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Path - Haemolytic Anaemia (ii) (Sickle cell anaemia (mutation = HbS (x50…
Path - Haemolytic Anaemia (ii)
Sickle cell anaemia
mutation = HbS
valine replaces glutamic acid
co-inheritance + another abnormal beta chain variant = full-blown severe disease
1 gene mutated: sickle cell trait
x50 less soluble than HbA
insoluble chains crystallise
distorted/deformed crescent-shaped membrane
more rigid
can't pass microcirculation
vasc occlusion
increased viscosity + stasis
infarcts + hypoxia
only survives 10-20 days
RBCs aggregate in a deoxygenated state
AR
affects mainly afro-Caribbeans
45% of people are carriers in some parts of Africa
also common in Mediterranean + Asia
chronic haemolytic anaemia
sickling can be spontaneous or precipitated by hypoxia, acidosis, hypotension, infection, dehydration, hypothermia
other complications
osteomyelitis (bone infection)
expanded marrow, seen on PET
pigment (from RBC breakdown) gallstones
renal + heart failure
chronic leg ulcer
thalassaemia
in Mediterranean, Asia + N Africa
genetic mutation
deleted/truncated global genes (alpha and/or beta)
1 chain is underproduced, other aggregates + damages membrane
vary in severity
reduced synthesis or completely absent
some transfusion-dependent
depends on no. + type of mutations
do DNA analysis
1 deleted gene: mild anaemia - thalassaemia trait
3 deleted genes: disease
4 deleted genes: hydrops fetalis
death in utero due to oedema
lab features
hypochromic microcytic anaemia
BM erythroid hyperplasia