haematology Flashcards
what are the two types of haemachromatosis
Primary Haemochromatosis
→ hereditary, most common form
Autosomal recessive inheritance
Mutations on the HFE gene
Secondary Haemochromatosis
→ caused by iron overload
Commonly transfusion related
which gene causes primary haemachromatosis and what is the inheritance pattern
HFE gene
Autosomal recessive
symptoms of haemachromatosis
fatigue
arthralgia
erectile dysfunction
grey/bronze pigmentation
polyuria / polydipsia
cirrhosis / hepatomegaly
what is the most useful marker for haemachromatosis
serum transferrin saturation >45%
what is the first test to become abnormal in haemachromatosis
serum transferrin saturation >45%
describe the iron study results for haemachromatosis
high serum iron
high serum ferritin
low TIBC
serum transferrin saturation >45%
management of haemachromatosis
1st line: therapeutic phlebotomy
2nd line: drug induced iron chelation - Deferoxamine
what globins make up HbF
2 alpha globin + 2 gamma globin
what globins make up HbA
2 alpha globin + 2 beta globin
what globins make up HbA2
2 alpha globin + 2 delta globin
what is the inheritance pattern of all haemaglobinopathies (sickle cell, thalassemia)
autosomal recessive
contrast alpha and beta thalassemia in terms of common pt population, number of alleles, and electrophoresis results
beta
- mediterranean descent
- 2 alleles
- no HbA, raised HbA2 and HbF
- no HbH
(look for raised HbA2 in Hb electrophoresis)
alpha
- asian and African descent
- 4 alleles
- present HbH
(look for HbH band in Hb electrophoresis)
what are the 2 forms of beta thalassemia and their symptoms
1 defective allele: Beta thalassemia minor
→ mild microcytic hypochromic anaemia.
Asymptomatic
2 defective alleles: Beta thalassemia major
→ severe haemolytic anaemia,
hepatosplenomegaly,
skeletal deformities
what are the 4 forms of alpha thalassemia and their symptoms
1 defective allele: Silent Carrier
→ asymptomatic.
No anaemia.
2 defective alleles: Αlpha Thalassaemia Trait
→ microcytic hypochromic red cells.
No anaemia.
3 defective alleles: Haemoglobin H (HbH) Disease
→ microcytic hypochromic anaemia with splenomegaly
4 defective alleles: Haemoglobin Bart Disease
→ intrauterine death
management of thalassemia major
lifelong blood transfusion therapy
(this may lead to iron overload so also give iron chelation therapy - Desferrioxamine)
genetic screening
individuals with an absent or dysfunctional spleen are at increased risk of severe infection esp caused by which bacteria?
the encapsulated bacteria - NHS
N. meningitidis
H. influenzae type b (Hib)
S. pneumoniae (pneumococcus)
what is seen on a blood film in hyposplenism / after splenectomy
howell-jolly bodies,
target cells,
pappenheimer bodies (siderocytes)
what do Howell jolly bodies indicate
splenic dysfunction
why is prophylactic aspirin usually indicted after a splenectomy
pt will have very high platelet count - thrombocytosis
(spleen is the primary site of destruction of platelets)
management of hypospelnism or splenectomy
prophylactic aspirin if they have thrombocytosis
Immunisations
→ vaccinations against
N. meningitidis,
H. influenzae type b and influenza virus
S. pneumoniae,
○ Pneumococcal vaccine 2 weeks before elective splenectomy
○ Annual influenza vaccination and Pneumococcal vaccine every 5 years
Prophylactic Antibiotics (Penicillin or Amoxicillin)
→ recommended in patients at high risk of pneumococcal infections
causes of DIC
STOP MT
⇒ sepsis/snakebites,
trauma,
osbtetric conditions,
pancreatitis,
malignancy,
Transfusion
acute vs chronic DIC
acute
- caused by trauma, sepsis and blood transfusions
- causes bleeding issues (petechiae, purpura, ecchymoses, epistaxis)
chronic
- caused by malignancy
- causes clotting issues (signs of DVT or arterial thrombosis)
significant FBC results in DIC
low platelets,
low haemoglobin
clotting results in DIC
low fibrinogen,
high D-dimer (fibrinogen degradation products),
prolonged PT + APTT