To the Editor: The description of a man with erythrocytosis and perinephric fluid collections recently appeared in the Case Records of the Massachusetts General Hospital1 (Patient 1 in Table 1), and the authors of that article appealed to readers to share similar cases. Two additional patients were identified (Patients 2 and 3), and a review of the literature identified three more patients with similar findings2–4 (Patients 4, 5, and 6). These six patients shared five characteristics — telangiectasias, elevated erythropoietin level and erythrocytosis, monoclonal gammopathy, perinephric-fluid collections, and intrapulmonary shunting — defining a syndrome that we have termed the TEMPI . . .