What is PKU?

PKU is short for Phenylketonuria, and it’s a rare genetic condition which affects around 1 in 10,000 people in the UK. It results in a fault where the liver can’t break down an amino acid called Phenylalanine properly. Amino acids are the building blocks of protein, and since most foods contain protein, the amount a person with PKU can eat needs to be very strictly controlled.

Luckily, all babies born in the UK are screened for PKU and many other genetic conditions in their heel prick test which is done when they’re 7 days old. I’m really thankful that we are, because when he was 16 days old we were told my son has PKU. By then he was already starting to show signs of brain damage, but luckily he started treatment straightaway and those signs  went completely within a few weeks. Two years later he’s a very happy, lively and bright little boy and there are certainly no signs of any lasting effects.

PKU Around The World

But in other parts of the world there are thousands of families not quite as fortunate as us. When PKU isn’t detected and treated in time, the levels of an amino acid called Phenylalanine (Phe) for short build up in the bloodstream and poison the brain. This can quickly lead to permanent brain damage with associated seizures, severe behavioural problems and mental impairment.

It seems tragic that a condition which can be entirely managed by diet is not screened for and treated globally, but the cost of the prescription food is too high for many countries. There are drugs available in some areas which are suitable for some PKU patients, but they tend to cost much more than the diet and it may be hard to justify the extra spend. If there are no other complications, provided that a person with PKU can stay on their diet and their Phe levels stay within a safe range, they can live a perfectly normal life with no adverse effects. There have been some concerns raised by Scientists recently about the effects of PKU on the grey matter in the brain even when its controlled by diet. However anecdotal evidence has shown so far that there’s nothing to worry about in terms of life expectancy or quality.

Life With PKU


Jacob in hospital due to high Phe levels.

We have to monitor Jacob’s Phe levels twice a week using a finger prick test. At the moment we have to post samples off to the hospital but we’re hoping that one day soon we’ll be able to get instant results in the same way as Diabetics do. Safe levels for someone with PKU would be below 300, and the unsafe range starts at above 350. Jacob’s were over 3000 when he was first diagnosed but on the whole they’ve stayed under control since. His dad and I make sure we stick to his diet, and his protein intake has to be reduced when his levels are very high, but when they settle down again he’s allowed back onto his normal amount. Levels usually increase due to illness, so we’ve done our best to keep his immune system strong and healthy in various ways since he was born. Despite that, like most children of his age, he’s prone to catching coughs and colds in particular, but with PKU it’s more complicated as when a child loses their appetite they start to break down their own muscle protein, raising their Phe levels. It’s not uncommon for PKU children to be hospitalised after they’ve refused food for a few days, and they need to be tube fed with their protein replacement in order to get their levels down again. We’ve been in hospital twice so far for this reason and the main challenge has been getting admitted in the first place. Most Doctors know very little about PKU because it’s so rare, so they don’t fully understand why it’s so important to get a child with PKU tube fed and levels back under control quickly. Lots of PKU families, including us find themselves teaching the Doctors about the condition.

All in all life with PKU for us certainly hasn’t  been as hard as we expected so far. I’ve quickly had to learn to cook PKU style and we’ve had to think on our feet when someone fed Jacob a sausage roll at a party (all meat and pastry is off the menu). Instead of remembering my purse, keys and phone when I leave the house I now remember purse, keys, phone and food for Jacob, but that’s pretty easy.  Like all PKU families, we have to take all his food with us on holiday, and making sure we have enough protein replacement with us if he needed to stay in hospital for any reason. I’m sure we’ll have more challenges as time goes by and he wants to fit in with his friends, but that’s only to be expected. Most of all, we’re eternally grateful at how lucky we’ve been so far, and that we’re getting some of the best care in the world from our hospital. Things could have been so different….

Would you like to know more about life with PKU? Read our story.

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