Page 531 - Clinical Hematology_ Theory _ Procedures ( PDFDrive )

CHAPTER 26 ■ Disorders of Primary Hemostasis and Thrombosis Vasculature and Platelets 515

Ly ho as or euke ias that arise ro B y hocytes are

the ost co on. Non-Ho gkin’s y ho a aking u

the ajority o cases.

Laboratory Findings

A e nitive iagnosis o WAS can be a e by sequencing

o the WAS gene to i enti y a utation an by stu ying the

atient’s b oo ce s to eter ine i the WAS rotein is

ex resse at nor a eve s. T ese tests are one in s ecia -

ize aboratories an require b oo or other tissue.

MYH9-Related Thrombocytopenia

Syndromes (May-Hegglin Anomaly)

MYH9-re ate isor er inc u es autoso a o inant ac- FIGURE 26.9 May-Hegg in ano a y shows arge ate ets an

rothro bocyto enia syn ro es revious y c assi e as ro inent Döh e bo ies in the cyto as . (Fro McC atchey KD.
Clinical Laboratory Medicine, 2n e , Phi a e hia, PA: Li incott
May-Hegg in ano a y; Sebastian, Fechtner, an E stein syn- Wi ia s & Wi kins, 2002.)

ro es; an so e inherite thro bocyto enias that have

the co on utations within MYH9, a ate et cytoske eta

contracti e rotein. T e biggest risk or a atient is ina ro- ate et unction stu ies o not show ajor e ects in MYH9

riate treat ent because o a is iagnosis o chronic auto- isor ers. Because o the a tere co osition o the ate et

i une thro bocyto enia. cytoske eton, the sha e change in the aggregation curve is
ty ica y absent, but the absence o sha e in an aggregation

Pathophysiology curve can a so be seen in other ate et isor ers.

Here itary acrothro bocyto enias are o en autoso a A bone arrow exa ination is not require or iagnosing

o inant, a though so e have an X- inke or recessive inher- MYH9 isor ers. I er or e , the arrow NMM-IIA in neu-
itance. Severa utations in the MYH9 gene ea to re ature tro hi s staine with an anti–NMM-IIA onoc ona antibo y

re ease o ate ets ro the bone arrow, acrothro bocy- (i unof uorescence) or May-Grünwa -Gie sa stain.
to enia, an cyto as ic inc usion bo ies within eukocytes. A iagnostic worku o MYH9 isor ers shou a so

Te MYH9 gene enco ing NMMHC-IIA consists o 40 inc u e exc usion o iron e ciency ane ia an o htha o-
exons an is ocate on chro oso e 22q12–13.50. U to ogic screening or cataracts an rena unction assess ent

now, 31 utations in 11 i erent exons have been escribe . (creatinine c earance an roteinuria).

Clinical Signs and Sym ptom s Types of Thrombocytosis

A though a roxi ate y 50% o atients o not have sy - Thrombocytosis is genera y e ne as a substantia increase in

to s; others have ani este abnor a b ee ing ten encies. circu ating ate ets over the nor a u er i it o 450 × 10 /L.
9
Te b ee ing ten ency is usua y o erate, with enorrha- T ro bocytosis can be c assi e into the ajor categories o

gia an easy bruising being ost requent.

T e cause o the he ostatic e ect is unc ear, but it is ro- 1. Pri ary thro bocytosis

ortionate to the egree o thro bocyto enia. 2. Reactive (secon ary thro bocytosis)

Laboratory Findings Prim ary Throm bocytosis

Macrothro bocyto enia is resent (Fig. 26.9). Abnor a y Essentia thro bocytosis (E ) is a c ona neo as char-

arge an oor y granu ate ate ets an thro bocyto enia acterize by a signi cant y e evate concentration o circu-

coexist in this con ition. It is a so characterize by the res- ating ate ets. Pri ary thro bocytosis can be here itary

ence o Döh e bo y– ike inc usions in neutro hi s, eosino- (rare) or acquire . E is associate with ye o ro i erative

hi s, an onocytes. neo as s (MPN) (see iscussion be ow an in Cha ter 23)

An MYH9-re ate acrothro bocyto enia shou be an in ye o ys astic syn ro es (MDSs) (Cha ter 24)

sus ecte in in ivi ua s who have arge ate ets, a high Pri ary thro bocytosis: thro bocytosis cause by

MPV, a broa ate et histogra , an a eak rece ing the an a teration in he ato oietic ce s; the seru eve o

eukocyte histogra . Chronic autoi une thro bocyto e- thro bo oietin ( o), the ain cytokine res onsib e or the

nia (chronic I P) is the ost i ortant con ition to istin- ro uction o ate ets, is ow or nor a .

guish ro MYH9 isor ers, eva uate ate et size using the

b oo , ate et size histogra , an (ca cu ate ) MPV. In Hereditary or Fam ilial Throm bocytosis

I P, usua y ess than 10% o ate ets are “giant” ate ets. Fa i ia thro bocytosis is a ty e o essentia thro bocythe-

T e current “go stan ar ” or e onstrating MYH9 ia (E ) with a sustaine e evation o circu ating ate ets.

eukocyte inc usion bo ies is the etection, by i unos- Tis con ition can create a risk or thro bosis an he or-

taining, o NMM-IIa c usters. P ate et aggrego etry an rhage but oes not cause ye o ro i eration.