Anti-glycoprotein VI mediated immune thrombocytopenia: An under-recognized and significant entity?

Idiopathic immune thrombocytopenia (ITP) is an autoimmune disorder characterized by relapsing/ remitting thrombocytopenia. Bleeding complications are infrequent with platelet counts above 30×109 /L, and this level is commonly used as a threshold for treatment. The question of another/ co-existent diagnosis or an alternate mechanism of platelet destruction arises when bleeding is experienced with platelet counts above this threshold. We report a case of anti-GPVI mediated ITP that was diagnosed following investigations performed to address this key clinical question. A patient with ITP experienced exaggerated bruising symptoms despite a platelet count of 91×109 /L. Platelet functional testing showed an isolated platelet defect of collagen-induced aggregation. Next generation sequencing excluded a pathogenic variant of GP6, and anti-GPVI antibodies that curtailed GPVI function were confirmed by extended platelet phenotyping. We propose that anti-GPVI mediated ITP may be under-recognized, and that inclusion of GPVI in antibody detection assays may improve their diagnostic utility and in turn, facilitate a better understanding of ITP pathophysiology and aid individualized treatment approaches.