Prenatal Tympanic Ring Anomaly Without Microtia: A Subtle Clue Toward Severe Early-Onset Monogenic Disorders

To investigate the genetic etiologies and clinical significance of fetal tympanic ring abnormalities detected during second-trimester ultrasound in the absence of microtia.

Between November 2019 and June 2024, we examined the fetal tympanic rings of 10,277 unselected pregnant women during the 20-22 weeks of morphology ultrasound. Fetal cases with abnormal tympanic rings, without microtia, underwent amniocentesis for genetic investigation, including chromosome microarray analysis and trio genome sequencing (30×).

Five fetuses (0.05%, 5/10,277) with abnormal tympanic rings in the absence of microtia were identified in this cohort, including three unilaterally (2 right, 1 left) and two bilaterally affected cases. Four fetuses had no other obvious structural abnormalities. One had an isolated unilateral hypoplastic tympanic ring with negative genetic findings and was postnatally found to have conductive hearing loss. The remaining four fetuses were diagnosed with severe early-onset genetic disorders (80%), including KBG syndrome, Noonan syndrome, Saethre-Chotzen syndrome, and Cornelia de Lange syndrome. All these four pregnancies were terminated.

Ultrasound evaluation of fetal tympanic ring abnormalities is feasible during the second trimester. Fetal tympanic ring anomalies even occurring with minor ultrasound markers may represent a significant indication for a comprehensive genetic assessment. More studies are needed to establish how tympanic ring anomalies should be integrated into routine clinical practice.