Concurrence of immune thrombocytopenic purpura and thrombotic thrombocytopenic purpura: a case report and review of the literature.

BACKGROUND: Immune thrombocytopenic purpura and thrombotic thrombocytopenic purpura are both causes of thrombocytopenia. Recognizing thrombotic thrombocytopenic purpura is crucial for subsequent treatment and prognosis. In clinical practice, corticosteroids and rituximab can be used to treat both immune thrombocytopenic purpura and thrombotic thrombocytopenic purpura; plasma exchange therapy is the first-line treatment in thrombotic thrombocytopenic purpura, while corticosteroids are strongly recommended as first-line treatment in immune thrombocytopenic purpura. The differential diagnosis of immune thrombocytopenic purpura and thrombotic thrombocytopenic purpura is essential in clinical practice. However, case reports have suggested that immune thrombocytopenic purpura and thrombotic thrombocytopenic purpura can occur concurrently. CASE PRESENTATION: We report the case of a 32-year-old Asian female without previous disease who presented with pancytopenia, concurrent with immune thrombocytopenic purpura and thrombotic thrombocytopenic purpura. The morphology of the megakaryocytes in the bone marrow indicated immune-mediated thrombocytopenia. The patient received glucocorticoid treatment, and her platelet count increased; however, schistocytes remained high during the course of the therapy. Further investigations revealed ADAMTS13 activity deficiency and positive ADAMTS13 antibodies. The high titer of antinuclear antibody and positive anti-U1-ribonucleoprotein/Smith antibody indicated a potential autoimmune disease. However, the patient did not fulfill the current criteria for systemic lupus erythematosus or mixed connective tissue disease. The patient responded well to plasma exchange therapy, and her platelet count remained normal on further follow-up. CONCLUSIONS: Concurrence of immune thrombocytopenic purpura and thrombotic thrombocytopenic purpura is rare, but clinicians should be aware of this entity to ensure prompt medical intervention. Most of the reported cases involve young women. Human immunodeficiency virus infection, pregnancy, and autoimmune disease are the most common underlying conditions.

Comparative analysis of depurination catalyzed by ricin A-chain on synthetic 32mer and 25mer oligoribonucleotides mimicking the sarcin/ricin domain of the rat 28S rRNA and E. coli 23S rRNA.

Ricin A-chain can inactivate eukaryotic ribosomes, but exhibits no N-glycosidase activity on intact E. coli ribosomes. In the present research, in order to avoid using radiolabeled oligoribonucleotides, two kinds of synthetic 5'-FAM fluorescence-labeled oligoribonucleotide substrates were used to mimic the sarcin/ricin domains of rat 28S rRNA and E. coli 23S rRNA (32mer and 25mer, named as Rat FAM-SRD and E. coli FAM-SRD, respectively). Ricin A-chain was able to specifically release adenine from the first adenosine of the GAGA tetraloop and exhibited specific N-glycosidase activity under neutral and weak acidic conditions with both substrates. However, under more acidic conditions, ricin A-chain was able to release purines from other sites on eukaryotic substrates, but it retained specific depurination activity on prokaryotic substrates. At pH 5.0, the Michaelis constant (K(m)) for the reaction with Rat FAM-SRD (4.57+/-0.28microM) corresponded to that with E. coli FAM-SRD (4.64+/-0.26microM). However, the maximum velocity (V(max)) for ricin A-chain with Rat FAM-SRD was 0.5+/-0.024microM/min, which is higher than that with E. coli FAM-SRD (0.32+/-0.011microM/min).