Trisulfated Heparin Disaccharide (TS-HDS) Antibody-Positive Small Fiber Neuropathy Involving Sweat Gland Nerve Fibers After the Second Moderna Vaccination: A Case Report

SARS-CoV-2 vaccinations (SC2V) may be complicated by small fiber neuropathy (SFN) in individual patients. Furthermore, SC2V-related SFN may be associated with antibodies against FGFR3 or recoverin, but no patient with SC2V-related SFN and elevated trisulfated heparin disaccharide (TS-HDS) antibodies has been described to date. The patient is a 74-year-old previously healthy woman who experienced temporary side effects after her second Moderna vaccination. One and two months later, more severe symptoms appeared, most of which persisted for the next four years. As sweat gland density was reduced and TS-HDS antibodies were elevated, she was diagnosed with TS-HDS-related SFN, which manifested as regional pain syndrome and autonomic dysfunction, but intravenous immunoglobulins (IVIGs) and naltrexone were ineffective. In addition to SFN, she was also diagnosed with mast cell activation syndrome (MCAS). This case demonstrates that SC2V with the Moderna vaccine can be complicated by long-lasting TS-HDS antibody-associated SFN and MCAS, which manifest as regional pain, autonomic dysfunction, cognitive impairment, anxiety, tinnitus, myalgia, fatigue, and easy fatigability. IVIGs may be ineffective, so immunosuppressants should be tried.