Phenylketonuria PKU (Nursing)

00:01 Phenylketonuria.

00:03 That is what we're going to talk about in this presentation, also known as PKU.

00:08 So what is PKU? It is really based on phenylalanine, which is a protein building block that's needed by the body.

00:19 Now, this is an essential amino acid that's needed for the synthesis of proteins, catecholamines, and melanins.

00:27 So it's responsible for a lot of important things.

00:30 And by essential amino acid, I mean that you actually have to take this in with your food.

00:38 Your body can't make this on its own.

00:40 So you have to ingest phenylalanine.

00:44 If our metabolism is normal, we're going to ingest phenylalanine.

00:49 And that's going to go through our systems, our blood vessels through our liver, and then it's going to come into contact with phenylalanine hydroxylase.

00:58 This phenylalanine hydroxylase is going to break up that phenylalanine.

01:04 And it's going to then interact with tyrosine and continue on through our metabolism.

01:10 Now, if you have an abnormal metabolism, then you don't have this phenylalanine hydroxylase.

01:16 So we can't break this up, and you get this phenylalanine buildup into your system.

01:23 It can't interact with the tyrosine.

01:25 And it can't continue on through the metabolic journey.

01:29 That also results in the inability of the body to make tyrosine.

01:36 So what happens with PKU? You can either have a complete enzyme deficiency, which is the classic PKU, or it can be a little less than complete.

01:46 That's going to give you degrees of symptoms.

01:49 They might be a little bit more mild to moderate than the classic PKU.

01:54 This is also an autosomal recessive condition.

01:58 So if you remember from previous presentation, that means that you have to have the recessive gene from both parents.

02:08 So what are some signs and symptoms of PKU? They largely have to do with brain development.

02:14 So you might see an infant that has microcephaly, because if your brain is not developing, then the head is not going to be as big as you would expect.

02:24 You're going to have some possibly irreversible intellectual disability, some behavioral abnormalities.

02:31 So these infants and children have frequent temper tantrums, and sometimes even engage in self-harm.

02:39 They might have seizures, skin diseases.

02:42 One of the hallmarks of PKU is that these children often have eczema, and much fairer skin, hair, and eyes than their siblings.

02:51 Remember that melanin production is part of what phenylalanine does for the body.

02:57 So if it is not able to transition into the metabolism, then you're going to have some of these skin findings.

03:06 There's also going to be a musty smell to the breath, the skin, and the urine.

03:11 something that just doesn't smell quite right.

03:15 So how do we figure out if this is what's going on with our patient? There is widespread neonatal screening for PKU in many countries.

03:24 And this is one of the things that the US does routinely.

03:29 If not detected via neonatal screening, though, the infant is really going to start exhibiting symptoms as soon as we feed them, because remember, breast milk and formula both have a lot of protein.

03:45 So, if we suspect PKU, because the infant starts to have symptoms, especially right after they're being fed, then we can send a serum amino acid profile.

03:57 In that profile, we should find an elevated concentration of the phenylalanine.

04:02 And remember, this is because the body can't break it down.

04:07 We can also do molecular genetic testing if we want to get a little bit more in depth.

04:13 Now, if we discover that our patient has PKU, what can we do for them? Really, we have to ingest phenylalanine and we get most of that through protein containing foods.

04:28 So anything that has high levels of protein - beef, eggs, chicken, those types of things are going to be a little problematic for patients with PKU.

04:38 We also get some phenylalanine from vegetables, fruits, and whole grains.

04:46 There's also phenylalanine that is present in breast milk.

04:51 So, what does that mean for our patients? We're really going to have to have them on a strict diet.

04:57 And there are some medications that we can do to help them break that phenylalanine down.

05:03 One of them is sapropterin and the other one is phenylalanine ammonia lyase.

05:09 So, the term "lyase", when you see A-S-E on the end of any medication, that means that it is formulated to help break something down.

05:23 Patients with PKU are going to need a lot of monitoring, and this is going to require a multidisciplinary team.

05:31 Infants that have PKU are we're really going to be checking those phenylalanine levels, weekly.

05:37 We want to make sure that they are in a good place, and that we've keep those levels low, especially because once neurologic changes, happen, then they become irreversible.

05:48 So we want to keep them from happening.

05:51 Once these children get a little bit older, we may not need to monitor them quite as frequently because their diet becomes a little bit more stable.

06:00 And then when they're older than 12 years, then we will be checking these levels monthly.

06:06 So what are the outcomes for patients with PKU? With really good dietary treatment, we can reverse all the signs of PKU except for cognitive impairment that's already occurred.

06:20 So if we already have learning problems, or cognitive issues, and we have not yet gotten the PKU under control, we're not going to be able to reverse those but we can reverse other symptoms.

06:33 We want to make sure that we have really good dietary restrictions, because that's what's going to give us these good cognitive outcomes.

06:42 When we have good dietary restriction, and we should be working with a metabolic dietitian, then these children can have IQ scores that are in the normal range.

06:53 So let's go through the clinical judgment model and think about PKU from this perspective.

07:01 So one of the first things we do in the clinical judgment model is we try to recognize the cues in our patient.

07:07 If we have an infant that presents with these symptoms like microcephaly, or seizures, or skin diseases, especially if these symptoms come on immediately after being fed, then we're going to suspect PKU.

07:24 So, how do we analyze what we're seeing in our patient? Many infants will be diagnosed with newborn screening.

07:32 But if this doesn't happen, then these symptoms are really going to start after a diet that contains phenylalanine, which is most commercial formulas.

07:41 So anything that's protein containing is going to cause these patients to have symptoms.

07:45 So that's a big cue that you might be dealing with PKU.

07:48 They're being fed and they develop symptoms.

07:52 So what are we going to do about that? There are a couple of different things that we can do.

07:57 But the mainstay of treatment is really going to view these dietary restrictions.

08:02 Which as children are growing older, and especially getting into the teenage years, it's really important to work with that metabolic dietician, because this diet in particular with the low protein can be really hard to stick to.

08:15 So you're going to need those dietary changes, and then there is some pharmacologic treatment that we can offer.

08:22 So as you're going through the clinical judgment model, just remember, that you're going to want to go through each one of these steps, and we've highlighted a few to help you think through this.