Bone Marrow Findings of Idiopathic Multicentric Castleman Disease: A Histopathologic Analysis and Systematic Literature Review

Idiopathic multicentric Castleman disease (iMCD) is a polyclonal lymphoproliferative disorder characterized by constitutional symptoms, generalized lymphadenopathy, cytopenias, and multi-organ dysfunction due to excessive cytokines, notably Interleukin-6. iMCD is often sub-classified into iMCD-TAFRO, which is associated with thrombocytopenia (T), anasarca (A), fever/elevated C-reactive protein (F), renal dysfunction (R), and organomegaly (O), and iMCD-NOS, which is typically associated with thrombocytosis and hypergammaglobulinemia. The diagnosis of iMCD is challenging as consensus clinico-pathological diagnostic criteria were only recently established and include several non-specific lymph node histopathological features. Identification of further clinico-pathological features commonly found in iMCD could contribute to more accurate and timely diagnoses. We set out to characterize bone marrow (BM) histopathological features in iMCD, assess differences between iMCD-TAFRO and iMCD-NOS, and determine if these findings are specific to iMCD. Examination of BM specimens from 24 iMCD patients revealed a high proportion with hypercellularity, megakaryocytic atypia, reticulin fibrosis, and plasmacytosis across patients with both iMCD-NOS and iMCD-TAFRO with significantly more megakaryocytic hyperplasia (p=0.001) in the iMCD-TAFRO cases. These findings were also consistent with bone marrow findings from 185 published cases of iMCD-NOS and iMCD-TAFRO. However, these findings are relatively nonspecific as they can be seen in various other infectious, malignant, and autoimmune diseases. This article is protected by copyright. All rights reserved.

Abstract TMP106: Intestinal Barrier Leakage Exacerbates Cerebral Cavernous Malformation Development in Murine Models

Introduction: A serendipitous discovery demonstrating a greater cerebral cavernous malformation (CCM) burden within a murine CCM disease model housed in an unclean vivarium than in a cleaner facility led to the observation of intestinal microbiome involvement in CCM development through lipopolysaccharide from gram negative bacteria. Hence we investigated the effect on CCM development in CCM models by genetic or chemical disruption of the intestinal barrier.

Hypothesis: Intestinal barrier disruption increases CCM burden in CCM murine models.

Methods: Acute iBECre; Ccm3 fl/fl mice were bred to be deficient ( Muc2 +/- , Muc2 -/- ) in the mucin 2 gene with CCM assessment at P21. CCM burden was assessed in the following 3 chronic models at 5 months of age. The murine model Ccm3 +/- housed in an unclean vivarium was treated with 1% p80 emulsifier starting at 21 days of age (n=22) or with placebo (n=16). Less CCM penetrant Ccm1 +/- mice housed in a clean facility were contemporaneously treated with 2% dextran sodium sulfate (DSS) starting at 21 days of age (n=22) or with placebo (n=17). More CCM penetrant Ccm1 +/- Msh2 -/- mice housed in an unclean vivarium were treated with 0.5% DSS starting at 2 months of age (n=11) or with placebo (n=6). We assessed CCM volume in brains by micro-computed tomography.

Results: Mean CCM volume in acute Ccm3 -/- models doubled from 1.8 mm 3 with no Muc2 loss (n=11) to 4.7 mm 3 with homozygotic Muc2 loss (p<0.001, n=10) with an increasing trend to 2.6 mm 3 with heterozygotic Muc2 loss (p=0.07, n=15). Mean CCM volume/brain volume (X 10 6 ) per mouse doubled from 10.7 in placebos to 24.4 (p=0.01) by emulsifier treatment in the Ccm3 +/- chronic model and significantly increased from 0.1 in placebos to 9.2 (p<0.001) by 2% DSS treatment in the Ccm1 +/- model, with an increasing trend from 11.0 in placebos to 15.2 (p=0.086) by 0.5% DSS treatment in the Ccm1 +/- Msh2 -/- model.

Conclusion: CCM lesion development was enhanced by intestinal barrier disruption in 4 CCM models, regardless of the method used (genetic or chemical), time of onset, murine genotype or vivarium cleanliness status. Ongoing investigations include an early onset studies in the unclean vivarium with the Ccm1 +/- Msh2 -/- mice receiving 0.5% DSS and the Ccm3 +/- mice receiving 2% DSS.