Aims The mucopolysaccharidoses (MPS) are a heterogeneous group of rare disorders characterised by accumulation of glycosaminoglycans within multiple organ systems. This study aimed to determine the prevalence and severity of ocular complications in patients with MPS. Methods Clinical ophthalmic features and electrodiagnostic results of 50 patients with a diagnosis of MPS were retrospectively reviewed. Results A total of 79% of MPS IH patients had a visual acuity of less than 6/12 equivalent in their better eye, compared to 44% of MPS IH/S and 25% of MPS VI patients. In total, 16% of MPS IH and 25% of MPS IH/S had severe corneal opacification, compared to 38% of MPS VI patients. 16% of MPS IH patients had optic atrophy; 21% of MPS VI patients had mild disc swelling, 29% had markedly swollen discs, and 14% had optic atrophy. One patient with MPS IH, one with MPS IH/S and six with MPS VI had ocular hypertension. One MPS VI patient had glaucoma that required topical therapy. Nine patients with MPS IH had electrodiagnostic evidence of retinopathy, as did one MPS VI patient. Conclusions Ocular complications causing significant reduction in vision are common in MPS. The majority of MPS I and MPS VI patients have corneal opacification, which can lead to difficulties in diagnosis and monitoring of glaucoma, optic disc changes, and retinopathy.

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We describe seven patients with KDM6A (located on Xp11.3 and encodes UTX) mutations, a rare cause of Kabuki syndrome (KS2, MIM 300867) and report, for the first time, germ-line missense and splice-site mutations in the gene. We demonstrate that less than 5% cases of Kabuki syndrome are due to KDM6A mutations. Our work shows that similar to the commoner Type 1 Kabuki syndrome (KS1, MIM 147920) caused by KMT2D (previously called MLL2) mutations, KS2 patients are characterized by hypotonia and feeding difficulties during infancy and poor postnatal growth and short stature. Unlike KS1, developmental delay and learning disability are generally moderate-severe in boys but mild-moderate in girls with KS2. Some girls may have a normal developmental profile. Speech and cognition tend to be more severely affected than motor development. Increased susceptibility to infections, join laxity, heart, dental and ophthalmological anomalies are common. Hypoglycaemia is more common in KS2 than in KS1. Facial dysmorphism with KDM6A mutations is variable and diagnosis on facial gestalt alone may be difficult in some patients. Hypertrichosis, long halluces and large central incisors may be useful clues to an underlying KDM6A mutation in some patients.