Expanding the Audiological Phenotype Associated With Activity-Dependent Neuroprotective Protein (ADNP) Syndrome: A Case Report and Literature Review Suggesting a Genotype/Phenotype Correlation.

ADNP syndrome, also known as Helsmoortel-Van der Aa syndrome, is a rare dominant syndromic neurodevelopmental diagnosis. ADNP syndrome is caused by pathogenic variants in the gene encoding the activity-dependent neuroprotective homeobox protein (ADNP) that plays a critical role in embryonic and postnatal hippocampal development. ADNP syndrome has a broad range of symptoms including intellectual deficits, dysmorphic features, and behavioral changes including autism spectrum disorder (ASD). Hearing loss has been reported in approximately 11.7% of individuals with ADNP syndrome. In this paper, we report the clinical findings of an individual with ADNP syndrome (c.2630_2633del; p.Asp877Valfs*36) who presents with unilateral hearing loss and confirmed ipsilateral cochlear nerve deficiency. This is the first report of cochlear nerve deficiency in an individual with ADNP syndrome and based on this review of published ADNP syndrome cases, hearing loss may be more prominent in this diagnosis than previously reported.