TAFRO Syndrome: A Syndrome or a Subtype of Multicentric Castleman Disease?

TAFRO (thrombocytopenia, anasarca, fever, reticulin fibrosis of bone marrow/renal dysfunction, organomegaly) syndrome is a systemic inflammatory disorder of unknown etiology. It has been recognized as a subtype of idiopathic multicentric Castleman disease (iMCD), and the international diagnostic criteria for iMCD-TAFRO require a lymph node histopathology consistent with iMCD. Furthermore, TAFRO syndrome is defined as a heterogeneous clinical entity caused by underlying diseases such as malignancy, autoimmune diseases, or infections. However, the cases that led to the proposal of TAFRO syndrome lacked recognizable lymphadenopathy and were inconsistent with any other diseases, despite vigorous efforts in differential diagnosis. Irrespective of the presence or absence of Castleman disease (CD)-like histology, TAFRO syndrome exhibits homogeneous clinical, laboratory, and prognostic features, setting it apart from iMCD without TAFRO syndrome. Defining iMCD-TAFRO apart from TAFRO syndrome is deemed meaningless and confusing. MCD is a heterogeneous lymphoproliferative disorder consisting of several subtypes with different pathogenesis, clinical manifestations, and histological features. Typical MCD in Japan, characterized by the histology of plasma cell type and marked polyclonal hypergammaglobulinemia, is identical to idiopathic plasmacytic lymphadenopathy with polyclonal hyperimmunoglobulinemia (IPL). Although IPL is classified into iMCD-NOS (not otherwise specified), it should be recognized as a distinct clinicopathological entity. Furthermore, we propose to separate TAFRO syndrome from the MCD category as a defined disorder.

TAFRO Syndrome: A Disease Requiring Immediate Medical Attention.

TAFRO syndrome was first described in 2010, standing for thrombocytopenia, anasarca, fever, reticulin fibrosis and organomegaly. Because the lymph node histopathology of TAFRO syndrome mimics idiopathic multicentric Castleman disease (iMCD), some researchers consider TAFRO syndrome to be a subtype of iMCD. However, the clinical features of TAFRO syndrome considerably differ from those of iMCD without TAFRO. The clinical features of patients with TAFRO syndrome with or without iMCD-histopathology are similar, and these patients require an accurate diagnosis and urgent treatment. Although a histological diagnosis, including a differential diagnosis, is important, lymph node involvement in patients with TAFRO syndrome is usually modest or sometimes absent. Furthermore, a bleeding tendency due to thrombocytopenia and severe anasarca hampers performing a biopsy. Nonetheless, patients with various other disorders may manifest TAFRO syndrome-like symptoms, making the differential diagnosis in borderline cases difficult. Therefore, the establishment of precise and specific biomarkers is important.

Castleman disease and TAFRO syndrome.

Although Castleman disease was first described in 1956, this disease includes various conditions, including unicentric Castleman disease with hyaline vascular histology, human herpesvirus-8 (HHV-8) related multicentric Castleman disease, idiopathic multicentric Castleman disease, and mimics of Castleman disease associated with other conditions. To date, Castleman disease remains incompletely understood due to its rareness and difficulties in clinical and pathological diagnosis. TAFRO syndrome was reported in Japan in 2010. Because lymph node histology is similar in patients with TAFRO syndrome and Castleman disease, TAFRO syndrome is described as a related disorder of Castleman disease. Clinically, however, these conditions differ markedly. Although elevated interleukin-6 (IL-6) expression is characteristic of Castleman disease, increased expression of IL-6 may occur in patients with other diseases, making elevated IL-6 unsuitable for differential diagnosis. Further understanding of these disorders requires the identification of novel disease-specific biomarkers. This review article therefore outlines the characteristics of Castleman disease and TAFRO syndrome.

Patient's age and D-dimer levels predict the prognosis in patients with TAFRO syndrome.

OBJECTIVES: To identify prognostic factors for TAFRO syndrome, a rare inflammatory disorder of unknown etiology characterized by thrombocytopenia, anasarca, fever, reticulin myelofibrosis, renal dysfunction, and organomegaly. METHODS: Data of patients with TAFRO syndrome were extracted from a Japanese patient registry. Patients were divided into groups according to the clinical and laboratory parameters at initial presentation. Cut-off values for the laboratory parameters were determined using receiver operating characteristic curve analysis and by clinical relevance. Patient survival was analyzed by the Kaplan-Meier method. Univariable analysis was performed using log-rank tests. Multivariable analyses were performed with the logistic regression model and the Cox proportional hazards model. RESULTS: We extracted the data of 83 patients with TAFRO syndrome from the registry. Univariable analysis identified several potential prognostic factors. Of these factors, age ≥60 years and D-dimer ≥18 µg/dL remained significant predictors of poor overall survival in the multivariable Cox proportional hazards model. Based on these results, we developed a simple prognostic scoring system for TAFRO syndrome (TS-PSS). CONCLUSION: Patients in our cohort were stratified into low, intermediate, and high-risk groups by the TS-PSS. This system should be verified with independent patient cohorts in future studies.

Optimal treatments for TAFRO syndrome: a retrospective surveillance study in Japan.

