ABSTRACT
BACKGROUND: Left atrial cardiac myxomas are among the most common cardiac masses. However, occurrence of left atrial myxomas in post-transplant patients is very rare and often misdiagnosed as left atrial thrombus formation. CASE REPORT: We report the case of a 67-year old female, who was referred due to suspected left atrial thrombus but was found to have a pediculated mass at the suture line of the left atrium on cardiac MRI. After resection, the diagnosis myxoma was confirmed histologically and the donor origin of the myxoma was proven by tissue typing. CONCLUSIONS: Despite a rare entity, atrial myxomas may occur in post cardiac transplant patients and may therefore support the role of advanced imaging techniques in patients with suspected left atrial masses.
Subject(s)
Heart Neoplasms/etiology , Heart Transplantation/adverse effects , Myxoma/etiology , Aged , Coronary Thrombosis/diagnosis , Diagnosis, Differential , Female , Heart Atria , Heart Neoplasms/diagnosis , Heart Neoplasms/surgery , Humans , Myxoma/diagnosis , Myxoma/surgery , Time Factors , Tissue DonorsABSTRACT
The complement anaphylatoxin C5a is a proinflammatory component of host defense that functions through two identified receptors, C5a receptor (C5aR) and C5L2. C5aR is a classical G protein-coupled receptor, whereas C5L2 is structurally homologous but deficient in G protein coupling. In human neutrophils, we show C5L2 is predominantly intracellular, whereas C5aR is expressed on the plasma membrane. Confocal analysis shows internalized C5aR following ligand binding is co-localized with both C5L2 and beta-arrestin. Antibody blockade of C5L2 results in a dramatic increase in C5a-mediated chemotaxis and ERK1/2 phosphorylation but does not alter C5a-mediated calcium mobilization, supporting its role in modulation of the beta-arrestin pathway. Association of C5L2 with beta-arrestin is confirmed by cellular co-immunoprecipitation assays. C5L2 blockade also has no effect on ligand uptake or C5aR endocytosis in human polymorphonuclear leukocytes, distinguishing its role from that of a rapid recycling or scavenging receptor in this cell type. This is thus the first example of a naturally occurring seven-transmembrane segment receptor that is both obligately uncoupled from G proteins and a negative modulator of signal transduction through the beta-arrestin pathway. Physiologically, these properties provide the possibility for additional fine-tuning of host defense.
