Fanconi Bickel syndrome (FBS) is a rare condition characterized by the accumulation of a substance called glycogen in different parts of the body. Glycogen is created when the body needs to store glucose (sugar). When the body needs sugar again, glycogen is transformed back into glucose for use. People with Fanconi Bickel syndrome do not store the appropriate amount of glycogen. Therefore, Fanconi Bickel syndrome is known as a glycogen storage disease. Specifically, glycogen accumulates in the liver and kidneys. Signs and symptoms begin in the first few months of life and include growing slower than expected (failure to thrive), excessive urination (polyuria), and weakened bones (rickets). Later in life, children may have short stature and a swollen liver and spleen (hepatosplenomegaly). Fanconi Bickel syndrome is caused by genetic changes to the SLC2A2 gene and is inherited in an autosomal recessive manner. Diagnosis of FBS is based on a clinical examination that shows signs of FBS. The condition can be confirmed by genetic testing.