BackgroundWhile most patients with Alzheimer’s disease (AD) present with memory complaints, 30% of patients with early disease onset present with non-amnestic symptoms. This atypical presentation is thought to be caused by a different spreading of neurofibrillary tangles (NFT) than originally proposed by Braak and Braak. Recent studies suggest a prominent role for neuroinflammation in the spreading of tau pathology.MethodsWe aimed to explore whether an atypical spreading of pathology in AD is associated with an atypical distribution of neuroinflammation. Typical and atypical AD cases were selected based on both NFT distribution and amnestic or non-amnestic clinical presentation. Immunohistochemistry was performed on the temporal pole and superior parietal lobe of 10 typical and 9 atypical AD cases. The presence of amyloid-beta (N-terminal; IC16), pTau (AT8), reactive astrocytes (GFAP), microglia (Iba1, CD68, and HLA-DP/DQ/DR), and complement factors (C1q, C3d, C4b, and C5b-9) was quantified by image analysis. Differences in lobar distribution patterns of immunoreactivity were statistically assessed using a linear mixed model.ResultsWe found a temporal dominant distribution for amyloid-beta, GFAP, and Iba1 in both typical and atypical AD. Distribution of pTau, CD68, HLA-DP/DQ/DR, C3d, and C4b differed between AD variants. Typical AD cases showed a temporal dominant distribution of these markers, whereas atypical AD cases showed a parietal dominant distribution. Interestingly, when quantifying for the number of amyloid-beta plaques instead of stained surface area, atypical AD cases differed in distribution pattern from typical AD cases. Remarkably, plaque morphology and localization of neuroinflammation within the plaques was different between the two phenotypes.ConclusionsOur data show a different localization of neuroinflammatory markers and amyloid-beta plaques between AD phenotypes. In addition, these markers reflect the atypical distribution of tau pathology in atypical AD, suggesting that neuroinflammation might be a crucial link between amyloid-beta deposits, tau pathology, and clinical symptoms.

Aims Lung tissue from COVID‐19 patients shares similar histomorphological features with chronic lung allograft disease, also suggesting activation of autoimmune‐related pathways in COVID‐19. To more clearly understand the underlying spectrum of pathophysiology in COVID‐19 pneumonia, we analysed mRNA expression of autoimmune‐related genes in post‐mortem lung tissue from COVID‐19 patients. Methods and results Formalin‐fixed, paraffin‐embedded lung tissue samples of 18 COVID‐19 patients and eight influenza patients were used for targeted gene expression profiling using NanoString technology. Multiplex immunofluorescence for tryptase and chymase was applied for validation. Genes related to mast cells were significantly increased in COVID‐19. This finding was strengthened by multiplex immunofluorescence also showing a significant increase of tryptase‐ and chymase‐positive cells in COVID‐19. Furthermore, receptors for advanced glycation end‐products (RAGE) and pro‐platelet basic protein (PPBP) were up‐regulated in COVID‐19 compared to influenza. Genes associated with Type I interferon signalling showed a significant correlation to detected SARS‐CoV2 pathway‐related genes. The comparison of lung tissue samples from both groups based on the presence of histomorphological features indicative of acute respiratory distress syndrome did not result in finding any specific gene or pathways. Conclusion Two separate means of measuring show a significant increase of mast cells in SARS‐CoV‐2‐infected lung tissue compared to influenza. Additionally, several genes involved in fibrosis and thrombosis, among which are RAGE and PPBP, are up‐regulated in COVID‐19. As mast cells are able to induce thrombosis and fibrosis, they may play an important role in the pathogenesis of COVID‐19.

The clinical features of COVID-19 have a considerable range from a mild illness to severe disease. Underlying pathophysiological mechanisms of the rapidly progressive, and often fatal, pulmonary disease frequently observed in COVID-19 need to be elucidated, in order to develop new treatment strategies for different disease endotypes. Fatal cases can display features of a cytokine storm, which may be related to hemophagocytic lymphohistiocytosis. Also, a spectrum of vascular changes, including microvascular damage, is known to accompany severe COVID-19. In this paper, we describe the co-occurrence of hemophagocytic lymphohistiocytosis and extensive pulmonary microvascular damage with thrombosis and its sequelae in a patient with fatal COVID-19. We believe these response patterns may be linked by common mechanisms involving hypercytokinemia and require further investigation as a fatal constellation in COVID-19, to generate appropriate treatment in patients who display these combined features.

Orbital metastasis may be the initial manifestation of a malignancy of unknown origin. The primary locations of orbital metastasis are usually the lung, prostate, gastrointestinal tract, skin, kidney, eye, or thyroid gland. Metastasis of gastric carcinoma to an extraocular eye muscle is extremely rare. A solitary thickening in an extraocular eye muscle with no inflammatory features is suspect for a tumor. Symptoms such as diplopia, proptosis, ptosis, vision loss, or pain may be associated with an orbital malignancy. Our patient, a 67-year-old man known with radically resected prostate cancer, presented with complaints of vertigo with a tendency to fall, headache, and diplopia when looking to the right. As a coincidental finding, swelling of the rectus lateralis muscle of the left eye was observed on imaging. Extensive additional investigations showed that a gastric carcinoma with intraorbital and leptomeningeal metastasis was the cause. In conclusion, a solitary thickened extraocular eye muscle should be recognized in time and examined further.