Characterization of hearing-impairment in Generalized Arterial Calcification of Infancy (GACI)

Background and importance: Hearing loss (HL) has been sporadically described, but not well characterized, in Generalized Arterial Calcification of Infancy (GACI), a rare disease in which pathological calcification typically presents in infancy.

Objectives: This study aims to describe the clinical audiologic and otologic features and potential etiology of hearing impairment in GACI and gain pathophysiological insight from a murine model of GACI.

Design: Cross-sectional cohort study of individuals with GACI. Murine ossicle micromorphology of the ENPP1^asj/asj mutant compared to wild-type.

Setting: Clinical research hospital; basic science laboratory.

Participants: Nineteen individuals with GACI who met clinical, biochemical, and genetic criteria for diagnosis.

Main outcomes and measures: Clinical, biochemical, and radiologic features associated with hearing status.

Results: Pure-tone thresholds could be established in 15 (n = 30 ears) of the 19 patients who underwent audiological assessments. The prevalence of HL was 50% (15/30) of ears, with conductive HL in 80% and sensorineural HL in 20%. In terms of patients with HL (n = 8), seven patients had bilateral HL and one patient had unilateral HL. Degree of HL was mild to moderate for 87% of the 15 ears with hearing loss. Of those patients with sufficient pure-tone and middle ear function data, 80% (8/10) had audiometric configurations suggestive of ossicular chain dysfunction (OCD). Recurrent episodes of otitis media (ROM) requiring pressure-equalizing tube placement were common. In patients who underwent cranial CT, 54.5% (6/11) had auricular calcification. Quantitative backscattered electron imaging (qBEI) of murine ossicles supports an OCD component of auditory dysfunction in GACI, suggesting loss of ossicular osteocytes without initiation of bone remodeling.

Conclusions and relevance: Hearing loss is common in GACI; it is most often conductive, and mild to moderate in severity. The etiology of HL is likely multifactorial, involving dysfunction of the ossicular chain and/or recurrent otitis media. Clinically, this study highlights the importance of early audiologic and otologic evaluation in persons with GACI. Novel findings of high rates of OCD and ROM may inform management, and in cases of unclear HL etiology, dedicated temporal bone imaging should be considered.