0521779407-18 CUNY1086/Karliner 0 521 77940 7 June 13, 2007 8:1
Red Cell Enzymes 1271■Ethnic Groups – G6PD Deficiency
➣African descent (less severe defect; not subject to hemolysis
induced by Fava beans),
➣Mediterranean (more severe defect; subject to more severe
hemolysis that may be also induced by Fava beans)
➣Asian (Indian & Southeast Asian): several endemic variants
Signs & Symptoms
■Nonspecific
■Jaundice, leg ulcers, splenomegaly, gallstones, may be present in
chronic hemolytic states
tests
■Basic blood tests
➣RBC morphology – mostly nonspecific
Heinz bodies – acute hemolytic episodes of G6PD, GC and GSH
synthase and rare congenital glutathione reductase deficien-
cies
Only specific finding is basophilic stippling in 5′nucleotidase
deficiency
➣Biochemical tests of hemolysis (hyperbilirubinemia, reticulo-
cytosis etc), but none specific for hemolysis from erythrocyte
enzyme defects
■Screening tests
➣Misses up to third of PK deficient mutants
➣G6PD screening tests not useful for heterozygous females (they
have proportion of deficient erythrocytes that are subject to
hemo-lysis) and may be falsely negative after acute hemolytic
episodes in males as older G6PD deficient cells have been
destroyed
■Specific quantitative assays and DNA-based assays
➣Only available in few reference laboratories (and decreasing in
number)
■Polycythemia – low P50 by hemoglobin oxygen dissociation study
or estimated from venous blood gasses is the best initial screening.
Confirm by measuring 2,3 BPG level and differentiate from high-
oxygen-affinity hemoglobin mutants.
differential diagnosis
■Other hemolytic states – autoimmune causes (positive Coombs
test), PNH (CD55 and CD 59 deficient cells), fragmentation syn-
dromes (schistocytes), and red cell membrane defects (character-
istic erythrocyte abnormalities [i.e., spherocytes, elliptocytes, pyro-
poikilocytes])