Another subtype, putatively referred to as MPS IIIE, is thought to result from arylsulfatase G (ARSG) dysfunction, but this has only been observed in animal models [16,17] and has yet to be described in a human patient (most ARSG mutations are instead associated with Usher syndrome type 4 [OMIM 6181440]) [18,19,20,21]. This evidence concerns the gene ARSG and Usher syndrome, type 4.