceptible cell lines, including epithelial, endothelial, and fibroblast, when compared to wild-type recombinant KSHV. We also provide the first evidence that KSHV lacking K8.1 or both KCP and K8.1 can infect human B cells in vivo in a humanized mouse model. Thus, these results suggest that neither KCP nor K8.1 is required for KSHV infection of various host cell types and that these glycoproteins do not determine KSHV cell tropism. IMPORTANCE: Kaposi sarcoma-associated herpesvirus (KSHV) is an oncogenic human gamma-herpesvirus associated with the endothelial malignancy Kaposi sarcoma and the lymphoproliferative disorders primary effusion lymphoma and multicentric Castleman disease. Determining how KSHV glycoproteins such as complement control protein (KCP) and K8.1 contribute to the establishment, persistence, and transmission of viral infection will be key for developing effective anti-viral vaccines and therapies to prevent and treat KSHV infection and KSHV-associated diseases. Using newly generated anti-KCP antibodies, previously characterized anti-K8.1 antibodies, and recombinant mutant KSHV viruses lacking KCP and/or K8.1, we show that KCP and K8.1 can be found on the surface of both virions and KSHV-infected cells. Furthermore, we show that KSHV lacking KCP and/or K8.1 remains infectious to diverse cell types susceptible to KSHV in vitro and to human B cells in vivo in a humanized mouse model, thus providing evidence that these viral glycoproteins are not required for KSHV infection.

A hypothesis on treatment strategy of severe multicentric Castleman disease with continuous renal replacement therapy.

Castleman disease (CD) is a rare lymphoproliferative disorder, with non-specific clinical manifestations, often delayed diagnosis and treatment, which pose a significant challenge in the present times. Patients diagnosed with this disease have poor prognosis due to the limited treatment options. Multicentric CD occurs at multiple lymph node stations and is associated with a proinflammatory response that leads to the development of the so-called 'B symptoms'. IL-6 seems to be a key cytokine involved in various manifestations such as lymphadenopathies, hepatosplenomegaly, and polyclonal hypergammaglobulinemia. Its levels correlate with the activity of the disease. Other consequences of MCD include increased fibrinogen levels leading to deep vein thrombosis and thromboembolic disorders, high hepcidin levels causing anaemia, elevated VEGF levels promoting angiogenesis and vascular permeability, which, along with hypoalbuminemia, induce oedema, ascites, pleural and pericardial effusions, and in severe cases, generalized anasarca. In extreme cases multiple organ failure can occur, often resulting in death. We propose the use of continuous renal replacement therapy (CRRT) in managing severe multicentric CD. Our arguments are based on the principles that CRRT is able to remove IL-6 from circulation thus attenuating the cytokine storm, can influence hepcidin levels, and reduction in oedema, and is often used in multiple organ failure to regain homeostasis control. Therefore, it could be used as a therapy or bridge therapy in severe cases. To sustain our hypothesis with evidence, we have gathered several studies from the literature confirming the successful removal of cytokines, especially IL-6 from circulation, which can be used as a starting point.

Idiopathic multicentric Castleman disease (iMCD)-idiopathic plasmacytic lymphadenopathy: A distinct subtype of iMCD-not otherwise specified with different clinical features and better survival.

Idiopathic multicentric Castleman disease (iMCD) is subclassified into iMCD-thrombocytopenia, anasarca, reticulin fibrosis, renal dysfunction, organomegaly (TAFRO) and iMCD-not otherwise specified (NOS) according to the Castleman Disease Collaborative Network (CDCN) consensus criteria. With a deeper understanding of iMCD, a group of patients with iMCD-NOS characterised by polyclonal hypergammaglobulinaemia, plasmacytic/mixed-type lymph node histopathology and thrombocytosis has attracted attention. This group of patients has been previously described as having idiopathic plasmacytic lymphadenopathy (IPL). Whether these patients should be excluded from the current classification system lacks sufficient evidence. This retrospective analysis of 228 patients with iMCD-NOS identified 103 (45.2%) patients with iMCD-IPL. The clinical features and outcomes of patients with iMCD-IPL and iMCD-NOS without IPL were compared. Patients with iMCD-IPL showed a significantly higher inflammatory state but longer overall survival. No significant difference in overall survival was observed between severe and non-severe patients in the iMCD-IPL group according to the CDCN severity classification. Compared with lymphoma-like treatments, multiple myeloma-like and IL-6-blocking treatment approaches in the iMCD-IPL group resulted in significantly higher response rates and longer time to the next treatment. These findings highlight the particularities of iMCD-IPL and suggest that it should be considered a new subtype of iMCD-NOS.

