Hereditary transthyretin amyloidosis (hATTR) is an ultra-rare illness. Inotersen is a 2'-O-methoxyethyl (2'MOE)-modified antisense oligonucleotides (ASO) approved in 2018 as a polyneuropathy treatment for adults with hereditary transthyretin amyloidosis stages 1 or 2. Inotersen can produce grade 4 thrombocytopenia as a severe adverse reaction that can lead to potentially fatal hemorrhage complications. We describe our experience in the management of severe thrombocytopenia with inotersen. The onset of the thrombocytopenia and the incidences described in the cases in our hospital are different from that described in the literature. Also, recovery of platelet levels was faster in our patient who was administered human immunoglobulin G, which suggests that there is an immunological component.