Primaquine Sensitivity (Glucose-6-Phosphate Dehydrogenase Deficiency)
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PRIMAQUINE SENSITIVITY (GLUCOSE-6-PHOSPHATE DEHYDROGENASE DEFICIENCY) .An Inborn Error of Metabolism of Medical and Biolo Significance Alvin R. Tarlov. M... D. .George J. Brewer, M. D. From the University of Chicago-Army Medical Research Unit, Department of Medicine, Chicago, Illinois. "he previously unpublished studies gf the authors included in this review were supported by the Medical' Research and Development Command, Office of the Surgeon General, Department of the Army, under contracts DA-49-007-MD- 566 and DA 49-007-MDWwith the University of Chicago and were supplernent- ed by grants from Burroughs- Wellcome and Company, Winthrop Laboratories, , and the Douglas Smith Foundation, SUBMITTED TO THE ARCHIVES OF INTERNAL MEDICINE 25 AUGUST I961 - 3. \, \, The potential danger of hemolysis from use of the 8-aminoquinoline antim larial drug, pamaquine (plasmoquine@J , has been known since i.\\ 1926 (l): Earle (2), in 1948, reported that pamaquine caused hemolysis . ' in 5-10 percent of American Negroes, but rarely in Caucasians. Similar observations were made in 1952 by Hockwald (3), during an evaluation of the related, but less toxic drug, primaquine; it was further noted that the severity of hemolysis was determined by the amount of drug administered. In 1954, Dern (4) discovered that the susceptibility to hemolysis by primaquine is due to an intrinsic abnormality of the erythrocyte. Dern, Beutler and Alving (5) reported that the hemolysis is self-limited in that clinical recovery occurs even if the daily dose of drug is continued. Many drugs can precipitate hemolysis (6 ) . This hypersusceptibility to hemolysis by drugs is a genetically transmitted inborn error of metabolism (7 ) , - The first biochemical abnormality to characterize drug-sensitive cells, a low content of reduced glutathione (GSH), was discovered by Beutler (8). This kind of susceptibility to drug-induced hemolysis is called primaquine-sensitivity because the initial stbdies which led to its charact- erization were made during investigations of the hemolytic property of this antimalarial drug. It has recently also been designated glucose-6- phosphate dehydrogenase (G-6-PD) deficiencx after the major known enzym- atic defect in primaquine-sensitive individuals (9) but the phenotypic name, ‘,’ primaquine sensitivity, should not be discarded until the primary genetic 9 \;. defectkor basic biochemical abnormality responsible for the destruction of erythrocytes has bcen established with certainty. Important contrib- utions to an understanding of this inborn error of metabolism have been made by many scientific workers, Intensive investigations have been carried out in the United States, Israel, Italy, Germany and, more recently, in other countries. Many drugs in common clinical use.__ may precieate hemolysis.___ ‘Nu-iIaiig(*r of ialrogc11ii::iIQ ~iiidut.cdacxitc aticmia sliould always be - ~ ~._-___-_____-. weighed by physicians in their selection-. of therapeutic agents. The possib- ility that _,some systemic discases -mznhancc the hemolytic effect of these drugs should alwTs be born in mind when an obscure hemolytic episode is encountered at the bedside. MODE- OF. IhYIERITANCE~. .. AND DISTRI- BUTION . - -- - __ Childs, Browne, and their co-workers (lo’ concluded from studies of American Negroes that primaquine-sensitivity is probably trans- mitted by a gene of partial dominance located on the X chromosome (sex- (12) linkage), Strong supporting evidence was soon presented by Gross , Szeinberg (I3), and Larizza (14). Definite proof for sex-linkage of the primaquine -sensitive gene in Sardinians was provided recently by chromosome; when colur blindness and primaquine-sensitivity coexist in a single individual the two gent’s segregate identically through succeed- ing generations in a given family (I5). Thcse conclusions are supported by the investigations of Adam (I6) in Sephardic Jews. Full expression of the genetic defect occurs in affected hemizygous males (E)because the mutant gene (2)is not opposed by a normal allele (X). Full expression is rare in females because the homozygous female -_ (XX) must inherit a mutant gene from both parents. Usually, affected females are heterozygous (e);they inherit a mutant gene from one parent and a normal allele from the 0th r, and, therefore, have partial expression of the trait. In our study of Negro* volunteers at two penal institutions in Illinois, 13 percent of the males and 3 percent of the females were fully (171 susceptible to hemolysis . Affected females manifested a wide ’ spectrum of expression of the clinical phenotype (hemolysis when 30 mg. of primaquine base was administered daily); in some hemolysis was only detectable by isotopic