The application of a multidisciplinary approach in the diagnosis of Castleman disease and Castleman-like lymphadenopathies: A 20-year retrospective analysis of clinical and pathological features.

BACKGROUND: Castleman disease (CD) comprises a group of rare and heterogeneous haematological disorders, including unicentric (UCD) and multicentric (MCD) forms, the latter further subdivided into HHV8-MCD, POEMS-MCD and idiopathic-MCD (iMCD). However, according to the Castleman Disease Collaborative Network guidelines, the diagnosis of CD can only be achieved through collaboration between clinicians and pathologists. METHODS: We applied these clinical and pathological criteria and implement with clonality testing to a retrospective cohort of 48 adult and paediatric Italian patients diagnosed with reactive lymphadenitis with CD-like histological features. RESULTS: We confirmed the diagnosis of CD in 60% (29/48) of the cases, including 12 (41%) UCD and 17 (59%; five HHV8-MCD, three POEMS-MCD and nine iMCD) MCD. Of the remaining 19 cases (40%) with multiple lymphadenopathy, 5 (26%) were classified as autoimmune diseases, 1 (5%) as autoimmune lymphoproliferative disorder, 1 (5%) as IgG4-related disease, 11 (83%) as reactive lymphadenitis and 1 (5%) as nodal marginal zone lymphoma. CONCLUSIONS: Our study emphasizes the importance of the multidisciplinary approach to reactive lymphadenitis with CD-like features in order to achieve a definitive diagnosis and choose the appropriate treatment.

Immune-mediated thrombocytopenia and IL-6-mediated thrombocytosis observed in idiopathic multicentric Castleman disease.

Idiopathic multicentric Castleman disease (iMCD) is a rare haematological disorder characterized by generalized lymphadenopathy with atypical histopathological features and systemic inflammation caused by a cytokine storm involving interleukin-6 (IL-6). Three clinical subtypes are recognized: thrombocytopenia, anasarca, fever, renal dysfunction, organomegaly (iMCD-TAFRO); idiopathic plasmacytic lymphadenopathy (iMCD-IPL), involving thrombocytosis and hypergammaglobulinaemia; and iMCD-not otherwise specified (iMCD-NOS), which includes patients who do not meet criteria for the other subtypes. Disease pathogenesis is poorly understood, with potential involvement of infectious, clonal and/or autoimmune mechanisms. To better characterize iMCD clinicopathology and gain mechanistic insights into iMCD, we analysed complete blood counts, other clinical laboratory values and blood smear morphology among 63 iMCD patients grouped by clinical subtype. Patients with iMCD-TAFRO had large platelets, clinical severity associated with lower platelet counts and transfusion-resistant thrombocytopenia, similar to what is observed with immune-mediated destruction of platelets in immune thrombocytopenic purpura. Conversely, elevated platelet counts in iMCD-IPL were associated with elevated IL-6 and declined following anti-IL-6 therapy. Our data suggest that autoimmune mechanisms contribute to the thrombocytopenia in at least a portion of iMCD-TAFRO patients whereas IL-6 drives thrombocytosis in iMCD-IPL, and these mechanisms likely contribute to disease pathogenesis.

Dysmorphic megakaryocytes in TAFRO syndrome: A case series from a single institute.

TAFRO syndrome is a rare systemic inflammatory disorder of unknown etiology characterized by thrombocytopenia, anasarca, fever, reticulin myelofibrosis, renal dysfunction, and organomegaly. The diagnosis of TAFRO syndrome can be challenging; however, prompt diagnosis is vital because TAFRO syndrome is a progressive and life-threatening disease. We have showcased five patients with TAFRO syndrome who had similar bone marrow (BM) findings that could be considered the findings that characterize TAFRO syndrome. All patients were treated with corticosteroids and tocilizumab; three of the five patients (60 %) responded positively to the treatment. The unique BM findings observed in this study were megakaryocytes with distinct multinuclei and three-dimensional and indistinct bizarre nuclei ("dysmorphic megakaryocyte"), similar to the megakaryocyte morphology observed in myeloproliferative neoplasms (MPNs). Notably, dysmorphic megakaryocytes were observed in all five cases, whereas only two of the five patients tested positive for reticulin myelofibrosis, and three of the five patients had megakaryocytic hyperplasia, which are considered typical findings of TAFRO syndrome. Thus, the BM findings of dysmorphic megakaryocytes could help in the correct and immediate diagnosis of TAFRO syndrome.

