On peripheral blood smear (blood film) spherocytes usually reflect
an extravascular hemolysis while schistocytes reflect an intravascular
hemolysis
Cases of Intra/Extra vascular Hemolysis
Intravascular hemolysis causes:
Mismatched blood transfusion
Glucose 6 phosphate dehydrogenase (G6PD) deficiency
Red cell fragmentation: Heart valves, Thrombotic thrombocytopenic
purpura (TTP), Disseminated intravascular coagulation (DIC), Hemolytic
uremic syndrome (HUS)
Paroxysmal nocturnal hemoglobinuria
COLD autoimmune hemolytic anemia
Extravascular hemolysis causes:
Hemoglobinopathies: sickle cell, thalassemia
Hereditary spherocytosis
Hemolytic disease of newborn
WARM autoimmune hemolytic anemia
Hemolytic anemia specific clinical features are:
Jaundice
Dark urine (hemoglobinuria, bilirubin)
Cholelithiasis (pigment stones)
Potential for an aplastic crisis (i.e. bone marrow suppression in
overwhelming infection)
Iron deficiency with intravascular hemolysis
Iron overload with extravascular hemolysis
Laboratory Findings in hemolytic anemia:
High reticulocyte count
Low haptoglobin (it mops up free hemoglobin, allowing its clearance
in the spleen; in hemolytic anemia the free hemoglobin is high, so haptoglobin
is consumed, and levels decrease)
High unconjugated bilirubin
High urobilinogen
High LDH
β-Thalassemia minor (thalassemia trait) usually asymptomatic; there
is mild microcyte anemia, and in rare cases palpable spleen
β-Thalassemia Major, initial presentation at age 6-12 months when
HbA (α2/β2) normally replaces HbF (α2/γ2)
In β-Thalassemia Major skull x-ray shows “hair-on-end” appearance
Sickle cell trait is a risk factor of renal medullary carcinoma
In sickle cell disease, there is splenomegaly in childhood (significant
pooling of blood in spleen); and splenic atrophy or asplenia in adulthood
because of repeated infarction
Sickle cell disease can cause a stroke or a silent myocadial infarction
Hand-foot syndrome or sickle cell dactylitis is a diffuse swelling,
tenderness, and warmth of the hands and feet in children with sickle cell
disease, it is self-limited and not associated with long-term damage.
Osteomyelitis is common in patients with sickle cell disease, especially
with salmonella
Avascular necrosis of the head of the femur occurs in about 5% of
patients with sickle cell disease
Gouty arthritis is uncommon in patients with sickle cell disease
although they are often hyperuricemic
Pulse oximetry may be inaccurate in patients with sickle cell
disease, so undertaking an arterial
blood gas measurement and direct measurement of PO2 is the best way
to assess hypoxia. The
absence of tachycardia may be a clue that the actual PO2 and
adequacy of oxygenation is better
than expected based on pulse oximetry.
Folic acid is indicated in the treatment of sickle cell anemia to
prevent folate deficiency
Cold autoimmune hemolytic anemia (AIHA) is usually by IgM and
causes hemolysis best at 4°C. Hemolysis is mediated by complement and is more
commonly intravascular.
Warm autoimmune hemolytic anemia (AIHA) the antibody (usually IgG)
causes hemolysis best at body temperature and hemolysis, tends to occur in
extravascular sites
Hereditary Spherocytosis
leads to chronic hemolysis and gallstone formation.
Most patients with Hereditary Spherocytosis have a moderate
illness with anemia, intermittent jaundice and palpable splenomegaly
Patients with Hereditary Spherocytosis can develop an aplastic
crisis following infection with parvovirus
Drugs causing hemolysis in Glucose 6 phosphate dehydrogenase
(G6PD) deficiency:
Anti malarial: primaquine
Ciprofloxacin
Sulfonamides
Co-trimoxazole (contains sulfa)
Safe drugs in Glucose 6 phosphate dehydrogenase (G6PD) deficiency:
Penicillins
Cephalosporins
Macrolides (Azithromycin, Clarithromycin, Erythromycins)
Tetracyclines
Trimethoprim
G6PD assay should not be done in acute crisis when reticulocyte count is
high because it may be falsely normal because reticulocytes have high G6PD
levels
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