Amyotrophic lateral sclerosis (ALS) is characterized by motor neurone loss 
resulting in muscle weakness, spasticity and ultimately death. 5-10% are caused 
by inherited mutations, most commonly C9ORF72, SOD1, TARDBP and FUS. Rarer 
genetic causes of ALS include mutation of optineurin (mt OPTN). Furthermore, 
optineurin protein has been localized to the ubiquitylated aggregates in several 
neurodegenerative diseases, including ALS. This study: (i) investigated the 
frequency of mt OPTN in ALS patients in England; (ii) characterized the clinical 
and neuropathological features of ALS associated with a mt OPTN; and (iii) 
investigated optineurin neuropathology in C9ORF72-related ALS (C9ORF72-ALS). We 
identified a heterozygous p.E322K missense mutation in exon 10 of OPTN in one 
familial ALS patient who additionally had a C9ORF72 mutation. This patient had 
bulbar, limb and respiratory disease without cognitive problems. Neuropathology 
revealed motor neurone loss, trans-activation response DNA protein 43 
(TDP-43)-positive neuronal and glial cytoplasmic inclusions together with 
TDP-43-negative neuronal cytoplasmic inclusions in extra motor regions that are 
characteristic of C9ORF72-ALS. We have demonstrated that both TDP-43-positive 
and negative inclusion types had positive staining for optineurin by 
immunohistochemistry. We went on to show that optineurin was present in 
TDP-43-negative cytoplasmic extra motor inclusions in C9ORF72-ALS cases that do 
not carry mt OPTN. We conclude that: (i) OPTN mutations are associated with ALS; 
(ii) optineurin protein is present in a subset of the extramotor inclusions of 
C9ORF72-ALS; (iii) It is not uncommon for multiple ALS-causing mutations to 
occur in the same patient; and (iv) studies of optineurin are likely to provide 
useful dataregarding the pathophysiology of ALS and neurodegeneration.