Hearing loss in patients with mucopolysaccharidosis II: Data from HOS - The Hunter Outcome Survey

Background Subjectively reported hearing loss is a common feature of mucopolysaccharidosis II (MPS II, Hunter syndrome). This study provides an epidemiological description of hearing loss and other otolaryngological manifestations reported by patients registered in the Hunter Outcome Survey (HOS), an international registry of patients with MPS II. Methods Data about ear signs and symptoms were available for 554 of the 605 patients alive at HOS entry. The degree of hearing loss for 162 pure-tone audiograms (PTAs) from 83 patients was classified by independent interpreters using both the age-specific International Institute of Standardization (ISO) 7029 standard and the ageindependent World Health Organization (WHO) clinical guidelines. A linear regression analysis using crosssectional data was conducted to investigate the relationship between hearing loss and age. Results The most prevalent otolaryngological manifestations and interventions reported were otitis (either acute otitis media or chronic otitis media [72%]), hearing loss (67%), insertion of ventilation tubes (50%), adenoidectomy (47%), and hearing aids (41%). According to the ISO standard, only one patient out of the 83 with audiogram data in HOS had normal hearing in both ears at all time points. According to the WHO classification, 16% had normal hearing; hearing loss was mild in 24%, moderate in 31%, severe in 22%, and profound in 7%. In the linear regression analysis, the hearing threshold in the cohort increased with age at an estimated rate of approximately 1 dB per year. Conclusions Hearing impairment is common in MPS II. Early otolaryngological evaluation and intervention is recommended.