Clinical phenotypes with predominant LMN involvement (LMN-predominant ALS, n = 22) showed higher serum p-tau 181 levels than bulbar ALS (n = 16, p = 0.007) and phenotypes with predominant upper motor neuron involvement (UMN-predominant ALS, n = 9, p = 0.002). This evidence concerns the gene MAPT and amyotrophic lateral sclerosis.