Transcription
This lesson is on lead poisoning. So, in this lesson, we're going to talk about where we might be exposed to lead. We're also going to talk about how lead causes toxicity. And then, we're going to get into the signs and symptoms, how it's diagnosed, and how it's treated.
So, lead poisoning is also known as lead toxicity. It is a condition caused by increased concentrations of lead in the blood. Now, lead itself is a heavy metal. It's found in the environment. It's an environmental toxin, but it has no physiological function. However, when exposed to it, it can cause both reversible and irreversible health effects, depending on what stage of life you are in when you are exposed to lead and how long you are exposed. We're going to talk a bit more about that in detail later on in this lesson.
Now, it's important to note that no level of lead exposure is safe. Children are going to be most commonly affected, and adult males are more frequently affected than females. And we're going to talk a bit more about why that is in the next slide.
So, lead poisoning or lead toxicity can be broken down into acute and chronic forms. So, acute lead poisoning is going to be most commonly caused by occupational exposure. So, this is the reason why adult males are going to be more likely to be affected than adult females. Some occupations that increase the risk for exposure include any occupation or any job that exposes the individual to lead. These are going to include battery manufacturing and recycling, lead mining and refining, auto repair, and certain types of construction. Now, there are other jobs or other occupations that can also increase your risk for being exposed to lead. If you want more information, please look up a list of those occupations.
With regards to chronic forms, this is going to most commonly affect children. It's going to be insidious. It's going to be a slow exposure over time, and this is most commonly going to be from environmental sources. These are going to include leaded paint. So, leaded paint has been phased out in much of the developed world. So, this is going to be most important when being exposed to paint in houses built before 1978. And the paint itself is going to be more problematic in those older houses when that paint is peeling or chipping. And if there are very small children in those environments and they were to actually ingest that chipped paint, this is a possible way that they can be exposed to leaded paint.
Another older source of lead comes from leaded gasoline. Gasoline used to have lead in it starting in the 1920s, and this has also been phased out as well. But during the time when there was lead in gasoline, the lead from the gasoline used to be sent out through the exhaust into the environment, into the air, and has essentially contaminated a lot of environments in some of the soil as well. So, there can still be lead in certain areas from this leaded gasoline. And then certain old toys. If children are playing with old toys, especially those that are painted with old paint that has lead in it, this is another source of exposure as well.
So, how does lead actually cause disease? What are some of the pathophysiological mechanisms as to how lead causes disease? First, we're going to talk about heme synthesis. So, we need heme synthesis to make hemoglobin, which is what carries oxygen in our red blood cells. So, lead is going to affect certain parts of the heme synthesis pathway. It's going to affect two enzymes in particular. One is known as ALA dehydratase, and the other one is ferrochelatase, the last enzyme in the heme synthesis pathway. So, because of these two affected enzymes, again, ALA dehydratase or amino levulinic acid dehydratase, and ferrochelatase, and that's going to lead to a backing up or an increase of precursors in the pathway. And then lead also has other functions as well. It actually leads to the inhibition of glutathione. So, glutathione is important in acting to neutralize reactive oxygen species. So, lead will actually inhibit the process of glutathione usage, and it also inhibits the enzyme superoxide dismutase. Both of these effects lead to increased levels of reactive oxygen species or ROS. And this increased reactive oxygen species then can lead to cell membrane damage.
So, all of these effects lead to a variety of signs and symptoms. So, some of these are going to include hematological findings, gastrointestinal findings, neurological findings, and renal findings or effects on the kidneys. So, we're going to talk about all of these in the next upcoming slides.
