No other second mutation was identified in the ALS patient with a pathogenic HTT repeat expansion which might have explained either his clinical ALS phenotype or the late-onset dementia syndrome in his ancestors (see below); except a variant in microtubule associated protein tau (MAPT), NM_001123066.4: c.509del, p.(Pro170LeufsTer24), GRCh38(chr17):g.45983312del. Here, MAPT is linked to amyotrophic lateral sclerosis.