Thrombocytopenia general Flashcards
Mechanisms of low platelets
Decreaxed production - bone marrow problem
Increased destruction or increased consumption - used faster than produced
Over-storage - splenic sequestration (pooled in spleen) - rarer
What platelet level is thrombocytopenia
<150x109/L
HOWEVER rare to get spont bleed <20
if <100 warratns further investiation
What is pseudo TP
Giant platelets
Goes away with citrate tube
What can cause dilutional thrombocytopenia
Post massive transfusion/fluids
Gestational TP
Causes of decreased production of platelets
Congenital – e.g. TAR (thrombocytopenia with absent radius), amegakaryocytic thrombocytopenia, VWD (type 2B)
Drugs (alcohol, chemotherapy, antiepileptics, psych and rehum drugs)
Radiation
Aplastic anaemia/myedodysplasia
Bone marrow replacement (e.g. malignancy, granuloma, fibrosis)
Infection/sepsis
B12 or folate deficiency
Ineffective haematopoiesis – myelodysplasia
What causes increased destruction of platelets
Microangiopathy
Macroangiopahty
Immune - allo, auto
AI causes of platelet destruction
ITP
ParoxNoct.H
Heparin induced TP
APS
Secondary eg CTDs, lymphoprolif eg CLL, NHL, infections, drugs, EVANS syndrome, primary immunodeficiencies
Infections causing AI platelet destruction
HIV, Hepatitis B+C, rubella, EBV, Helicobacter pylori),
Microangiopathies-> platelet destruction
TTP, HU, aHUS, DIC, vasculitis, HELLP, HPTNsive crisis, scleroderma crisis, acute rejection
Basic evaluation of TP
Full blood count, blood film, reticulocyte count
LDH
B12/folate
LFTs, U+Es, , INR, APTT(clotting)
HIV, Hep
Clinical - alcohol (portal HPTN) and meds history, acute illness
Targeted investigations for TP
US abdomen
Vit B12/folate
Viral screen
ANA
Quantiative IGs
HIT assay
APS testing
PNH, VWD screen
Platelet functioning test
Bone marrow biopsy
ITP treatment - what and what trying to prevent
The primary problem in ITP is formation of antibodies against platelets, which are then de-stroyed in the spleen (i.e. increased destruction).
Thus, conventional treatment for ITP has focused on suppression of the antibodies (prednisone, cytotoxic agents) or amelioration of splenic destruction (splenectomy, IVIg).
Newer developments include thrombopoiesis-stimulating agents (romiplostim, eltrombopag).
Consumptive causes of low platelets
Sepsis
Hyperslepnism and liver disease
DIC
TTP
What to consider when seeing low platelet counts
Context - if in doubt repeat - history and exam, meds
Is it new
Is it potentially clinically significant - bleeding etc
What other tests need
When refer to haematology with low platelet count
Acute and platelets <50 without cause or 50-100 and chronic
Bleeding
Abnormal blood film
Concern about HIT or TTP