Let's first talk about hematological effects. So, the hematological effect that's going to occur from lead poisoning is anemia because we talked about those enzymes that are inhibited in the heme synthesis pathway. This is going to lead to anemia or a low hemoglobin level in the blood, low red blood cell level. And again, that is from lead inhibiting two of those enzymes, ALA dehydratase and ferrochelatase. It's going to lead to a microcytic anemia, a microcytic anemia meaning that the MCV or the mean corpuscular volume is less than 80. This essentially means that the average size of a red blood cell is small. So, it's a microcytic anemia. And that microcytic anemia is going to have particular characteristics. There are going to be certain characteristics that are found in the cells, and this includes basophilic stippling. Basophilic stippling is where there are these little granules that are found in the cells. And another important feature of this microcytic anemia is that there are oftentimes going to be normal iron studies. The reason I bring this up is because iron deficiency anemia is also another cause of microcytic anemia. So, microcytic anemia is not only found in lead poisoning but can also be found in iron deficiency anemia. But because this is a microcytic anemia that is not caused by iron deficiency, there are going to be normal iron studies. There is going to be normal levels of iron. This is going to be caused by the lead itself. And this microcytic anemia is going to lead to signs and symptoms of anemia, including fatigue, weakness, shortness of breath, pallor, and dizziness as well.
Now, there are gastrointestinal effects that can occur from lead poisoning as well. These include abdominal pain, nausea, vomiting, and diarrhea. And in some cases, constipation. The constipation is something that's going to be found in children. So, abdominal pain, nausea, vomiting, and diarrhea are more likely to be found in lead poisoning.
And then there are particular neurological effects as well. These include irritability and being more aggressive than usual, decreased concentration, encephalopathy, so an altered mental status, so confusion. This is also termed lead encephalopathy. And wrist drop can also occur. This is a neuropathy of the radial nerve, so this is radial neuropathy. So, lead poisoning or lead toxicity can cause certain neuropathies, and one of them can lead to wrist drop. So, the patient will not be able to raise the wrist.
There are other neurological features I want to discuss here that occur in children. These include changes in activity level. So, if there's a very young child that their activity levels begin to change, either an increase in their activity levels, hyperactivity, or decrease in their activity levels, this can be a sign of lead poisoning. Behavioral changes in general, developmental delay. This is going to be very important if there's some issue in development. So, in very young children, following the developmental stages is going to be very important. And if there is developmental delay along with some other findings we talked about before, this may be a sign of lead exposure or lead poisoning. And one other one as part of this is delayed language ability. So, this is also going to play a role in this as well. And then school difficulties. If there are school difficulties, this can also tie in with the developmental delay.
So, in summary, the neurological effects are oftentimes going to be separated by the central nervous system, which is going to be the brain and the spinal cord. This is going to be more likely to occur in children. So, the central nervous system, brain, and spinal cord is more likely to be affected by lead exposure in children. So, a lot of those irritability, changes in activity level, behavioral changes, and developmental delay, it's all going to be more found in children. Whereas the effects on the peripheral nervous system, like the wrist drop that we talked about before, that neuropathy is more likely to occur in adults.
And serum lead levels are associated with changes in levels of aggression and IQ. So, where there have been findings of average serum lead levels in different societies, different communities, and different areas, if there is high serum lead levels, this is associated with levels of aggression. So, if there's on average higher serum lead levels, there's often going to be an associated increase in aggression levels. And there's going to be an inverse relationship with IQ. So, as the average serum lead level increases, there's often times going to be a decrease in IQ levels. So, that's also interesting to make note of as well.
Now, there are other findings that are important to make note of as well. These are called lead lines. So, it's going to be easy to remember these. Include lead lines in the gingiva of the mouth, so the gums. And these lines in particular are going to be called Burton lines or Burton's lines. So, Burton lines or Burton's lines are going to be these black bluish lines that are visible on the underside of the tooth on each tooth. So, you can see here these blackish blue lines under the teeth. Those are Burton lines. That's a sign of lead poisoning. And then we can also see the lead lines on the epiphyses of long bones as well. So, here is an image showing lead lines as well. So, these are also some findings to make note of.
And then we talked about the kidneys being affected by lead. In lead exposure, this is going to lead to renal impairment or impairment of kidney functioning. So, this can lead to decreased urine output, but overall can lead to something called Fanconi's syndrome. This is going to be due to a tubular defect in the nephron of the kidney. This is going to lead to phosphaturia, so urine excretion of phosphate, glucosuria, excreting glucose in the urine or abnormally high level of glucose in the urine, or aminoaciduria, having amino acids in your urine. So, phosphate in your urine, glucose in your urine, and amino acids in your urine. These are all due to tubular defects in the nephron. And these are all findings in Fanconi's syndrome. And then we can also see chronic lead nephropathy occurring in patients as well.
