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Disease Profile

Congenital bile acid synthesis defect, type 1

Prevalence estimates on Rare Medical Network websites are calculated based on data available from numerous sources, including US and European government statistics, the NIH, Orphanet, and published epidemiologic studies. Rare disease population data is recognized to be highly variable, and based on a wide variety of source data and methodologies, so the prevalence data on this site should be assumed to be estimated and cannot be considered to be absolutely correct.


US Estimated

Europe Estimated

Age of onset






Autosomal dominant A pathogenic variant in only one gene copy in each cell is sufficient to cause an autosomal dominant disease.


Autosomal recessive Pathogenic variants in both copies of each gene of the chromosome are needed to cause an autosomal recessive disease and observe the mutant phenotype.


dominant X-linked dominant inheritance, sometimes referred to as X-linked dominance, is a mode of genetic inheritance by which a dominant gene is carried on the X chromosome.


recessive Pathogenic variants in both copies of a gene on the X chromosome cause an X-linked recessive disorder.


Mitochondrial or multigenic Mitochondrial genetic disorders can be caused by changes (mutations) in either the mitochondrial DNA or nuclear DNA that lead to dysfunction of the mitochondria and inadequate production of energy.


Multigenic or multifactor Inheritance involving many factors, of which at least one is genetic but none is of overwhelming importance, as in the causation of a disease by multiple genetic and environmental factors.


Not applicable


Other names (AKA)

CBAS1; 3-alpha beta-hydroxy-delta-5-c27-steroid oxidoreductase, deficiency of; 3-beta-hydroxy-delta-5-C27-steroid oxidoreductase deficiency;


Congenital and Genetic Diseases; Digestive Diseases; Metabolic disorders


The following summary is from Orphanet, a European reference portal for information on rare diseases and orphan drugs.

Orpha Number: 79301

Congenital bile acid synthesis defect type 1 (BAS defect type 1) is the most common anomaly of bile acid synthesis (see this term) characterized by variable manifestations of progressive cholestatic liver disease, and fat malabsorption.

Prevalence is unknown but may be around 1-9/1,000,000 for overall BAS defects, excluding cerebrotendinous xanthomatosis.

Clinical description
The clinical presentation is heterogeneous, however most patients present with features of neonatal cholestasis. Clinical features include hepatomegaly with or without splenomegaly, jaundice, fat and fat-soluble vitamin malabsorption, and mild steatorrhea. In most cases, pruritus is absent. Liver function tests present elevated serum transaminases (AST, ALT), conjugated hyperbilirubinemia, and normal gamma-GT. The liver histology shows inflammation, giant cells, evidence of cholestasis, and variable degrees of liver fibrosis. The clinical course of early-onset disease is heterogeneous with some patients resolving jaundice and being identified later in life, or with more fulminant disease that results in death or requires liver transplantation at an early age. The disorder may also present as late-onset chronic cholestasis. In such patients, liver disease is not always evident and patients may have fat-soluble vitamin malabsorption with rickets, corrected by vitamin supplementation, and/or other complications including bleeding diathesis (hematochezia or intracranial bleeding), neuroaxonal dystrophy and night blindness. Serum liver enzymes are initially often normal but later show increases with progression of liver disease to fibrosis. Children and adolescents may also present with extensive fibrosis and/or cirrhosis.

The disease is caused by a mutation in the gene encoding 3-beta-hydroxy-delta-5-C27 steroid oxidoreductase (HSD3B7, 16p12-p11.2). Transmission is autosomal recessive.

Diagnostic methods
Diagnosis is based on detection of sulfate and glycosulfate conjugates of 3-beta-hydroxy-delta-5 bile acids, which are the signature metabolites of this bile acid defect, on liquid secondary ionization mass spectrometry (LSIMS) analysis of urine. Gas chromatography mass spectrometry (GC-MS) or electroscopy and tandem mass spectrometry may also be used.

Differential diagnosis
Differential diagnoses include progressive familial intrahepatic cholestasis, diseases that present with neonatal cholestasis, which includes alpha-1-antitrypsin deficiency of ZZ phenotype, Alagille syndrome, biliary atresia, cystic fibrosis, and metabolic diseases (tyrosinemia type I, galactosemia, hereditary fructose intolerance) (see these terms), diseases that present with fat and fat soluble vitamin malabsorption, including other liver diseases, and intestinal disease, or diseases that present with growth failure.

