Identification of a novel FGF3 variant and a new phenotype in three LAMM syndrome families

Over 700 syndromes associated with hearing loss (HL) have been identified. Labyrinthine aplasia, microtia, and microdontia (LAMM syndrome, OMIM: 610706) is a rare HL syndrome characterized by congenital sensorineural HL, labyrinthine aplasia, type I microtia and microdontia, which is caused by biallelic variants in the FGF3 gene. Using Whole-exome sequencing (WES), we identified a novel missense FGF3 variant (c.137G > C, p. Arg46Pro (NM_005247.4) in three unrelated Uyghur ethnic families. This variant is classified as a variant of uncertain significance according to ACMG guidelines, with the applied criteria of PM3, PM2_Supporting, PP3 and PP4. Patients from the three families revealed variable clinical features. We found a novel phenotype, sparse hair, in one of the proband. Our findings expanded the variant and phenotype spectrum of LAMM syndrome and provided new insights to the diagnose and pathogenesis investigation of the disease.