IGKV4-1 and Thrombocytopenia: Also proplatelet formation on fibrinogen was abnormal in our patients, with a reduced number of proplatelets with enlarged tips, in agreement with two recent reports describing patients with gain-of-function mutations of αIIbβ3 associated with thrombocytopenia, one at the cytoplasmic tail of β3[19] and the second at the cytoplasmic domain of αIIb[20].