Bi-allelic expansions were absent in controls (0 out of 13 515).<h4>Discussion</h4>Here we report an apparently novel autosomal recessive form of familial ALS caused by bi-allelic intermediate <i>ATXN2</i> repeat expansions, which is characterised by high penetrance, lower limb onset and slow progression. The gene discussed is ATXN2; the disease is amyotrophic lateral sclerosis.