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Foundation Sciences · Genetics

Phenylketonuria and Newborn Screening

⏱️ 30 mins read 📖 Genetics 🎯 MLA Relevance: High

Phenylketonuria (PKU) is an autosomal recessive disorder of phenylalanine metabolism (PAH deficiency) detected on newborn screening to prevent irreversible neurological damage.

📌 Learning Objectives

  • Describe the underlying mechanism of Phenylketonuria and Newborn Screening.
  • Identify the key clinical features and complications of Phenylketonuria and Newborn Screening.
  • Outline the appropriate investigations and management of Phenylketonuria and Newborn Screening.
  • Discuss the implications for patients and families of Phenylketonuria and Newborn Screening.
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Curriculum Mapped
UK MLA Curriculum

📋 Overview

Untreated, PKU causes severe intellectual disability, seizures, eczema and a 'mousy' odour. Strict low-phenylalanine diet from infancy prevents these complications.

🔬 Basic Science

Untreated, PKU causes severe intellectual disability, seizures, eczema and a 'mousy' odour. Strict low-phenylalanine diet from infancy prevents these complications.

🏥 Clinical Relevance

Maternal PKU can cause foetal microcephaly and congenital heart disease if not strictly controlled in pregnancy.

🧪 Investigations

Investigation depends on clinical context: relevant blood tests, imaging, and specific genetic or histopathological tests as appropriate. Refer to specialist services where indicated.

💊 Management

Management is condition-specific and typically multidisciplinary, combining medical therapy, surgical intervention where appropriate, supportive care, and family/genetic counselling.

Revision Resources – expand the sections below for high-yield notes, exam pearls, key facts and further reading.

🎯 MLA High-Yield Notes & Quick Revision ⌄
Common SBA themes: recognising the underlying mechanism, identifying classic clinical features, and choosing the first-line investigation or management step. Watch for inheritance pattern and characteristic associations.
pku phenylketonuria guthrie newborn screening pah
  • PKU is caused by phenylalanine hydroxylase (PAH) deficiency.
  • Untreated PKU causes severe intellectual disability and seizures.
  • Treatment is a lifelong low-phenylalanine diet, sometimes with sapropterin.
  • UK Guthrie screen tests for nine conditions on day 5.
  • Maternal PKU in pregnancy causes foetal microcephaly and cardiac defects.
⭐ Exam Pearls ⌄
⭐ High Yield
PKU is caused by phenylalanine hydroxylase (PAH) deficiency.
Untreated PKU causes severe intellectual disability and seizures.
Treatment is a lifelong low-phenylalanine diet, sometimes with sapropterin.
UK Guthrie screen tests for nine conditions on day 5.
Maternal PKU in pregnancy causes foetal microcephaly and cardiac defects.
💡 Clinical Pearl
Pku: Maternal PKU can cause foetal microcephaly and congenital heart disease if not strictly controlled in pregnancy.
⚠️ Exam Tip — Common Mistakes
Confusing the mechanism of Phenylketonuria and Newborn Screening with related conditions.
Missing classic clinical features of Phenylketonuria and Newborn Screening in SBA stems.
Failing to consider Phenylketonuria and Newborn Screening in the differential diagnosis.
🔑 Key Facts ⌄
PKU is caused by phenylalanine hydroxylase (PAH) deficiency.
Untreated PKU causes severe intellectual disability and seizures.
Treatment is a lifelong low-phenylalanine diet, sometimes with sapropterin.
UK Guthrie screen tests for nine conditions on day 5.
Maternal PKU in pregnancy causes foetal microcephaly and cardiac defects.
🔗 Related Topics ⌄
📚 Newborn Screening 🔬 Autosomal Recessive Disorders Foundation Sciences → 📚 Inborn Errors of Metabolism
📚 References ⌄
  1. GMC MLA Content Map
  2. NICE Clinical Knowledge Summaries
  3. BMJ Best Practice

Further Resources

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