There are some findings that lead poisoning can lead to cardiovascular impairment as well. So, there can be findings of hypertension. This can be related to renal impairment, but there may be a renal independent mechanism. And then there is also an increased risk or a possible increased risk of cardiovascular disease and stroke in patients who have been exposed to lead as well.
And then there are certain reproductive issues in patients who are exposed to lead. And these include reduced libido, abnormal spermatogenesis, and infertility in males, and an increased risk of miscarriage and stillbirth in females. So, acute and chronic exposure to lead can lead to some of these reproductive issues.
Now, there's a particular way of remembering the clinical findings of lead poisoning, and that is by the mnemonic LEAD or L-E-A-D. So, L is going to stand for lead lines on the gingiva and long bone epiphyses. So, L for lead lines. E is going to be for encephalopathy and erythrocyte basophilic stippling. So, we talked about that particular cellular finding. A is going to be for abdominal pain or colic and anemia. And again, this is going to be a microcytic anemia. And D is going to be for drops. So, this is from that neuropathy we talked about before, wrist drops, but also foot drops can occur as well.
So, the diagnosis is oftentimes going to be by measuring a whole blood lead level. Anything above 5 micrograms per deciliter is going to be considered a positive finding. But really, any exposure to lead again is going to be problematic. But when there starts to be some significance, it's going to be past 5 micrograms per deciliter. And then if there's a finding of 10 to 20 micrograms per deciliter, this is going to require immediate removal of the source of lead and retesting.
Now, another way of looking at the effects of lead is going to be by looking at free erythrocyte protoporphyrin levels or FEP. This is going to indicate the effect on heme synthesis. And then we can also see findings of lead poisoning from a CBC or complete blood count when we see microcytic anemia, again, a low hemoglobin level with an MCV less than 80, normal iron studies. So, it's important to look at iron studies as well. And a key finding with lead poisoning with microcytic anemia is going to be that basophilic stippling we talked about before. And as I mentioned, it's important to look at iron studies. So, ferritin levels are going to be important to look at as well.
Imaging can be important in some cases. So, long bone lead lines. If that's found, that's going to be important. In some cases, there may even be radio-opacities of the abdomen. So, there can be findings if there is ingestion of lead can be found in the abdomen. That's going to be an important finding as well.
In some cases, when a clinician has diagnosed lead poisoning, how do they treat it? So, again, it's important to identify the lead source and remove the source. And a lot of times, the treatment is going to depend on the lead level. So, if it is a lower blood lead level, if it is a lead level near 5 micrograms per deciliter, for instance, it's important to still monitor for potential health problems. This may not cause any overt problem at the time, but it's important to reassess that patient as the lead level begins to increase more and more.
Chelation therapy is going to be very important, especially if a lead level has been found greater than 45 micrograms per deciliter, and especially in the case where there is greater than 70 micrograms per deciliter. Chelation therapy is going to be the mainstay of treatment. Chelation therapy can be undertaken by giving the patient DMSA, EDTA, or dimercaprol. In some cases, a gastric lavage and a whole bowel irrigation may be important. So, these can be important to help reduce the absorption of ingested lead. Succimer and penicillamine can also be important as well. So, again, a lot of times it's going to be related to the lead level. Oftentimes, again, it's going to be looking for the source of lead and removing the source, removing the individual from the source if possible. And then if it becomes very, very high, if a lead level is measured to be significant, again, some of these levels we talked about before, greater than 45 micrograms per deciliter, chelation therapy is going to be important.
Now, there are certain dietary factors that can contribute to lead poisoning findings or issues from lead poisoning. Some of these are going to include a vitamin C deficiency and iron deficiency. So, it's important to actually get enough vitamin C and enough iron. Calcium is also going to be important as well. And vitamin D supplementation is also important. This is going to help reduce some of that effect on the long bones that we see with patients who are exposed to lead for long periods of time.
If you want to learn more about other hematological conditions, please check out my hematology playlist. And if you haven't already, please like, subscribe for more lessons like this one. Thank you so much for watching and hope to see you next time.