In autoimmune thrombocytopenia, platelet-associated IgG (PA-IgG) frequently displays specificity against glycoprotein (GP) IIbIIIa and/or GP IbIX. Because in a high proportion of patients positive PA-IgG may not be explained by these GP specificities, studies on other target proteins are needed. We studied the presence of GP V-specific PA-IgG by direct monoclonal antibody-specific immobilization of platelet antigens (MAIPA) with the monoclonal antibody SW16. We focused on 69 consecutive random patients with histories of thrombocytopenia who were strongly positive for PA-IgG detected by the direct platelet immunofluorescence test (PIFT). PA-IgG against GP V (ratio > or = 1.5) was noted in 15 (22%) patients. The degree of PA-IgG measured by PIFT, and of GP IIbIIIa-and/or GP IbIX-specific PA-IgG measured by direct MAIPA, correlated directly with the GP V-specific PA-IgG (P < 0.001). In one patient, GP V-specific antibodies were associated with quinidine-induced thrombocytopenia. Although this patient had strongly positive GP V-specific PA-IgG, she remained negative in GP IIbIIIa- and GP IbIX-specific direct MAIPA. Two patients studied because of thrombocytopenia associated with gold therapy had strongly positive GP V-specific PA-IgG. In one patient with rheumatoid arthritis and severe gold-induced thrombocytopenia, the amount of GP V-specific PA-IgG decreased during the recovery phase. Thus, GP V may represent an important target antigen in autoimmune-mediated thrombocytopenia, especially in drug-induced thrombocytopenia.

The reasons for diagnostic evaluation and the clinical and laboratory data at diagnosis of 170 patients with essential thrombocythemia (ET) were studied retrospectively. The age distribution was 19-88 years (median 52 years), and 52 patients were under the age of 45 years. In 111 patients (65%) thrombocytosis was a chance finding, but the past history of 37 of these patients revealed symptoms known to be related to ET. The diagnosis was based on a chance finding in a significantly higher proportion of female (74%) than male (53%) patients. The diagnosis of ET is based mostly on negative findings, i.e., on the exclusion of other causes of thrombocytosis, and positive diagnostic tests would be useful. We evaluated the presence of positive diagnostic findings of myeloproliferative disorders in ET. Splenomegaly was seen in 26% and an abnormal karyotype in 5% of the patients. Abnormal megakaryocyte morphology was seen in 80%, abnormal in vitro growth of hematopoietic progenitors in 74%, and abnormal platelet function in 83% of the patients. Both in vitro cultures of hematopoietic progenitors and platelet functions were studied in 36 patients, and in only two of these were both tests normal. We conclude that in most patients with ET the diagnosis can be strongly supported by positive findings, especially by in vitro cultures of hematopoietic progenitors and studies of platelet function.

A 46-year-old woman suffering from non-Hodgkin's lymphoma was admitted to the hospital because of high fever. Multiple blood cultures revealed an unusual finding, a Brevibacterium species, which was reisolated 16 days later from the tip of her long-term central venous catheter. This case indicates that Brevibacterium species isolated from normally sterile sites should be considered as a potential pathogen, especially in immunocompromised patients.