Biomedical subjects
Publications and source records attributed to M M Nelson.
Limb reduction malformations of the arms are well documented in the trisomy 18 syndrome. Four cases of trisomy 18 syndrome with limb reduction malformations of the legs are described and compared with the upper limb malformations.
Congenital rigidity of multiple joints poses a difficult diagnostic and therapeutic problem. There are also semantic difficulties as the non-specific term "arthrogryposis" is often used for any individual with congenital limitation of joint movement. Many distinct syndromes present in this way and as they differ in their course, prognosis and genetic implications, diagnostic precision is crucial. A diagnostic analysis is given of 247 South African patients in whom "arthrogryposis" had been recorded, and the pathogenesis and nosology of congenital contractures are discussed in this paper. Three of these stiff joint conditions were originally described in South African patients, i.e. Liebenberg synostosis syndrome, digitotalar dysmorphism, and the Gordon syndrome of autosomal dominant cleft palate, camptodactyly and club feet.
During the period 1975-1980, 105 infants out of a total of 116 859 delivered at selected hospitals in the Cape Town area had a neural tube defect. The combined incidence of spina bifida and anencephaly in Whites was approximately 1/300 births, which is similar to that generally encountered in the UK. However, the incidence in other ethnic groups was appreciably lower at 1/1250 and 1/2000 births for the Coloured (mixed ancestry) and Black groups respectively.
During the period 1 January 1977 - 31 December 1979, 9 661 patients underwent cytogenetic investigation at seven participating laboratories in South Africa. The chromosome data were coded using a standard protocol and the results tabulated, being listed according to the clinical signs which led to referral for investigation. Cytogenetic investigation was most commonly requested for prenatal studies, and 22% of the group's effort was directed towards this. One in 27 amniotic cell specimens was reported to have shown anomalous chromosomes, trisomy 21 being the most frequent abnormality. The majority of postnatal investigations were requested because congenital abnormalities suggested an underlying chromosomal defect. In 42,3% of 2 420 patients a chromosome defect was confirmed. Results of chromosome studies are tabulated by indication for referral and the findings summarized. This collaborative study gives an indication of the nature and frequency of chromosome disorders in South Africa.
Thirty-one sets of conjoined twins were born in Southern Africa during the period February 1974 to May 1982 with a striking increase in incidence in 1974 and 1975. There was no ethnic or social predilection, but clustering of cases occurred in a remote area of Zimbabwe. No aetiological agent was discovered, and there was no seasonal variation in the time of conception. Female conjoined twins accounted for 62% of cases, and twenty sets were of the thoracopagus type. Four pairs were separated, three of which were of the xiphopagus subtype and have survived.
Amniotic fluid acetylcholinesterase electrophoresis has become available as a test for the prenatal diagnosis of open neural tube defects. The results of acetylcholinesterase electrophoresis on 125 amniotic fluid samples, including 18 from fetuses with open neural tube defects, are presented. These results indicate that this test, in conjunction with alpha-fetoprotein measurement, is of considerable practical value.
The chromosomal status of 720 patients in a large hospital for mental retardates in the Cape Province is reported. Chromosomes 21 and X were involved in 127 and 7 patients respectively, while other autosomes were implicated in 14 patients. Chromosomes abnormalities were therefore noted in 20,5% of patients. Details are given of the ages and sexes of the patients and of the structural chromosome anomalies.
A family is reported in which the father and 2 of his 3 daughters have hypoplasia or absence of the nipples with varying degrees of breast hypoplasia. The mode of inheritance of this combination of defects is autosomal dominant.
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We report two unrelated patients, a three-year-old girl and an 88/12 year-old boy with the newly described "acrocallosal" syndrome. The main manifestations of the syndrome are unusual facial appearance, pre- and postaxial polydactyly, mental retardation, and absence of the corpus callosum. Cause remains unknown.
In order to obtain metaphases plates from amniotic fluid cells for chromosome analysis, amniocentesis is performed on patients who are at risk of carrying a fetus with genetic disorders. Ultrasound examination is routinely done before amniocentesis as an aid to the latter procedure and to obtain clinical data concerning the fetus. Speculation that ultrasound examination would reduce the number of blood-stained taps obtained at amniocentesis and maybe also inhibit the growth of amniotic fluid cells in culture is discussed, based on findings in this laboratory over a 3-year period.
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A genetic clinic has been held once a week at the Red Cross War Memorial Children's Hospital for the past 6 years. During the period 1971--1977, 579 patients were seen, of whom 56% had genetic conditions due to chromosome defects, Mendelian traits or a multifactorial type of inheritance. In these, genetic counselling was a prime importance regarding prognosis, risk of recurrence and possibility of antenatal diagnosis. A further 25% of patients seen had conditions of non-genetic origin and could be reassured, while in the remaining 19% no specific causation was detected.
Two unrelated children with the fetal alcohol syndrome are described. Features of the syndrome include mental deficiency, growth delay, and craniofacial, limb and cardiac anomalies. The finding of this spectrum of abnormalities raises the possibility of alcohol ingestion during pregnancy. The deleterious effects of alcohol on the developing fetus are emphasized. In view of the high prevalence of alcoholism in this country the fetal syndrome must be regarded as a serious and preventable cause of morbidity.
The results of buccal smear examinations of patients in five institutes for mental retardates, a psychiatric hospital, a home for physically handicapped children, two schools for the deaf, a normal primary school and a newborn nursery are reported. Extra X chromosomes were found in 4/1 000 mentally retarded males, in 1,8/1 000 mentally ill patients and in 1,3/1 000 newborn females. Extra Y chromosomes were found in 1,5/1 000 males, and 3,6/1 000 males were noted to have non-fluorescing Y chromosomes, a normal variant.
Over a period of 5 years, 434 women at risk of having abnormal babies have had antenatal daignostic tests carried out during the first half of their pregnancy by the laboratories of the Department of Human Genetics, University of Cape Town. From these investigations, it was predicted that 13 fetuses had chromosomal abnormalities, 6 had severe central nervous system defects and 4 had autosomal recessive metabolic disorders. In addition, 4 cases with X-linked recessive traits were monitored and 3 male fetuses were recognized. Affected pregnancies were terminated except for 1 with a fetal sex-linked disorder where the parents revoked their original decision. The diagnosis was confirmed by fetal autopsies in all cases except 4 (2 spontaneous abortions and 2 out-of-town terminations). There was only 1 case where culture failed and the pregnancy went to term with the birth of a baby with Down syndrome. Antenatal diagnosis is now an important part of normal clinical practice. The fact that the fetal abnormalities were recognized in 6% of pregnancies is justification for the use of this procedure.
Degenerative diseases of the cerebral white matter are rare, but have severe consequences. The diagnosis of one such disorder, Krabbe's disease, may be made by biochemical analysis of cultured fibroblasts. As the disease is inherited as an autosomal recessive trait, there is a high risk of affected children being born to a heterozygote couple. A description is given of an infant with Krabbe's disease and of the monitoring of the mother's second pregnancy in which an affected fetus was found.
In the first phase of a programme for the prevention of neural tube defects at a population level, information has been obtained concerning 285 infants born with open neural tube defects. As in other parts of the world, the months of conception of affected infants clustered in the second quarter of the year and the majority of the parents were members of lower income groups. In the years 1975-1977, the incidence of anencephaly and spina bifida in White South African patients was similar to that generally encountered in Western Europe. However, in the non-White populations the separate and combined incidence were significantly lower. It is emphasized that these are preliminary figures and that they might be subject to ascertainment biases.