Auditory system involvement in late onset Pompe disease: a study of 20 Italian patients

Glycogen storage disease type II (GSD II), also known as Pompe disease, is an autosomal recessive inherited disorder caused by a reduced activity of acid alpha glucosidase (GAA). Two different clinical entities have been described: rapidly fatal infantile and late onset forms. Hearing loss has been described in classic infantile Pompe patients but rarely in late onset cases. The main purpose of this study was to investigate the involvement of the auditory system in a cohort of Italian patients with late onset GSD II. We have enrolled 20 patients, 12 males and 8 females. The auditory system assessment included speech and pure tone audiometry, impedance audiometry and auditory brainstem responses (ABR). A combined interpretation of those tests allowed us to define the origin of the hearing impairment (sensorineural, conductive or mixed). Clinically, all patients but one denied subjective hearing disturbances. On the other hand, audiological evaluation revealed that 21/40 patient ears (52.5%) had a hearing impairment: 57% had a sensorineural deficit, 33% showed a conductive hearing loss whereas 10% presented with a mixed pattern. Our study revealed that, in this group of GSDII late onset patients, the auditory system impairment was more frequently present than thought with a prominent cochlear involvement. Our results emphasize the importance of a routinely auditory function evaluation in all forms of Pompe disease.