Ophthalmic Manifestations of Heimler Syndrome in Two Siblings with PEX1 Variants

Purpose: To report two new cases with confirmed diagnosis of Heimler syndrome and describe their systemic and ophthalmic phenotype and visual rehabilitation. Methods: Retrospective review of medical records. Results: Both siblings were diagnosed as having sensori-neural hearing loss and retinal dystrophy with exuberant intraretinal cystoid spaces and cone–rod dysfunction. The older sibling also had amelogenesis imperfecta and neither had nail abnormalities. Genetic analysis identified homozygosity for the pathogenic variant c.2528G>A p.(Gly843Asp) in the PEX1 gene in both siblings. The parents were heterozygous carriers of the variant. Conclusions: The authors report a familial case of Heimler syndrome due to biallelic PEX1 pathogenic variants that manifested as macular dystrophy characterized by cone–rod dysfunction and complicated by intraretinal cystoid spaces. Review of the literature shows that ocular phenotype is variable in patients with Heimler syndrome. [ J Pediatr Ophthalmol Strabismus . 2024;61(1):59–66.]