Early-Onset Retinal Dystrophy in Alpha-Mannosidosis: A Case Report

Purpose: Alpha-mannosidosis is a rare inherited lysosomal storage disorder characterized by immune deficiency, intellectual disability, hearing loss, and skeletal and facial dysmorphism. It results from biallelic pathogenic variants in MAN2B1 on chromosome 19. Ophthalmic manifestations previously described in alpha-mannosidosis include corneal opacities, lenticular changes, wheel-like cataracts, and strabismus. Although a few reports have documented retinal dystrophy in affected individuals, these cases have typically occurred later in life, between the fourth and sixth decades. Observations: We report a 17-year-old female with genetically confirmed alpha-mannosidosis who presented with decreased visual function. Ophthalmic evaluation revealed bilateral optic nerve atrophy, peripapillary hyperpigmentation, salt-and-pepper retinopathy, and optic coherence tomography evidence of photoreceptor disruption. Fundus imaging demonstrated tilted discs and generalized pallor. These features are consistent with early-onset retinal dystrophy. Conclusions and Importance: This case represents one of the youngest reported patients with alpha-mannosidosis and retinal dystrophy. Our findings underscore the importance of routine ophthalmologic surveillance, including OCT, ERG, and dilated fundus examination, to facilitate early detection, guide family counseling, and optimize visual outcomes.