30 0 Med Genet 1992; 29: 30-35 The cyclops and the mermaid: an epidemiological study of two types of rare J Med Genet: first published as 10.1136/jmg.29.1.30 on 1 January 1992. Downloaded from malformation* Bengt Kallen, Eduardo E Castilla, Paul A L Lancaster, Osvaldo Mutchinick, Lisbeth B Knudsen, Maria Luisa Martinez-Frias, Pierpaolo Mastroiacovo, Elisabeth Robert Abstract complex depends on which forms are in- Infants with cyclopia or sirenomelia are cluded, and also on the frequency with which born at an approximate rate of 1 in necropsy is performed on infants dying in the 100 000 births. Eight malformation moni- neonatal period. However, the two extreme toring systems around the world jointly forms, cyclopia and sirenomelia, are easily Department of studied the epidemiology of these rare recognised and usually clearly defined, but Embryology, University of Lund, malformations: 102 infants with cyclopia, both forms are very rare and it is therefore Biskopsgatan 7, S-223 96 with sirenomelia, and one with both difficult to collect material large enough to 62 Lund, Sweden. conditions were identified among nearly permit detailed epidemiological studies. B Kalln 10-1 million births. Maternal age is some- We have collected such material by using ECLAMC/Genetica/ what increased for cyclopia, indicating data from eight malformation monitoring sys- Fiocruz, Rio de Janeiro, Brazil, and the likely inclusion of some chromoso- tems around the world, all members of the IMBICE, Casilla 403, mally abnormal infants which were not International Clearinghouse for Birth Defects 1900 La Plata, identified. About half of the infants are Monitoring Systems,7 and we report some Argentina. E E Castilla stillborn. There is a female excess among findings on the prevalence at birth, other epi- infants with cyclopia. Excess twinning demiological features, and associated malfor- AIHf National Perinatal Statistics occurred for cyclopia and possibly also mations. Unit, Building A27, for sirenomelia. An analysis ofassociated University of Sydney, malformations indicates the similarity Sydney, NSW 2006, Australia. between the two conditions, which is in agreement with recent embryological Material and methods P A L Lancaster Data were collected from the following eight RYVEMCE, analysis. Departamento de malformation monitoring systems which will be described a GenCtica, Instituto very briefly. Australia: national, http://jmg.bmj.com/ Nacional de Nutrici6n A recent paper' reported an interpretation of population based monitoring system covering Salvador Zubiran, some 240 000 Vasco de Quiroga 15, cyclopia and symmelia, based on a detailed annual births.8 Denmark: a Tlalpan, 14000 Mexico embryological study of human embryos and national, population based registry of congen- DF, Mexico. ital malformations covering approximately 0 published reports. The authors pointed out a Mutchinick number of similarities in the development of 55 000 annual births.9 France, Rhone-Alps- National Board of Auvergne (RAA): a regional, population based Health, Amaliegade these two lethal conditions. They both arise by a failure of lateralisation of rudiments, the monitoring system based on nearly 90 000 13, PO Box 2020, on September 28, 2021 by guest. Protected copyright. DK-1012 Copenhagen, early brain rudiment, which gets its laterality annual births.'0 Italy, IPIMC: a hospital based Denmark. monitoring system including reports from 147 L B Knudsen from the influence of the prechordal meso- derm,2 and the 'caudal eminence', the caudal hospitals and covering approximately 130 000 Hospital Universitario annual births (about 25% of all Italian San Carlos, continuation of the primitive node and there- INSALUD, ECEMC, fore also a basic structure in the development births)." Mexico: a hospital based monitoring Facultad de Medicina, of axial mesoderm.' system including 21 hospitals in 11 cities with Universidad an annual birth rate of approximately 50000.12 Complutense, 280 40 Cyclopia is an extreme form of holoprosen- Madrid, Spain. cephaly, which covers a broad spectrum of South America, ECLAMC: a hospital based M L Martinez-Frias conditions from cyclopia to infants who are monitoring system including approximately 70 IPIMC, Servizio externally normal but have more or less pro- hospitals in all South American countries and Epidemiologia e nounced disturbance ofthe pairing of the brain covering a total number of annual births of Clinica Difetti about 215 000."3 Spain, ECEMC: a hospital Congeniti, Policlinico hemispheres.4 Similarly, symmelia or sireno- Universitario A melia is an extreme form of a spectrum of based monitoring system including reports Gemelli, Largo malformations which have been summarised from 45 hospitals, covering nearly 60 000 Gemelli 8, 00168 annual births (about 15% of all Spanish Rome, Italy. as the caudal regression malformation complex that spans sirenomelia to kidney agenesis or births).'4 Sweden: a