Page 584 - Clinical Hematology_ Theory _ Procedures ( PDFDrive )

568 PART 7 ■ Principles and Disorders of Hemostasis and Thrombosis

T e ajority o these inhibitors exhibit bioche ica ro - wo en have been re orte to eve o actor VIII inhibitors

erties, suggesting that they are i unog obu ins. Inhibitors uring the ost artu erio , ost requent y a er the

ay arise o owing trans usion o b oo ro ucts or in birth o their rst chi . Patients with un er ying i u-

atients with no revious he ostatic isor ers. Acquire no ogica isor ers such as rheu atoi arthritis, syste ic

inhibitors can be a signi cant cause o he orrhage. u us erythe atosus, rug a ergies, u cerative co itis, an

S eci c inhibitors against actors II, V, VII, VIII, IX, XII, bronchia asth a a so have an increase ten ency to eve o

XIII, an vWF have been etecte in atients with in ivi - actor VIII inhibitors. Many atients have been observe to

ua actor e ciencies. However, so e inhibitors o actors eve o actor VIII inhibitors with no un er ying isease.

II, V, VII, IX, XII, an vWF have been observe in atients T e ajority o these atients are i e age or o er, an

having no e ciencies o coagu ation actors. Patients with both gen ers are a ecte .

acquire s eci c inhibitors ay exhibit he orrhagic e i- Inhibitors against vWF occur in atients with von

so es, whereas nons eci c inhibitors are not genera y asso- Wi ebran ’s isease an un er ying iseases such as a ig-

ciate with b ee ing ten encies. nancy or syste ic u us erythe atosus an in revious y

So e inhibitors wi e onstrate a e aye -ty e inhibitor hea thy ersons. A a i ia ten ency or the eve o ent o

attern, with ti e an /or te erature e en ence. In cases vWF inhibitors has been note .

with a e aye -ty e inhibitor, the activate artia thro -

bo astic ti e (AP ) i e iate ixing stu y wi correct Factor IX Inhibitor

to within the re erence range, but the incubate AP ix- Inhibitors are oun in a roxi ate y 2% to 3% o actor IX–

ing stu y wi be ro onge . A though rare, the resence o e cient (he o hi ia B) atients, but the inci ence o inhibi-

a actor inhibitor, such as a actor VIII inhibitor, wi increase tors in severe he o hi ia B ay be as high as 12%. A though

the risk o i e-threatening b ee ing. T e resence o a ac- these inhibitors are re o inant y a resu t o trans usion o

tor inhibitor can be con r e by a Bethes a assay or that b oo ro ucts, s ontaneous inhibitor or ation has been

actor. re orte .

T e resence o u us anticoagu ants, antibo ies against

rotein- hos ho i i co exes, increases the risk o Factor V Inhibitor

thro boe bo is . I the c inica history suggests an LA, Factor V inhibitors are rare an are not genera y associate

urther testing inc u es hos ho i i -base screening tests, with here itary actor V e ciency. So e atients have ha

hos ho i i e en ency assays, an exc usion o the res- ex osure to stre to ycin but no causa re ationshi has been

ence o inhibitors, an in a ition, an incubate activate estab ishe .

artia thro bo astic ti e (AP ), is necessary.
Fibrinogen, Fibrin, and Factor XIII Inhibitors

Etiology Inhibitors o brinogen, brin, an actor XIII have been

T e inci ence o circu ating anticoagu ants has been bench- re orte . T ese inhibitors have occurre o owing as a

arke at 0.75% o the genera o u ation, but certain trans usions or a eare s ontaneous y. So e atients have

atient o u ations have a higher inci ence o inhibitor a co on eno inator o taking isoniazi , an antitubercu-

eve o ent. Inhibitors, oun in both seru an as a, osis rug.

are not inactivate by heating at 56°C or 30 inutes an

re ain stab e when store at −20°C. Inhibitors are ore Factor II, VII, IX, and X Inhibitors

stab e than c otting actors an ore to erant o changes in Factor II, VII, IX, an X inhibitors are rare. T e causes or

H an te erature. Inhibitors ay re ain in the circu a- actor inhibitor eve o ent are varie an inc u e congeni-

tion or onths an in so e instances have been oun in ta e ciencies, i une isor ers, an a y oi osis.

atient’s years a er eve o ent.
Factor XI and XII Inhibitors

Speci c Inhibitors Inhibitors o actors XI an XII have been re orte in re-

S eci c inhibitors irect y against s eci c actors such as quent y in atients with SLE, Wa enstro acrog obu in-

actor VIII or actor V inhibitors. e ia, an other isor ers, as we as with ch or ro azine

a inistration.
Factor VIII Inhibitor

Factor VIII inhibitors are the ost co on s eci c ac- Nonspeci c Inhibitors

tor inhibitors. Inhibitors o actor VIII eve o in 10% to Nons eci c inhibitors inc u e inhibitors such as u us anti-

15% o atients with actor VIII e ciency (he o hi ia A), coagu ant an anticar io i in antibo ies.

an the ajority occur in atients with severe he o hi ia

(those having ess than 1% actor VIII activity). Inhibitors Antiphospholipid Antibodies (Lupus Anticoagulant

have eve o e in atients ex ose to actor VIII a er as ew and Anticardiolipin Antibodies)

as 10-ex osure ays but ay eve o a er severa hun re Te lupus anticoagulant (LA) occurs in a roxi ate y 30% to

ays. A roxi ate y 65% o atients with he o hi ia who 40% o atients with SLE. LA is the ost co on coagu a-

eve o inhibitors o so be ore the age o 20. Nonhe o hi iac tion inhibitor oun in SLE atients, a though these atients