Living with Hyperphenylalaninemia due to tetrahydrobiopterin deficiency
A rare inherited condition with a shortage of a molecule called BH4, causing high phenylalanine and nervous system problems.
Understanding Hyperphenylalaninemia due to tetrahydrobiopterin deficiency
It changes levels of several substances, including phenylalanine, an amino acid found in protein foods and some artificial sweeteners. It also changes brain chemicals (neurotransmitters). Babies appear typical at birth, but mild to severe problems appear over time. These can include intellectual disability, delays in development, movement problems, swallowing trouble, seizures, behavior problems, and trouble controlling body temperature.
Signs & symptoms
Symptoms vary from person to person. GARD lists these among the most common:
- Developmental delay
- Low muscle tone (hypotonia)
- Behavior differences
- Extra drooling
- Seizures
- Movement problems
Not everyone has every symptom. GARD's list comes from the Human Phenotype Ontology.
Diagnosis
- 1Talk with your doctor
Share the symptoms you've noticed, when they started and your family health history. Notes and photos can help.
- 2See a specialist
Specialists who may be involved include brain and nervous system specialists and genetic specialists.
- 3Ask which tests can help
Your care team will decide which exams and tests can confirm the diagnosis.
Care & treatment
- Care team
- Brain and nervous system specialists (neurologists); Genetic specialists (geneticists)
- Expert care
- Ask about multidisciplinary care centers for rare conditions
- Treatment
- GARD doesn't list specific treatments for this condition. Your care team will tailor care to your symptoms.
- Research
- Clinical trials and observational studies may be options. See the research section below.
General information, not medical advice. Your care team makes the decisions.
Everyday life
Living with a rare condition is easier with support.
- Connect with Pediatric Neurotransmitter Disease Association
- Keep notes on symptoms, changes and questions for appointments
- Ask about patient registries that help research
- Look into financial aid and travel resources for care visits
Quick facts
Changes in genes (also called variants) cause this condition. It is autosomal recessive, so a child inherits a changed copy of the gene from each parent.
Also known as: bh4-deficient hyperphenylalaninemia; deficiency of tetrahydrobiopterin; hyperphenylalaninemia due to bh4 (tetrahydrobiopterin) deficiency; hyperphenylalaninemia due to bh4 deficiency; non-phenylketonuric hyperphenylalaninemia; tetrahydrobiopterin deficiency
Patient organizations
- Pediatric Neurotransmitter Disease AssociationHyperphenylalaninemia due to tetrahydrobiopterin deficiency · United States
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Perspectives from people navigating life with Hyperphenylalaninemia due to tetrahydrobiopterin deficiency.
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