Kisho is an information platform, not a medical provider. Nothing on this site constitutes medical advice, diagnosis, or treatment recommendations. All content is aggregated from publicly available sources (including ClinicalTrials.gov, PubMed, FDA.gov, and Orphanet) and is provided for informational purposes only. Clinical trial eligibility, treatment decisions, and any health-related actions should always be discussed with a qualified healthcare professional. Kisho does not endorse any specific therapy, organization, or clinical trial. Terms of use · Privacy policy
Fumaric aciduria (FA), an autosomal recessive metabolic disorder, is most often characterized by early onset but non-specific clinical signs: hypotonia, severe psychomotor impairment, convulsions, respiratory distress, feeding difficulties and frequent cerebral malformations, along with a distinctive facies. Some patients present with only moderate intellectual impairment.
Features include always present findings: Hepatic failure, Mitochondrial swelling, Agenesis of corpus callosum, and Intrahepatic cholestasis and others; and very common findings: Decreased fumarate hydratase activity. 72 total HPO annotations.
Organ System | Phenotype Count | Example Features |
|---|---|---|
Brain and nerves | 14 | Hypoplasia of the brainstem, Abnormal speech pattern, Profound intellectual disability |
FH encodes fumarate hydratase (510 aa). Catalyzes the reversible stereospecific interconversion of fumarate to L-malate. Highest expression in Cells EBV-transformed lymphocytes (139.4 TPM) and Cells Cultured fibroblasts (128.8 TPM).
Fumaric aciduria is associated with mutations in the FH gene on chromosome 1.
The FH protein participates in STRN(1-265)-PDGFRA(580-1089) fusion, WDR48(1-323)-PDGFRB(559-1106) fusion, and p-11Y-STRN(1-265)-PDGFRA(580-1089) fusion pathways.
FH is classified as a druggable target (Clinically Actionable, Dna Repair, and Enzyme categories) with score 10.4.
Fumarate hydratase (FH) deficiency should be suspected in individuals with the following clinical, laboratory, and imaging findings.
Clinical findings
Neonatal and early-infantile severe encephalopathy, which may include poor feeding, hypotonia, and decreased levels of consciousness (lethargy, stupor, and coma)
Seizures, present in many but not all affected individuals
No approved treatments are currently available for fumaric aciduria. The disease remains an area of unmet medical need.
Evaluations Following Initial Diagnosis To establish the extent of disease and needs in an individual diagnosed with fumarate hydratase (FH) deficiency, the evaluations summarized (if not performed as part of the evaluation that led to the diagnosis) are recommended. Table 3. Recommended Evaluations Following Initial Diagnosis in Individuals with Fumarate Hydratase Deficiency
Table 5. Recommended Surveillance for Individuals with Fumarate Hydratase Deficiency
System/Concern |
|---|
2 clinical trials registered, 1 recruiting. Interventions under study include other interventions. Pipeline includes 1 PHASE2, 1 NA. Research is primarily sponsored by academic and government institutions.
72 publications have been identified in PubMed for fumaric aciduria. Research spans Case Report / Case Series (39%), Basic Science / Preclinical (21%), and Diagnostic / Biomarker (11%).
