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The mechanism of isolated thrombocytopenia in septicemia is unknown, but compensated disseminated intravascular coagulation (DIC) has been suggested as a possible cause. To investigate this possibility, platelet counts and sensitive assays for in vivo thrombin and plasmin generation, including fibrinogen gel chromatography and fibrinopeptide A (FPA) assays, were obtained on 31 septicemic patients. Fifteen of 17 patients with gram-negative septicemia and 8 of 14 patients with gram- positive septicemia had thrombocytopenia. Platelet survival studied demonstrated a decreased platelet survival. In 11 of 12 patients with severe thrombocytopenia (platelet count less than 50,000mul), there was laboratory evidence of intravascular coagulation. In contrast, there was little evidence of intravascular coagulation in 8 of 11 patients with moderate thrombocytopenia (platelet counts 50,000 to less than 150,000/mul) or in 7 of 8 patients with normal platelet counts. This report indicates that while DIC accompanies thrombocytopenia in many patients with severe thrombocytopenia, there is frequently little evidence for intravascular coagulation in patients with moderate thrombocytopenia. It is apparent that factors other than intravascular thrombin must play a role in producing the thrombocytopenia of septicemia.

The mechanism of thrombocytopenia, a frequent complication of septicemia, is obscure, but indirect evidence suggests that the immune system may be involved. To investigate this possibility, we quantitated platelet-associated IgG on platelets obtained from 44 patients during 46 episodes of septicemia. Thrombocytopenia occurred in 21 of 46 episodes (46 per cent). Platelet-associated IgG was elevated in eight of 11 episodes of gram-negative septicemia and thrombocytopenia (47.3 +/- 11.7 fg of IgG per platelet [mean +/- S.E.]) and in one of 20 patients with gram-negative septicemia and normal platelet counts (5.9 +/- 1.1) (P less than 0.001). Elevated levels occurred in eight of 10 patients with gram-positive septicemia and thrombocytopenia (55.3 +/- 14.7 fg of IgG per platelet) and in none of 11 patients with gram-positive septicemia and normal platelet counts (5.6 +/- 1.7) (P less than 0.001). Serial testing during the thrombocytopenia and recovery showed an inverse relation between the platelet count and platelet-associated IgG. Thrombocytopenia in some patients with septicemia may be related to the binding of IgG to platelets.

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Early diagnosis of t(15;17) acute promyelocytic leukemia (APL) is essential because of the associated disseminated intravascular coagulation and the unique response of the disease to all-trans retinoic acid (ATRA) therapy. Early diagnosis depends primarily on morphological recognition. The French-American-British (FAB) classification, however, does not describe all morphological variations that occur in APL. In 25 cases with evidence of APL confirmed by cytogenetic and/or molecular analysis, we found a heterogeneous morphological group. The most common form of APL was heterogeneous and consisted of various combinations of cells in which hypergranular cells and some cells with multiple Auer rods were obvious. In some cases, one cell predominated. This led to the description of five subcategories. These included the classical FAB M3 with hyper-granular cells and multiple Auer rods; the FAB variant with hypogranular bilobed cells; the basophilic cell type of McKenna et al. [Br. J. Haematol 50:201, 1982]; and two additional subtypes, one consisting of differentiated promyelocytes and a few blast cells (M2-like), and the other consisting largely of blast cells and a few early promyelocytes (M1-like). Immunophenotyping revealed a pattern of CD33 and/or CD13 positivity, and CD14 and HLA-DR negativity in 96% of cases. CD2 was positive in the FAB variant and in the subtype with basophilic cells, but negative with other subtypes. Three out of five cases with basophilic cell predominance [McKenna et al.: Br J Haematol 50:201, 1982], and one out of two M2-like cases, responded to ATRA therapy. Awareness of the hetero-geneity and the atypical morphologic subtypes found in t(15;17) APL will contribute to improved recognition and early institution of ATRA therapy. Am.

The syndrome of thrombotic thrombocytopenic purpura (TTP) is an often fatal illness characterized clinically by thrombocytopenia, microangiopathic hemolytic anemia, fluctuating neurologic abnormalities, plus fever and renal damage, associated, on histology, with microcirculatory platelet and plateletfibrin thrombi [3,63]. Although the etiology and pathogenesis of TTP remain unknown, a disseminated lesion of the microcirculation has been considered to be the major factor in the pathogenesis of the disorder [90]. The disease has at various times been ascribed to thrombin action (disseminated intravascular coagulation) [88,90], which is no longer considered an important factor [36,63], to primary microvascular damage with secondary platelet thrombosis [2,23,30,42], or to disseminated intravascular platelet aggregation resulting from an intravascular stimulus [62]. Immunologic abnormality has been noted in patients suffering from TTP [6,46,50] and because of these findings and the fact that dramatic therapeutic response has been noted after blood [16,74] or plasma [17,82] exchange transfusion, where removal of circulating immune complexes has been postulated [16,17], it has been suggested that TTP might be immunologically mediated [6,16,17,64,82]. In this paper the relationship between immunologic factors and TTP will be reviewed. TTP or a TTP-like Disorder Associated with Immune Related DiseaseTTP has been described in association with disorders considered to be immune-mediated, including systemic lupus erythematosus (SLE) [8,11,22,29,41,44,46,81,85], rheumatoid spondylitis [57], polyarteritis [12] and Sjögren's syndrome [87]. A TTP-like disorder has also been noted in association with infective endocarditis [10] and penicillin allergy [70]. All the diseases can be associated with some degree of vasculitis of the small blood vessels. SLE and TTP: Perhaps the first evidence to suggest the immune system might be involved in TTP were reports of the association of TTP and SLE [8, 11,29,44,85]. In 1964, Levine and Shearn analyzed the necropsy findings of 151 cases of TTP, including 3 of their own [46]. In their opinion, 23% of patients with TTP had shown evidence of SLE on histologic criteria. Amorosi and Ultmann [3] in 1966, when reviewing 271 cases of TTP, found that in 64 patients LE preparations had been -performed and only 7 were positive, an incidence of 9%. Dekker [22] in 1974 after reporting 2 cases and reviewing the literature felt the association of TTP and SLE occurred, but on rare

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