Extreme warfarin sensitivity in siblings associated with multiple cytochrome P450 polymorphisms.

Warfarin use is complicated by an erratic dose response. Warfarin is metabolized by two distinct subfamilies of the cytochrome P450 (CYP) complex. We describe two siblings with extreme sensitivity to warfarin who share an unusual CYP genotype. These individuals illustrate both the importance of genetics in influencing the metabolism of warfarin as well as the potential utility of genetic testing as a guide to prescribing this medication.

Acute promyelocytic leukemia with additional chromosomal abnormalities and absence of Auer rods.

We report 4 acute promyelocytic leukemia cases that demonstrated karyotypic abnormalities in addition to the classic t(15;17) translocation and did not contain any Auer rods in leukemic blasts and dysplastic promyelocytes, either in the peripheral blood or in the bone marrow. Morphologically, 2 cases were characterized as the common or hypergranular type, and 2 were otherwise typical of the microgranular variant. Three patients had typical clinical and laboratory signs of disseminated intravascular coagulation. Immunophenotypic analysis of the blasts and dysplastic promyelocytes by dual-color flow cytometry revealed an immunoprofile consistent with acute promyelocytic leukemia. Cytogenetic analysis of the bone marrow revealed the following karyotypes: case 1, [47,XY,t(15;17)(q22;q12),+21]; case 2, [47,XY,t(15;17)(q22;q12),-16,+2 mar]; case 3, [47,XX,t(15;17)(q22;q12)ider(17)(q10),+8]; and case 4, [47,XY,der(5)t(5;?9)(p15;q12).t(15;17)(q22;q12]. Review of an additional 7 cases with t(15;17) as the sole cytogenetic abnormality revealed Auer rods in all cases. Our findings emphasize the importance of cytogenetics in evaluating acute myeloid leukemias. Acute promyelocytic leukemia without Auer rods, which may be morphologically confused with other types of leukemia (in particular, acute myeloblastic leukemia, type M2 or M5) or agranulocytosis with maturation arrest, appears to be associated with additional chromosomal abnormalities and possibly a poorer prognosis.

Allosteric effects of a monoclonal antibody against thrombin exosite II.

We previously isolated a monoclonal antithrombin IgG from a patient with multiple myeloma [Colwell et al. (1997) Br. J. Haematol. 97, 219-226]. Using a panel of 55 surface mutants of recombinant thrombin, we now show that the epitope for the IgG most likely includes Arg-101, Arg-233, and Lys-236 in exosite II. The IgG affects the rate at which thrombin cleaves various peptide p-nitroanilide substrates with arginine in the P1 position, increasing the kcat for substrates with a P2 glycine residue but generally decreasing the kcat for substrates with a P2 proline. The allosteric effect of the IgG is altered by deletion of Pro-60b, Pro-60c, and Trp-60d from the 60-loop of thrombin, which lies between exosite II and the catalytic triad. The effect of the IgG, however, does not depend on the presence or absence of sodium ions, a known allosteric regulator of thrombin. The IgG does not affect the conformation of thrombin exosite I as determined by binding of a fluorescent derivative of hirudin54-65. These results provide evidence for a direct allosteric linkage between exosite II and the catalytic site of thrombin.

Clinical utility of the soluble transferrin receptor and comparison with serum ferritin in several populations.

Soluble transferrin receptor (sTfR) and ferritin concentrations were measured in a variety of clinical settings to compare the ability of these two tests to identify iron deficiency. Among 62 anemic patients who either had a bone marrow aspirate performed or had a documented response to iron therapy, the diagnostic sensitivity and specificity of sTfR (at a diagnostic cutoff of > 2.8 mg/L) were 92% and 84%, respectively, with a positive predictive value of 42% in this population. Ferritin (< or = 12 microg/L) had a sensitivity of 25% and a specificity of 98%. However, the sensitivity and specificity of ferritin could be improved to 92% and 98%, respectively, by using a diagnostic cutoff value of < or = 30 microg/L, resulting in a positive predictive value of 92%. Ferritin and sTfR were also measured in 267 outpatient samples and 112 medical students. In the outpatient group, the two tests agreed in 73% of the samples; however, 25% of the samples had ferritin values > 12 microg/L and increased sTfR. Among the medical students, there was 91% agreement between the two tests, but 7% of the samples had ferritin < or = 12 microg/L and normal sTfR. Together, these data suggest that measurement of sTfR does not provide sufficient additional information to ferritin to warrant routine use. However, sTfR may be useful as an adjunct in the evaluation of anemic patients, whose ferritin values may be increased as the result of an acute-phase reaction.

