Epidemiological aspects of hereditary fructose intolerance: A database study

A Case Study of a Rare Disease (Fructosemia) Diagnosed in a Patient with Abdominal Pain

Hereditary fructose intolerance is a rare genetic disorder that is inherited in an autosomal recessive manner, with mutations sometimes occurring spontaneously. Consuming fructose triggers biochemical abnormalities, disrupting liver processes like glycogenolysis and gluconeogenesis. Recent studies have revealed elevated intrahepatic fat levels in affected individuals. Symptoms include aversion to fructose-containing foods, hypoglycemia, liver and kidney dysfunction, and growth delays, with severe cases leading to liver enlargement, fatty liver disease, kidney failure, and life-threatening hypoglycemia. In this case study, we present a 20-month-old child with symptoms including difficulty passing stool, abdominal rigidity, abdominal pain with bloating and hypoglycemia. Initial clinical findings revealed elevated liver enzymes, a mildly enlarged hyperechoic liver, hypercholesterolemia, and borderline alpha-fetoprotein values. Diagnostic assessments identified hereditary fructose intolerance (HFI) with pathogenic variants in the ALDOB gene, along with a diagnosis of celiac disease. Genetic testing of the parents revealed carrier status for pathological aldolase B genes. This case underscores the importance of comprehensive clinical evaluation and genetic testing in pediatric patients with complex metabolic presentations.

Descriptive Analysis of Carrier and Affected Hereditary Fructose Intolerance in Women during Pregnancy

(1) Background: Hereditary fructose intolerance (HFI) is a rare autosomal recessive metabolic disorder resulting from aldolase B deficiency, requiring a fructose, sorbitol and sucrose (FSS)-free diet. Limited information exists on the relationship between pregnancy outcomes and HFI. This study aims to analyze pregnancy-related factors in a cohort of thirty Spanish women, with twenty-three being carriers and seven being HFI-affected (45 pregnancies). (2) Methods: A descriptive, cross-sectional and retrospective study utilized an anonymous questionnaire. (3) Results: Findings encompassed physical and emotional states, nutritional habits, pathology development and baby information. Notable results include improved physical and emotional states compared to the general population, with conventional analyses mostly within normal ranges. Persistent issues after pregnancy included hepatic steatosis, liver adenomas and hemangiomas. Carrier mothers' babies exhibited higher weight than those of patient mothers, while the weights of carrier children born with HFI were similar to disease-affected children. (4) Conclusions: Pregnant women with HFI did not significantly differ in physical and emotional states, except for nausea, vomiting, and cravings. Post-pregnancy, HFI patients and carriers exhibited persistent hepatic issues. Significantly, babies born to HFI-affected mothers had lower weights. This study sheds light on pregnancy outcomes in HFI, emphasizing potential complications and the need for ongoing monitoring and care.

Combined PMM2-CDG and hereditary fructose intolerance in a patient with mild clinical presentation

We report a patient with an extremely rare, combined diagnosis of PMM2-CDG and hereditary fructose intolerance (HFI). By comparing with other patients, under-galactosylation was identified as a feature of HFI. Fructose/sorbitol/sucrose restriction was initiated right afterwards. The patient is at the mild end of the PMM2-CDG spectrum, raising the question of sorbitol's role in the pathogenesis of PMM2-CDG and whether fructose/sorbitol/sucrose restriction could benefit other PMM2-CDG patients. Additionally, epalrestat, an emerging potential PMM2-CDG therapy, may benefit HFI patients.

Quality of life of adult patients with hereditary fructose intolerance

BACKGROUND

Although patients with hereditary fructose intolerance (HFI) generally have a good prognosis on a fructose-restricted diet, relatively little is known about their quality of life. The aim of this study was to investigate the quality of life in adult patients with HFI in comparison to patients with dietary-treated, classical phenylketonuria (PKU).

METHODS

Patients with HFI and patients with classical PKU were recruited from the adult metabolic centers in The Netherlands and Belgium and via social media. Patients were asked to fill out the 36-item Short Form Health survey (SF-36) and a modified PKU Quality Of Life (PKU-QoL) questionnaire.

RESULTS

Patients with HFI (n = 19) did not report any restrictions in their health-related quality of life, except for vitality and general mental health, which were scored more unfavorable compared to patients with PKU (n = 19) (p < 0.05, adjusted for level of education and country of origin). The results from the modified PKU-QoL demonstrated a statistically significantly greater impact of the disease in the social domain in HFI. A substantial proportion of both HFI and PKU patients (21%) reported a great to severe emotional impact of their disease. Finally, patients with HFI experienced statistically significantly less food temptations, less guilt if dietary restrictions not followed, and less overall difficulty following dietary restrictions.

CONCLUSIONS

Although patients with HFI showed to have a generally good quality of life, they scored lower on vitality and general mental health, and reported a greater social impact of the disease. These aspects deserve further study and clinical attention.

