Phenylketonuria (PKU)

What this deck covers

Phenylketonuria (PKU) in fourteen clinical teaching cases with worked explanations. Each case gives you a clinical vignette, four options, the correct answer, and an explanation of why each of the other three is wrong.

Diagnoses and management options tested

Across the fourteen cases you are asked to choose between options such as: Premature discharge before adequate protein intake, Laboratory technical error in the screening assay, Maternal low-phenylalanine diet during pregnancy, Concomitant neonatal jaundice interfering with the assay, Maple syrup urine disease (MSUD), Classic phenylketonuria (PKU), Biotinidase deficiency, Elevated phenylalanine directly destroys melanocytes, A separate genetic mutation affects pigmentation genes, Tyrosine deficiency impairs melanin production, Autoimmune destruction of pigment-producing cells, Excess serotonin causing neuronal overstimulation, GABA deficiency leading to motor instability, Glutamate excitotoxicity triggering cortical seizures, Reduced dopamine due to impaired tyrosine availability, Phenylalanine hydroxylase (PAH), Tyrosine aminotransferase, Dihydropteridine reductase (DHPR), GTP cyclohydrolase I, Pyridoxal phosphate (vitamin B6), Flavin adenine dinucleotide (FAD), Tetrahydrobiopterin (BH4), Nicotinamide adenine dinucleotide (NAD+), Immediately start a low-phenylalanine diet, Confirmatory plasma phenylalanine and tyrosine levels, Initiate sapropterin (BH4) therapy.

Clinical pearls from this deck

• Newborn screening for PKU needs a phenylalanine load to detect. Phe only starts climbing once protein feeding begins, so a sample drawn at 18 hours of age can be genuinely normal in a baby who has classic PKU. Optimal timing is after 48 hours of established feeding.
• Developmental delay, hypotonia, eczema, fair colouring and a musty or mousy odour with plasma Phe above 1200 µmol/L is classic PKU. Symptoms emerge at 3–6 months — never at birth — because damage requires accumulated exposure after protein feeding starts.

The fourteen worked cases in this deck, with the images and the full explanation of every option, are part of Pediatric Case Review membership. See what is included.

More from this system: all metabolic and genetic decks and question sets · pediatric reference values.