C9orf72 and amyotrophic lateral sclerosis: In addition, we have recently shown that C9orf72 repeat expansions are present in sporadic PMA patients, but at a lower frequency than in sporadic ALS patients (1.6% versus 6.1%) [12]; other studies have shown that C9orf72 repeat expansions were present in approximately 7% of white sporadic ALS patients from the USA, Europe and Australia, and that bulbar onset ALS is frequently encountered in patients with these expansions [51], [52], [53], [54].