Genetic deafness and blindness syndromes — branching viva

A six-week-old infant referred after failing the universal newborn hearing screen. The diagnostic ABR confirms bilateral severe sensorineural hearing loss and the examination is normal. The universal newborn hearing screen has transformed the early identification of congenital deafness, making the six-week diagnostic window the standard of care. [1] [2]

Opening stem. The examiner asks the candidate to build the aetiological workup from the bedside outward. The expected answer names diagnostic ABR and OAE confirmation, CMV PCR within the first three weeks of life, temporal bone imaging, an ECG to exclude Jervell and Lange-Nielsen long QT, and GJB2 sequencing as the highest-yield single genetic test. The timing rationale for each investigation is where marks are won. [2] [3]

Branch one — the enlarged vestibular aqueduct. The examiner reveals that temporal bone MRI shows bilateral enlarged vestibular aqueducts. The candidate names Pendred syndrome, explains the SLC26A4 pendrin mechanism that links the inner ear and the thyroid, states that the goitre may be absent in childhood and euthyroid, and describes the genetic counselling for a 25 per cent autosomal-recessive recurrence risk. [5]

Branch two — the deaf child who develops night blindness. The examiner shifts to a four-year-old with known hearing loss who now bumps into furniture in dim light. The candidate recognises Usher syndrome immediately, explains the two-wave presentation, confirms the diagnosis with electroretinography and molecular testing, and counsels on the progressive retinitis pigmentosa and the gene-therapy horizon. The examiner probes the distinction between Usher types I, II and III and the reason every deaf child of unknown cause needs a baseline ophthalmology review by school age. [4] [11]