Retinal dystrophies have been described in patients with single sulfatase deficiencies including MPS type II (IDS), III-A (SGSH), III-D (GNS), IV-A (GALNS), X (ARSK) as well as Usher syndrome type IV (ARSG) (15–20), and the retinopathy identified in patients 1-3 are likely due to the resulting deficiencies in one or more of these sulfatases. Here, ARSK is linked to Usher syndrome, type 4.