Boutaina Bousellam, Hibat Allah Eddaoui, Aniss Regragui, Nabiha Benchekroun, Mohamed Belmekki
A nine-year-old boy, the only child of non-consanguineous parents, presented with progressive bilateral visual impairment and corneal clouding since birth. Ocular examination showed bilateral epithelial-stromal corneal dystrophy associated with photophobia, blepharospasm, alternating esotropia, and nystagmus. Visual acuity was limited to light perception in both eyes, with normal intraocular pressure. Anterior segment optical coherence tomography (OCT) demonstrated diffuse epithelial-stromal thickening with hyperreflective anterior stroma. Flash electroretinography (ERG) was normal, while flash visual evoked potentials (VEP) revealed bilateral optic neuropathy. Systemic examination noted severe psychomotor impairment, hypotonia, and facial dysmorphism. Whole-exome sequencing identified a homozygous nonsense mutation in MCOLN1 (c.169C>T p.Arg57*), confirming mucolipidosis type IV. Mucolipidosis type IV is a rare autosomal-recessive lysosomal storage disorder combining ocular and neurological manifestations. In children with congenital corneal opacity and developmental delay, metabolic and genetic evaluation should be systematically pursued. Corneal transplantation is not recommended because of recurrence risk; management is supportive and multidisciplinary.