Research Type | Count | % of Total |
|---|---|---|
Patient case studies | 28 |
Data assembled from 8 of 12 sources · Last updated Sep 18, 2026, 7:38 PM UTC
Online Mendelian Inheritance in Man
European rare disease database
Genetic and Rare Diseases Info Center
Digestive system |
6 |
Hepatic failure, Intrahepatic cholestasis, Ascites |
Head and neck | 5 | Relative macrocephaly, High palate, Microcephaly |
Muscles | 4 | Low muscle tone (hypotonia), Generalized hypotonia, Brain shrinkage (cerebral atrophy) |
Eyes | 4 | Conjunctival icterus, Damage to the optic nerve (optic atrophy), Visual impairment |
Growth and development | 3 | Failure to thrive, Failure to thrive in infancy, Intrauterine growth retardation |
Lab test results | 3 | Hyperbilirubinemia, Decreased fumarate hydratase activity, Increased urine alpha-ketoglutarate concentration |
Heart and blood vessels | 1 | Perimembranous ventricular septal defect |
Metabolism | 1 | Metabolic acidosis |
Pregnancy and birth | 1 | Bilateral fetal pyelectasis |
Skin | 1 | Reduced subcutaneous adipose tissue |
Blood and immune system | 1 | Decreased total neutrophil count |
To date, approximately 50 individuals have been identified with fumarate hydratase (FH) deficiency [, , , , , , , , , , ]. The following description of the phenotypic features associated with this condition is based on these reports. Table 2. Select Features of Fumarate Hydratase Deficiency
Feature | % of Personsw/Feature | Comment |
|---|---|---|
Antenatal manifestations | 12/51 (23%) | Oligohydramnios, polyhydramnios, IUGR, maternal intrahepatic cholestasis, preeclampsia |
Prematurity | 15/51 (30%) | — |
DD | 44/51 (86%)1 | Severe |
Mild-moderate ID | 4/51 (8%) | — |
Hypotonia | 35/51 (68%) | — |
Seizures | 22/51 (43%) | — |
Cortical visual impairment | 13/51 (25%) | — |
Dysmorphic facial features | 20/51 (39%) | Frontal bossing, depressed nasal bridge, anteverted nares |
Microcephaly | 17/51 (33%) | — |
Macrocephaly | 10/51 (20%) | — |
Abnormal brain imaging | 47/51 (92%) | Incl MRI, CT, antenatal ultrasound findings; most notably: cerebral atrophy, white matter volume loss, polymicrogyria |
Acute metabolic perturbations | 4/51 (8%) | Metabolic acidosis, lactic acidosis, hypoglycemia, hyperammonemia |
Hematologic abnormalities | 11/51 (22%) | Neonatal polycythemia (9 persons); neutropenia (2 persons) |
Dystonic posturing | 4/51 (8%) | — |
Excessive irritability | 3/51 (6%) | — |
Hepatic involvement | 5/51 (10%) | Cirrhosis, acute hepatic neonatal hepatic failure, biliary atresia DD = developmental delay; ID = intellectual disability; IUGR = intrauterine growth retardation 1. Note: Some infants died in the neonatal period. Few clinical reports comment on complications of affected pregnancies. |
Source: GeneReviews — "Fumarate Hydratase Deficiency"
No genotype-phenotype correlations have been identified.
Source: GeneReviews — "Fumarate Hydratase Deficiency"
Intellectual disability / developmental delay
Dysmorphic facial features including frontal bossing, depressed nasal bridge, and widely spaced eyes
Laboratory findings
Source: GeneReviews — "Fumarate Hydratase Deficiency"
Increased excretion of fumaric acid in urine. Transient excretion of fumaric acid in urine is common in young infants and has been observed in metabolically stressed infants, such as those with cardiac failure resulting from severe congenital cardiac anomalies. When the infant with cardiac failure is in stable condition, urine organic acid analysis should be repeated to confirm the presence of increased isolated fumaric acid excretion.
Source: GeneReviews — "Fumarate Hydratase Deficiency"
Genetic testing for FH is available. Testing is considered confirmatory for diagnosis.
Biomarker and diagnostic research for fumaric aciduria has been reported in the published literature.
System/Concern | Evaluation | Comment |
|---|---|---|
Neurologic | Eval by pediatric neurologist | Eval will likely incl brain MRI exam. |
Nutrition | Feeding assessment eval of nutritional status | — |
Other | Consultation w/clinical geneticist /or genetic counselor | Treatment of Manifestations Table 4. |
Treatment of Manifestations in Individuals with Fumarate Hydratase Deficiency Manifestation/Concern | Treatment | Considerations/Other |
Seizures | Eval mgmt by pediatric neurologist | Ketogenic diet is considered contraindicated.; Seizures are often difficult to control. Developmental |
delay | Gastrostomy tube feeding | May be appropriate in hypotonic /or lethargic children w/feeding difficulties /or aspiration Special needs services |
Contractures | Physical therapy | To minimize contractures Wheelchair /or other mobility device |
Scoliosis | Mgmt per orthopedist | One individual with FH deficiency has been treated with a high-fat/low-carbohydrate diet with 60% of the dietary energy goals coming from fat, 30% from carbohydrate, and 10% from protein . |
Recommended Surveillance for Individuals with Fumarate Hydratase Deficiency System/Concern | Evaluation | Frequency |
Seizures | Eval by pediatric neurologist | At least annually to monitor for /or treat epilepsy |
Musculoskeletal complications | Physical medicine eval | At least annually to monitor for equipment needs to monitor for /or treat manifestations of spasticity Orthopedics eval |
Ophthalmology | Ophthalmology eval for visual acuity nystagmus | As recommended by ophthalmologist The ketogenic diet is usually considered to be contraindicated for treating epilepsy associated with FH deficiency or other enzymatic defects within the Krebs tricarboxylic acid cycle. |
Source: GeneReviews — "Fumarate Hydratase Deficiency"
The ketogenic diet is usually considered to be contraindicated for treating epilepsy associated with FH deficiency or other enzymatic defects within the Krebs tricarboxylic acid cycle.
