title: Fatal congenital thrombotic thrombocytopenic purpura with apparent ADAMTS13 inhibitor: in vitro inhibition of ADAMTS13 activity by hemoglobin.
abstract: Severe ADAMTS13 deficiency in thrombotic thrombocytopenic purpura (TTP) is either constitutional and caused by ADAMTS13 mutations, or acquired and most often due to ADAMTS13 inhibitory autoantibodies. In strongly hemolytic serum of a pediatric patient, diagnosed with TTP postmortem, ADAMTS13 activity was less than 3%. Both parents had an ADAMTS13 activity of approximately 50%. Sequencing of the ADAMTS13 gene revealed an intronic 687-2A>G substitution affecting exon 7, homozygous in the propositus and heterozygous in both parents, confirming constitutional ADAMTS13 deficiency. ADAMTS13 activity of normal plasma was inhibited by incubation with the propositus' serum, suggesting alloantibody formation to ADAMTS13. However, immunoglobulin purified from serum had no ADAMTS13 inhibitory effect, whereas the immunoglobulin-depleted hemolytic serum inhibited ADAMTS13 activity of normal plasma, suggesting an inhibitory effect of hemolysis products. Incubation of hemoglobin, recombinant and from lysed erythrocytes, with normal plasma revealed an ADAMTS13 inhibitory effect at hemoglobin concentrations of 2 g/L or higher.
authors.affiliation: Department of Hematology and Central Hematology Laboratory, Inselspital, University Hospital, Bern, Switzerland.
authors.forename: Jan-Dirk
authors.initials: JD
authors.lastname: Studt
authors.forename: Johanna A
authors.initials: JA
authors.lastname: Kremer Hovinga
authors.forename: Gerhard
authors.initials: G
authors.lastname: Antoine
authors.forename: Martin
authors.initials: M
authors.lastname: Hermann
authors.forename: Manfred
authors.initials: M
authors.lastname: Rieger
authors.forename: Friedrich
authors.initials: F
authors.lastname: Scheiflinger
authors.forename: Bernhard
authors.initials: B
authors.lastname: Lämmle
mesh_terms: D051722:ADAM Proteins; D000071120:ADAMTS13 Protein; D001323:Autoantibodies / Q000097:blood; D002648:Child; D004789:Enzyme Activation / Q000502:physiology; D017809:Fatal Outcome; D006454:Hemoglobins / Q000378:metabolism*; D006461:Hemolysis; D006801:Humans; D008297:Male; D008666:Metalloendopeptidases / Q000235:genetics* / Q000276:immunology / Q000378:metabolism; D017354:Point Mutation; D011697:Purpura, Thrombotic Thrombocytopenic / Q000151:congenital / Q000235:genetics* / Q000276:immunology
chemical_list: D001323:Autoantibodies; D006454:Hemoglobins; D051722:ADAM Proteins; D008666:Metalloendopeptidases; D000071120:ADAMTS13 Protein; C099604:ADAMTS13 protein, human