Lymphadenopathy in the rheumatology practice: a pragmatic approach.

Lymphadenopathy is a common clinical finding and diagnostic challenge within general medicine and rheumatology practice. It may represent a primary manifestation of an underlying immune-mediated disease or indicate an infectious or neoplastic complication requiring differing management. Evaluating lymphadenopathy is of particular relevance in rheumatology, given that lymph node enlargement is a common finding within the clinical spectrum of several well-known rheumatologic disorders including RA, SLE and SS. In addition, lymphadenopathy represents a hallmark manifestation of rare immunological diseases such as Castleman disease and IgG4-related disease that must be considered in the differential diagnosis because effective targeted treatments can now impact the prognosis of these conditions. In this review we present an overview of the clinical significance of lymphadenopathy in common and rare rheumatologic diseases and propose a practical approach to lymphadenopathy in the rheumatology practice. Differential diagnosis of Castleman disease and therapeutic options for this condition of increasing rheumatologic interest will be discussed in detail.

Longitudinal, natural history study reveals the disease burden of idiopathic multicentric Castleman disease.

Idiopathic multicentric Castleman disease (iMCD) is a rare hematologic disorder with heterogeneous presentations ranging from moderate constitutional symptoms to life-threatening multiorgan system involvement. There are vastly different clinical subtypes, with some patients demonstrating thrombocytopenia, anasarca, fever/elevated C-reactive protein, reticulin fibrosis/renal failure, and organomegaly (TAFRO) and others having milder/more moderate symptoms with potential for severe disease (not otherwise specified, NOS). Due to its rarity and heterogeneity, the natural history and long-term burden of iMCD are poorly understood. We investigated real-world medical data from ACCELERATE, a large natural history registry of patients with Castleman disease, to better characterize the long-term disease burden experienced by these patients. We found that iMCD-TAFRO patients face a significant hospitalization burden, requiring more time in the hospital than iMCDNOS patients during the year surrounding diagnosis (median [interquartile range]: 36 [18-61] days vs. 0 [0-4] days; P<0.001). In addition, we found life-sustaining interventions, such as mechanical ventilation (17%) and dialysis (27%), were required among iMCD patients, predominantly those with iMCD-TAFRO. iMCD-NOS patients, however, spent a significantly greater proportion of time following disease onset in a state of disease flare (median 52.3% vs. 18.9%; P=0.004). Lastly, we observed severe iMCD-related morbidities, such as acute renal failure, sepsis and pneumonia, among others, arising after iMCD diagnosis, impairing the patients' quality of life. These data demonstrate a substantial disease burden experienced by iMCD patients and emphasize the importance of ongoing research into iMCD to aid disease control.

Retrospective cohort evaluation of non-HIV Castleman disease from a single academic center in Beijing, China.

The purpose is to ascertain the clinical impact of Castleman disease (CD) by reassessment of the real-world data from Peking University First Hospital (PKUFH). The results will contribute to the standardization of diagnosis and treatment on CDs. Based on the last 15-year retrospective real-world data from Peking University First Hospital (PKUFH), we reclassified and re-evaluated the clinical and pathological information of patients with pathologically suspected diagnosis of CD. A total of 203 patients were included in our study, in which the diagnosis of CD was confirmed in 189 cases, including 118 patients with unicentric CD (UCD, n = 118, 62.4%) and 71 patients with multicentric CD (MCD, n = 71, 37.6%). A total of 44.1% (n = 52) of UCDs in our cohort were complicated with paraneoplastic pemphigus (PNP). The treatment of UCD is primarily surgical, with a 5-year overall survival (OS) of 88.1%. Patients with PNP had a poorer prognosis than those without PNP (82.9% (95% CI 123-178) vs 92.8% (95% CI 168-196), log-rank p = 0.041). The rate of concurrent systemic symptoms was 74.6% (n = 53), and renal involvement occurred in 49.3% (n = 35) MCD patients. The MCD treatments were mainly chemotherapy regimens, with a 5-year OS of 77.6% (95% CI, 143-213). Patients with UCD demonstrate a better overall prognosis than patients with MCD. But the prognosis of those complicated with PNP was poor. The differential diagnosis of MCD is extensive. MCD treatment in China is heterogeneous. The inaccessibility of anti-IL-6-targeted drugs in China may contribute to the poor prognosis for patients with MCD.A preprint has previously been published (Guo et al. 34).

