Clinical remission of acquired thrombasthenia with low-dose methotrexate in a patient with systemic lupus erythematosus

Acquired Glanzmann thrombasthenia: From antibodies to anti-platelet drugs

In contrast to the inherited platelet disorder given by mutations in the ITGA2B and ITGB3 genes, mucocutaneous bleeding from a spontaneous inhibition of normally expressed αIIbβ3 characterizes acquired Glanzmann thrombasthenia (GT). Classically, it is associated with autoantibodies or paraproteins that block platelet aggregation without causing a fall in platelet count. However, inhibitory antibodies to αIIbβ3 are widely associated with primary immune thrombocytopenia (ITP), occur in secondary ITP associated with leukemia and related disorders, solid cancers and myeloma, other autoimmune diseases, following organ transplantation while cytoplasmic dysregulation of αIIbβ3 function features in myeloproliferative and myelodysplastic syndromes. Antibodies to αIIbβ3 occur during viral and bacterial infections, while drug-dependent antibodies reacting with αIIbβ3 are a special case. Direct induction of acquired GT is a feature of therapies that block platelets in coronary artery disease. This review looks at these conditions, emphasizing molecular mechanisms, therapy, patient management and future directions for research.

A unique phenotype of acquired Glanzmann thrombasthenia due to non-function-blocking anti-αIIbβ3 autoantibodies

Essentials Acquired Glanzmann thrombasthenia (aGT) is generally caused by function-blocking antibodies (Abs). We demonstrated a unique aGT case due to marked reduction of αIIbβ3 with anti-αIIbβ3 Abs. The anti-αIIbβ3 Abs of the patient did not inhibit platelet function but reduced surface αIIbβ3. Internalization of αIIbβ3 induced by the Abs binding may be responsible for the phenotype. SUMMARY: Background Acquired Glanzmann thrombasthenia (aGT) is a bleeding disorder generally caused by function-blocking anti-αIIbβ3 autoantibodies. Aim We characterize an unusual case of aGT caused by marked reduction of surface αIIbβ3 with non-function-blocking anti-αIIbβ3 antibodies (Abs). Methods A 72-year-old male suffering from immune thrombocytopenia since his 50s showed exacerbation of bleeding symptom despite mild thrombocytopenia. Platelet aggregation was absent with all agonists but ristocetin. Analysis of αIIbβ3 expression and genetic analysis were performed. We also analyzed effects of anti-αIIbβ3 Abs of the patient on platelet function and αIIbβ3 expression. Results Surface αIIbβ3 expression was markedly reduced to around 5% of normal, whereas his platelets contained αIIbβ3 to the amount of 40-50% of normal. A substantial amount of fibrinogen was also detected in his platelets. There were no abnormalities in ITGA2B and ITGB3 cDNA. These results indicated that reduced surface αIIbβ3 expression caused a GT phenotype, and active internalization of αIIbβ3 was suggested. Anti-αIIbβ3 IgG Abs were detected in platelet eluate and plasma. These Abs did not inhibit PAC-1 binding, indicating that the Abs were non-function-blocking. Surface αIIbβ3 expression of a megakaryocytic cell line and cultured megakaryocytes tended to be impaired by incubation with the patient's Abs. After 2 years of aGT diagnosis, his bleeding symptom improved and surface αIIbβ3 expression was recovered to 20% of normal with reduction of anti-αIIbβ3 Abs. Conclusion We demonstrated a unique aGT phenotype due to marked reduction of surface αIIbβ3. Internalization induced by anti-αIIbβ3 Abs may be responsible in part for the phenotype.

The potential contribution and role of a blood platelets in autoimmune thyroid diseases

The blood platelets are multifunctional blood cells which are involved in the initiation of atheroma, endothelial dysfunction, and modulation of inflammatory and immune responses in the pathophysiology of many diseases. Because of their multifaceted pro-inflammatory activity, platelets may be involved in the pathogenesis of autoimmune thyroid diseases (AITDs), such as Hashimoto's thyroiditis and Graves' disease. The aim of this study was to assess the level of activation and response ability of platelets in AITDs. We used the flow cytometry technique and kinetic measurement of aggregation to analyse platelet function immediately after blood collection and to demonstrate their activation in the circulation of patients with AITDs. We noted reorganization of platelet subpopulations (normal platelets, microparticles and aggregates) in AITDs, dependent on the degree of cell activation. We proved the elevated expression of the active form of integrin receptor GPIIb/IIIa, responsible for platelet aggregation, and in the kinetic test we confirmed the increased aggregation of platelets in different intracellular signal pathways (dependent on ADP, collagen, arachidonic acid). Our study demonstrates the high platelet activation level found in AITDs.

Inactive disease and remission in childhood-onset systemic lupus erythematosus

OBJECTIVE

To define inactive disease (ID) and clinical remission (CR) and to delineate variables that can be used to measure ID/CR in childhood-onset systemic lupus erythematosus (cSLE).

METHODS

Delphi questionnaires were sent to an international group of pediatric rheumatologists. Respondents provided information about variables to be used in future algorithms to measure ID/CR. The usefulness of these variables was assessed in 35 children with ID and 31 children with minimally active lupus (MAL).

RESULTS

While ID reflects cSLE status at a specific point in time, CR requires the presence of ID for >6 months and considers treatment. There was consensus that patients in ID/CR can have <2 mild nonlimiting symptoms (i.e., fatigue, arthralgia, headaches, or myalgia) but not Raynaud's phenomenon, chest pain, or objective physical signs of cSLE; antinuclear antibody positivity and erythrocyte sedimentation rate elevation can be present. Complete blood count, renal function testing, and complement C3 all must be within the normal range. Based on consensus, only damage-related laboratory or clinical findings of cSLE are permissible with ID. The above parameters were suitable to differentiate children with ID/CR from those with MAL (area under the receiver operating characteristic curve >0.85). Disease activity scores with or without the physician global assessment of disease activity and patient symptoms were well suited to differentiate children with ID from those with MAL.

CONCLUSION

Consensus has been reached on common definitions of ID/CR with cSLE and relevant patient characteristics with ID/CR. Further studies must assess the usefulness of the data-driven candidate criteria for ID in cSLE.