In an 18-month-old girl affected by mucolipidosis IV (ML IV) with mild corneal clouding, normal retinal activity was documented by electroretinogram (ERG) and slightly delayed optic pathway conduction was revealed by visual evoked potential (VEP). Re-examination 9 years later disclosed severe retinal alterations resulting in atrophy with reduced photopic and missing scotopic ERG components and flat VEP. These fundoscopic and electrophysiologic deteriorations in ML IV suggest progressive rod-cone impairment similar to tapetoretinal dystrophy.