Castleman disease- demographics, associations, and outcomes: an analysis of adult 791 cases.

BACKGROUND: Castleman disease (CD), also known as angiofollicular lymph node hyperplasia or large lymph node hyperplasia, is a rare medical condition. Despite its rarity, it exhibits diverse clinical presentations and outcomes, which pose challenges for comprehensive understanding and management. This study aims to shed light on the demographics, associations, and outcomes of CD by conducting a retrospective analysis. METHODS: The National Inpatient Sample (US) was used to identify patients with the diagnosis of Castleman disease using ICD-10 diagnosis code D47.Z2, during the years 2016-2019. Data was collected on demographics, associated diagnoses, treatments and outcomes. Data analysis was performed using STATA Version 17, College Station, TX: Stata Corp LLC. RESULTS: Our study identified 791 hospitalizations involving adult CD patients. The mean age of these patients was 52.4 years, with a male predominance (56.1%). Whites comprised the largest racial group affected (50.1%). Most patients were covered by Medicare (39.6%). The majority received treatment in urban teaching hospitals (84.0%) and large-bed size facilities (62.5%). In-hospital mortality was low at 2.8%, with an average length of stay of 7.5 days and average total charges of $109,308. Common associations included acute kidney injury (27.0%), congestive heart failure (17.1%), sepsis (16.4%), and acute respiratory failure (12.6%). Hematological and lymphatic associations featured anemia (47.5%), thrombocytopenia (12.2%), and other conditions. Red blood cell transfusions were administered to 11.1% of patients. CONCLUSION: This study contributes valuable insights into CD, a rare and clinically heterogeneous disease. It underscores the importance of recognizing its associations and complications. Additionally, it highlights the need for further research and improved diagnostic and treatment guidelines to address the complexity of this condition.

Sirolimus is effective for refractory/relapsed idiopathic multicentric Castleman disease: A single-center, retrospective study.

Refractory/relapsed idiopathic multicentric Castleman disease (R/R iMCD) has limited treatment options. With studies showing increased mTOR activation in iMCD patients, sirolimus becomes an attractive and promising therapy for R/R iMCD. Here we report the results of a retrospective study involving 26 R/R iMCD patients treated with sirolimus-containing regimen. The median age at sirolimus initiation was 40.5 years (23-60), with a median prior treatment line of 2 (1-5). 18 patients (69.2%) achieved symptomatic and biochemical response, with a median time to at least overall partial remission of 1.9 months (0.5-14.6). The median follow-up time from sirolimus initiation was 11.7 months (1.6-50.7) and the median time to next treatment (TTNT) was 46.2 months. No patients died at the end of follow-up. Most of the patients in the cohort are in ongoing responses and continue sirolimus therapy. Sirolimus is well tolerated with minor adverse effects. In conclusion, sirolimus is effective for R/R iMCD patients with good tolerance.

Outcomes in Kaposi's sarcoma-associated herpesvirus -associated primary effusion lymphoma and multicentric Castleman's disease in patients with human immunodeficiency virus (HIV) in a safety-net hospital system.

OBJECTIVE: To describe cases of Kaposi's sarcoma-associated herpesvirus (KSHV)-associated multicentric Castleman's disease (MCD) and primary effusion lymphoma (PEL) in patients with HIV from a large, safety-net hospital system in Dallas, Texas, USA. METHODS: We conducted a retrospective review of patients with HIV-associated PEL and/or MCD. RESULTS: Twelve patients with PEL and 10 patients with MCD were identified. All patients were male and 17 of 20 were men who have sex with men; 66.7% of PEL patients and 50% of MCD patients had concurrent KS at the time of diagnosis; 42% of patients with PEL and 20% of patients with MCD died during the follow-up period. We noted improved survival in our cohort compared to previous studies, particularly in our PEL patients with a median survival of 11.4 months compared to 3-6-month median survival historically. Median follow-up time for MCD patients was 17.5 months. This improved survival is despite suboptimal antiretroviral therapy (ART) adherence at diagnosis, with only 50% of patients on ART at the time of MCD/PEL diagnosis. CONCLUSION: These data highlight the importance of early recognition of PEL and MCD, and the larger-scale efforts needed to better understand the pathogenetic drivers of clinical outcomes in patients affected by KSHV-related diseases.

