hey everyone this lesson is on vitamin b12 deficiency so in this lesson we're going to talk
about the signs and symptoms of vitamin b12 deficiency we're also going to talk
about why we get those particular signs and symptoms and we're also going to
talk about laboratory investigations to make the diagnosis and what we can do to
treat it so generally b12 is acquired from our diet and generally it's from
animal products so if we have a vitamin b12 deficiency either through reduced
dietary intake of vitamin b12 or through one of many different compromised
absorption processes either through use of certain medications certain disease
processes or autoimmune conditions or even having a fish tapeworm if you haven't
already please check out my lesson on causes of vitamin b12 deficiency the
vitamin b12 is so important because it's required for the production and health
of red blood cells and also the health of the central nervous system we're
going to talk about why that is and what happens when we don't have enough
vitamin b12 in our bodies vitamin b12 is required
for two specific and very important enzymes within our body and there's one
enzyme in particular I want to talk about in this lesson that I want you to
remember so generally when we ingest the amino acid methionine methionine gets
converted to methylmalonic acid methylmalonic away gets acted on by the
enzyme methylmalonyl CoA mutase and this is the enzyme that actually
requires vitamin b12 and what this enzyme does is it converts methyl
malonyl CoA to Succinyl CoA so without vitamin B12 anything before that it's gonna be
backed up and what happens is methyl malonyl CoA increases in
concentrations and when that happens it gets converted to methylmalonic acid now
methylmalonic acid is the problem here this methylmalonic acid will eventually
continue to increase in concentration and will lead to axonal neuropathy so it
starts to damage neurons and it does so in a specific part of the central
nervous system the dorsal column medial lemniscus system the DCMLS
so this is what I want you to really take away from this because we don't
have any vitamin b12 we're gonna have issues with using methylmalonyl CoA mutase
leading to backing up of methylmalonyl CoA increased concentrations of methylmalonic
acid which eventually leads to damage to neurons so it leads to axonal neuropathy
in the dorsal column medial lemniscus system so this leads into the clinical
presentation of b12 deficiency you get irreversible neurological
symptoms from prolonged b12 deficiency because of the axonal neuropathy so again
axonal neuropathy within the dorsal column medial lemniscus system DC MLS
you're going to get damage to those neurons those neurons are not going to come back
they're not going to be repaired so what you're going to get is you're gonna have
issues with two-point discrimination, proprioception, vibratory sense and you're
going to have symmetric paresthesias and a shuffling gait they feel unsteady on
their feet they're not able to walk well because they just don't have that
proprioception so if b12 deficiency lasts and is
prolonged it can lead to irreversible symptoms such as these there are also
some possibly reversible neurologic and psychiatric symptoms including depression,
irritability, insomnia, forgetfulness all of these things can be things where if
someone comes in with some psychiatric symptoms just out of the blue sometimes
it's a good practice to actually check a b12 level just to see you know maybe
they're just low in b12 and some of these symptoms could just be caused by
the b12 deficiency b12 deficiency also leads to a megaloblastic macrocytic
anemia so what does that mean if you haven't already checked out my anemia
lesson please check out that lesson for a good overview of anemia but macrocytic
anemia means that the MCV of a red blood cell is generally greater than 100 and
megaloblastic means that there's impaired DNA synthesis and specifically
that when you look at neutrophils or white blood cells they
are hyper segmented and there's about five or more lobes in the neutrophils so
you can see in this image here we're seeing more than five of these lobes so
it's hyper segmented it is megaloblastic and you're also going to get symptoms of anemia so
there's many symptoms of anemia it could be shortness of breath, pallor, fatigue all
those types of signs and symptoms of anemia are important to look out for as
well so how do we make the diagnosis and how do we treat b12 deficiency? The
diagnosis of b12 includes looking at a b12 level so we're gonna see low b12
level that's pretty easy but we can also look at methylmalonic acid levels and
again we're going to see elevated levels of methylmalonic acid now this may come up and
I just want to quickly touch on this but sometimes you may come across
homocysteine now homocysteine can be elevated in b12 deficiency but it's also
elevated in folate deficiency so it's not a good marker to look at when making
the diagnosis. Methylmalonic acid is the one you always want to check even when
you're thinking of a folate deficiency so again methylmalonic acid is going to be
elevated in b12 deficiency and actually normal in folate deficiency and we can
also use the Schillings test you're not gonna use the Schillings test but it's
something that's good to know about. In the Schillings test there's a few steps the
first one is you're going to give an IM injection of b12 so you're going to
saturate the b12 within someone's body you're going to give oral b12 and then
you're gonna check their urine and if their urine is positive for b12 the
original problem was nutritional so if you think about it the first thing was
an injection of b12 it saturates all the b12 it in their body if we give oral b12
they're just gonna pee it out so if it's if they're absorbing it well through the
oral route they're going to just pedo because they're just already saturated
in b12 so that's where you're gonna get you're gonna find that if you see it in
the urine it wasn't a nutritional problem but if you don't see it in the
urine it was impaired absorption so again if b12 already been saturated
through that I am injection you give oral b12 and you're not seeing them pee
it out well that leads you to believe that they didn't actually absorb that
oral b12 that you just gave them so that is the basis of the Schillings test so
it's just something to know about generally not going to do it in
treatment of b12 deficiency depends on whether it was due to impaired
absorption or nutritional deficiency if it's impaired absorption you're gonna
probably give it by I am injection of b12 if it was a nutritional deficiency
you may just be able to get away with just giving them oral b12 supplements so
he can kind of distinguish that from the history and if it's on a test maybe the
Schillings test and I just want to quickly talk about some dietary options
we talked about b12 coming from animal products but two specific foods with
extremely high levels of b12 are clams in liver and it makes sense right liver
is the place where item b12 is stored within our body so it's gonna be it's
gonna have high levels of b12 so these are the two main foods that have
extremely high levels of vitamin b12 and other animal products also have vitamin
b12 as well but I just wanted to quickly mention them so if you haven't already
please check out my vitamin b12 lesson on metabolism and absorption because it
gives some more detail some more information on the process in general
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