Van der Beek and others have studied the hearing loss in adult patients with Pompe disease. The results are good news for the patients because the "prevalence [of hearing loss] is similar to that in the general population. Therefore, we conclude that hearing loss is not a specific feature of Pompe disease in adults".
Source: van der Beek NA, Verschuure H, Reuser AJ, van der Ploeg AT, van Doorn PA, Poublon RM: Hearing in adults with Pompe disease. J Inherit Metab Dis. 2011 Oct 15. [Epub ahead of print]