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Fructose-1,6-biphosphatase (FBP) deficiency is a disorder of fructose metabolism characterized by recurrent episodes of fasting hypoglycemia with lactic acidosis, that may be life-threatening in neonates and infants.
Organ System | Phenotype Count | Example Features |
|---|---|---|
Brain and nerves | 5 | Seizure, Irritability, Intellectual disability |
Digestive system | 5 | Enlarged liver (hepatomegaly), Vomiting, Diarrhea |
Lungs and breathing | 3 | Dyspnea, Apnea, Respiratory distress |
Metabolism | 2 | Fever, Metabolic acidosis |
Pregnancy and birth | 2 | Neonatal hypoglycemia, Neonatal hyperbilirubinemia |
Lab test results | 2 | Elevated circulating hepatic transaminase concentration, Neonatal hyperbilirubinemia |
Muscles | 1 | Low muscle tone (hypotonia) |
Kidneys and urinary system | 1 | Increased urinary glycerol |
Heart and blood vessels | 1 | Tachycardia |
The manifestations of fructose-1,6-bisphosphatase (FBP1) deficiency are generally episodic due to lactic acidosis and ketotic hypoglycemia, which are often triggered by fasting or febrile infections. The episodes of acute crisis are most frequent in early life – neonatal period, infancy, and early childhood – and subsequently decrease in frequency. In FBP1 deficiency, several metabolic derangements can occur with or without hypoglycemia. Classically, FBP1 deficiency manifests in the first year of life. Nearly half of affected infants present within the first four days of life with an acute crisis. Neonatal presentation results from hypoglycemia due to deficient glycogen stores .
Source: GeneReviews — "Fructose-1,6-Bisphosphatase Deficiency"
FBP1 encodes fructose-bisphosphatase 1 (338 aa). Catalyzes the hydrolysis of fructose 1,6-bisphosphate to fructose 6-phosphate in the presence of divalent cations, acting as a rate-limiting enzyme in gluconeogenesis. Highest expression in Liver (341.4 TPM) and Lung (138.9 TPM).
Fructose-1,6-bisphosphatase deficiency is caused by mutations in the FBP1 gene on chromosome 9.
The FBP1 protein participates in FBP1 gene:H3K4me3 nucleosome, TCF19:NuRD represses FBP1 gene expression, and Regulation of CDH1 Gene Transcription pathways.
FBP1 is classified as a druggable target (Druggable Genome and Enzyme categories) with score 26.1.
Formal diagnostic criteria for fructose-1,6-bisphosphatase (FBP1) deficiency have not been established.
FBP1 deficiency should be suspected in individuals with the following characteristic clinical features and metabolic findings.
Clinical features
Episodes of acute crisis may manifest as hyperventilation, apneic spells, seizures, and/or coma, most commonly in neonates and infants. The course of illness is precipitous and may be lethal, especially in neonates and infants.
Other features can include episodic irritability, tachycardia, hypotonia, and hyperhidrosis.
Hepatomegaly is common.
Inter-crisis periods are uneventful with normal development and growth.
Source: GeneReviews — "Fructose-1,6-Bisphosphatase Deficiency"
provides a comparative analysis of disorders with clinical similarities to fructose-1,6-bisphosphatase (FBP1) deficiency. compares the biochemical parameters of these disorders. Information on mitochondrial respiratory chain and Krebs cycle disorders and fatty acid oxidation defects follows . Table 2a. Disorders (and Associated Genes) of Interest in the Differential Diagnosis of Fructose-1,6-Bisphosphatase Deficiency
Gene(s) | Disorder1 | Differential Diagnosis Disorder: Features Overlapping w/FBP1 Deficiency | Distinguishing Between FBP1 Deficiency Differential Diagnosis Disorder |
|---|---|---|---|
ACAT1 | Beta-ketothiolase deficiency(OMIM 203750) | Ketolytic defect characterized by ketotic hypoglycemia or hyperglycemia metabolic acidosis |
Genetic testing for FBP1 is available. Testing is considered confirmatory for diagnosis.
Biomarker and diagnostic research for fructose-1,6-bisphosphatase deficiency has been reported in the published literature.
No approved treatments are currently available for fructose-1,6-bisphosphatase deficiency. The disease remains an area of unmet medical need.
To establish the extent of disease and needs in a child diagnosed with fructose-1,6-bisphosphatase (FBP1) deficiency who is not in acute crisis, the evaluations summarized (if not performed as part of the evaluation that led to the diagnosis) are recommended . Note that the management of possible multisystem complications resulting from early and prolonged hypoglycemia are not discussed in this GeneReview.
Table 3.
Recommended Evaluations Following Initial Diagnosis of Fructose-1,6-Bisphosphatase Deficiency for a Child Not in Acute Crisis
Evaluation/Concern | Comment
Consultation w/metabolic physician / biochemical geneticist specialist metabolic dietician | • Consider obtaining baseline blood gas, lactate, ketones, CK.1
Assess growth parameters (height, weight, head circumference).
Assess diet nutritional status.
Hepatomegaly | • Abdominal ultrasound to assess for hepatomegaly
Baseline liver function tests
Baseline serum lipid panel2
Baseline serum uric acid
Developmental assessment | Referral to developmental pediatrician to assess motor, adaptive, cognitive, speech-language skills; need for early intervention / special education
Consultation w/clinical geneticist /or genetic counselor | Incl genetic counseling
Family support/resources | Assess:
Use of community or online resources such as Parent to Parent;
Need for social work involvement for parental support.
