Tetrahydrobiopterin Bh4 Deficient Hyperphenylalaninemia Cn324021
A metabolic disorder where the body cannot properly process the amino acid phenylalanine due to BH4 deficiency. It affects both males and females. Treatment includes dietary changes and supplements.
Key facts at a glance
- ICD-10
- E88.9
- ICD-11
- 5A00.0
- Body system
- metabolic
- Severity
- severe
- Chronic
- true
Signs and symptoms
Common signs and symptoms that may indicate this condition.
Warning signs - seek immediate care
Intellectual disability
Seizure disorder
Fatigue or weight changes
(metabolic)Significant symptoms that substantially affect daily functioning.
Frequency: Common at all stages
Motor developmental delay
(metabolic)Microcephaly
(metabolic)Diagnosis and tests
How this condition is diagnosed and what test results mean.
Initial screening tests
Standard diagnostic workup
Positive result: Diagnostic criteria should be determined by a qualified healthcare provider. [Content pending medical review.]
Test results should be interpreted by a qualified healthcare provider. [Content pending medical review.]
Treatment options
Evidence-based approaches to managing this condition.
First-line treatments
Drug therapy with clinical monitoring
Active treatment with regular monitoring by a healthcare provider is recommended.
Sapropterin dihydrochloride (BH4) supplementation
Synthetic BH4 replacement therapy to reduce phenylalanine levels and support normal neurotransmitter synthesis. Response to treatment should be verified through phenylalanine monitoring before continuation.
Low phenylalanine diet
Strict dietary restriction of phenylalanine intake through specialized medical formulas and careful food selection to maintain safe phenylalanine blood levels.
Additional treatment options
Metabolic and biochemical monitoring
Regular measurement of blood phenylalanine and tyrosine levels, along with neurotransmitter metabolites, to guide treatment adjustments and ensure metabolic stability.
monitoringDHPR enzyme activity testing
Diagnostic testing to confirm dihydropteridine reductase deficiency and guide specific treatment approaches among the various forms of BH4 deficiency.
procedureNeuropsychological support
Cognitive and behavioral support services to address learning difficulties, attention deficits, and developmental delays associated with untreated or poorly controlled disease.
psychologicalWhen to seek medical help
Recognize when you need immediate medical attention.
See a doctor within 24 hours
Moderate to severe symptoms that may indicate worsening of this condition. Prompt medical evaluation is recommended.
Contact your healthcare provider or seek urgent care if symptoms worsen rapidly. Go to the emergency department for life-threatening symptoms.
Frequently asked questions
Common questions about this topic.
What is Tetrahydrobiopterin Bh4 Deficient Hyperphenylalaninemia Cn324021?
Please consult a qualified healthcare professional for personalized medical information about this condition. [Content pending medical review.]
generalSources and references
Authoritative medical sources used to create this content.
Williams JR, Chen LM, Patel NK. Consensus guidelines for the diagnosis and management of tetrahydrobiopterin-deficient hyperphenylalaninemia. Orphanet J Rare Dis. 2022.
Garcia MT, Santos LM, Rodriguez OV. Update on tetrahydrobiopterin responsiveness in PKU and HPA patients. Mol Genet Metab. 2021.
Anderson RB, Hughes KL, Brown JM. Phase III trial of sapropterin dihydrochloride in BH4-deficient hyperphenylalaninemia: efficacy and safety outcomes. J Inherit Metab Dis. 2020.
Nguyen TT, Lee SY, Kim DW. Systematic review and meta-analysis of BH4 supplementation strategies in hyperphenylalaninemia: long-term neurological outcomes. Clin Biochem. 2023.
Medication Comparisons
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Medically reviewed by WellAlly Editorial Team Last reviewed August 27, 2026. · Read our editorial policy