Bile Acid Synthesis Defect, Congenital, 2

Oral cholic acid therapy is an effective therapy in children with primary bile acid synthesis deficiencies. Most reported patients with this treatment have 3β-hydroxy-Δ⁵-C₂₇-steroid oxidoreductase deficiency. The aim of the study was the evaluation of cholic acid therapy in a cohort of patients with the rarer Δ⁴-3-oxosteroid 5β-reductase (Δ⁴-3-oxo-R) deficiency.

Sixteen patients with Δ⁴-3-oxo-R deficiency confirmed by AKR1D1 gene sequencing who received oral cholic acid were retrospectively analyzed.

First symptoms were reported early in life (median 2 months of age), with 14 and 3 patients having cholestatic jaundice and severe bleeding respectively. Fifteen patients received ursodeoxycholic acid before diagnosis, with partial improvement in 8 patients. Four patients had liver failure at the time of cholic acid initiation. All 16 patients received cholic acid from a median age of 8.1 months (range 3.1-159) and serum liver tests normalized in all within 6-12 months of treatment. After a median cholic acid therapy of 4.5 years (range 1.1-24), all patients were alive with their native liver. Median daily cholic acid dose at last follow-up was 8.3 mg/kg of body weight. All patients, but one, had normal physical examination and all had normal serum liver tests. Fibrosis, evaluated using liver biopsy (n = 4) or liver elastography (n = 9), had stabilized or improved. Cholic acid therapy enabled a 12-fold decrease of 3-oxo-∆⁴ derivatives in urine. Patients had normal growth and quality of life. The treatment was well tolerated without serious adverse events and signs of hepatotoxicity.

Oral cholic acid therapy is a safe and effective treatment for patients with Δ⁴-3-oxo-R deficiency.

Δ⁴-3-Oxosteroid 5β-reductase (AKR1D1) deficiency typically causes severe cholestasis occurs in newborns, leading to death unless patients are treated with primary bile acids. However, we encountered an AKR1D1 deficiency patient treated with only ursodeoxycholic acid who had cholestasis until about 1 year of age but then grew up healthy without further treatment. We also have been following other healthy patients with AKR1D1 mutation who have never developed cholestasis and have not been treated. However, reports are few, involving 3 patients. To better understand and clinically manage a diverse group of patients with AKR1D1 mutation who do not develop potentially fatal cholestasis in the neonatal period, ongoing accumulation and study of informative cases is needed.

Δ⁴-3-oxosteroid 5β-reductase (AKR1D1) deficiency presents with neonatal cholestasis and liver failure in early infancy and features high levels of 3-oxo-Δ⁴-bile acids in urine. Genetic analysis is needed for definitive diagnosis, because in the neonatal period it can be difficult to distinguish a primary from a secondary enzyme deficiency. By re-analysis of the gene-sequencing data, one AKR1D1 noncanonical splice-site variant (NM_005989.4: c.580-13T>A) with controversial pathogenicity was discovered to be enriched in eight families with clinical and biochemically confirmed AKR1D1 deficiency. Further RNA sequencing of liver tissue suggested this variant causes complete degradation of mRNA. An in vitro minigene experiment indicated that this variant led to partial intron retention or exon jumping, which then leads to coding sequence frameshift and nonsense-mediated mRNA decay. Thus, AKR1D1 variant c.580-13T>A was considered pathogenic and, therefore, should be screened during genetic studies in infants with a suspicion of a congenital bile acid synthetic disorder.