본태성 혈소판증가증. Essential thrombocythemia (ET)

다양한 혈액종양질환을 정리하고 있습니다.

 

오늘은 골수증식성 종양 (Myeloproiferative neoplasm, MPN) 중 

본태성 혈소판증가증 (Essential thrombocythemia, ET)에 대해 알아보겠습니다.

 

귀여운 라이언이 본태성 혈소판증가증, Essential thrombocythemia를 가리키고 있네요!

 

1. Definition

Essential thrombocythemia(ET) is a chronic MPN that primarily involves the megakaryocytic lineqge.

It is characterized by sustained thrombocytosis (platelet count ≥450 × 10^9/L) in the peripheral blood and increased numbers of large, mature megakaryocytes in the bone marrow.

ET 진단기준

 

Q) 본태성 혈소판증가증에서 골수 검사가 필요한 이유는 무엇일까?

혈소판(PLT) 수치 상승과 JAK2-related mutation만 증명되면 진단 내릴 수 있는 것 아닌가?

 

A) ET와 Prefibrotic/early PMF를 감별하기 위해서 골수 검사가 필요합니다!

두 질환에서 Megakaryocyte의 크기, 모양이 서로 다르고 fibrosis grade 또한 차이가 나죠.

더 자세한 설명은 아래 게시물을 참고하세요!

골수 검사(6) - 본태성 혈소판증가증. Essential Thrombocythemia

골수 검사(6) - 본태성 혈소판증가증. Essential Thrombocythemia

 

2. Localization

The blood and bone marrow are the principal sites of involvement. The spleen does not show significant extramedullary hematopoiesis, but is a sequestration site for platelets.

 

3. Clinical features

More than half of all cases are asymptomatic at the time of diagnosis, discovered incidentally when an elevated platelet count is found on a routine CBC.

The other half present with some manifestation of vasular occlusion or hemorrhage.

- TIA, transient ischemic attacks

- Digital ischemia with paresthesia or gangrene

- Splenic/Hepatic vein thrombosis

- Mucosal bleeding

 

4. Microscopy

Peripheral Blood

- Mared Thrombocytosis

- Platelets often display anisocytosis, ranging from tiny forms to atypical large/giant platelets.

- Leukoerythroblastosis and tear-drop cells are not seen in ET.

Bone marrow

- Normal cellularity, but a small proportion of cases showed hypercellular marrow

- Marked proliferation of megakaryocytes, with predominance of large to giant forms displaying abundant, mature cytoplasm and deeply lobed and hypersegmented (staghorn-like) nuclei.

- The network of reticulin fiber is usually normal, or is very rarely(<5%) minimally increased but never more than WHO grade 1.

- Emperipolesis of bone marrow elements is frequently observed in ET, but is not a specific finding.

 

5. Prognosis and Progression

ET is an indolent disorder characterized by long Sx-free intervals interrupted by occasional live-threatening thromboembolic or hemorrhagic events.

10% 가량의 ET 환자들은 수 년 후, fibrosis grade MF-2/3의 골수 섬유화가 진행되기도 한다. 이를 Post-ET myelofibrosis라고 한다. 그 진단 기준은 아래와 같다.

Post-ET myelofibrosis 진단기준

ET의 blast phase로의 transformation도 가능은 하나, 5% 미만으로 추정되고 대부분 cytotoxic therapy에 의한 therapy-related myeloid neoplasm (t-RMN)인 것으로 파악된다.

 

 

Ref)

The WHO Classification of Tumours of Haematopoietic and LymphoidTissues, IARC 2017