Integrated PBL: Phenylketonuria (PKU) Flashcards
What is phenylalanine?
Crystalline, water-soluble, essential amino acid necessary to the nutrition of humans and most animals, obtained chiefly from egg white or skimmed milk
What is a teratogenic substance?
A drug or other substance capable of interfering with the development of a foetus
What is microcephaly?
Abnormal smallness of the head, a congenital condition associated with incomplete brain development
What is anaemia?
Condition where there is a deficiency of red cells or of haemoglobin in the blood
What is folate?
One of the B vitamins that is a key factor in the synthesis of nucleic acids (RNA and DNA)
What is the cause of PKU?
Caused by a genetic mutation to human phenylalanine hydroxylase (PAH) gene leading to the body not producing a functioning PAH enzyme
When do symptoms of PKU occur?
If untreated; at birth most babies with PKU appear normal and symptoms only develop because of complications that arise if the condition isn’t treated properly
When should treatment of PKU be initiated?
Within the first 3 weeks of life to minimise the chance of them experiencing severe learning difficulties associated with the condition
What are the most widely reported conditions in adults with treated PKU?
Depression, anxiety disorders, phobias (particularly agoraphobia) and low self-esteem
What are the symptoms of untreated PKU?
Severe learning disability, behavioural difficulties,
Why may those with untreated PKU have fairer skin, hair and eyes?
Phenylalanine is involved in the body’s production of melanin, the pigment responsible for skin and hair colour
What is PKU?
Disorder where there are insufficient PAH enzyme so any excess phenylalanine can’t be broken down, and therefore phenylalanine can build up in the blood and brain to toxic levels, affecting brain development and function
How is PKU diagnosed?
Heel prick test in the first 7 days of life, testing for phenylalanine levels; if they are higher than normal a diagnosis of PKU is given (if greater than 3mg/dL) and dietary treatment is begun
How is PKU treated?
With a low-protein diet and regular dietary supplements containing essential nutrients and amino acids absent from the diet; taken 3 to 4 times a day
What are ‘green foods’ in a low-protein diet for treating PKU?
Foods that are safe to eat because they contain low levels of protein, though they shouldn’t be eaten in excess. These include most fresh fruit, most vegetables, low-fat and low-protein butter and margarine
What are ‘amber foods’ in a low-protein diet for treating PKU?
Foods that contain moderate levels of protein and must be carefully weighed and eaten in different quantities according to the blood phenylalanine level. These include potatoes, cereals, baked beans, milk and rice
What are ‘red foods’ in a low-protein diet for treating PKU?
High-protein foods that should never be eaten under any circumstances. These include all types of meat, fish, eggs, cheese, nuts, flour-based foods and quorn/tofu
Why can’t individuals with PKU consume aspartame/artificial sweetener?
Aspartame is converted to phenylalanine in the body
Why do excessive phenylalanine levels cause microcephaly?
Phenylalanine is a large, neutral amino acid (LNAA). LNAAs compete for transport across the blood–brain barrier (BBB) via the large neutral amino acid transporter (LNAAT). If phenylalanine is in excess in the blood, it will saturate the transporter. Excessive levels of phenylalanine tend to decrease the levels of other LNAAs in the brain. As these amino acids are necessary for protein and neurotransmitter synthesis, Phe buildup hinders the development of the brain, causing intellectual disability
Why is tyrosine a conditionally essential amino acid in PKU?
PAH converts the phenylalanine to other essential compounds in the body, in particular tyrosine. Tyrosine is a conditionally essential Amino acid for PKU patients because without PAH it cannot be produced in the body through the breakdown of phenylalanine. Tyrosine is necessary for the production of neurotransmitters like epinephrine, norepinephrine, and dopamine
Describe the epidemiology of PKU
Affects 1:10,000 babies born in the UK and both sexes are affected equally
Why may the pregnant woman with PKU have symptoms of tiredness, paleness and weight loss?
Likely to have stopped taking nutritional supplements, and due to the lack of iron present in the low-protein diet, are likely to have developed iron-defiency anaemia and have begun to lose weight due to lack of essential vitamins and minerals
How may PKU be inherited?
It’s an autosomal recessive condition; so both partners would have to have PKU or both be a carrier, or a carrier and someone with PKU.
Describe the symptoms of an ACL tear
Acute knee pain and pain when climbing the stairs
