ERBB4 and amyotrophic lateral sclerosis: Assessing novel variants in known ALS disease genes revealed > 30 distinct mutations in SOD1, TARDBP, CHMP2B, ERBB4, DCTN1, FIG4, FUS, MATR3, NEK1, SETX, SQSTM1, TBK1 and UBQLN2 that were present in cases but not controls (Additional file 1: Table S9).