Endogenous Fructose Production and Metabolism Drive Metabolic Dysregulation and Liver Disease in Mice with Hereditary Fructose Intolerance

Excessive intake of sugar, and particularly fructose, is closely associated with the development and progression of metabolic syndrome in humans and animal models. However, genetic disorders in fructose metabolism have very different consequences. While the deficiency of fructokinase, the first enzyme involved in fructose metabolism, is benign and somewhat desirable, missense mutations in the second enzyme, aldolase B, causes a very dramatic and sometimes lethal condition known as hereditary fructose intolerance (HFI). To date, there is no cure for HFI, and treatment is limited to avoiding fructose and sugar. Because of this, for subjects with HFI, glucose is their sole source of carbohydrates in the diet. However, clinical symptoms still occur, suggesting that either low amounts of fructose are still being consumed or, alternatively, fructose is being produced endogenously in the body. Here, we demonstrate that as a consequence of consuming high glycemic foods, the polyol pathway, a metabolic route in which fructose is produced from glucose, is activated, triggering a deleterious mechanism whereby glucose, sorbitol and alcohol induce severe liver disease and growth retardation in aldolase B knockout mice. We show that generically and pharmacologically blocking this pathway significantly improves metabolic dysfunction and thriving and increases the tolerance of aldolase B knockout mice to dietary triggers of endogenous fructose production.

Development of tools to facilitate the diagnosis of hereditary fructose intolerance

Although hereditary fructose intolerance (HFI) is an inborn error of fructose metabolism that classically presents at infancy, the diagnosis is often missed or delayed. In this study, we aimed to develop tools to facilitate the diagnosis of HFI. The intake of fructose-containing food products, that is, fruit, fruit juice and sugar-sweetened beverages, was assessed by a 3-day food diary in adult HFI patients (n = 15) and age, sex, and BMI-matched controls (n = 15). Furthermore, glycosylation of transferrin was examined using high-resolution mass spectrometry and abnormally glycosylated transferrin was expressed as ratio of normal glycosylated transferrin. We found that the sensitivity and specificity of the 3-day food diary for the intake of at least one fructose-containing food product were both 100%. Both mono-glyco:diglyco transferrin and a-glyco+mono-glyco:di-glyco transferrin were greater in HFI patients and had a high-discriminatory power (area under the receiver operating characteristic curve: 0.97 and 0.94, respectively). In this well-characterized cohort of adult HFI patients, the 3-day food questionnaire and the glycosylation pattern of transferrin are valuable tools to facilitate the recognition and diagnosis of HFI in adult patients.

Genomic analysis of lean individuals with NAFLD identifies monogenic disorders in a prospective cohort study

Background & Aims

Lean patients with non-alcoholic fatty liver disease (NAFLD) represent 10-20% of the affected population and may have heterogeneous drivers of disease. We have recently proposed the evaluation of patients with lean NAFLD without visceral adiposity for rare monogenic drivers of disease. Here, we aimed to validate this framework in a well-characterised cohort of patients with biopsy-proven NAFLD by performing whole exome sequencing.

Methods

This prospective study included 124 patients with biopsy-proven NAFLD and paired liver biopsies who underwent standardised research visits including advanced magnetic resonance imaging (MRI) assessment of liver fat and stiffness.

Results

Six patients with lean NAFLD were identified and underwent whole exome sequencing. Two lean patients (33%) were identified to have monogenic disorders. The lean patients with monogenic disorders had similar age, and anthropometric and MRI characteristics to lean patients without a monogenic disorder. Patient 1 harbours a rare homozygous pathogenic mutation in ALDOB (aldolase B) and was diagnosed with hereditary fructose intolerance. Patient 2 harbours a rare heterozygous mutation in apolipoprotein B (APOB). The pathogenicity of this APOB variant (p.Val1856CysfsTer2) was further validated in the UK Biobank and associated with lower circulating APOB levels (beta = -0.51 g/L, 95% CI -0.65 to -0.36 g/L, p = 1.4 × 10-11) and higher liver fat on MRI (beta = +10.4%, 95% CI 4.3-16.5%, p = 8.8 × 10-4). Hence, patient 2 was diagnosed with heterozygous familial hypobetalipoproteinaemia.

Conclusions

In this cohort of well-characterised patients with lean NAFLD without visceral adiposity, 33% (2/6) had rare monogenic drivers of disease, highlighting the importance of genomic analysis in this NAFLD subtype.

Impact and Implications

Although most people with non-alcoholic fatty liver disease (NAFLD) are overweight or obese, a subset are lean and may have unique genetic mutations that cause their fatty liver disease. We show that 33% of study participants with NAFLD who were lean harboured unique mutations that cause their fatty liver, and that these mutations had effects beyond the liver. This study demonstrates the value of genetic assessment of NAFLD in lean individuals to identify distinct subtypes of disease.

