Macrocytic anemia

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Macrocytic anemia
Megaloblastic anemia blood smear
ICD-10 D51.1, D52.0, D53.1
ICD-9 281
DiseasesDB 29507
MeSH D000749

Macrocytic anemia Microchapters

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor-In-Chief: Cafer Zorkun, M.D., Ph.D. [2]

Overview

Historical Perspective

Classification

Pathophysiology

Causes

Differentiating Macrocytic anemia from other Diseases

Epidemiology and Demographics

Risk Factors

Screening

Natural History, Complications and Prognosis

Diagnosis

History and Symptoms

Physical Examination

Laboratory Findings

Electrocardiogram

Chest X Ray

CT

MRI

Echocardiography or Ultrasound

Other Imaging Findings

Other Diagnostic Studies

Treatment

Medical Therapy

Surgery

Primary Prevention

Secondary Prevention

Cost-Effectiveness of Therapy

Future or Investigational Therapies

Case Studies

Case #1

Hematological findings

MCV is often >110. Hct can often be as low as 15. Elevated LDH and bilirubin are seen since dyserythopoesis leads to destruction of >90% of RBC precursors. Hypersegmentation of PMNs is quite sensitive (>5% with 5 or more lobes or >1% with 6 lobes). Reticulocyte, WBC and platelets are low to normal. In one series of patients with B12 deficiency, 64% had a MCV greater than 100, and only 29% had anemia. In general the blood film can point towards vitamin deficiency:

Blood chemistries will also show:

  • Increased homocysteine and methylmalonic acid in B12 deficiency
  • Increased homocysteine in folate defiency

Analysis

The Schilling test was performed in the past to determine the nature of the vitamin B12 deficiency, but due to the lack of available radioactive B12, it is now largely a historical artifact. Vitamin BTemplate:Ssub is a necessary prosthetic group to the enzyme methylmalonyl-coenzyme A mutase. BTemplate:Ssub deficiency leads to dysfunction of this enzyme and a buildup of its substrate, methylmalonic acid, the elevated level of which can be detected in the urine and blood. Since the level of methylmalonic acid is not elevated in folic acid deficiency, this test provides a one tool in differentiating the two. However, since the test for elevated methylmalonic acid is not specific enough, the gold standard for the diagnosis of B12 deficiency is a low blood level of B12. Unlike the Shilling test, which often included B12 with intrinsic factor, a low level of blood B12 gives no indication as to the etiology of the low B12, which may result from a number of mechanisms.

Treatment

  • Folate is administered 1mg QD. Higher doses may be required in malabsorptive syndromes. It is empirically given to those with SCD and those on HD.
  • B12 must be given as a load then maintenance. Most advocate 1000 mcg IM Qweek x4 then 100mcg/month.
  • LDH falls in 2 days. Hypokalemia requiring replacement can occur in the acute phase as new cells are being generated rapidly.
  • A reticulocytosis begins in 3-5 days and peaks in 10 days. The HCT will rise within 10days. If it does not, suspect another disorder. Hypersegmented PMNs disappear in 10-14 days.
  • Neurologic abnormalities may take up to 6 months to resolve if ever. The longer the disease has been present, the worse is the prognosis for recovery.
  • Persons with PA have a 2x risk of gastric CA (in some studies). Screen for occult blood.

el:Μακροκυτταρική αναιμία sq:Anemi makrocitike

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References

gl:Anemia megaloblástica he:אנמיה מגלובלסטית it:Anemia megaloblastica sl:Megaloblastna anemija sr:Мегалобластна анемија


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