TAFRO syndrome is a systemic inflammatory disorder of unknown etiology characterized by thrombocytopenia, anasarca, fever, reticulin myelofibrosis, renal dysfunction, and organomegaly. Mortality in patients with this syndrome is high; however, an optimal treatment strategy has not been established. To explore the strategy, we retrospectively analyzed 81 patients with TAFRO syndrome registered in the Multicenter Collaborative Retrospective Study for Establishing the Concept of TAFRO Syndrome in Japan by December 2019. Sixty-eight patients received corticosteroid therapy as the first-line treatment, and as the second-line treatment, 21 received tocilizumab (Toc), 14 received cyclosporine A (CsA), and 8 received rituximab (Rit) in addition to corticosteroids. We compared these second-line treatment groups by setting the primary endpoint as time to next treatment or death (TTNT). Kaplan-Meier analysis showed that the median TTNT in the Toc, CsA, and Rit groups were 2.8 months, 9.2 months, and not reached, respectively. The TTNT of the Rit group was significantly longer than that of the Toc group. In contrast, there were no significant differences in overall survival between groups, indicating that subsequent salvage therapies rescued a large proportion of patients who failed the second-line treatments. Further studies are warranted to establish the optimal treatment strategies for this syndrome.

Epidemiological analysis of multicentric and unicentric Castleman disease and TAFRO syndrome in Japan.

Castleman disease is a polyclonal lymphoproliferative disease which is clinically classified into unicentric (UCD) and multicentric (MCD). TAFRO syndrome is a relatively new concept that partly overlaps with MCD. Due to their rarity, their incidence remains unknown. This study investigated the incidence and prevalence of UCD, MCD, and TAFRO syndrome in Japan using a fixed-point observation method based on their incidence in Ishikawa prefecture. The annual incidences of MCD, UCD, and TAFRO syndrome in Japan were 309-731, 71-542, and 110-502, respectively, yielding annual incidence rates per million individuals of 2.4-5.8, 0.6-4.3, and 0.9-4.9, respectively, and nationwide prevalence of 4,180-14,900, 1,350-10,300, and 860-7,240, respectively. In conclusion, MCD, UCD and TAFRO syndrome may not be as rare as previously estimated in Japan.

The potential role of follicular helper T cells in idiopathic multicentric Castleman disease with and without TAFRO syndrome.

Idiopathic multicentric Castleman disease (iMCD) is a systemic inflammatory disease of unknown etiology caused by hypercytokinemia. Recently, TAFRO (thrombocytopenia, anasarca, fever, renal failure or reticulin fibrosis, and organomegaly) syndrome has been reported, which shows similar histopathological findings to iMCD and factors associated with a poor prognosis. iMCD shows no plasma cell infiltration in the germinal center (GC), but CD38-positive (CD38+)-plasma cells are observed in the interfollicular area. Our previous report revealed that atrophic change of GC, glomeruloid vascular proliferation, and abnormal proliferation of follicular dendritic cells are more prominent in iMCD with TAFRO (TAFRO+) in comparison to iMCD without TAFRO (TAFRO-). In addition, the numbers of CD38+ and immunoglobulin G4-positive (IgG4+) plasma cells were decreased in the interfollicular area. The roles of T follicular helper cells (Tfh) are well-known to assist B-cell proliferation, maturation, and differentiation．It maintains the formation of GC and is also related in the class switching of IgG isotypes, including IgG4. Thus, we immunohistochemically examined the number of Tfh in GCs in both TAFRO- and TAFRO+ iMCD. The number of Tfh was significantly decreased in TAFRO- iMCD (n = 9) and was further decreased in TAFRO+ iMCD (n = 18) in comparison to non-specific lymphadenopathy (n = 6) and IgG4-related disease (n = 4). These results suggest that decreased Tfh may be one etiology of iMCD.

Is TAFRO syndrome a subtype of idiopathic multicentric Castleman disease?

Castleman disease (CD) is a rare lymphoproliferative disorder that can be unicentric or multicentric. Multicentric CD (MCD) is further subdivided into human herpesvirus type-8-associated, POEMS syndrome-associated, and idiopathic (iMCD). TAFRO syndrome is a newly identified disorder of unknown etiology characterized by thrombocytopenia, anasarca, fever, reticulin myelofibrosis, renal dysfunction, and organomegaly. The TAFRO syndrome is sometimes regarded as a subtype of iMCD (TAFRO-iMCD), whereas iMCD without TAFRO syndrome is considered "not otherwise specified" (iMCD-NOS). However, a proportion of patients with TAFRO syndrome have been diagnosed without lymph node biopsies (TAFRO syndrome without proven iMCD; TAFRO-w/op-iMCD). To clarify the clinical features of iMCD-NOS, TAFRO-iMCD, and TAFRO-w/op-iMCD, we retrospectively analyzed 220 patients extracted from the database of the Multicenter Collaborative Retrospective Study for Establishing the Concept of TAFRO Syndrome. The patients included 87 with iMCD-NOS, 63 with TAFRO-iMCD, and 19 with TAFRO-w/op-iMCD. Patients in all three groups exhibited anemia, hypoalbuminemia, and elevated serum C-reactive protein and interleukin-6 levels. No significant differences in clinical, laboratory, and prognostic features were noted between the TAFRO-iMCD, and TAFRO-w/op-iMCD groups. However, the iMCD-NOS group exhibited polyclonal hyper-γ-globulinemia. The five-year survival rates of patients in the iMCD-NOS and TAFRO-involved groups were 100% and 66.5%, respectively (dropping markedly during the first few months in the latter). The iMCD-NOS and the TAFRO-iMCD samples typically showed plasma cell and mixed-type histologies, respectively. Thus, iMCD can be classified into two distinct subtypes, iMCD-NOS and TAFRO-iMCD. As such, TAFRO-iMCD and TAFRO-w/op-iMCD may be considered the same entity, requiring prompt diagnosis and intensive care.