Vitamin C and folate status in hereditary fructose intolerance

BACKGROUND

Hereditary fructose intolerance (HFI) is a rare inborn error of fructose metabolism caused by the deficiency of aldolase B. Since treatment consists of a fructose-, sucrose- and sorbitol-restrictive diet for life, patients are at risk of presenting vitamin deficiencies. Although there is no published data on the status of these vitamins in HFI patients, supplementation with vitamin C and folic acid is common. Therefore, the aim of this study was to assess vitamin C and folate status and supplementation practices in a nationwide cohort of HFI patients.

METHODS

Vitamin C and folic acid dietary intake, supplementation and circulating levels were assessed in 32 HFI patients and 32 age- and sex-matched healthy controls.

RESULTS

Most of the HFI participants presented vitamin C (96.7%) and folate (90%) dietary intake below the recommended population reference intake. Up to 69% received vitamin C and 50% folic acid supplementation. Among HFI patients, 15.6% presented vitamin C and 3.1% folate deficiency. The amount of vitamin C supplementation and plasma levels correlated positively (R = 0.443; p = 0.011). Interestingly, a higher percentage of non-supplemented HFI patients were vitamin C deficient when compared to supplemented HFI patients (30% vs. 9.1%; p = 0.01) and to healthy controls (30% vs. 3.1%; p < 0.001).

CONCLUSIONS

Our results provide evidence for the first time supporting vitamin C supplementation in HFI. There is great heterogeneity in vitamin supplementation practices and, despite follow-up at specialised centres, vitamin C deficiency is common. Further research is warranted to establish optimal doses of vitamin C and the need for folic acid supplementation in HFI.

Estimation of hereditary fructose intolerance prevalence in the Chinese population

Background

Hereditary fructose intolerance (HFI) caused by aldolase B reduction or deficiency that results in fructose metabolism disorder. The disease prevalence in the Chinese population is unknown, which impedes the formulation of HFI screening and diagnosis strategies.

Materials and methods

By searching a local cohort (Chinese Children’s Rare Disease Genetic Testing Clinical Collaboration System, CCGT) and public databases (ClinVar and Human Gene Mutation Database) and reviewing HFI-related literature, we manually curated ALDOB pathogenic or likely pathogenic (P/LP) variants according to ACMG guidelines. Allele frequency (AF) information from the local database CCGT and the public databases HuaBiao and gnomAD for ALDOB P/LP variants was used to estimate and the HFI prevalence in the Chinese population and other populations by the Bayesian framework. We collected the genotype and clinical characteristics of HFI patients from the CCGT database and published literature to study genotype–phenotype relationships.

Result

In total, 81 variants of ALDOB were curated as P/LP. The estimated Chinese HFI prevalence was approximately 1/504,678, which was much lower than that for non-Finland European (1/23,147), Finnish in Finland (1/55,539), admixed American (1/132,801) and Ashkenazi Jewish (1/263,150) populations. By analyzing the genetic characteristics of ALDOB in the Chinese population, two variants (A338V, A338G) had significantly higher AFs in the Chinese population than in the non-Finland European population from gnomAD (all P values < 0.05). Five variants (A150P, A175D, N335K, R60*, R304Q) had significantly lower AFs (all P values < 0.1). The genotype–phenotype association analyses were based on 68 reported HFI patients from a literature review and the CCGT database. The results showed that patients carrying homozygous variant sites (especially A150P) were more likely to present nausea, and patients carrying two missense variant sites were more likely to present aversion to sweets and fruit (all P values < 0.05). Our research reveals that some gastrointestinal symptoms seem to be associated with certain genotypes.

Conclusion

The prevalence of HFI in the Chinese population is extremely low, and there is no need to add HFI testing to the current newborn screening programs if medical costs are considered. A genetic testing strategy is suggested for early diagnosis of HFI.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13023-022-02487-3.

Hereditary fructose intolerance: A comprehensive review

Hereditary fructose intolerance (HFI) is a rare autosomal recessive inherited disorder that occurs due to the mutation of enzyme aldolase B located on chromosome 9q22.3. A fructose load leads to the rapid accumulation of fructose 1-phosphate and manifests with its downstream effects. Most commonly children are affected with gastrointestinal symptoms, feeding issues, aversion to sweets and hypoglycemia. Liver manifestations include an asymptomatic increase of transaminases, steatohepatitis and rarely liver failure. Renal involvement usually occurs in the form of proximal renal tubular acidosis and may lead to chronic renal insufficiency. For confirmation, a genetic test is favored over the measurement of aldolase B activity in the liver biopsy specimen. The crux of HFI management lies in the absolute avoidance of foods containing fructose, sucrose, and sorbitol (FSS). There are many dilemmas regarding tolerance, dietary restriction and occurrence of steatohepatitis. Patients with HFI who adhere strictly to FSS free diet have an excellent prognosis with a normal lifespan. This review attempts to increase awareness and provide a comprehensive review of this rare but treatable disorder.