In our study the amide I maximum frequency was significantly lower in CSF samples from ALS cases (1639.5 ± 2.6 cm−1 SD) compared to PD subjects (1651 ± 7.7 cm−1 SD) and Ctrl (1646 ± 5.5 cm−1 SD), suggesting misfolding of TDP‐43 in ALS cases (Fig. 2A, P < 0.0001). Here, TARDBP is linked to amyotrophic lateral sclerosis.