Fanconi syndrome is a disorder of the kidney tubes in which certain substances normally absorbed into the bloodstream by the kidneys are released into the urine instead.
Fanconi syndrome can be caused by faulty genes, or it may result later in life due to kidney damage. Sometimes the cause of Fanconi syndrome is unknown.
Common causes of Fanconi syndrome in children are genetic defects that affect the body's ability to break down certain compounds such as:
- Cystine (cystinosis)
- Fructose (fructose intolerance)
- Galactose (galactosemia)
- Glycogen (glycogen storage disease)
Cystinosis is the most common cause of Fanconi syndrome in children.
Other causes in children include:
- Exposure to heavy metals such as lead, mercury, or cadmium
- Lowe syndrome, a rare genetic disorder of the eyes, brain, and kidneys
- Wilson disease
- Dent disease, a rare genetic disorder of the kidneys
In adults, Fanconi syndrome can be caused by various things that damage the kidneys, including:
- Passing large amounts of urine, which can lead to dehydration
- Excessive thirst
- Severe bone pain
- Fractures due to bone weakness
- Muscle weakness
Exams and Tests
Laboratory tests may show that too much of the following substances may be lost in the urine:
Loss of these substances can lead to a variety of problems. Further tests and a physical exam may show signs of:
Many different diseases can cause Fanconi syndrome. The underlying cause and its symptoms should be treated as appropriate.
The prognosis depends on the underlying disease.
When to Contact a Medical Professional
Contact your health care provider if you have dehydration or muscle weakness.
De Toni-Fanconi-Debré syndrome
Bonnardeaux A, Bichet DG. Inherited disorders of the renal tubule. In: Yu ASL, Chertow GM, Luyckx VA, Marsden PA, Skorecki K, Taal MW, eds. Brenner and Rector's The Kidney. 11th ed. Philadelphia, PA: Elsevier; 2020:chap 44.
Foreman JW. Fanconi syndrome and other proximal tubule disorders. In: Feehally J, Floege J, Tonelli M, Johnson RJ, eds. Comprehensive Clinical Nephrology. 6th ed. Philadelphia, PA: Elsevier; 2019:chap 48.
Review Date 1/25/2022
Updated by: Todd Gersten, MD, Hematology/Oncology, Florida Cancer Specialists & Research Institute, Wellington, FL. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.