labeling of the erythrooytes. In iit hers the hemolytic susceptibility and the biochemical abnormalities of the erythrocytes were ~~ ~~ +This paper concerns the inherited disorder of primaquine- sensitive American Negroes unless otherwise specified. Sensitive Caucasians (Sardinians, Sephardic Jews) are more severely affected and differ in some respects from sensitive Negroes. .. c- -4- as severe, possibly even more severe, than in males with full expression. Judged by the clinical phenotype 20 percent of the Negro women were heterzygous. ** Yet, deficient G-6-PD*** in the erythrocytes could be demonstrated unequivocally only in approximately three-fourths of the heterozygous females. This may mean that several enzymatic abnormal- ities can influence the expression of the clinical phenotype or, alternatively, that the --in vitro assay of G-6-PD in hemolysates does not accurately reflect a slight decrease in the --in vivo activity of this enzyme in the circulating erythrocyte6. Primaquine- sensitiyity has a broad geographic distribution. Among Caucasians the defect is particularly concentrated in the Mediterranean area. Racial and ethnic groups having a high incidence usually are more darkly pigmented; the mutant gene rarely occurs in peoples of Northern European origin. Primaquine-sensitivity occurs in 48 percent of some Sardinian groups (") and in 2 to 36 percent of Mediterranean and Asiatic (Sephardic) Jews (13' 22); it is rare in European (Ashkenazic) Jews. The incidence in American Negro males is approximately 13 percent (1 1,17). - **This figure is slightly lower than the expected incidence of heterozygosity calculated from 13 percent incidence of sensitivity in Negro men. This may ir$Licate that som heterozygous females are so weakly expressed that detection is impossible even when primaquine is administered. ***The correlation between hemolysis and enzyme defi ienc was not improved when the Clock and McLean assay of G-6-PDb, 1% was substituted for the Kornberg method (21,23,24,25) it is even higher in some African Negro tribes . Prima- quine-sensitivity has also been reported in Greeks (26), Iranian Moslems (27), Asiatic Indians (28), Chinese (29), Filipinos(Z1) and many others (‘l). The incidence is highest in tropical and semi-tropical zones. It tends to parallel the distribution of falciparum malaria (21). GENETICAL AND ENVIRONMENTAL INFLUENCES Analysis of gene frequencies often yield information concerning the adaptive values of the trait. Many mutant genes decrease fitness; therefore, they tend to disappear from the population. A mutant gene, if it increases fitness, may exist in a population in a greater frequency than would be expected if it did not produce this biological advantage. I. Falciparum Malaria and Primaquine-Sensitivity:- The geographic distribution of primaquine-sensitivity (high frequency in tropical and semi-tropical malarious areas) suggests that the trait provides an evolutionary selective advantage against malaria*, as hypo- (31) thesized by Motulsky (‘”, and supported by the studies of Allison . Malaria parasites require glutathione (GSH). (32) and an oxidative pathway of carbohydrate metabolism (32* a3) for optimum growth. The low GSH *The incidence of the trait, however, is very low in Armenians who have lived for years in Iran where falciparum malaria is common and y&re the incidence of this trait in native Iranians varies from 5-1570. ( ) -. content and the diminished activity of the pentose phosphate pathway of primquine-sensitive erythrocytes mymake it difficult for the intracellular parasites to survive. The lower parasite density in the blood of young children whose erythrocytes are deficient in G-6-PD compared to children with normal enzyme activity has been interpreted as supporting this hypothesis. (31) Protection against malaria may similarly explain the geographic variation in frequency of sickle- (34, 35, 36) hemoglobin and thalassemia . Recently, however, caution (37, 65) has been advocated in interpreting data based on parasite densities I. II. Favism, Thalassemia and Primaquine-Sensitivity: Favism, hemolytic anemia caused by the fava bean, occurs only in primaquine- (38, 39.40.41 1 sensitive individuals . This condition is most common in Sardinians. The mortality rate in children who experience acute hemolysis after ingestion of the beans is reported to be 8 percent (42) . Clinical manifestations of acute icteric favism, however, are rare among primaquine-sensitive individuals who have thalassemia minor (41’43) and the observed frequency of individuals havinb both traits is . The erythrocytes of individuals with thalassemia minor have high\Y’ (45,46, 41.33.40) a shortened survival and consequently, a young erythrocyte population. Young cells are relatively resistant to hemolysis deficiency is rare. Similarly, Rh negativity is