national, population based P Mastroiacovo registry of congenital malformations covering Institut Europeen des even anal atresia.56 The delimitation of holo- G6nomutations, 86 prosencephaly is difficult4 which is reflected in approximately 100 000 annual births.'5 Rue Edmond Locard, the fact that data on its prevalence at birth vary From each registry, data were extracted for F-69005 Lyon, France. the two conditions according to the following E Robert considerably. Similarly, the actual prevalence at birth of the caudal regression malformation definitions. Cyclopia: infants born with one Correspondence to orbit in the middle of the face and with one or Dr Kallen. two eyes. Known chromosome anomalies are Received 18 February 1991. *The malformation monitoring programmes that participated Revised version accepted in this study are all members of the International Clearinghouse not included (because in some programmes 15 April 1991. for Birth Defects Monitoring Systems. they are often registered only as such), but a The cyclops and the mermaid 31 Table 1 Number of cases and number of births recorded in each programme (rates per 100 000 births). Cyclopia Sirenomelia No of Programme Years births No Rate No Rate J Med Genet: first published as 10.1136/jmg.29.1.30 on 1 January 1992. Downloaded from Australia 1982-1989 1 945 888 23 1-2 22 1-1 Denmark 1983-1988 328 254 0 - 2 0-6 France, RAA 1976-1987 943 579 5 0 5 7 0-7 Italy, IPIMC 1983-1988 824478 11 1-3 5 0-6 Mexico 1978-1988 358 590 8 2-2 3 0-8 South America 1967-1989 2 278 771 30 1-3 32 1-4 Spain 1976-1989 728368 6* 0-8 7* 1 0 Sweden 1965-1988 2 258 613 20 0 9 19 0-8 Total 10 097 383 103 1.03 97 0-96 *One infant had both cyclopia and sirenomelia. special study was made of trisomy 13. Sireno- rate is probably higher (estimated to be 0 99 melia: complete or partial fusion of the lower per 100 000 births). limbs. Fig 1 compares the recorded numbers of In general the conditions under study are cyclopia and sirenomelia in the different pro- easily defined and clear cut. Two infants with a grammes. It can be seen that the recorded proboscis and without eyes were reported but differences in rate (table 1) may well be not included because they did not fulfil the explained by random fluctuations. working definition, even though they actually Table 2 shows the recorded number of in- may represent the most severe forms. Simi- fants with trisomy 13, how many of them were larly, an infant with rotated lower limbs, and described with respect to the malformations therefore with feet facing backwards, was not present, and how many of these had cyclopia. included. These few borderline cases do not It can be seen that cyclopia occurred in 2-7% affect the registered rates much. Fewer than of all trisomy 13 infants where malformations 10% of the cases of each type of malformation were described. As the rate of recorded tri- were karyotyped (nine with cyclopia, six with somy 13 is about 1 in 17200, it can be esti- sirenomelia). mated that to the rate of cyclopia described For each infant information was given above can be added 0 15 per 100 000 of cyclo- (when available) on date of birth, matemal and pia recorded as trisomy 13, giving a total of paternal age at birth, parity, sex, birth weight, 1-20 per 100 000. survival (stillborn, liveborn dying in the peri- Fig 2 shows the time trend: for both malfor- natal period, liveborn surviving the perinatal mations the rates up to 1974 were higher than period), necropsy, whether cytogenetic invest- igation was performed, and multiple birth, in ® Cyclopia which case sex and status of co-twin or co- 401 triplets. Population data (when available) were http://jmg.bmj.com/ also given for these variables. *Sam Stillbirths were not included in the Spanish material until 1980 and in the South American / Aus I,- 0 material until 1978. Stillbirth definition var- * Swe - ied: in Australia, all stillbirths are registered after the 20th completed week, in Denmark, France, and Sweden after the 28th week, in Italy after 180 days, while in Mexico, Spain, on September 28, 2021 by guest. Protected copyright. and South America the definition is a birth weight of 500 g or more. 40' Sirenomelia Results PREVALENCE AT BIRTH 30' The total number of births which represents the denominator is given in table 1 for each No programme. A total of 103 infants with cyclo- 20- pia was identified. This gives a crude rate of * Swe 1-03 per 100000 births, but as roughly one- third of the identified cases were stillbirths and 10' these were not included in part of the South Spai *FFran, - American and Spanish programmes (a total of . Mex oItal 873 897 births before inclusion of stillbirths), /Dk - the rate will be somewhat underestimated. By 0 1 2 3 adding 1/3 of cases for those programmes for Million births Figure 1 Diagrams showing number of births in each that period, the true rate can be estimated to be programme and number of malformed infants recorded.