The most common skeletal defect found in Alagille syndrome involves the vertebrae (the small bones that make up the spine). These "butterfly" vertebrae have an X-ray appearance of flying butterflies. While butterfly vertebrae are an important way doctors recognize the diagnosis of AGS in a child, they do not cause any medical problems and therefore do not require treatment.
Because children with Alagille syndrome may develop fat-soluble vitamin (A, D, E and K) deficiencies, it is important to have the vitamin D level in their blood checked. If children are deficient in vitamin D and are not adequately supplemented, they can develop rickets. Rickets is a disease of infants and children that disturbs normal bone formation (ossification). Common features of rickets include softness of the infant's skull (craniotabes) and enlargement of the front end of the ribs (creating the "rachitic rosary"). As a child with rickets begins to walk, he or she may have bowed legs. Rickets can be treated with large doses of vitamin D.
Some children with AGS have frequent long bone fractures. The reason why children with AGS may be prone to fractures is unknown, although several factors may include: abnormally-shaped bones due to the defect in JAG1, poor calcium intake and/or calcium malabsorption and decreased physical activity. A doctor and/or dietitian can help determine if a child with AGS is consuming enough calcium and if calcium supplementation is needed.
Reviewed by: Binita M. Kamath, MD
Date: January 2009