A (t) We will give a
general answer, concerning healthy as well as HIV infected
persons. Then, we will indicate some features specific to
HIV infection and AIDS.
Megaloblastic anaemia is
an anaemia (blood hemoglobin level lower than 12g/100ml)
with a very high mean globular volume (MGV) (higher than
120µm3). Megaloblasts can be observed on the myelogram,
indicating an alteration of the DNA synthesis at the level
of the red blood cell precursor. The origin may be obvious :
folic acid deficiency (intake deficiency secundary to an
important denutrition), malabsorption (secundary to a
surgical resection of the small intestine, gastrectomy,
intestine stenosis, intestinal fistula, and over all by
intestine malabsorption, whatever the reason, which leads to
diarrhea), relative deficiency (multipara women), in case of
a chronic stimulation of the marrow, due to haemolytic or
refractory anaemia, use deficiency (alcoholism, antifolic
drugs).
In all these cases, folic
acid dosage allows to confirm the diagnostic and the test
treatment by folic acid is justified.
When the cause is not
obvious, a Biermer disease may be suspected. The
confirmation of this diagnostic is based on the existence of
a vitamin B12 deficiency by blood dosage (acid folic level
being normal in these case) and stomach anomalies (lack of
chlorhydric acidity, stomach atrophy visualised by
fibroscopy, lack of intrinsic factor (protein synthetised at
the stomach level allowing the absorption of vitamin B12) in
the gastric liquid, or Schilling test, revealing a drastic
decrease of vitamine B112 absorption with a possible
correction of the discorder by administration of intrinsic
factor, and to eventually demonstrate the presence of anti
intrinsic factor antibodies).
Apart from Biermer
disease, other causes should be investigated :
botriocephalic anaemia (over all in lake regions) in wich
vitamin B12 is consumned by the worm (as well as in the case
of an intestinal infection, particularly " anse borgne "
syndrome), unknown intestinal malabsorption (whithout
diarrhea and weight loss) often associated with a folic
acid, vitamin B12 and iron deficiency. There is another form
of rare megaloblastic anaemia, primitive and pre-leukemic
that should be considered when the blood levels of the two
vitamins are normal. There are also some rare genetic causes
responsible for vitamin B12 malabsorption among
children.
Concerning HIV infected
persons, vitamin B12 blood level is frequently very low when
T4 lymphocytes count is very low. Actually, some minors
intestinal vitamin B12 absorption disorders may exist at
early stages of the infection, due to the presence of HIV in
intestinal cells. At an early stage of HIV infection,
vitamin B12 deficiency is present for 24 to 36% of persons
living in occidental countries. When vitamin B12 level is
normalised by supplementation, an improvement of T4
lymphocytes count and cognitive functions is sometimes
noted. A more recent study showed that the risk of evolution
to AIDS is twice higher for persons with a low blood level
of vitamin B12 (this study is summed up on our internet
website <http://www.positifs.org/> C.22, chap. V paragraph 1). Another
study that we also summed up (C.22,
chapter V,
paragraph 4) showed that vitamin B12 and folic acid blood
levels are not influenced by oral supplementation, wich
could be explained by a decrease of the intestinal
absorption.
It has been also shown
that for persons wich almost normal T4 lymphocytes level,
low level of vitamin B12 is secundary to AZT treatment.
Concerning AZT, an isolated and often moderate macrocytosis
is frequently observed (without anaemia), signing a
moderated marrow toxicity. (9709)
