Not available.

Erdheim-Chester disease (ECD) is a rare disease characterized by the accumulation of neoplastic histiocytes in various extra-nodal tissues. Tissue biopsies involved by ECD are difficult to distinguish from reactive inflammatory infiltrates given the bland appearance of the neoplastic histiocytes. Confirmation of the ECD diagnosis often relies on molecular studies to confirm BRAF V600E mutation or other activating mutations involving MAPK pathway genes. In this study, we examined the diagnostic utility of cyclin D1 and pERK as immunohistochemical markers of MAPK pathway activation in ECD compared with its histopathologic mimics. The cohort included 41 clinically confirmed ECD patients, most with known genetic alterations in MAPK pathway genes (n=38). In 3 cases no mutation was identified. 37 of 41 (90%) of ECD cases showed cyclin D1 overexpression, with frequent staining in the cytoplasm as well as the nucleus. pERK expression was observed in 32 of 39 (82%) cases. Cyclin D1 staining was negative in histopathologic mimics of ECD, apart from weak patchy staining in fat necrosis and uniform staining in a subset of cases of juvenile/adult xanthogranuloma. While not entirely sensitive or specific, in the proper clinical and radiologic context strong nuclear and cytoplasmic cyclin D1 expression within histiocytic infiltrates helps to support a diagnosis of ECD.

Severe optic neuritis (ON) is a common clinical manifestation in myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD) and neuromyelitis optica spectrum disorder (NMOSD). Given distinct prognoses and often the necessity of early plasma exchange in NMOSD, prompt differentiation is crucial. In this study, we investigated the utility of optical coherence tomography (OCT) in differentiating between first acute NMOSD-ON and MOGAD-associated optic neuritis (MOGAD-ON), as well as specific factors associated with disc edema. In this retrospective multicenter study, 111 adult patients with MOGAD or aquaporin-4 antibody-positive NMOSD who experienced a first ON and underwent OCT within 2 weeks of symptom onset were included from 14 centers across 8 countries. Peripapillary retinal nerve fiber layer (pRNFL) thickness in µm was analyzed, including the average of both eyes in cases of bilateral manifestation. Eighty-three patients with MOGAD (51 women; 124 ON eyes; bilateral ON 48.2%) and 28 with NMOSD (24 women; 36 ON eyes; bilateral ON 21.4%) were enrolled. A significant increase in pRNFL thickness (>2SD), suggestive of disc edema, was observed in 73.4% of MOGAD-ON eyes and 11.1% of NMOSD-ON eyes (p < 0.001). The pRNFL thickness cutoff of 117.5 µm provided 92.9% specificity and 71.1% sensitivity in distinguishing between MOGAD-ON and NMOSD-ON (area under the curve = 0.838). There was no association between pRNFL thickening and MOG-IgG titer (high vs low), body mass index, or the delay between ON onset and OCT. Simultaneous bilateral MOGAD-ON was associated with significantly more pronounced pRNFL thickening. Acute-stage OCT contributes to the rapid and accurate differentiation between MOGAD-ON and NMOSD-ON prior to antibody confirmation, which can be critical for timely therapeutic decisions.

The mechanisms contributing to progressive kidney damage in autosomal dominant polycystic kidney disease (ADPKD) remain unclear. Renal microvascular (MV) rarefaction plays an important role in kidney disease, but its natural history, underlying mechanisms, and contributions to renal disease progression in ADPKD remain unknown. We hypothesized that intrarenal MV rarefaction is present early on and is preceded by vascular transcriptional and metabolic changes. Pkd1RC/RC and wild type (WT) mice (n = 16 each) were studied at 1, 6, and 12 mo. Total kidney volume (TKV) was measured in vivo (MRI), whereas renal MV architecture [three-dimensional (3-D) micro-computed tomography, 3-D micro-CT], capillary density, perivascular fibrosis, and histomorphometric parameters were assessed ex vivo. In randomly selected Pkd1RC/RC and WT kidneys (n = 5, each/time point), mRNA-sequencing was performed to identify differentially expressed vasculature-related genes (differentially expressed genes, DEGs). Next, in young humans with ADPKD and matched controls (n = 10 each), plasma cellular energy metabolites were determined (LC-MS/MS), validated in an extended cohort (n = 32 and n = 16, respectively), and correlated with markers of disease severity and progression. Gene-metabolite interaction networks were generated to integrate DEGs in Pkd1RC/RC at 1 mo with metabolites dysregulated in individuals with ADPKD, which were further quantified in WT and Pkd1RC/RC kidneys. Renal MV density was preserved at 1 mo but progressively decreased at 6 and 12 mo, associated with capillary loss and perivascular fibrosis. A total of 110, 48, and 201 DEGs were identified at 1, 6, and 12 mo, respectively. Plasma gamma-aminobutyric acid (GABA), homocysteine (Hcy), and asymmetric dimethyl arginine (ADMA) levels were higher in humans with ADPKD vs. controls, interacted with DEGs implicated in inflammatory and innate immune response and Hcy metabolism, and correlated with TKV and renal blood flow. Our data demonstrate that intrarenal MV abnormalities present early in ADPKD and are preceded by vascular transcriptional and metabolic changes. The renal microcirculation may constitute an important therapeutic target in ADPKD, and its underlying biomarkers may serve to monitor its progression.NEW & NOTEWORTHY We provide the first longitudinal and most comprehensive analysis of the intrarenal microvasculature in a slowly progressive model of autosomal dominant polycystic kidney disease (ADPKD) and integrate the findings with studies in a young cohort of individuals with ADPKD. We identified vasculature-related pathways that could be targeted for therapeutic interventions and contribute promising, noninvasive biomarkers in patients with ADPKD. Alterations of the intrarenal microcirculation may affect drug delivery; a better understanding of its longitudinal changes may aid in treatment management.