Differentials
Sickle cell disease
SIGNS / SYMPTOMS
History of intermittent painful crises.
May have skin/cardiac/pulmonary/skeletal manifestations.
INVESTIGATIONS
Blood film shows presence of nucleated RBCs, sickle-shaped cells, and Howell-Jolly bodies.
High-performance liquid chromatography (HPLC) shows abnormal sickle cell hemoglobin (Hb S).
Hb electrophoresis shows Hb S present in sickle cell disease.
Autoimmune hemolytic anemia
SIGNS / SYMPTOMS
History of precipitant (e.g., causal drug, infection).
May have associated connective tissue disease, splenomegaly.
INVESTIGATIONS
Blood film shows presence of spherocytes, elliptocytes, and schistocytes.
Direct antiglobulin test is positive.
Isoimmune hemolytic anemia: for example, ABO incompatibility
SIGNS / SYMPTOMS
Mother typically blood group O.
Infant typically group A or B.
INVESTIGATIONS
Blood film shows presence of spherocytes, elliptocytes, and schistocytes.
Direct antiglobulin test is positive.
Unstable hemoglobin
SIGNS / SYMPTOMS
Rare.
No history of precipitant.
INVESTIGATIONS
Blood film may show Heinz bodies.
Screening tests for unstable Hb positive.
HPLC and Hb electrophoresis demonstrate abnormal Hb.
Methemoglobinemia
SIGNS / SYMPTOMS
Rare.
May be precipitated by oxidative drugs.
INVESTIGATIONS
G6PD fluorescent tests and assay normal.
Methemoglobin reductase deficient.
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