Pediatric TAFRO syndrome: A multi-institution case series illustrating clinical challenges and excellent outcomes.

A rare lymphoproliferative disorder involving thrombocytopenia (T), anasarca (A), fever (F), reticulin fibrosis (R), renal dysfunction (R), and organomegaly (O), called TAFRO syndrome, was first reported in 2010. Considered a variant of idiopathic multicentric Castleman's disease, the recent discovery and rarity of this syndrome pose challenges to diagnosis and management. Herein, we review three pediatric cases, including an infant, that illustrate the heterogeneity of TAFRO syndrome. Despite differences in presentation and treatment responses, all patients experienced excellent outcomes. This multi-institutional case series highlights the need to work toward earlier diagnosis and improved long-term management recommendations for patients with TAFRO syndrome.

A Multicentric Castleman Disease Associated with Mixed Warm and Cold Antibody-Mediated AHA Responsive to Siltuximab.

Castleman disease is non-clonal lymphoproliferative disorders defined by hypertrophy of lymph nodes. The multicentric form (MCD), in which multiple lymph node stations are involved, is not associated with HHV8 infection, but considered idiopathic, although IL-6 appears to play a central role in its pathogenesis. Here, we report the case of a patient who presented with mixed autoimmune hemolytic anemia (AIHA) and adenopathy that was very challenging to diagnose due to very low values of hemoglobin and refractoriness of obtaining any improvement of AIHA with standard first and second lines of therapy (steroids, rituximab, immunoglobulin, erythropoietin, and cyclosporine). When we safely proceeded to lymph node biopsy, a diagnosis of MCD was established. This permitted the treatment with siltuximab, an anti-IL-6 monoclonal antibody. After only 1 week, hemoglobin raised and he was discharged. After 1 year, he was still in remission. This case underlines the challenges in diagnosis of MCD, and the first case of response to siltuximab after the failure of rituximab to relieve mixed AIHA.

IgG4-related lymphadenopathy.

IgG4-related lymphadenopathy is a nodal manifestation of IgG4-related disease (IgG4RD) which is characterized by increased polytypic IgG4+ plasma cells and IgG4+/IgG+ plasma cell ratio in lymph nodes and morphologically manifested as various patterns of reactive lymphadenopathy: Castleman disease-like, follicular hyperplasia, interfollicular expansion, progressive transformation of germinal centers and inflammatory pseudotumor-like. It typically presents with solitary or multiple, mild to moderate lymph node enlargement in otherwise asymptomatic patients. The serum IgG4 level is frequently elevated but C-reactive protein often remains normal. In patients not having a history of IgG4RD or manifestation of extranodal IgG4RD, a diagnosis of IgG4-lymphadenopathy should only be made with great caution given the non-specific morphologic features that can overlap with ANCA-associated vasculitis, interleukin-6 syndromes, Rosai-Dorfman disease, inflammatory myofibroblastic tumor, syphilis, lymphoma, and plasma cell neoplasia. Elevated IgG4 parameters, appropriate morphologies, and clinical correlation are essential to make the diagnosis of IgG4-lymphadenopathy more specific and clinically meaningful.

The Cytokine Storm of Multicentric Castleman Disease.

As described throughout this book, different triggers can elicit a variety of different cytokine storm disorders that share overlapping clinical features (Fig. 31.1). Even within a particular cytokine storm disorder, multiple different triggers can elicit the syndrome. Like HLH, multicentric Castleman disease (MCD) serves as a great example of this as it can be caused by a viral infection, neoplastic cell population, or an unknown cause. Furthermore, the idiopathic subtype of MCD (iMCD) provides one of the first examples of a cytokine storm disorder that could be abrogated with targeted neutralization of a single cytokine when inhibition with the anti-interleukin-6 (IL-6) receptor monoclonal antibody tocilizumab was shown to effectively treat iMCD in the 1990s. Of course, this "iMCD treatment," tocilizumab, has been used in a variety of cytokine storm settings over the last 30+ years.