Mild and severe Hunter syndrome (MPS II) within the same sibships

Abstract

X-linked Hunter syndrome (MPS II) is presently thought to exist in 2 clinically and genetically distinct forms, mild and severe, which are biochemically indistinguishable. However, 2 sibships were studied in which both mildly and severely affected children are present. Therefore, genetic counseling for families with MPS II should be reconsidered to take into account the possibility of heterogeneity within a family in terms of the degree of psychomotor retardation and potential longevity.