Audiometric characteristics of a Dutch family with Muckle-Wells syndrome

Description of the audiometric and vestibular characteristics of a Dutch family with Muckle-Wells syndrome (MWS). Examination of all family members consisted of pure tone audiometry, otoscopy and genetic analysis. In addition, a selected group underwent speech audiometry, vestibulo-ocular examination, acoustic reflex testing and tests assessing loudness scaling, gap detection, difference limen for frequency and speech perception in noise. Linear regression analyses were performed on the audiometric data. Six clinically affected family members participated in this study and all were carriers of a p.Tyr859His mutation in the NLPR3 gene. Most affected family members reported bilateral, slowly progressive hearing impairment since childhood. Hearing impairment started at the high frequencies and the low- and mid-frequency threshold values deteriorated with advancing age. Annual threshold deterioration (ATD) ranged from 1.3 to 1.9 dB/year with the highest values at the lower frequencies. Longitudinal linear regression analysis demonstrated significant progression for a number of frequencies in five individuals. Speech recognition scores were clearly affected. However, these individuals tended to have higher speech recognition scores than presbyacusis patients at similar PTA(1,2,4 kHz) levels. The loudness growth curves were steeper than those found in individuals with normal hearing, except for one family member (individual IV:6). Suprathreshold measurements, such as difference limen for frequency (DL(f)), gap detection and particularly speech perception in noise were within the normal range or at least close to data obtained in two groups of patients with a so-called conductive type of hearing loss, situated in the cochlea. Hearing impairment in MWS is variable and shows resemblance to previously described intra-cochlear conductive hearing impairment. This could be helpful in elucidating the pathogenesis of hearing impairment in MWS. Other associated symptoms of MWS were mild and nonspecific in the present family. Therefore, even without any obvious syndromic features, MWS can be the cause of sensorineural hearing impairment, especially when combined with (mild) skin rash and musculoskeletal symptoms. An early diagnosis of MWS is essential to prevent irreversible damage from amyloidosis. The effect of IL-1β inhibitors on hearing impairment is more controversial, but an early start of treatment seems to be essential. Therefore, our results are of importance in patient care and counselling.