Diagnostik der glykogenose type 1a: DNA-analyse aus leukozyten als alternative zum enzymassay aus einem frischen leberbiopsat

Background: The gold standard for the diagnosis of glycogen storage disease type Ia is still the enzyme assay necessitating fresh liver tissue. In 1993, the gene encoding for the human phosphatase (G-6-Pase) of the glucose-6-phosphatase system was isolated and consequently, mutations have been identified in glycogen storage disease type Ia patients. We analysed the G-6-Pase gene of 18 patients with glycogen storage disease type Ia. The diagnosis had previously been established by the enzyme assay in 13 patients. The remaining 5 patients were diagnosed on the basis of the clinical presentation. Methods: DNA was isolated from EDTA-blood, and all 5 exons of the G-6-Pase gene were screened for mutations by SSCP analysis following PCR amplification. Mutations found by SSCP analysis were further characterised by DNA sequencing. In the event of normal band-patterns in the SSCP analysis, all exons were sequenced. Results: The diagnosis could be verified by the finding of a mutation on each allele of the G-6-Pase gene in 17 patients. For 1 patient no mutation was identified. The most prevalent mutation among this population is R83C, followed by Q347X and G118R. In 3 patients we found a mutation that has not been reported so far. Conclusion: We believe that the analysis of the G-6-Pase gene in a blood sample for verifying the clinical diagnosis of glycogen storage disease type Ia is a valuable alternative to the enzyme assay. It can spare most patients the risky and unpleasant liver biopsy.