Poly-GA immunohistochemistry is a reliable tool for detecting C9orf72 hexanucleotide repeat expansions.

Poly-GA immunohistochemistry (A) on formalin fixed paraffin embedded cerebellum sections shows a similar distribution to p62 antibody (B) and reliably identifies neuronal cytoplasmic inclusions and neurites in cases with known C9orf72 repeat expansion. This is useful in the research setting where genetic testing has not been performed in life or suitable tissue is not avilable post-mortem.