Cochlear implantation in a Chinese patient with a novel frameshift variant in POU3F4 gene and incomplete partition type III: a case report

Variations in the POU Class 3 Homeobox 4 (POU3F4) gene are associated with X-linked mixed deafness. Here, the identification of a novel variant of POU3F4 in a male paediatric patient (the proband) with incomplete partition type III (IP-III) hearing impairment, is described. Clinical data were collected from the proband and his biological parents. Whole exome sequencing of the proband revealed a novel frameshift insertion mutation in POU3F4 (c.717_718ins GTGCCTTGCAG: p.Leu240Valfs*5) in a hemizygous state. This variant likely truncates the protein within the POU-specific domain, and the proband's biological mother was found to be a carrier of this variant. After excluding all contraindications, the proband underwent cochlear implantation in the right ear in June 2020. Cerebrospinal fluid (CSF) gushing was observed during surgery, but there were no postoperative complications, such as CSF leak, meningitis, or facial nerve stimulation. A novel pathogenic frameshift variant of POU3F4 was identified, enriching the known mutation spectrum of POU3F4. Effective perioperative prevention and response measures should be taken to reduce the incidence of CSF gushing and meningitis in patients receiving IP-III cochlear implantation.