A six-month-old infant with liver steatosis

An Infant With Hereditary Fructose Intolerance and a Novel Presentation of Disseminated Intravascular Coagulopathy Following Pyloromyotomy

Hereditary fructose intolerance is a rare autosomal recessive metabolic disorder characterized by liver failure, renal tubulopathy, growth retardation, and occasionally death upon exposure to fructose. We present a 2-month-old male infant diagnosed with pyloric stenosis who developed disseminated intravascular coagulopathy following pyloromyotomy. Unexplained persistent coagulopathy, acute liver failure, and metabolic dysfunction led to whole-exome sequencing, which revealed compound heterozygous variants in ALDOB (p.Arg60Ter and p.Ala150Pro), diagnostic of hereditary fructose intolerance. Shortly after initiating a fructose-free diet, our patient had resolution of his coagulopathy, hepatic, and metabolic dysfunction.

Epidemiological aspects of hereditary fructose intolerance: A database study

Hereditary fructose intolerance (HFI) is an inborn error of fructose metabolism of autosomal recessive inheritance caused by pathogenic variants in the ALDOB gene that lead to aldolase B deficiency in the liver, kidneys, and intestine. Patients manifest symptoms, such as ketotic hypoglycemia, vomiting, nausea, in addition to hepatomegaly and other liver and kidney dysfunctions. The treatment consists of a fructose-restricted diet, which results in a good prognosis. To analyze the distribution of ALDOB variants described in patients and to estimate the prevalence of HFI based on carrier frequency in the gnomAD database, a systematic review was conducted to assess ALDOB gene variants among patients with HFI. The prevalence of HFI was estimated from the carrier frequency of variants described in patients, as well as rare variants predicted as pathogenic by in silico tools. The p.(Ala150Pro) and p.(Ala175Asp) variants are the most frequent and are distributed worldwide. However, these variants have particular distribution patterns in Europe. The analysis of the prevalence of HFI showed that the inclusion of rare alleles predicted as pathogenic is a more informative approach for populations with few patients. The data show that HFI has a wide distribution and an estimated prevalence of ~1:10,000.

Acute liver failure in neonates with undiagnosed hereditary fructose intolerance due to exposure from widely available infant formulas

Hereditary fructose intolerance (HFI) is an autosomal recessive disorder caused by aldolase B (ALDOB) deficiency resulting in an inability to metabolize fructose. The toxic accumulation of intermediate fructose-1-phosphate causes multiple metabolic disturbances, including postprandial hypoglycemia, lactic acidosis, electrolyte disturbance, and liver/kidney dysfunction. The clinical presentation varies depending on the age of exposure and the load of fructose. Some common infant formulas contain fructose in various forms, such as sucrose, a disaccharide of fructose and glucose. Exposure to formula containing fructogenic compounds is an important, but often overlooked trigger for severe metabolic disturbances in HFI. Here we report four neonates with undiagnosed HFI, all caused by the common, homozygous mutation c.448G>C (p.A150P) in ALDOB, who developed life-threatening acute liver failure due to fructose-containing formulas. These cases underscore the importance of dietary history and consideration of HFI in cases of neonatal or infantile acute liver failure for prompt diagnosis and treatment of HFI.

Aldolase-B knockout in mice phenocopies hereditary fructose intolerance in humans

The rise in fructose consumption, and its correlation with symptoms of metabolic syndrome (MBS), has highlighted the need for a better understanding of fructose metabolism. To that end, valid rodent models reflecting the same metabolism as in humans, both biochemically and physiologically, are critical. A key to understanding any type of metabolism comes from study of disease states that affect such metabolism. A serious defect of fructose metabolism is the autosomal recessive condition called hereditary fructose intolerance (HFI), caused by mutations in the human aldolase B gene (Aldob). Those afflicted with HFI experience liver and kidney dysfunction after fructose consumption, which can lead to death, particularly during infancy. With very low levels of fructose exposure, HFI patients develop non-alcoholic fatty acid liver disease and fibrosis, sharing liver pathologies also seen in MBS. A major step toward establishing that fructose metabolism in mice mimics that of humans is reported by investigating the consequences of targeting the mouse aldolase-B gene (Aldo2) for deletion in mice (Aldo2(-/-)). The Aldo2(-/-) homozygous mice show similar pathology following exposure to fructose as humans with HFI such as failure to thrive, liver dysfunction, and potential morbidity. Establishing that this mouse reflects the symptoms of HFI in humans is critical for comparison of rodent studies to the human condition, where this food source is increasing, and increasingly controversial. This animal should provide a valuable resource for answering remaining questions about fructose metabolism in HFI, as well as help investigate the biochemical mechanisms leading to liver pathologies seen in MBS from high fructose diets.

