To test whether MIg and/or FHAA affect complement regulation, IgG was purified from four patients with TMA and coexisting MG (i.e. M04516, M09719, M00920, and COM004), one patient with ‘hereditary’ C-TMA on the background of a pathogenic variant in CFI (i.e. c.355G > A; p.Gly119Arg) and variant of uncertain significance in CFI (i.e. c.1397C > T; p.Thr466Ile), and pooled NHS. Here, CFI is linked to myasthenia gravis.