Bile acid synthesis defect with cholestasis and malabsorption

Bile acid synthesis defects with cholestasis and malabsorption represent a group of rare inherited metabolic disorders in which the liver cannot properly produce bile acids due to deficiencies in specific enzymes involved in the bile acid biosynthetic pathway. Bile acids are essential for the digestion and absorption of dietary fats and fat-soluble vitamins (A, D, E, and K) in the intestine, and they also play a critical role in regulating bile flow from the liver. When bile acid synthesis is impaired, toxic intermediate metabolites accumulate in the liver, leading to progressive cholestasis (impaired bile flow), liver damage, and fat malabsorption. Key clinical features typically present in infancy or early childhood and include prolonged neonatal jaundice, hepatomegaly (enlarged liver), steatorrhea (fatty stools), failure to thrive, and fat-soluble vitamin deficiencies that can cause rickets, coagulopathy, and neurological problems. Progressive liver disease may develop, potentially leading to cirrhosis and liver failure if untreated. Laboratory findings often show elevated serum transaminases, conjugated hyperbilirubinemia, and characteristically low or absent serum levels of primary bile acids, with abnormal bile acid metabolites detectable in urine by mass spectrometry. Treatment depends on the specific enzymatic defect but may include oral bile acid replacement therapy, most commonly with cholic acid or chenodeoxycholic acid. This approach can suppress the production of toxic bile acid intermediates, improve bile flow, and correct fat-soluble vitamin malabsorption. Cholic acid (marketed as Cholbam in the United States) has been approved for certain bile acid synthesis disorders. Supplementation with fat-soluble vitamins is also an important component of management. In severe or refractory cases, liver transplantation may be considered. Early diagnosis and treatment are critical, as timely intervention can prevent progressive liver damage and significantly improve outcomes.

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