Page 521 - Clinical Hematology_ Theory _ Procedures ( PDFDrive )

CHAPTER 26 ■ Disorders of Primary Hemostasis and Thrombosis Vasculature and Platelets 505

FIGURE 26.1 Petechiae. (Fro Weber JR, Ke ey JH. Health

Assessment in Nursing, 5th e , Phi a e hia, PA: Li incott Wi ia s FIGURE 26.3 Here itary he orrhagic te angiectasia. A c uster o

& Wi kins, 2013.) s a i ate vesse s is resent in the he atic arenchy a. (Biopsy
Interpretation o the Liver. Phi a e hia, PA: Li incott Wi ia s &

Wi kins, 2014.)
are evi ent, it is ca e petechiae (Fig. 26.1); i the atches

o b ee ing into the tissues are arger, this is re erre to as

ecchymosis (Fig. 26.2). Blood Vessel Malformations

Pur ura can be ro uce by nu erous ty es o vascu ar

con itions. T ese abnor a ities inc u e echanica orce, Hereditary Hem orrhagic Telangiectasia (HHT)

genetic structura a or ation, inf a ation an obstruc- Here itary he orrhagic te angiectasia (HH ), a so known

tion o b oo vesse s, isor ers o erivascu ar tissue, an as Os er-Weber-Ren u isease or Os er-Weber-Ren u

isce aneous causes such as in ection, skin iseases, an syn ro e, is cause by genetic utations. Mutations

sychogenic reasons. in b oo vesse eve o ent can resu t in a variety o

a or ations.

Mechanical Force An in ivi ua with HH , an autoso a o inant trait,

has a re uce a ount o unctiona rotein avai ab e in the
Mechanica orce is a requent cause o ur ura. It has to tissue ining the b oo vesse s. T e ack o avai abi ity o

have a ini u o intensity in or er to a age the wa unctiona rotein is the resu t o au ty ro uction o associ-

o the b oo vesse . Externa ressure such as b unt trau a ate rotein or ro uction o a e ective rotein that cannot

resu ts in bruising when the orce is su cient to isru t u its unction.

vascu ar integrity an a ows eakage o RBCs into the skin. Tis unctiona rotein e ciency is be ieve to resu t

Minor trau a ex erience by anticoagu ate atients or vig- in the characteristic esions (Fig. 26.3), invo ving skin an

orous scratching can cause echanica ur ura. T e size o ucous e brane–associate e istaxis an other b ee -

the resu ting a age e en s in art on the vascu arity o ing co ications. B ee ing rob e s occur ro ru ture

the region an the ensity o the surroun ing tissue. or eakage o vascu ar a or ations. T e c inica signs

an sy to s e en on the ocation o the ru ture or

b ee ing.

Te ENG, ACVRL1, an SMAD4 genes rovi e instruc-

tions or aking roteins that are oun in the ining o the

b oo vesse s. T ese roteins interact with growth actors

that contro b oo vesse eve o ent. T ere are three ty es

o HH : ty e 1, ty e 2, an ty e 3.

■ y e 1 is cause by utations in the gene ENG.

■ y e 2 is cause by utations in the gene ACVRL1.

■ y e 3 is cause by an unknown utation.

Juveni e o y osis/HH syn ro e is cause by uta-

tions in the gene SMAD4.

FIGURE 26.2 Se ecte cutaneous ani estations o syste atic is-

eases. Ecchy osis (bruise). (Fro S e tzer SC, Bare BG. extbook Other Vasculopathies
o Medical-Surgical Nursing, 9th e , Phi a e hia, PA: Li incott Patients with u ti e ye o a or syste ic a y oi osis can

Wi ia s & Wi kins, 2000.) have ight chain i unog obu in e osits in the cutaneous