and to match structural abnormalities of the X chromosome with their
Dr. Victor Babes Institute of Pathology and Medical Genetics, Bucharest, Rumania.
Giulesti Hospital of
NON-TUBEROUS NEURAL-TUBE DEFECTS 1,2 proposed that an as yet undefined chemical associated with the potato blight is the specific teratogen responsible for anencephalus and spina bifida (A.S.B.). In Western countries, such as the United Kingdom, where the potato is a staple food, there is a social-class gradient in potato consumption, with more potatoes eaten by the poor than by the affluent. It is this class gradient in potato consumption that Renwick uses to explain the But A.S.B. certainly socioeconomic gradient in A.S.B.1 occurs in countries where the white potato represents a negligible contribution to the total nutritional intake. For instance, in our study of 26,000 consecutive births in Taipei, Taiwan,3 the incidence-rate of neural-tube defects
(anencephaly, spina bifida, encephalocele, iniencephaly) was
1-42 per 1000 total births.
In 1966, the middle year
I-FATHER’S OCCUPATION AND NEURAL-TUBE DEFECTS
of the study, the per caput annual consumption ([production + imports - exports] — population) of potatoes in Taiwan was 1 lb., compared to 266 lb. in the United Kingdom,4,55 where most of the highest rates ofA.s.B. have been reported. A lower but comparable rate for closure defects of the central nervous system has been reported recently from Sweden 1 (109/1000 births), where the potato consumption was 387 lb. per caput. Similarly, the incidence of anenin France was 0-54 per 1000 total births,7 compared cephaly with 1 15 in Taiwan. In 1966, in France, the home of Parmentier, potato consumption was 464 lb. per caput. The Taiwan, Swedish, and French studies were all based on hospital data and are subject to the errors of such methodology. Nevertheless, the similarity in incidencerates of neural-tube defects in these countries in the face of great differences in potato production and consumption at the very least cannot be said to support the potato teratogen hypothesis, since one might expect the prevalence of blight to be somewhat related to the quantity of potatoes grown. 1. 2. 3.
4. 5. 6.
Renwick, J. H. Br. J. prev. soc. Med. 1972, 26, 67. Renwick, J. H. Lancet, Aug. 12, 1972, p. 336. Emanuel, I., Huang, S. W., Gutman, L. T., Yu, F. C., Lin, C. C. Teratology, 1972, 5, 159. U.N.-F.A.O., Production Yearbook 1970. Food and Agricultural Organization, Rome. U.N.-F.A.O., Trade Yearbook 1971. Food and Agricultural Organization, Rome. Kallen, B., Winberg, J. Pediatrics, 1968, 41, 765. Frezal, J., Kelley, J., Guillemot, M. L., Lamy, M. Am. J. hum. Genet. 1964,
Z2=977, r < 001.
In Taiwan, as in such Western countries as the United Kingdom,S the United States,9 Canada, 1 and Israeli there is a significant social-class effect for neural-tube defects, with excesses in the poorer groups. In our study, public-health nurses interviewed the parents of all stillborns, miscarriages, and babies with congenital malformations. The next normal baby born in the same hospital Known was taken as a control and similarly treated. information on 41 cases (34 anencephalics, 3 spina bifidas, 3 encephaloceles, 1 iniencephalus) was compared with that A fivefold occupational classification was of controls. used; the two highest classes were combined and the unemployed were grouped with the unskilled workers because of small sample size. Since there were no significant maternal age or parity effects in this sample,
standardisation for these factors was not necessary. Table i shows the usual kind of paternal occupational relationship to neural-tube defects, while table ii shows the relationship to father’s education. Additionally, in Taiwan, what few potatoes are available are probably more apt to be consumed by the substantial resident Occidental population, tourists, and the financially better-offWesternised local people. It therefore seems unlikely that the social-class relationship in neuraltube defects in Taiwan can be attributed to a potatoassociated teratogen. It is theoretically possible that the social-class relationship in the Western countries is produced by different factors than the social-class relationship in Taiwan. However, a simpler and probably more biologically plausible conclusion would be that the same factors produce the social-class relationship wherever it is seen, since of all the epidemiological relationships in A.s.B., the social-class effect is the most striking and constant. There is urgency in determining the aetiological factors in these devastating defects, and the evidence cited here and elsewhere 12 indicates the need to continue the search. Department of Epidemiology and International Health and Department of Pediatrics, University of Washington, Seattle, Washington 98195, U.S.A.
HÆMORRHOIDECTOMY VERSUS MANUAL DILATATION OF THE ANUS out rectal examinations with great frequency have felt the pecten band which the Lord technique is meant to rupture. In order to test this hypothesis, I have, in a number of my patients, carried out a lateral proctotomy under local anaathesia, presuming that the more precise division of a hypothetical pecten band with the knife, and the use of a finger in the rectum to
SIR,-Few of us who carry
8. 9. 10. 11. 12.
Fedrick, J. Ann. Hum. Genet. Lond. 1970, 34, 31. Naggan, L., MacMahon, B. New Engl. J. Med. 1967, 277, 1119. Horowitz, I., McDonald, A. D. Can. med. Ass. J. 1969, 100, 748. Naggan, L. Pediatrics, 1971, 47, 577. Lancet, July 29, 1972, p. 222.