Hunter disease (mucopolysaccharidosis type II) in a karyotypically normal girl

A female child of healthy, unrelated parents presented at 12 months of age with a history of moderately severe developmental delay, macrocephaly, dysmorphic facies, hypotonia, hepato‐splenomegaly, mild generalized dysostosis multiplex, mucopolysacchariduria (dermatan and heparan sulfates), and Alder‐Reilly bodies in peripheral blood leukocytes. Iduronate sulfatase activity in plasma was markedly depressed: 0.11 units/ml/h (normal, 1.75 ±0.56, N = 6). Analyses of arylsulfatases A, B, and C, heparan N‐sulfatase, α‐mannosidase, β‐mannosidase, β‐glucuronidase, β‐hexosaminidase, β‐galactosidase, and α‐fucosidase activities in plasma, leukocytes, and/or cultured skin fibroblasts were all normal. Urinary sulfatide excretion was also within normal limits. Karyotypes of peripheral blood leukocytes and cultured skin fibroblasts were normal. Serum iduronate sulfatase activities in the parents were in the normal range (father, 1.63 units/ml/h; mother, 1.25 units/ml/h). The results of analyses of restriction fragment length polymorphisms (RFLP) of DNA from cultured skin fibroblasts with the use of probes for loci extending from Xpter to Xq28 showed X chromosome heterozygosity and confirmed the paternal origin of one of the X chromosomes. Studies on sulfur‐35 uptake in mixed fibroblast cultures showed cross‐correction of [35S]‐glycosaminoglycan accumulation between cells from the patient and normal cells or cells from a patient with Hurler disease; however, there was no cross‐correction between cells from the patient and those from boys affected with classical Hunter disease. This represents only the second confirmed case of Hunter disease reported in a karyotypically normal girl.