Fanconi-Bickel syndrome

Fanconi-Bickel syndrome (FBS), also known as glycogen storage disease type XI (GSD XI) or hepatorenal glycogen storage disease with renal Fanconi syndrome, is a rare autosomal recessive disorder of carbohydrate metabolism caused by mutations in the SLC2A2 gene, which encodes the GLUT2 facilitative glucose transporter. GLUT2 is expressed in hepatocytes, pancreatic beta cells, renal tubular epithelial cells, and intestinal enterocytes, and its dysfunction leads to impaired glucose and galactose transport across these tissues. The disease typically presents in infancy with hepatomegaly due to glycogen accumulation in the liver, failure to thrive, and a characteristic generalized proximal renal tubular dysfunction known as renal Fanconi syndrome. Key clinical features include a protuberant abdomen from hepatomegaly and nephromegaly, short stature, rickets (due to hypophosphatemia from renal phosphate wasting), fasting hypoglycemia, postprandial hyperglycemia, hypergalactosemia, glucosuria, phosphaturia, generalized aminoaciduria, and bicarbonate wasting. Affected children often develop a doll-like facies with fat deposition in the cheeks. Glycogen also accumulates in the kidneys, contributing to nephromegaly. There is no specific curative treatment for Fanconi-Bickel syndrome. Management is primarily supportive and symptomatic, focusing on dietary modifications including frequent meals, uncooked cornstarch supplementation to prevent hypoglycemia, galactose restriction, and correction of electrolyte imbalances and metabolic acidosis. Phosphate and vitamin D supplementation are used to manage rickets. With appropriate management, patients can survive into adulthood, though short stature often persists. Prognosis varies, and long-term complications may include osteoporosis and chronic kidney disease.

Common questions about Fanconi-Bickel syndrome