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.

IgG4-related disease is a recently recognized systemic syndrome characterized by mass-forming lesions with lymphoplasmacytic infiltration, increase in the number of IgG4 þ cells in affected tissues and elevation of serum IgG4 levels. In 2009, we were the first to report skin lesions in patients with IgG4-related disease, but no large case series has been reported and clinicopathological findings remain unclear. To clarify these features, we herein report 10 patients (9 men and 1 woman; median age, 64 years; age range, 46-81 years) with IgG4-related skin disease. All patients had erythematous and itchy plaques or subcutaneous nodules on the skin of the head and neck, particularly in the periauricular, cheek, and mandible regions, except for one patient, whose forearm and waist skin were affected. In addition, eight patients had extracutaneous lesions: these were found on the lymph nodes in six patients, the lacrimal glands in three patients, the parotid glands in three patients, and the kidney in one patient. Histologically examined extracutaneous lesions were consistent with IgG4-related disease; five of six lymph node lesions showed progressively transformed germinal centers-type IgG4-related lymphadenopathy. Cases of IgG4-related skin disease were classified into two histological patterns: those exhibiting a nodular dermatitis pattern and those with a subcutaneous nodule pattern. The infiltrate was rich in plasma cells, small lymphocytes, and eosinophils; the majority of the plasma cells were IgG4 þ . The IgG4 þ cell count was 49-396 per high-power field (mean±s.d., 172±129), with an IgG4 þ /IgG þ cell ratio ranging from 62 to 92%. Serum IgG4 levels were elevated in all examined patients. In conclusion, patients with IgG4-related skin disease had uniform clinicopathology. Lesions were frequently present on the skin of the periauricular, cheek, and mandible regions, and were frequently accompanied by IgG4-related lymphadenopathy.

Patients with rheumatoid arthritis often develop methotrexate‐associated lymphoproliferative disorders (MTX‐LPD) during MTX treatment. MTX‐LPD occasionally regresses spontaneously after simply discontinuing MTX treatment. In patients without spontaneous regression, additional chemotherapy is required to avoid disease progression. However, the differences between spontaneous and non‐spontaneous regression have yet to be elucidated. To clarify the factors important for spontaneous regression, we analyzed the clinicopathological features of 51 patients with rheumatoid arthritis who developed MTX‐LPD (diffuse large B‐cell lymphoma [DLBCL]‐type [n = 34] and classical Hodgkin lymphoma [CHL]‐type [n = 17]). We examined the interval from MTX discontinuation to the administration of additional chemotherapy. The majority of DLBCL‐type MTX‐LPD patients (81%) exhibited remission with MTX discontinuation alone. In contrast, the majority of CHL‐type MTX‐LPD patients (76%) required additional chemotherapy. This difference was statistically significant (P = 0.001). However, overall survival was not significantly different between DLBCL‐type and CHL‐type (91% vs 94%, respectively; P > 0.05). Thus, the morphological differences in the pathological findings of MTX‐LPD may be a factor for spontaneous or non‐spontaneous regression after discontinuation of MTX.

Thrombocytopenia, anasarca, fever, reticulin fibrosis, renal insufficiency, and organomegaly (TAFRO) syndrome is a heterogeneous entity manifesting with a constellation of symptoms described above that can occur in the context of idiopathic multicentric Castleman disease (iMCD) as well as infectious diseases, malignancies, and rheumatologic disorders. So, iMCD-TAFRO is an aggressive subtype of iMCD with TAFRO syndrome and often hyper-vascularized lymph nodes. Since we proposed diagnostic Yoshito Nishimura and Noriko Iwaki contributed equally to this study.

