Genetic aspects of sickle cell anemia and microdrepanocytic disease.

By E. SILvEsTR0NI, M.D. AND I. BIANCO, M.D. S ICKLE CELL ANEMIA is a severe chromsic disease usually confined to the Negro race l ttt occasiotsally foutsd its imidividuals of the white race mostly of Southerti Italians on Greek stock. Clitsically there is chromsic hemolytic amsemia s ’iths crises, osteo-muscular pains, bouts of severe abcbomitsal pain and ulceratiomis of the legs. Hematologicallv, the disease is characterized by the ability of tise red cells to assume aim elommgatecl amid curved shape (‘‘sickling”) when blood is sealed umsder a cover slip amid kept at 37 C. for a few hours. The disease occurs its families, all of whiom presetit sicklimug, altisough sickle cell anemia is presetit its oislv a few. Simmee, moreover, sickle cell anemia affects cotssecutive generatiotms, tliete is iio doubt that tlse (lisease amid the trait Isave a genetic basis. It has beenm tlsouglmt that tIse al)ility of the re(l cell to sickle vas clue to a single clomitmatit factor, \ l1i(h is respotisible for the tratmsmissiois of all types of the disease, from the simple, asymptomatic sicklemia to the severe sickle cell atiemia.2’ 16, 17, This tlseotv, althougls getmerally accepted, is not its agreemetst with the climsical obsem\‘tttioti that sickle cell atmemia occurs almost exclusively amommg those individuals its wlsom 1)0th paretits preseimt the sickle (eli trait.’ Ilti 1947, Ned5 ptesemsted a gemsetic theory for sickle cell aisemia analogoits to tlsat postlllate(l fot’ i\ie(litemratueatl atmemia, ati(l singgested “that there is presetit its the colored populations a certaimi factor w-hicls, ‘heis heterozygous may have hO discernible effects, hut usually results its sicklitug amsd, when homozygous, tetm(ls to result iii sickle cell atiemia.” Its 1949, Ned8 tested this hypothesis by stu(lyinmg 42 pareimts of 29 patietsts with sickle cell anemia amid fotnnsd that the 1)100(1 of all tise iti(livi(luals tested sickled. Beet’ working with a Bamstu tribe its Africa, coisfirmed these results, and showed further that while only 55 per cent of time offspring of 32 families of sickle cell trait Negroes presensted sickling, tise sickle cell trait was always presetmt its botis paremsts of pat iemsts with sickle cell amsemia. Its tlse course of atm itmvest igations omu microcythsemia (Mediterratueats atsemia, Tisalassemia), we were able to study families of healthsv insdivicluals with (lrepatiocythemia (sickle cell trait), amid of patients with sickle cell amsemia, all of Sicilians on’ (‘emmtral aiscl Southserts Italian stock. The study of two families of healthy its(lividuals showitmg tise sickhnsg trait indicated that tise sickle cell trait its tise wusite as well as its the Negro behaves as a Meisdeliamu (bominsant tratssmitted its coissecutive getserations (fig. 2, families 4 and 5). Asymptomatic individuals are