Bone marrow findings of the newly described TEMPI syndrome: when erythrocytosis and plasma cell dyscrasia coexist.

TEMPI syndrome (telangiectasias, elevated erythropoietin level and erythrocytosis, monoclonal gammopathy, perinephric fluid collections, and intrapulmonary shunting) is a recently described syndrome that, owing to erythrocytosis, may be confused with polycythemia vera. It is best classified as a type of plasma cell dyscrasia with paraneoplastic manifestations, similar to POEMS syndrome (polyneuropathy, organomegaly, endocrinopathy, M-protein, and skin abnormalities). To date, 11 patients have been identified. This is the first morphologic review of TEMPI syndrome bone marrow samples, in order to define pathologic features that may aid in the recognition of the syndrome and to identify post-therapy changes. Seven bone marrow aspirates and biopsies from three patients, including two post-treatment marrows, were examined. Patients were 36, 49, and 49 years old at time of diagnosis. In all cases, erythropoietin levels were extremely elevated at >5000 IU/l, the paraprotein was IgG kappa, JAK2 V617F was negative and vascular endothelial growth factor levels were normal. In one case, the increase in clonal plasma cells reached levels of smoldering myeloma (18%), but remaining marrows showed few monoclonal plasma cells (<5%). All pre-treatment biopsies showed erythroid hyperplasia, with mild nonspecific megakaryocytic, and erythroid cytologic atypia in one marrow. Prominent plasma cell vacuolization and reactive-appearing lymphoid aggregates were noted in one case. Findings of myeloproliferative neoplasms, including megakaryocyte clusters and fibrosis, were not identified. In conclusion, TEMPI syndrome should be considered when erythrocytosis and plasma cell dyscrasia coexist. The bone marrow findings, although nonspecific, differ significantly from polycythemia vera. Peculiar clinical and laboratorial findings of TEMPI, including elevated erythropoietin and normal vascular endothelial growth factor level, allow the diagnosis and distinction from POEMS syndrome. Significant decrease in erythropoietin level following treatment suggests a role of erythropoietin in monitoring therapeutic response.