Tirabrutinib is a second‐generation Bruton’s tyrosine kinase inhibitor with greater selectivity than ibrutinib. Here, we conducted a multicenter, phase II study of tirabrutinib in patients with treatment‐naïve (Cohort A) or with relapsed/refractory (Cohort B) Waldenström’s macroglobulinemia (WM). Patients were treated with tirabrutinib 480 mg once daily. The primary endpoint was major response rate (MRR; ≥ partial response). Secondary endpoints included overall response rate (ORR; ≥ minor response), time to major response (TTMR), progression‐free survival (PFS), overall survival (OS), and safety. In total, 27 patients (18 in Cohort A; 9 in Cohort B) were enrolled. The median age was 71 y, and the median serum immunoglobulin M level was 3600 mg/dL. Among the patients, 96.2% had the MYD88L265P mutation. MRR and ORR were 88.9% and 96.3%, respectively (Cohort A: MRR, 88.9%; ORR, 94.4%; Cohort B: MRR, 88.9%; ORR, 100%). Median TTMR was 1.87 mo. PFS and OS were not reached with a median follow‐up of 6.5 and 8.3 mo for Cohorts A and B, respectively. The most common adverse events (AEs) were rash (44.4%), neutropenia (25.9%), and leukopenia (22.2%), with most AEs classified as grade 1 or 2. Grade ≥ 3 AEs included neutropenia (11.1%), lymphopenia (11.1%), and leukopenia (7.4%). No grade 5 AEs were noted. All bleeding events were grade 1; none were associated with drug‐related atrial fibrillation or hypertension. Although the follow‐up duration was relatively short, the study met the primary endpoint. Therefore, tirabrutinib monotherapy is considered to be highly effective for both untreated and relapsed/refractory WM with a manageable safety profile. (JapicCTI‐173646).

Multicentric Castleman disease (MCD) is a heterogeneous lymphoproliferative disorder. It is characterized by inflammatory symptoms, and interleukin (IL)-6 contributes to the disease pathogenesis. Human herpesvirus 8 (HHV-8) often drives hypercytokinemia in MCD, although the etiology of HHV-8-negative MCD is idiopathic (iMCD). A distinct subtype of iMCD that shares a constellation of clinical features including thrombocytopenia (T), anasarca (A), fever (F), reticulin fibrosis (R), and organomegaly (O) has been reported as TAFRO-iMCD, however the differences in cytokine profiles between TAFRO-iMCD and iMCD have not been established. We retrospectively compared levels of serum interferon γ-induced protein 10 kDa (IP-10), platelet-derived growth factor (PDGF)-AA, interleukin (IL)-10, and other cytokines between 11 cases of TAFRO-iMCD, 6 cases of plasma cell type iMCD, and 21 healthy controls. During flare-ups, patients with TAFRO-iMCD had significantly higher serum IP-10 and tended to have lower PDGF-AA levels than the other 2 groups. In addition, serum IL-10, IL-23, and vascular endothelial growth factor-A were elevated in both TAFRO-iMCD and iMCD. Elevated serum IP-10 is associated with inflammatory diseases including infectious diseases. There was a strong correlation between high serum IP-10 and the presence of TAFRO-iMCD, suggesting that IP-10 might be involved in the pathogenesis of TAFRO-iMCD.

Recently, atypical Castleman's disease (CD) was reported in Japan. This disease is considered as TAFRO syndrome or non-idiopathic plasmacytic lymphadenopathy (IPL), a constellation of clinical symptoms, namely, thrombocytopenia, anasarca, fever, reticulin fibrosis, and organomegaly without hyper-γ-globulinemia. Histopathologically, this disease is similar to hyaline vascular (HV)-type CD. Here, we present a 43-year-old Japanese woman meeting the clinical criteria of TAFRO syndrome who was successfully treated with combined corticosteroid therapy. She showed a rapidly progressive course of thrombocytopenia, systemic lymphadenopathy, fever, anasarca, and increase in acute inflammatory proteins without hyper-γ-globulinemia. Lymph node biopsy was performed and revealed HV-type CD without human herpes virus 8 infection, which was clinicopathologically compatible with non-IPL. The association of these atypical features with well-known multicentric Castleman's disease (MCD), namely, HV-type histology with systemic lymphadenopathy, marked thrombocytopenia even with a high level of interleukin-6, and increased acute inflammatory proteins without hyper-γ-globulinemia, suggests that TAFRO syndrome as presented in our case is a novel entity, which may have been diagnosed as MCD in the past. To define this novel entity more clearly and to demonstrate its etiology, further nationwide surveys of this syndrome and MCD are needed.

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