Mucolipidosis Type IV
https://www.cureus.com/articles/464301#!
This case report describes a nine‑year‑old boy whose severe corneal clouding (loss of transparency in cornea) and visual loss since birth led to the diagnosis of mucolipidosis type IV (MLIV), a very rare inherited lysosomal storage disorder. Although MLIV usually appears in infants with developmental delay and progressive neurological problems, this child’s earliest and most visible symptom was bilateral epithelial‑stromal corneal dystrophy, a disease affecting the outermost layers of the cornea, causing extreme light sensitivity and near‑blindness. Beyond the eye findings, the child had seizures, hypotonia (low muscle tone), psychomotor delay (slowing of movement and thought processing), and facial dysmorphism, suggesting a multisystem disorder. Electrophysiology revealed normal retinal function but abnormal visual pathways, consistent with optic nerve involvement. Genetic testing confirmed a homozygous MCOLN1 nonsense mutation (c.169C>T; p.Arg57), which stops the mucolipin‑1 protein from functioning properly and is known to cause MLIV. The report emphasizes that MLIV should be considered in children with congenital corneal opacity plus developmental delay, even outside the Ashkenazi Jewish population where the disease is more common. Early diagnosis prevents unnecessary corneal transplantation, which is ineffective due to recurrence, and allows families to receive appropriate genetic counselling and supportive multidisciplinary care.