Recurrent Missense Variant Identified in Two Unrelated Families with MPZL2-related Hearing Loss, Expanding the Variant Spectrum Associated with DFNB111

MPZL2-related hearing loss is a rare form of autosomal recessive hearing loss characterized by progressive, mild sloping to severe sensorineural hearing loss. Thirty-five previously reported patients had biallelic truncating variants in MPZL2, with the exception of one patient with a missense variant of uncertain significance and a truncating variant. Here, we describe the clinical characteristics and genotypes of five patients from four families with confirmed MPZL2-related hearing loss. A rare missense likely pathogenic variant [NM_005797.4(MPZL2):c.280C>T,p.(Arg94Trp)] located in exon 3 was confirmed to be in trans with a recurrent pathogenic truncating variant that segregated with hearing loss in three of the patients from two unrelated families. This is the first recurrent likely pathogenic missense variant identified in MPZL2. Apparently milder or later-onset hearing loss associated with rare missense variants in MPZL2 indicates that some missense variants in this gene may cause a milder phenotype than that resulting from homozygous or compound heterozygous truncating variants. This study, along with the identification of truncating loss of function and missense MPZL2 variants in several diverse populations, suggests that MPZL2-related hearing loss may be more common than previously appreciated and demonstrates the need for MPZL2 inclusion in hearing loss testing panels.