Hematology 101
Start iron supplementation at 4-6 months for full-term infants and at 2 months for preterm
infants. Iron supplements also are commonly given during pregnancy and lactation (because of
the increased demand).
13. What are the classic laboratory abnormalities in iron deficiency anemia? What weird
cravings may occur with iron deficiency?
Look for low iron and low ferritin levels, elevated total iron-binding capacity (TIBC; also
known as transferrin), and low TIBC saturation. Rare patients may develop a craving for ice or
dirt (pica).
14. What is Plummer-Vinson syndrome?
A triad of unknown etiology: esophageal web resulting in dysphagia; iron deficiency anemia;
and glossitis.
15. How is iron deficiency treated?
First you must determine the cause. In a menstruating woman, a presumptive diagnosis of
menstrual blood loss is often made. In patients over 40, be sure to test the stool for occult blood
and strongly consider colonoscopy to detect occult colon cancer. Postmenopausal vaginal bleed-
ing may also cause anemia and warrants screening for gynecologic cancer. Treat with iron sup-
plements for 3-6 months in uncomplicated cases to replete body iron stores.
16. What causes folate deficiency? In what patient populations is it commonly seen?
Folate deficiency is commonly seen in alcoholics (poor intake) and pregnant women
(increased need). All women of reproductive age should take folate supplements to prevent neural
tube defects in their offspring. Rare causes of folate deficiency include poor diet (e.g., tea and
toast), methotrexate, prolonged therapy with trimethoprim-sulfamethoxazole, anticonvulsant
therapy (especially phenytoin), and malabsorption. Look for macrocytes and hypersegmented
neutrophils (either one should make you think of the diagnosis) with no neurologic symptoms
or signs and low folate levels in serum or red blood cells. Treat with oral folate,
17. What is the most common cause of vitamin B 12 deficiency?
Pernicious anemia. This megaloblastic anemia is caused by antiparietal cell antibodies.
Remember the physiology of B, 2 absorption with intrinsic factor secretion by parietal cells and
absorption of the B 12—intrinsic factor complex in the ileum. Achlorhydria (no stomach acid
secretion and elevated stomach pH) and antibodies to parietal cells are generally present in per-
nicious anemia.
18. What else may cause vitamin B, 2 deficiency? How is B,2 deficiency diagnosed?
Gastrectomy, terminal ileum resection or disease (e.g., Crohn's disease), strict vegan diet,
chronic pancreatitis, and the infamous Diphyilobothrium latum (fish tapeworm) infection. The
peripheral smear looks the same as in folate deficiency (macrocytes, hypersegmented neu-
trophils), but patients have neurologic deficiencies (e.g., loss of sensation and position sense,
paresthesias, ataxia, spasticity, hyperreflexia, positive Babinski sign, dementia). Diagnosis is
clinched by a low serum B, 2 level. A Schilling test usually determines the etiology.
19. How is vitamin B 12 deficiency treated?
Vitamin B 12 supplements are given. The usual replacement is via parenteral (intramuscular)
injection, because most patients cannot absorb the vitamin through the gut. Supplementation may
be required for life.
20. How is thalassemia differentiated from iron deficiency?
Both cause microcytic, hypochromic anemia, but thalassemia must be differentiated from
iron deficiency because iron levels are normal in thalassemia. Iron supplementation is con-
traindicated in patients with thalassemia because it may cause iron overload. Look for elevations
