Apparent allelism of the Hurler, Scheie, and Hurler/Scheie syndromes

The Hurler, Scheie, and Hurler/Scheie syndromes are clinically distinct disorders due to inherited deficiencies of lysosomal alpha-iduronidase activity. The genetic relationship of these disorders was investigated by complementation analysis using a heterokaryon enrichment procedure. Fusions between fibroblasts derived from Hurler, Scheie, or Hurler/Scheie subjects in any combination resulted in no detectable correction of alpha-iduronidase activity, indicating that they form a single complementation group. Control fusions between these fibroblasts and mucolipidosis II or III cells, which are also alpha-iduronidase deficient due to an enzyme processing defect, resulted in restoration of up to 57% of normal alpha-iduronidase activity. These results also suggest allelism of the Hurler, Scheie, and Hurler/Scheie syndromes. However, the genetic make-up of the Hurler/Scheie syndrome was not resolved.