HUS and TTP Flashcards
what is microangiopathic haemolytic anaemia?
process of microthrombi shredding RBCs (like a cheese grater) in the micro circulation to produce schistocytes
what is HUS a triad of?
Microangiopathic haemolytic anaemia (MAHA) – intravascular haemolysis and red cell fragmentation -> schistocytes
Acute renal failure
Thrombocytopaenia
what is the most common cause of HUS?
Escherichia coli O157- typicallly in you children who eat undercooked meat and present with bloody diarrhoea
describe how HUS is causes AKI?
EHEC O157:H7- produces a Shiga-like toxin-> capable of binding to endothelial cells within the kidney
enters these cells and damages them
damaged endothelium attracts widespread platelet plug formation
leads to microthrombi which shear red blood cells
leads to AKI and haemolytic anaemia
kidney function is reduced-> urea not excreted-> uraemia
summarise the epidemiology of HUS and TTP?
UNCOMMON
D+ HUS often affects YOUNG CHILDREN
It is the most common cause of acute renal failure in children
TTP mainly affects ADULT FEMALES
describe the pathophysiology of TTP?
congenital deficinecy or acquired antibodies to ADAMTS13 protease which normally cleaves multimers of von willebrand factor
large vWF multimers cause platelet aggregation and fibrin deposition in small vessels
leads to mutisystemic thrombotic microangiopathy
what is TTP a pentad of?
( overlaps with HUS)
- Microangiopathic haemolytic anaemia
- decreased platelets
- AKI
- neurological symptoms ( headaches, palsies, seizure, confusion, coma)
- fever
what are the presenting symptoms of HUS and TTP?
GI
- Severe abdominal colic
- Watery diarrhoea that becomes bloodstained
- Abdo pain
General
- Malaise
- Fatigue
- N+V
- Fever < 38 degrees (D+)
Renal
- Oliguria or anuria
- Haematuria
what are the signs of HUS and TTP on physical examination?
General
- Pallor
- Slight jaundice (due to haemolysis)
- Bruising
- Generalised oedema
- Hypertension
- Retinopathy
GI- Abdominal tenderness
CNS Signs
- Occurs in TTP
- Weakness
- Headache
- Confusion
- Reduced vision
- Fits
- Reduced consciousness
what are the appopriate investigations for HUS and TTP?
- FBC
- Blood film
- U and Es
- clotting
- LFTs
- urinalysis
- stool samples- MC+ S
describe the FBC?
Normocytic anaemia
High neutrophils
Very low platelets
Low haptoglobin
Raised reticulocytes
Describe the blood film?
Schistocytes
High reticulocytes and spherocytes
describe Us and Es?
High urea
High creatinine
High K+
Low Na+
describe the clotting results?
Normal APTT and fibrinogen levels(abnormality may indicate DIC)
describe LFTs?
High unconjugated bilirubin
High LDH from haemolysis
describe the urine test?
1+ g protein/24 hrs
Haematuria
why is stool sample important?
MC&S – detect shiga toxin from Ecoli(can also do PCR to confirm shigatoxin)
what additional test is important for TTP and interpret the results?
DAT/Coombs Negative
Describe how the DAT/ direct coombs test work and explain why it is useful?
DAT and direct Coombs test are synonymous. The DAT test is useful because it tells you if there is an auto-immune problem directly attacking the red blood cells. Anti-human globulin antibodies detect the antibodies that are attacking the red cells. The lab given ‘anti-human antibody’ antibodies capture multiple auto-immune antibodies which are stuck to RBCs. This causes RBCs to amass together (agglutination, in this case). This agglutination is detected and when present indicated the presence of so called antiglobulins.
summarise the features of DIC, TTP, HUS?
What is the simple difference between TTP and ITP?
that ITP involves an auto-immune attack on the RBCs
TTP does not
