Isolated Congenital Ossicular Chain Anomalies

Isolated congenital ossicular chain anomalies (COCAs) are an uncommon cause of conductive hearing loss in patients with a normal external auditory canal and tympanic membrane, and familial clustering is rarely described. We report three siblings with non-progressive conductive hearing loss and normal otoscopic findings. Two siblings exhibited bilateral involvement, whereas the third had unilateral disease with a normal contralateral ear. High-resolution temporal bone computed tomography suggested incudostapedial (I-S) discontinuity caused by defects in the long process of the incus, without external or inner ear anomalies. Exploratory tympanotomy in two siblings confirmed congenital-appearing I-S discontinuity without evidence of chronic otitis media. Ossiculoplasty using autologous incus interposition (type III reconstruction) achieved marked postoperative improvement. There was no reported family history of middle ear malformation outside this sibship, and a targeted next-generation sequencing panel (63 known deafness genes) performed in two siblings did not identify a definitive pathogenic variant. This case series highlights that COCAs can cluster among siblings and may show variable laterality (bilateral and unilateral) within the same family, underscoring the value of early imaging and surgical evaluation when conductive hearing loss persists despite normal tympanic membranes.