Blood/plasma secretome and microvesicles.

A major but hitherto overseen component of the blood/plasma secretome is that of extracellular vesicles (EVs) which are shed from all blood cell types. These EVs are made up of microvesicles (MVs) and exosomes. MVs, 100nm-1µm in diameter, are released from the cell surface, and are a rich source of non-conventionally secreted proteins lacking a conventional signal peptide, and thus not secreted by the classical secretory pathways. Exosomes are smaller vesicles (≤100nm) having an endocytic origin and released upon multivesicular body fusion with the plasma membrane. Both vesicle types play major roles in intercellular cross talk and constitute an important component of the secretome especially in the area of biomarkers for cancer. The release of EVs, which are found in all the bodily fluids, is enhanced in cancer and a major focus of cancer proteomics is therefore targeted at EVs. The blood/plasma secretome is also a source of EVs, potentially diagnostic of infectious disease, whether from EVs released from infected cells or from the pathogens themselves. Despite the great excitement in this field, as is stated here and in other parts of this Special issue entitled: An Updated Secretome, much of the EV research, whether proteomic or functional in nature, urgently needs standardisation both in terms of nomenclature and isolation protocols. This article is part of a Special Issue entitled: An Updated Secretome.

Distinguishing aortic valve thrombus from Libman-Sacks endocarditis in antiphospholipid syndrome: imaging and management.

Aortic valve (AV) thrombus, a rare complication of antiphospholipid syndrome (APLS), is important to distinguish from Libman-Sacks endocarditis because of its responsiveness to anticoagulation. This may be attributed to immunopathologic differences underpinning their development. We present the case of a 45-year-old woman with high-risk primary APLS who developed an AV mass and was taken for valvular repair surgery but found to have pure thrombus and normal valve leaflets. In such cases, a trial of conservative management with anticoagulation may be adequate. Echocardiography, computed tomography and MRI findings suggestive of thrombus without endocarditis are presented. A literature review of histopathologic, imaging and treatment implications of pure AV thrombus in the context of APLS is included.

Pulmonary embolism as the presenting symptom and a confounder in ACTH-secreting bronchial carcinoid

Summary: Ectopic ACTH-secreting pulmonary neuroendocrine tumors are rare and account for less than 5% of endogenous Cushing's syndrome cases. We describe an unusual case of metastatic bronchial carcinoid tumor in a young woman presenting with unprovoked pulmonary emboli, which initially prevented the detection of the primary tumor on imaging. The source of ectopic ACTH was ultimately localized by a Gallium-DOTATATE scan, which demonstrated increased tracer uptake in a right middle lobe lung nodule and multiple liver nodules. The histological diagnosis was established based on a core biopsy of a hepatic lesion and the patient was started on a glucocorticoid receptor antagonist and a somatostatin analog. This case illustrates that hypercogulability can further aggravate the diagnostic challenges in ectopic ACTH syndrome. We discuss the literature on the current diagnosis and management strategies for ectopic ACTH syndrome. Learning Points: In a young patient with concurrent hypokalemia and uncontrolled hypertension on multiple antihypertensive agents, secondary causes of hypertension should be evaluated. Patients with Cushing's syndrome can develop an acquired hypercoagulable state leading to spontaneous and postoperative venous thromboembolism. Pulmonary emboli may complicate the imaging of the bronchial carcinoid tumor in ectopic ACTH syndrome. Imaging with Gallium-68 DOTATATE PET/CT scan has the highest sensitivity and specificity in detecting ectopic ACTH-secreting tumors. A combination of various noninvasive biochemical tests can enhance the diagnostic accuracy in differentiating Cushing's disease from ectopic ACTH syndrome provided they have concordant results. Bilateral inferior petrosal sinus sampling remains the gold standard.