16/11/19

Question 1

Tell me about Hereditary spherocytosis

Answer 1

• autosomal dominant (spectrin)
• genetic defect of red cell membrane
• causes Jaundice and gallstones. Higher the retic count, higher the risk of developing gallstones. Causes splenomegaly, anemia with spherocytes and increased MCHC.
• increased incidence of pseudohyperkalaemia as RBC’s lyse after blood draw and intracellular potassium leaks
• +ve osmotic fragility test. EMA has sensitivity of 93%, used as a screening test to detect structural defects in the red cell membrane.
• Parvovirus B19 leads to sudden drop in Hb in HS (reduced lymphocytes and reduced platelets). You will think it’s cancer but it’s not. What will indicate HS over cancer is spherocytes on blood film and enlarged spleen.
• treatment: folic acid, RBC transfusion in extreme anemia, and splenectomy in mod to severe cases

Question 2

G6PD

Answer 2

Pentose phosphate pathway
maintains glutathione in RBC
needed to protect RBC from oxidative damage
X-linked recessive
Non-immune haemolytic anemia (DAT -ve)

Triggers (Spleen Purges Nasty Inclusions From Damaged Cells)

• Sulfonamides
• Primaque (anti-malarial)
• Nitrofurantoin (UTI)
• Isoniazid (TB)
• Fava beans
• Dapsone (Leprosy)
• Chloroquine (Anti-malarial)

Peripheral smear: Heinz bodies, Bite cells

Dx: reduced G6PD activity, avoid oxidants

Question 3

Sickle cell Anemia

Answer 3

On the beta-globin chain, at position 6, a hydrophilic gluatamic acid is replaced by hydrophobic valine. This is inherited as a AR condition. This protects against malaria.
Triggers for sickling: hypoxia, acidosis, deoxygenation, Increased HbS, high MCHC, dehydration, fever

Pathophysiology of sickle cell: HbS polymerisms, increased adhesive of sickle RBC to endothelium, hemolysis

Hydroxyurea cn be used: if retic count >80, Neut >2