Successful treatment of an infant with congenital bile acid synthesis disorder type 3 by ursodeoxycholic acid: a case report

Background: Congenital bile acid synthesis disorder type 3 caused by oxysterol 7 alpha-hydroxylase deficiency is an extremely rare genetic liver disease. As it may cause rapid progression to end-stage liver disease, a high cautiousness in diagnosis and early treatment are required. Here we describe the first case of congenital bile acid synthesis disorder type 3 in China that was confirmed by genetic analysis. Case presentation: A 5-month-old Chinese male infant suffered skin yellowing since birth. The patient showed significantly increased alanine transaminase, aspartate transaminase, and total and direct bilirubin levels, and enlarged liver at admission. Whole-exome sequencing confirmed homozygous mutation in the CYB7B1 gene that encodes oxysterol 7 alpha-hydroxylase. Ursodeoxycholic acid treatment significantly mitigated the condition of the patient and lowered biochemical indicators. Unfortunately, the patient developed septicemia and gave up treatment. Conclusions: The patient was successfully treated with ursodeoxycholic acid, which has not been reported previously. Ursodeoxycholic acid replacement therapy is an effective and affordable treatment for congenital bile acid synthesis disorder type 3 caused by oxysterol 7 alpha-hydroxylase deficiency.