Two siblings, a 56-year-old white man and a 44-year-old white woman, with systemic mucopolysaccharidosis I-S (Scheie's syndrome) developed acute glaucoma successively in each eye. Their management was complicated by an inability to visualize the anterior chamber angle due to corneal clouding by acid mucopolysaccharide (AMP) deposition. The mechanism of their glaucoma resembled angle closure, which may have been related to thickening of anterior ocular structures due to abnormal AMP storage.