Heimler syndrome with a complaint of blurred vision caused by compound heterozygous variants in PEX1

Introduction Heimler syndrome (HS) is a rare disorder that includes sensorineural hearing loss (SNHL), nail abnormalities, and enamel hypoplasia. Patients with this syndrome can also exhibit ocular manifestations. At present, only a few cases of HS have been reported, existing knowledge of this syndrome is limited, and many cases have been misdiagnosed or even missed. This is the first report of Heimler syndrome with blurred vision as the first complaint, which was diagnosed by genetic analysis in the ophthalmology department. Case description An 8-year-old girl complained of bilateral visual blur and night blindness from birth. Ophthalmic examinations revealed bilateral retinitis pigmentosa with cystoid macular edema, visual impairment with hyperopia and astigmatism. Hearing test revealed bilateral severe sensorineural hearing loss. Dental examinations revealed enamel hypoplasia. In addition, whole-exome sequencing (WES) identified two pathogenic variants in PEX1: the previously reported missense variant c.2966T > C (p.I989 T), and the novel frameshift variant c.1671_1672del (p.G558Sfs*33). Conclusion Heimler syndrome is caused by compound heterozygous PEX1 pathogenic variants, c.2966T > C (p.I989 T) and c.1671_1672del (p.G558Sfs*33), which contributed to the diversity of clinical and genetic profiles in this patient. The main clinical manifestations include bilateral retinitis pigmentosa with cystoid macular edema, sensorineural hearing loss, and enamel hypoplasia. Systemic examinations are suggested for patients suspected of having pigmentary retinal dystrophy, especially combined with hearing-related impairments. Genetic testing can help us to make a definitive diagnosis.