Report of a Large Brazilian Family With a Very Attenuated Form of Hunter Syndrome (MPS II)

Abstract

Hunter syndrome, or Mucopolysaccharidosis type II (MPS II), is a rare X-linked recessive disorder caused by a deficiency of the lysosomal enzyme iduronate-2-sulfatase (IDS). The phenotypic spectrum varies from severe to attenuated clinical forms. We report a large Brazilian family with 16 affected individuals exhibiting a very attenuated form of MPS II. Fourteen female carriers were also identified. Twelve affected male patients, whose ages ranged from 1 to 35 years, were examined. Molecular analysis showed a novel missense mutation (p.A77D) in the IDS gene, confirming the diagnosis. Nine of the family members presented some degree of heart damage, though only the proband became symptomatic and required heart transplantation. One 19-year-old adult and 1-year-old twin boys each had a normal echocardiogram. Short stature was found in two adults while macrocephaly was found in one; the remaining adults had anthropometric measures within normal range. All affected adults had normal cognitive development and were able to perform normal daily activities, except one who had mild learning disability. Two patients died due to natural causes beyond 70 years of age. The female carriers did not present any signs of disease. In this large family with a mild form of MPS II and variable degree of clinical manifestations, it is noteworthy that several affected individuals have remained asymptomatic even at advanced age and even without enzyme replacement therapy.