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Malabsorption of liposoluble vitamins in a child with bile acid deficiency
Insights
This study identifies a rare genetic disorder causing severe vitamin deficiencies and abnormal bile acid metabolism in a child. The findings highlight a novel defect in bile acid synthesis, impacting nutrient absorption and overall health.
Area of Science:
- Biochemistry
- Genetics
- Pediatrics
Background:
- Genetic disorders can manifest with complex nutritional deficiencies.
- Bile acid metabolism is crucial for lipid and vitamin absorption.
Observation:
- A child presented with hypocalcemia, rickets, vitamin deficiencies (A, E, K), and altered liver function.
- Exclusion of common malabsorption syndromes and bile acid synthetic pathway defects.
Findings:
- Extremely low serum levels of vitamins A, E, and beta-carotene.
- Abnormal duodenal and urinary bile acid composition with undetectable cholic acid metabolites.
- Extremely low cholic acid and chenodeoxycholic acid pool sizes despite normal turnover rates.
Implications:
- Suggests a novel genetic defect affecting bile acid synthesis.
- Underscores the importance of comprehensive metabolic evaluation in pediatric cases with unexplained symptoms.
- Potential for new diagnostic and therapeutic strategies for rare metabolic disorders.
Abstract:
A male born to first cousins presented at 12 months with hypocalcemic convulsions, rickets, epistaxis due to vitamin K deficiency, and extremely low serum levels of beta-carotene and vitamin A. Liver function was altered moderately (glutamic-oxaloacetic transaminase, 55 U/L; glutamic-pyruvic transaminase, 37 U/L; lactate dehydrogenase, 255 U/L; alkaline phosphatase, 437 U/L). To correct the deficiencies, 8,000 IU vitamin D/day, 10,000 IU vitamin A/day, and intramuscular administration of vitamin K1 were required. At 9 years, he presented signs of neuromuscular affection, and the serum vitamin E level (measured for the first time) was extremely low. Classic lipid malabsorption syndromes (abetalipoproteinemia, chronic cholestasis, mucoviscidosis, coeliac disease, Whipple's disease) were excluded by appropriate examinations. Composition of duodenal bile acids was characterized by undetectable levels of cholic acid metabolites, and only chenodeoxycholic acid metabolites were present. Serum total bile acid concentration was normal, with an atypical low cholic acid/chenodeoxycholic acid ratio and abnormal presence of 3 beta-OH-delta 5-cholenic acid and 6-OH-bile acids. Urinary bile acid composition was also characterized by elevated 6-OH-bile acids. Known enzymopathies of the bile acid synthetic pathway were excluded (cerebrotendinous xanthomatosis, cerebro-hepato-renal syndrome of Zellweger, coprostanic acidemia). Bile acid pool sizes were determined by using stable isotopes: cholic acid pool size [2.90 (N, 32 +/- 16) microM/kg] and chenodeoxycholic acid pool size [10.8 (N, 32.6 +/- 9.9) microM/kg] were extremely low; fractional turnover rates of both bile acids were in a normal range.(ABSTRACT TRUNCATED AT 250 WORDS)