Antenatal diagnosis
Antenatal diagnosis can be made on embryonic tissue obtained when there has been a previously identified sibling. Urine LSIMS in a suspect infant can confirm the diagnosis in the first neonatal days.

Management and treatment
Treatment is based on oral administration of cholic acid which leads to gradual resolution of biochemical and histologic abnormalities and prevents progression of the disease, even in cases with hepatic fibrosis and cirrhosis. Cholic acid therapy stimulates bile flow and suppresses synthesis of atypical bile acids and production of toxic intermediates via the bile acid pathway linked to the pathogenesis of disease.

With early treatment the long-term prognosis is excellent.

Visit the Orphanet disease page for more resources.


This table lists symptoms that people with this disease may have. For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed. This information comes from a database called the Human Phenotype Ontology (HPO) . The HPO collects information on symptoms that have been described in medical resources. The HPO is updated regularly. Use the HPO ID to access more in-depth information about a symptom.

Medical Terms Other Names
Learn More:
80%-99% of people have these symptoms
Biliary tract abnormality
Elevated hepatic transaminase
High liver enzymes
Failure to thrive
Faltering weight
Weight faltering

[ more ]

Enlarged liver
Yellow skin
Yellowing of the skin

[ more ]

Intestinal malabsorption
Neonatal cholestatic liver disease
30%-79% of people have these symptoms
Abnormality of coagulation
Gastrointestinal hemorrhage
Gastrointestinal bleeding
Increased spleen size
5%-29% of people have these symptoms
Scar tissue replaces healthy tissue in the liver
Night blindness
Poor night vision

[ more ]

Peripheral neuropathy
Itchy skin
Skin itching

[ more ]

Percent of people who have these symptoms is not available through HPO
Abnormality of the coagulation cascade
Acholic stools
Clay colored stools
Autosomal recessive inheritance
Watery stool
Giant cell hepatitis
Hepatic failure
Liver failure
High blood bilirubin levels
Decreased circulating cholesterol level
Intrahepatic cholestasis
Neonatal onset
Weak and soft bones
Fat in feces


Making a diagnosis for a genetic or rare disease can often be challenging. Healthcare professionals typically look at a person’s medical history, symptoms, physical exam, and laboratory test results in order to make a diagnosis. The following resources provide information relating to diagnosis and testing for this condition. If you have questions about getting a diagnosis, you should contact a healthcare professional.

Testing Resources

  • The Genetic Testing Registry (GTR) provides information about the genetic tests for this condition. The intended audience for the GTR is health care providers and researchers. Patients and consumers with specific questions about a genetic test should contact a health care provider or a genetics professional.


FDA-Approved Treatments

The medication(s) listed below have been approved by the Food and Drug Administration (FDA) as orphan products for treatment of this condition. Learn more orphan products.

  • cholic acid(Brand name: Cholbam) Manufactured by Asklepion Pharmaceuticals, LLC
    FDA-approved indication: Treatment of bile acid synthesis disorders due to single enzyme defects and as adjunctive treatment of peroxisomal disorders including Zellweger spectrum disorders in patients who exhibit manifestations of liver disease, steatorrhea or complications from decreased fat soluble vitamin absorption.
    National Library of Medicine Drug Information Portal

Learn more

These resources provide more information about this condition or associated symptoms. The in-depth resources contain medical and scientific language that may be hard to understand. You may want to review these resources with a medical professional.

Where to Start

  • Genetics Home Reference (GHR) contains information on Congenital bile acid synthesis defect, type 1. This website is maintained by the National Library of Medicine.

In-Depth Information

  • The Monarch Initiative brings together data about this condition from humans and other species to help physicians and biomedical researchers. Monarch’s tools are designed to make it easier to compare the signs and symptoms (phenotypes) of different diseases and discover common features. This initiative is a collaboration between several academic institutions across the world and is funded by the National Institutes of Health. Visit the website to explore the biology of this condition.
  • Online Mendelian Inheritance in Man (OMIM) is a catalog of human genes and genetic disorders. Each entry has a summary of related medical articles. It is meant for health care professionals and researchers. OMIM is maintained by Johns Hopkins University School of Medicine. 
  • Orphanet is a European reference portal for information on rare diseases and orphan drugs. Access to this database is free of charge.
  • PubMed is a searchable database of medical literature and lists journal articles that discuss Congenital bile acid synthesis defect, type 1. Click on the link to view a sample search on this topic.