Uric acid and fructose: potential biological mechanisms

Excessive fructose consumption is associated with the development of metabolic syndrome and type II diabetes. Both conditions are well-known risk factors for cardiovascular and renal diseases. Uric acid synthesis is linked biochemically to fructose metabolism, thus the widespread consumption of this monosaccharide has been related to steady increasing levels of serum uric acid during the past few decades. Recent evidence has suggested that uric acid may act as a cardiorenal toxin. In this regard, experimental studies have suggested that the primary noxious effect of uric acid occurs inside the cell and is likely the stimulation of oxidative stress. More studies to disclose the harmful mechanisms associated with increasing intracellular uric acid levels after a fructose load are warranted.

Increased prevalence of mutant null alleles that cause hereditary fructose intolerance in the American population

Mutations in the aldolase B gene (ALDOB) impairing enzyme activity toward fructose-1-phosphate cleavage cause hereditary fructose intolerance (HFI). Diagnosis of the disease is possible by identifying known mutant ALDOB alleles in suspected patients; however, the frequencies of mutant alleles can differ by population. Here, 153 American HFI patients with 268 independent alleles were analyzed to identify the prevalence of seven known HFI-causing alleles (A149P, A174D, N334K, Delta4E4, R59Op, A337V, and L256P) in this population. Allele-specific oligonucleotide hybridization analysis was performed on polymerase chain reaction (PCR)-amplified genomic DNA from these patients. In the American population, the missense mutations A149P and A174D are the two most common alleles, with frequencies of 44% and 9%, respectively. In addition, the nonsense mutations Delta4E4 and R59Op are the next most common alleles, with each having a frequency of 4%. Together, the frequencies of all seven alleles make up 65% of HFI-causing alleles in this population. Worldwide, these same alleles make up 82% of HFI-causing mutations. This difference indicates that screening for common HFI alleles is more difficult in the American population. Nevertheless, a genetic screen for diagnosing HFI in America can be improved by including all seven alleles studied here. Lastly, identification of HFI patients presenting with classic symptoms and who have homozygous null genotypes indicates that aldolase B is not required for proper development or metabolic maintenance.

Elevated carbohydrate-deficient transferrin (CDT) and its normalization on dietary treatment as a useful biochemical test for hereditary fructose intolerance and galactosemia

Abnormalities in protein glycosylation are reported in fructosemia (HFI) and galactosemia, although, particularly in HFI, the published data are limited to single cases. The purpose was to investigate the usefulness of the carbohydrate-deficient transferrin (CDT) profile for identification and monitoring of these disorders. First we analyzed CDT values before and shortly after the diagnosis in 10 cases of HFI and 17 cases of galactosemia. In all patients, elevated CDT levels were found that significantly (p < 0.0001) decreased with the therapeutic diet (27.3 +/- 11.5% versus 9.3 +/- 5.1% for HFI and 43.8 +/- 14.1% versus 11.2 +/- 4.0% for galactosemia). To evaluate the use of CDT test in monitoring compliance, the test was performed in 25 HFI patients on fructose-restricted diet. We found an elevated CDT level on 104 from 134 tests (mean 11.3 +/- 5.5%, control 1.5%-6.2%). The fructose intake was found to be 90 +/- 70 mg/kg/d, and the diet was unbalanced. A number of patients presented lower height, elevated urinary uric acid excretion, and hypercalciuria. In conclusion, abnormal percentage of CDT (%CDT) values may allow prompt detection of HFI (or galactosemia). Persistence of some abnormalities in HFI on treatment may be caused by trace amounts of fructose ingestion and/or a deficient diet. Regular %CDT measurements are suggested for HFI treatment monitoring.