KCND2 and Hearing impairment: The most poorly predicted diagnosis was KCND2 (c.1207C > G, p.Pro403Ala, ENST00000331113) in P6, a patient presenting with infantile-onset bilateral sensorineural hearing impairment, blindness, retinal dystrophy, hypotonia, chorea, profound global developmental delay, intellectual disability, and dystonia.