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.