Inborn Errors: Overview (Nursing)

by Amy Howells, PhD, CPNP-AC/PC

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    00:01 In this presentation, we're going to talk about Inborn Errors of Metabolism.

    00:06 And this is just going to be an overview because there are many.

    00:10 So what are Inborn Errors of Metabolism.

    00:14 This is a congenital condition, and it's the absence or abnormality of an enzyme, or that enzymes cofactor.

    00:24 So what does that mean for our patient? We have many substances in our bodies, and many that we take in like protein, for example.

    00:34 And you need enzymes or the cofactor of those enzymes to break those substances down so that our body can use them.

    00:43 When these substances are not able to be broken down, because there's a deficiency of an enzyme or the cofactor, what happens is we get an accumulation of metabolites or an accumulation of those substances in the body.

    00:58 And that can have really extreme consequences.

    01:03 Now, sometimes, if the enzyme is missing or abnormal, we'll actually have a deficiency of the metabolites.

    01:10 We don't have the substances in the body that we need for our metabolism and for general functioning.

    01:18 So what causes an inborn error of metabolism? These are mostly autosomal recessive.

    01:25 So this means if you remember from your genetics, that the offspring is going to inherit two copies of the gene, one from each parent.

    01:33 And the genes usually come from non sex chromosomes.

    01:36 And those copies must both have the condition that's going to cause the inborn error.

    01:44 So there are many types of inborn errors of metabolism.

    01:48 And I want to stress that you do not need to know each inborn error.

    01:54 There's some broad categories of these inborn errors.

    01:57 You'll see organic acidemia or amino acid disorders.

    02:03 And these cause specific diseases. These also have categories.

    02:08 So you might have a lysosomal storage disease.

    02:12 A disease like phenylketonuria, where you have too many ketones in your body.

    02:18 There's peroxisomal disorders, mitochondrial diseases, where your mitochondria just are not working correctly.

    02:28 Glycogen storage diseases.

    02:31 And we know if you have trouble storing glycogen that you're going to have trouble with your metabolism.

    02:37 Urea cycle disorders.

    02:40 So there are many different types.

    02:43 So, inborn errors of metabolism can either be a single enzyme deficiency and that's the most common thing that happens or you might have abnormalities in more than one enzyme.

    02:54 And when you have abnormalities in more than one, you're usually going to affect several metabolic steps.

    03:02 So what does this mean for our patients? When you have a single enzyme deficiency, which is the most common, you might have an accumulation of metabolites.

    03:12 An example of this would be Alkaptonuria.

    03:16 And this results in an accumulation of homogentisic acid.

    03:22 You might have a deficiency of metabolites as what happens in the MCAD disease, and that is going to result in an inability for the body to make keto acids.

    03:35 Additionally, if you have abnormalities in more than one enzyme, as in the case of vitamin B 12 transport and synthesis, you might have an accumulation of methylmalonic acid and homocysteine.

    03:49 So this affects multiple steps in the metabolism.

    03:53 So how often does this happen? It turns out that the individual inborn error rates is actually pretty rare.

    04:00 It's low, it's less than 100,000 live births.

    04:04 But when you combine this with the fact that there are many, many different types of inborn errors of metabolism, it actually becomes a little more common.

    04:13 So one in 800 to 2500 live births, depending on where you are, may have an inborn error of metabolism.

    04:24 So what are patients going to look like if they have inborn errors? Well, when your metabolism is affected, it's going to include findings in almost every body system.

    04:35 Primarily what we're going to notice first our problems with the neurologic system and with the gastrointestinal system.

    04:43 So you might see things and especially chronic symptoms like failure to thrive and growth delay.

    04:50 Maybe these patients aren't getting their developmental milestones.

    04:53 They have a developmental delay, or they might even lose developmental milestones.

    04:59 Infants that were able to sit up and smile at you now no longer have the ability to sit on their own.

    05:05 So that's what is meant by regression of milestones.

    05:09 They might experience cardiomyopathy, they might have hepatomegaly.

    05:13 So their liver is really big.

    05:14 You can feel it way down below their ribs.

    05:17 They might have spastic diplegia, meaning that they have difficulty walking.

    05:23 More acute symptoms are going to be symptoms that are consistent with shock.

    05:28 So you might have dehydration.

    05:30 They might be hypoglycemic, making them shaky.

    05:33 They might be in a prolonged fasting state, because they just haven't been able to eat because they're nauseous, and they're vomiting.

    05:41 And they are under extreme amounts of stress.

    05:46 So that can progress into a metabolic emergency.

    05:51 If your patient is continually vomiting, they're becoming lethargic. Maybe even falling into a coma.

    05:58 Experiencing seizures, or rapid deep breathing.

    06:02 That is all metabolic emergency.

    06:05 Additionally, they might be breaking down their own muscles, which is rhabdomyolysis.

    06:10 Might be experiencing hypothermia.

    06:13 Hypothermia is often associated with more minor illness and then hyperthermia or high temperatures might follow that.

    06:22 If you have a patient that has any of these symptoms that can't be explained by an illness or other condition, we have to consider the possibility of an inborn error of metabolism.

    06:35 Inborn errors can really occur in any age group.

    06:38 But the most severe forms are usually going to be found as a neonate.

    About the Lecture

    The lecture Inborn Errors: Overview (Nursing) by Amy Howells, PhD, CPNP-AC/PC is from the course Inborn Errors of Metabolism – Pediatric Nursing.

    Included Quiz Questions

    1. The six-year-old client with a respiratory rate of 35 who has had ten episodes of vomiting in the last four hours and is becoming very difficult to rouse.
    2. The four-year-old client with hyperglycemia presenting as irritable, with a fever and a pulse rate of 110.
    3. The ten-year-old client with a known seizure disorder presenting as confused and lethargic following a partial seizure.
    4. The seven-year-old client complaining of a headache and neck pain with a fever, photosensitivity, and nausea.
    1. Hypoglycemia
    2. Shock
    3. Developmental delay
    4. Failure to thrive
    5. spastic diplegia
    1. It is an absence or abnormality of an enzyme or cofactor.
    2. It always results in a deficiency of metabolites in the body.
    3. It is an acquired condition.
    4. It is primarily autosomal dominant.

    Author of lecture Inborn Errors: Overview (Nursing)

     Amy Howells, PhD, CPNP-AC/PC

    Amy Howells, PhD, CPNP-AC/PC

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