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Pernicious Anemia (B12 Deficiency)

Background

1.Definition

o Anemia due to lack of intrinsic factor in gastric secretions, which leads to

impaired vitamin B12 absorption

2.General informationo Intrinsic factor binds B12 absorption of B12 in intestine

B12 cannot be absorbed unless bound to intrinsic factor

o ther causes of vitamin B12 deficienc! e"ist

Inade#uate dietar! intake, gastrectom!, abnormal intrinsic factor

function, bacterial overgrowth, ileal d!sfunction

o $ernicious anemia is classicall! defined as above

Pathophysiology

1.$atholog!

o Gastric parietal cells fail to make%secrete intrinsic factor

&hought to be due to an autoimmune disorder with geneticpredisposition

Associated with '(A A2, A), B*, and t!pe A blood

Antiparietal cell antibodies +- of pts./ as well as intrinsic0factor

antibodies +-0* of pts./ are present

Antibodies are postulated to lead to severe gastric atroph!

and achlorh!dria +lack of secretion of h!drochloric acid/

+Gastroenterolog! 1 3un45+5/416)6

2.Incidence%prevalence

o ccurs most fre#uentl! in individuals of 7uropean origin

1-02- cases per 1--,--- people per !ear

Incidence of subclinical pernicious anemia appears to behigher4 1. of surve! population had unrecogni8ed and

untreated pernicious anemia +Arch Intern 9ed 15 9a!

2*:15+1-/1-*.

;itamin B12 deficienc! affects about of people aged 50

*6 !ears and over 1- of people aged * !ears or older.

+Age Ageing 2--6: ))+1/4)6061.

o (ess common in other races

o 9ale to female ratio is 141

o nset usuall! 6-0*- !o

o isk factorso '(A0A2, A), B*

o &!pe A blood

o 7uropean descent

o Associated with

&h!roid disorders, t!pe 1 diabetes mellitus, ulcerative colitis

Addison?s disease, infertilit!, ac#uired agammaglobulinemia

6.9orbidit!%mortalit!

o $ts. on appropriate therap! have normal lifespan

$ernicious Anemia $age 1 of 11.)-.1-

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o @ntreated disease can lead to permanent neurological d!sfunction and

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Formal >B< folate

o ther studies

chilling test

9easures cobalamin absorption after an oral dose of

radioactive cobalamin

@seful in demonstrating that anemia is caused b! lack of

intrinsic factor and not due to other causes of cobalamin

deficienc!

7"pensive and not usuall! necessar! to make diagnosis

Bone0marrow biops! and aspiration

how h!percellularit! and megaloblastic changes

6.Diagnostic criteriao (ow vitamin B12 serum level

o 7levated serum meth!lmalonic acid and homoc!steine

o B< folate/

Iron0deficienc! anemia +iron studies/

Immune thromboc!topenic purpura +low platelets bone marrow b"/

Aplastic anemia

Bone0marrow failure

'emol!tic anemia%other megaloblastic anemias

9acroc!tosis

9!eloproliferative disease

$ernicious Anemia $age ) of 11.)-.1-

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Feutropenia

Disorder of plasma transport of cobalamin%&

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1.h >, Brown D(4 ;itamin B12 deficienc!.Am Fam Physician. 2--) 9ar 1: 5*+/4*05.

2.'offman >, Ben8 73 3r, hattil 34Hematology: Basic Principles and Practice. )rd

ed. Few Jork, FJ4 , >osenblatt D, atkins D4 @pdate on cobalamin, folate, and

homoc!steine.Hematology+Am oc 'ematol 7duc $rogram/. 2--)4 5201.

%#idence!&ased 'nuiries

1.'ow do we evaluate a marginall! low B12 levelK

Author *e#in Deighton+ ,D+ St. Joseph Mercy Livingston, MI

%ditor Da#id -akulchik+ ,D+Altman FM!P, "H

$ernicious Anemia $age of 11.)-.1-

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