Identification of a monoclonal thrombin inhibitor associated with multiple myeloma and a severe bleeding disorder.

We investigated a patient with a long-standing IgGkappa monoclonal gammopathy who developed severe haemorrhagic complications. At IgG concentrations of approximately 50g/l the patient had severe bleeding associated with prolongation of the thrombin time, activated partial thromboplastin time, and reptilase time. Plasmapheresis resulted in improvement in the thrombin time and resolution of bleeding. Depletion of the IgG by absorption of plasma with protein G-Sepharose in vitro resulted in normalization of the thrombin time and reptilase time. The purified IgG bound to immobilized thrombin and immunoprecipitated human alpha-, beta- and gamma-thrombin but not prothrombin, other vitamin K-dependent coagulation factors, or fibrinogen. Purified IgG at concentrations >1 x 10(-2) g/l decreased (approximately 50%) the rate of hydrolysis of a chromogenic substrate by thrombin. Addition of purified IgG to normal pooled plasma at concentrations >1 x 10(-2) g/l prolonged the thrombin time and activated partial thromboplastin time, but the reptilase time was prolonged only at IgG concentrations >1 g/l. This finding suggests that at low concentrations the IgG produces a specific antithrombin effect, but at higher concentrations it also affects fibrin polymerization; the combination of these effects probably produced clinical bleeding. This is the first report of a monoclonal antithrombin antibody associated with bleeding in a patient with multiple myeloma.

Complete nucleotide sequence of the gene for human heparin cofactor II and mapping to chromosomal band 22q11.

Heparin cofactor II (HCII) is a 66-kDa plasma glycoprotein that inhibits thrombin rapidly in the presence of dermatan sulfate or heparin. Clones comprising the entire HCII gene were isolated from a human leukocyte genomic library in EMBL-3 lambda phage. The sequence of the gene was determined on both strands of DNA (15,849 bp) and included 1749 bp of 5'-flanking sequence, five exons, four introns, and 476 bp of DNA 3' to the polyadenylation site. Ten complete and one partial Alu repeats were identified in the introns and 5'-flanking region. The HCII gene was regionally mapped on chromosome 22 using rodent-human somatic cell hybrids, carrying only parts of human chromosome 22, and the chronic myelogenous leukemia cell line K562. With the cDNA probe HCII7.2, containing the entire coding region of the gene, the HCII gene was shown to be amplified 10-20-fold in K562 cells by Southern analysis and in situ hybridization. From these data, we concluded that the HCII gene is localized on the chromosomal band 22q11 proximal to the breakpoint cluster region (BCR). Analysis by pulsed-field gel electrophoresis indicated that the amplified HCII gene in K562 cells maps at least 2 Mbp proximal to BCR-1. Furthermore, the HCII7.2 cDNA probe detected two frequent restriction fragment length polymorphisms with the restriction enzymes BamHI and HindIII.

Relapse of acute leukemia after marrow transplantation: natural history and results of subsequent therapy.

Of 455 acute nonlymphocytic leukemia (ANL) patients who underwent marrow transplantation, 95 (21%) relapsed a median of 6.5 months posttransplantation and 62 received further treatment. Twenty achieved remission. Success of therapy was related to the length of time from marrow transplant to relapse and to the use of cytarabine (Ara-C) and daunomycin. Aggressive chemotherapy for patients relapsing within 100 days of marrow transplant was associated with a high incidence of early death (six of 14 patients) and a low probability of remission (one of 14). Of 23 patients who relapsed in excess of 1 year from marrow transplant, 15 achieved a complete remission. The median disease-free survival is 6 months (range, 0.4 to 53+ months). Acute lymphocytic leukemia (ALL) recurred in 130 of 366 patients (36%), and 94 received further therapy. Fifty-two achieved a remission. Remissions were more common in late relapse patients (greater than 1 year from transplantation): 65% v 7% for those relapsing within 100 days from transplant (P less than .05). Testicular relapse occurred in 11 patients and was the sole site of relapse in seven. Three are alive and free of disease 58 to 109+ months after relapse. The median survival for the treated patients is 10.5 months (range, 5 to 109+ months). We propose that reinduction be attempted in all patients relapsing greater than 1 year from marrow transplantation. Ara-C and daunomycin should be employed in the treatment of ANL. The decision for treatment of patients relapsing earlier than 1 year should be made on an individual basis.

Brain metastasis from esophageal carcinoma.

Metastatic esophageal carcinoma to the brain is a rare occurrence that may account for abnormal neurological findings.