HGSNAT and inherited retinal dystrophy: Pericentral retinitis pigmentosa, a specific subtype of retinal dystrophy, has been observed as sole symptom in association with mutations in the HGSNAT gene, encoding the lysosomal enzyme heparin-alpha-glucosaminide N-acetyltransferase a deficiency of which causes MPS IIIC (OMIM #252930) [29, 30].