A 12-month-old female infant exhibits severe developmental delay with associated macrocephaly, dysmorphic facies, hypotonia, and hepatosplenomegaly. Clouding of the corneas is not evident. A pebbly ivory-colored lesion is present over the infant's back. The activity of iduronate sulfatase in the plasma is not detectable. These symptoms are indicative of which of the following diseases?

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Quizplus · Accepted Answer

Hunter syndrome is characterized by developmental delay, macrocephaly, dysmorphic facies, hypotonia, hepatosplenomegaly, and pebbly skin lesions. The absence of corneal clouding and undetectable iduronate sulfatase activity are key indicators of Hunter syndrome.  Although multiorgan involvement, liver and spleen enlargement, and skeletal abnormalities are common to all the mucopolysaccharidotic (MPS) diseases, each encompasses specific and unique features. Each different MPS is caused by defects in different enzymes which allows for specific diagnosis. Hunter syndrome is characterized by progressive multiorgan failure and premature death. Hallmark features include enlargement of the spleen and liver, severe skeletal deformity, and coarse facial features (which are associated with the constellation of defects referred to as dystosis multiplex). Unlike Hurler syndrome, whose symptoms are similar (but more severe), Hunter syndrome does not cause corneal opacities. Hunter syndrome results from a defect in iduronidate sulfatase activity and this activity can be measured in the plasma.

A 12-Month-Old Female Infant Exhibits Severe Developmental Delay with Associated