Hypochromic microcytic anemias
Hypochromic microcytic anemias, characterized by the
presence in the circulating blood of red cells that
are smaller than normal and poorly filled with hemoglobin,
fall into two main categories. The first is that due
to deficiency of iron, and the second is that due to
impaired production of hemoglobin (the globin); in either
case there is an inadequate amount of the final product
in the red cell.
Deficiency of iron is probably the most common cause
of anemia throughout the world. Iron isrequired for
hemoglobin formation; if the supply is insufficient
to produce normal quantities of hemoglobin, the bone
marrow ultimately is forced to produce cells that are
smaller than normal and poorly filled with hemoglobin.
Iron is derived from the diet and absorbed in the intestinal
tract. Once in the body, it is retained and used over
and over again, only minimal amounts being lost through
shedding of cells from the skin and the exposed membranes
and through normal menstruation. In the adult the body
content is approximately 3.7 grams of iron, of which
more than half is hemoglobin. In the male there is virtually
no further need for iron. Deficiency results if the
dietary supplies of iron are insufficient to meet the
needs; if absorption is faulty, as in malabsorption
disorders; or if blood loss is occurring. Common causes
of iron deficiency are excessive menstrual loss in women
and bleeding peptic ulcer inmen. Iron deficiency is
common in infancy and childhood because demands are
great for the ever-expanding pool of circulating hemoglobin
in the growing body and in pregnancy when the fetus
must be supplied with iron. Hookworm infestation is
a common cause of iron deficiency where conditions for
the worm are favourable, because the intestinal blood
loss caused by the myriad of worms attached to the wall
is great.
Victims of iron-deficiency anemia are pale but not
jaundiced. The deficiency of iron-containing enzymes
in the tissues, if sufficiently great, results in a
smooth tongue; brittle, flattened fingernails; and lustreless
hair. Under the name of chlorosis, this type of anemia
was mentioned in popular literature and depicted in
paintings, especially those of theDutch masters, until
the 20th century. Although it is not necessarily less
common now, there is no doubt that it is less severe
in Europe and North America than it once was. The only
treatment required is oral administration of iron salts
in some palatable form, such as ferroussulfate.
Small red cells poorly filled with hemoglobin are characteristic
of a hereditary disorder of hemoglobin formation, thalassemia,
that is common among people of Mediterranean stock and
is discussed below. With the exception of iron deficiency
and thalassemia, hypochromic microcytic anemia is rare.
It is seen in anemia responsive to the vitamin pyridoxine,
where the anemia probably results from a metabolic fault
in the synthesis of the heme portion of hemoglobin.
Sideroblastic anemia, characterized by the presence
in the bone marrow of nucleated red cells, the nucleus
of which is surrounded by a ring of iron granules (“ringed
sideroblasts”) and by a proportion of small, pale red
cells in the blood, is of unknown cause and difficult
to treat.