Source: GeneReviews — "Fumarate Hydratase Deficiency"
Increasingly sophisticated models of mitochondrial function are being used to study the metabolic derangements associated with identified defects of intermediary metabolism, including FH deficiency . These models may suggest treatment interventions with supplements or dietary changes that are not presently established. Search ClinicalTrials.gov in the US and EU Clinical Trials Register in Europe for access to information on clinical studies for a wide range of diseases and conditions.
Source: GeneReviews — "Fumarate Hydratase Deficiency"
2 trials found
Evaluation
Frequency |
|---|
Seizures | Eval by pediatric neurologist | At least annually to monitor for /or treat epilepsy |
Musculoskeletal complications | Physical medicine eval | At least annually to monitor for equipment needs to monitor for /or treat manifestations of spasticity Orthopedics eval |
Ophthalmology | Ophthalmology eval for visual acuity nystagmus | As recommended by ophthalmologist |
Source: GeneReviews — "Fumarate Hydratase Deficiency"
Phenotype severity distribution: 5 always present features, 1 very common feature, 20 common features.
Estimated prevalence: <1 in 1,000,000 (VERY_RARE).
Laboratory research | 15 | 21% |
Testing and diagnosis research | 8 | 11% |
Research summaries | 6 | 8% |
Clinical study results | 6 | 8% |
Disease patterns and progression | 5 | 7% |
New treatment approaches | 3 | 4% |
Other research | 1 | 1% |
Gemmell LC (2026). [PMID: 40865753](https://pubmed.ncbi.nlm.nih.gov/40865753/). *Fertil Steril*. [Diagnostic / Biomarker]
Hoffman TL (2026). [PMID: 42120995](https://pubmed.ncbi.nlm.nih.gov/42120995/). *Hered Cancer Clin Pract*. [Epidemiology / Natural History]
Sun T (2026). [PMID: 40991420](https://pubmed.ncbi.nlm.nih.gov/40991420/). *Int J Gynecol Pathol*. [Diagnostic / Biomarker]
Sigdel S (2026). [PMID: 41585615](https://pubmed.ncbi.nlm.nih.gov/41585615/). *Cureus*. [Case Report / Case Series]
Liu Y (2026). [PMID: 41496563](https://pubmed.ncbi.nlm.nih.gov/41496563/). *The Journal of pathology*. [Epidemiology / Natural History]
He J (2026). [PMID: 41911282](https://pubmed.ncbi.nlm.nih.gov/41911282/). *Clin Nucl Med*. [Case Report / Case Series]
Ting SL (2026). [PMID: 41968386](https://pubmed.ncbi.nlm.nih.gov/41968386/). *Am J Med Genet A*. [Diagnostic / Biomarker]
Jaafar W (2026). [PMID: 41438660](https://pubmed.ncbi.nlm.nih.gov/41438660/). *Radiology case reports*. [Case Report / Case Series]
Alguacil Martínez P (2026). [PMID: 41707421](https://pubmed.ncbi.nlm.nih.gov/41707421/). *Semergen*. [Review / Meta-Analysis]
Gray MT (2026). [PMID: 41637165](https://pubmed.ncbi.nlm.nih.gov/41637165/). *Journal of neuropathology and experimental neurology*. [Case Report / Case Series]