Coexistence of PDB and ALS-FTLD is apparently rare and precisely how different SQSTM1 mutations (some of which are common to both disorders) can lead to either neurodegeneration or PDB is currently unknown, although in some cases co-occurrence of an additional mutation such as a pathogenic C9orf72 expansion may account for the neurodegenerative phenotype (Almeida et al., 2015). Here, SQSTM1 is linked to amyotrophic lateral sclerosis.