Bile Acid Synthesis Disorders
& Peroxisomal Biogenesis Disorder-Zellweger Spectrum Disorder

Bile acid synthesis disorders (BASDs) are rare, inherited metabolic disorders caused by defects in the enzymes that make bile acids. Bile acids promote the flow and excretion of bile, excess cholesterol and waste, and help the intestines absorb fat and fat-soluble vitamins.

When the body is unable to produce normal bile acids, it can result in abnormal bile flow (cholestasis), often resulting in malabsorption of vital nutrients and the buildup of toxic materials in the body. BASDs are typically detected during infancy.

If left untreated, buildup of toxic bile acids may result in progressive liver disease.

Learn more about how Retrophin is supporting earlier diagnosis of rare diseases.

Resources: National Organization for Rare Disorders ; " Mechanisms of Disease: inborn errors of bile acid synthesis," Nature Clinical Practice Gastroenterology & Hepatology

Peroxisomal Biogenesis Disorder-Zellweger Spectrum Disorder (PBD-ZSD)

Peroxisomes are important parts of each cell in the body, and are necessary for cell function, normal brain and nervous system development, and metabolism. Loss of peroxisome function can affect all major organ systems in the body. Until recently, PBD-ZSD was viewed as three separate diseases, but we now know PBD-ZSD is a set of disorders that form a spectrum, or continuum, of disease. This spectrum can range from mild (infantile Refsum disease), to moderate (neonatal adrenoleukodystrophy), to severe (Zellweger syndrome).

PBD-ZSD affects each patient differently, and severity can vary with the age of onset. Individuals with Zellweger syndrome, at the severe end of the spectrum, develop signs and symptoms of the condition as newborns. These infants experience weak muscle tone (hypotonia), feeding problems, hearing and vision loss, liver dysfunction and seizures. Survival is usually not beyond the first year of life.

Individuals on the less-severe end of the spectrum may have hypotonia, vision problems, hearing loss, liver and kidney dysfunction, decreased bone mineral density developmental delay, and some degree of intellectual disability.

PBD-ZSD is estimated to occur in 1 in 50,000 individuals in the United States. It is inherited in an autosomal recessive pattern, meaning that a child is affected when each parent passes on one copy of the mutated gene.

Learn more about how Retrophin is supporting earlier diagnosis of rare diseases.

Resources: ; " Zellweger spectrum disorders: clinical overview and management approach," Orphanet Journal of Rare Diseases , National Organization for Rare Disorders .

The following organizations may be a resource for information and support for people with Bile Acid Synthesis Disorders and Zellweger Spectrum Disorders, as well as those around them:

Global Foundation for Peroxisomal Disorders

The mission of the Global Foundation for Peroxisomal Disorders is to fund and promote Peroxisomal Disorder research and to assist families and professionals through educational programs and support services related to Zellweger Spectrum Disorders.

Global Genes

Global Genes is a non-profit patient advocacy organization working to eliminate the challenges of rare disease by building awareness, educating the global community, and providing critical connections and resources that equip advocates to become activists for their disease.  Global Genes promotes the needs of the rare disease community under a unifying symbol of hope – the Blue Denim Genes Ribbon™. Numerous tools, resources and educational events can be found on the Global Genes website

National Organization for Rare Disorders

The National Organization for Rare Disorders (NORD) is a unique federation of voluntary health organizations dedicated to helping people with rare "orphan" diseases and assisting the organizations that serve them. NORD is committed to the identification, treatment and cure of rare disorders through programs of education, advocacy, research and service. In the US, NORD is also the official sponsor of Rare Disease Day, an annual global observance that raises awareness of rare diseases and elevates them into the public consciousness as an important health issue that cannot be ignored.


EURORDIS is a non-governmental patient-driven alliance of more than 700 rare disease patient organisations in more than 60 countries. EURORDIS strives to build a strong pan-European community of patient organisations and people living with a rare disease, to be their voice at the European level, and - directly or indirectly - to fight against the impact of rare diseases on their lives. EURORDIS leads global efforts for Rare Disease Day and the online social platform for people living with or affected by a rare diseases RareConnect. EURORDIS represents the voice of an estimated 30 million people living with a rare disease in Europe. Follow @eurordis or see the EURORDIS Facebook page. For more information visit: