Mutation analysis of two Japanese patients with Fanconi-Bickel syndrome

Fanconi-Bickel syndrome (FBS), or glycogen storage disease type XI, is a ra re autosomal recessive disorder characterized by hepatorenal glycogen accum ulation, Fanconi nephropathy, and impaired utilization of glucose and galac tose. Recently, this disease was elucidated to link mutations in the glucos e transporter 2 (GLUT2) gene. Only three mutations in three FBS families ha ve been reported. Therefore, it is important to elucidate mutations in the GL Un gene in FBS by answering the question of whether the syndrome is a si ngle gene disease. In this report, we describe two patients in two unrelate d families clinically diagnosed with FBS. No mutation in the entire protein coding region of the GLUT2 gene was detected in patient, which suggested t hat no mutation existed in the GLUT2 gene, or that some mutations had affec ted the expression of the GLUT2 gene. In patient 2, a novel homozygous nons ense mutation (W420X, Trp at codon 420 to stop codon) was detected. These r esults support the correlation between GLTU2 gene mutation and FBS syndrome . However, many patients must be analyzed to determine whether other genes are involved in FBS.