Source: GeneReviews — "Fructose-1,6-Bisphosphatase Deficiency"
View trials for fructose-1,6-bisphosphatase deficiency
No formal guidelines for long-term surveillance for individuals with FBP1 deficiency exist. summarizes long-term surveillance based on the natural history of the disorder.
Table 6.
Recommended Long-Term Surveillance for Individuals with Fructose-1,6-Bisphosphatase Deficiency
Manifestation/Concern | Evaluation | Frequency/Comment
| Monitor developmental milestones. | At each visit
Neuropsychological testing using age-appropriate standardized assessment batteries | As needed
Standardized quality-of-life assessment tools for affected individuals parents/caregivers | As needed
| Measurement of growth, weight, head circumference | At each visit
Source: GeneReviews — "Fructose-1,6-Bisphosphatase Deficiency"
Phenotype severity distribution: 1 always present feature, 4 very common features, 5 common features.
Estimated prevalence: Unknown (Unknown prevalence).
No clinical trials have been registered for fructose-1,6-bisphosphatase deficiency.
14 publications have been identified in PubMed for fructose-1,6-bisphosphatase deficiency. Research spans Case Report / Case Series (29%), Review / Meta-Analysis (21%), and Epidemiology / Natural History (21%).
Research Type | Count | % of Total |
|---|---|---|
Patient case studies | 4 | 29% |
Research summaries | 3 | 21% |
Disease patterns and progression | 3 | 21% |
Laboratory research | 2 | 14% |
Testing and diagnosis research | 1 | 7% |
Clinical study results | 1 | 7% |
Yazbeck N (2026). [PMID: 41590664](https://pubmed.ncbi.nlm.nih.gov/41590664/). *Metabolites*. [Diagnostic / Biomarker]
Magdy RM (2025). [PMID: 41327277](https://pubmed.ncbi.nlm.nih.gov/41327277/). *Ital J Pediatr*. [Epidemiology / Natural History]
Naito S (2025). [PMID: 41254878](https://pubmed.ncbi.nlm.nih.gov/41254878/). *Pediatr Int*. [Case Report / Case Series]
Wang M (2025). [PMID: 40100307](https://pubmed.ncbi.nlm.nih.gov/40100307/). *Discov Oncol*. [Review / Meta-Analysis]
Goksoy E (2025). [PMID: 41141354](https://pubmed.ncbi.nlm.nih.gov/41141354/). *Front Endocrinol (Lausanne)*. [Clinical Trial Publication]
Bai Q (2025). [PMID: 41350584](https://pubmed.ncbi.nlm.nih.gov/41350584/). *Sci Rep*. [Basic Science / Preclinical]
Elsayed SM (2025). [PMID: 41267090](https://pubmed.ncbi.nlm.nih.gov/41267090/). *Orphanet J Rare Dis*. [Basic Science / Preclinical]
Cullufi P (2025). [PMID: 40964200](https://pubmed.ncbi.nlm.nih.gov/40964200/). *Case Rep Med*. [Case Report / Case Series]
Liu Y (2025). [PMID: 40763970](https://pubmed.ncbi.nlm.nih.gov/40763970/). *Zhonghua Yi Xue Yi Chuan Xue Za Zhi*. [Review / Meta-Analysis]
Ferguson C (2024). [PMID: 39512430](https://pubmed.ncbi.nlm.nih.gov/39512430/). *JIMD Rep*. [Epidemiology / Natural History]
Data assembled from 8 of 12 sources · Last updated Sep 19, 2026, 1:06 PM UTC
Online Mendelian Inheritance in Man
European rare disease database
Genetic and Rare Diseases Info Center
ALDOB | Hereditary fructose intolerance2 | When weaned onto sucrose- or fructose-containing foods, infants can manifest nausea, bloating, vomiting, sweating, abdominal pain, growth restriction.; Chronic liver kidney disease occur in untreated children. | Overall, HFI has a more chronic course than FBP1D.; Children w/HFI have strong aversion to sweets often have renal tubular dysfunction, (not seen in FBP1D).; Children w/FBP1D do not have GI symptoms or FTT w/chronic fructose ingestion. G6PC1 |
SLC37A4 | Glycogen storage disease type I3 | Accumulation of glycogen fat in liver kidneys, resulting in hepatomegaly renomegaly; Untreated infants present at age 3-4 mos w/hepatomegaly, lactic acidosis, hyperuricemia, hyperlipidemia, hypertriglyceridemia, /or hypoglycemic seizures. | Detection of glycerol in FBP1D (on urine organic acid analysis) is useful in differentiating the disorders. |
PC | Pyruvate carboxylase deficiency4 | Episodes of acute vomiting, tachypnea, acidosis are usually precipitated by metabolic stress or infection; episodes may be very similar to FBP1D (w/ lactate-to-pyruvate ratio, hyperalaninemia, hypoglycemia, metabolic acidosis). | The neurologic involvement, severe ID, recurrent seizures characteristic of PCD types A B are not observed in FBP1D. |
PGM1 | PGM1-CDG(See Congenital Disorders of N-Linked Glycosylation and Multiple Pathway Overview.) | Presents more commonly w/rhabdomyolysis; however, episodic hypoglycemia metabolic acidosis may also occur. | Short stature, birth defects (incl cleft palate, bifid uvula), dilated cardiomyopathy may be present in PGM1-CDG. |
Transferrin isoforms are abnormal aid in diagnosis of PGM1-CDG. Multiple | Fatty acid oxidationdefects (FAODs) | FAODs can present in neonates w/hypoglycemia, hyperammonemia, /absent ketones. | — |
Source: GeneReviews — "Fructose-1,6-Bisphosphatase Deficiency"