LAUSR

Bile acid synthesis defects (BASDs) comprise a group of rare, often severe, metabolic disorders. Bile acid replacement therapy decreases toxic bile acid intermediates production and improves biochemical profiles, potentially delaying or stabilizing disease progression. An open label, non‐randomized trial with cholic acid (CA) supplementation included six patients with α‐methylacyl‐CoA racemase (AMACR) deficiency and one patient with 3β‐hydroxy‐Δ5‐C27‐steroid oxidoreductase deficiency. Patients received up to 20 mg/kg/day CA for 3.5 years, adjusted for biochemical response, side effects, and clinical evaluation. Bile acid metabolites, liver enzymes, liver stiffness, and neurological symptoms were evaluated at baseline and during follow‐up. CA was well tolerated in children (n = 3), allowing for higher doses. Adults (n = 4) experienced more side effects, primarily diarrhea and other gastrointestinal symptoms. Children's transaminase levels normalized during treatment, while adults' levels remained normal throughout. Elevated C27‐bile acid intermediates, C29‐dicarboxylic acid, and pristanic acid were observed in all AMACR patients. C27‐bile acids and C29‐dicarboxylic acid decreased with treatment, while pristanic acid fluctuated and remained elevated. No clinically relevant changes were observed in liver elasticity, fat‐soluble vitamin levels, neurological assessment, or growth (in children). One adult developed hepatocellular carcinoma during treatment. CA treatment is generally safe, with acceptable tolerance and a marked biochemical response observed in children, although biomarker levels remained markedly elevated. In adults, however, the balance shifts negatively, with side effects outweighing the (biochemical) benefits. A longer study is necessary to evaluate the impact of CA treatment on the clinical relevance of the observed biochemical response.